As filed with the Securities and Exchange Commission on March 31, 2023.

Registration No. 333-

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

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FORM S-1
REGISTRATION STATEMENT
UNDER THE SECURITIES ACT OF 1933

_________________

OS THERAPIES INCORPORATED
(Exact name of registrant as specified in its charter)

_________________

Delaware	2834	82-5118368
(State or other jurisdiction of incorporation or organization)	(Primary SIC Code)	(IRS Employer Identification No.)

15825 Shady Grove Road, Suite 135
Rockville, Maryland 20850
(410) 297-7793
(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

_________________

Paul A. Romness, MPH
President and Chief Executive Officer
OS Therapies Incorporated
15825 Shady Grove Road, Suite 135
Rockville, Maryland 20850
(410) 297-7793(Name, address, including zip code, and telephone number, including area code, of agent for service)

_________________

Copies to:

Spencer G. Feldman, Esq.
Olshan Frome Wolosky LLP
1325 Avenue of the Americas,
15th Floor
New York, New York 10019
(212) 451-2300 Ralph V. De Martino, Esq.
Cavas Pavri, Esq.
Johnathan Duncan, Esq.
ArentFox Schiff, LLP
1717 K Street, NW
Washington, DC 20006

_________________

Approximate date of commencement of proposed sale to the public:

As soon as practicable after the effective date of this registration statement.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, as amended, check the following box. ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large Accelerated Filer	☐	Accelerated Filer	☐
Non-Accelerated Filer	☒	Smaller Reporting Company	☒
		Emerging Growth Company	☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided to Section 7(a)(2)(B) of the Securities Act. ☐

_________________

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE

This registration statement contains two prospectuses, as set forth below:

•Public Offering Prospectus.    A prospectus to be used for the initial public offering of 2,000,000shares of common stock of OS Therapies Incorporated (the “Public Offering Prospectus”), with such shares to be sold in an underwritten offering through the underwriters named on the cover page of the Public Offering Prospectus.

•Resale Prospectus.    A prospectus to be used for the resale from time to time by the selling stockholders named therein of 536,336shares of common stock to be issued before the effectiveness of this registration statement upon the automatic conversion of convertible promissory notes issued in our recent private placement, as set forth in the resale prospectus (the “Resale Prospectus”).

The Resale Prospectus is substantially identical to the Public Offering Prospectus, except for the following principal differences:

•they contain different outside and inside front cover and back cover pages;

•they contain different “Summary of the Offering” sections on page Alt-1;

•they contain different “Use of Proceeds” sections on page Alt-2;

•no “Dilution” section in the Resale Prospectus;

•a “Selling Stockholders” section is included in the Resale Prospectus;

•a Selling Stockholders “Plan of Distribution” is included in the Resale Prospectus in lieu of the section “Underwriting” in the Public Offering Prospectus; and

•the “Legal Matters” section in the Resale Prospectus on page Alt-6 deletes the reference to counsel for the underwriters.

The registrant has included in this registration statement a set of alternate pages after the back cover page of the Public Offering Prospectus (the “Alternate Pages”) to reflect the foregoing differences in the Resale Prospectus as compared to the Public Offering Prospectus. The Public Offering Prospectus will exclude the Alternate Pages and will be used for the initial public offering by the registrant. The Resale Prospectus will be substantially identical to the Public Offering Prospectus except for the addition or substitution of the Alternate Pages and will be used for the resale offering by the selling stockholders. Consummation of the offering made by the Resale Prospectus is conditioned on consummation of the initial public offering of shares of common stock by OS Therapies Incorporated pursuant to the Public Offering Prospectus.

The information in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the Registration Statement filed with the Securities and Exchange Commission becomes effective. This preliminary prospectus is not an offer to sell nor does it seek an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

PRELIMINARY PROSPECTUS SUBJECT TO COMPLETION DATED MARCH 31, 2023

2,000,000 Shares

OS THERAPIES INCORPORATED
Common Stock

This is the initial public offering of common stock of OS Therapies Incorporated. Prior to this offering, no public market has existed for our common stock. We are offering 2,000,000shares. The initial public offering price is $5.00 per share. We have applied to list our shares of common stock for trading on the NYSE American under the symbol “OSTX.” This listing is a condition to the offering.

Concurrently with this offering, we are registering for resale by selling stockholders an aggregate of 536,336shares of common stock to be issued to them before the effectiveness of this offering upon the automatic conversion of convertible promissory notes sold in our private placement commenced in November 2022. The notes will convert at a price of $2.47 per share. These shares are being registered to satisfy a contractual obligation owed by us to the selling stockholders pursuant to a convertible note purchase agreement. The selling stockholders have represented to us that they will not offer or sell their shares prior to the closing of this offering. Sales of these shares, or the potential of such sales, may have an adverse effect on the market price of the shares offered hereby.

Our business and investment in our common stock involve significant risks. These risks are described under the caption “Risk Factors” beginning on page 13 of this prospectus.

	Per Share	Total
Initial public offering price	$	$
Underwriting discounts and commissions(1)	$	$
Proceeds to us, before expenses	$	$

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(1)Does not include a non-accountable expense allowance equal to 1% of the gross proceeds of this offering payable to Boustead Securities, LLC, the representative of the underwriters. We have also agreed to issue warrants to the representative of the underwriters. See the section entitled ‘‘Underwriting’’ beginning on page 105 of this prospectus for additional information regarding compensation payable to the underwriters.

We have granted a 45-day option to the underwriters to purchase up to 300,000 additional shares of our common stock, solely to cover over-allotments, if any, at the public offering price less underwriting discounts and commissions.

We are an “emerging growth company” and “smaller reporting company” as defined under the U.S. federal securities laws and, as such, have elected to comply with certain reduced public company reporting requirements for this prospectus and may elect to do so after this offering in future filings.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares of our common stock to purchasers on or about _____, 2023.

Boustead Securities, LLC

The date of this prospectus is __________, 2023

OST-HER2

OST-TDC

OS Therapies’ pipeline includes two drug technologies — our lead core product candidate OST-HER2, an off-the-shelf immunotherapy, and OST-TDC, our next generation tunable antibody-drug conjugate platform that is in preclinical development.

TABLE OF CONTENTS

	Page
PROSPECTUS SUMMARY	1
RISK FACTORS	13
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS	49
USE OF PROCEEDS	50
DIVIDEND POLICY	52
CAPITALIZATION	53
DILUTION	54
MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS	56
BUSINESS	67
MANAGEMENT	84
EXECUTIVE COMPENSATION	91
SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT	95
CERTAIN RELATIONSHIPS AND RELATED PARTY TRANSACTIONS	96
DESCRIPTION OF CAPITAL STOCK	98
SHARES ELIGIBLE FOR FUTURE SALE	103
UNDERWRITING	105
LEGAL MATTERS	109
EXPERTS	109
WHERE YOU CAN FIND MORE INFORMATION	109
INDEX TO FINANCIAL STATEMENTS	F-1

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ABOUT THIS PROSPECTUS

We have not authorized anyone to provide any information or to make any representations other than those contained in this prospectus or any accompanying prospectus supplement. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. This prospectus is an offer to sell only the securities offered hereby and only under circumstances and in jurisdictions where it is lawful to do so. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus or any applicable prospectus supplement. You should assume that the information appearing in this prospectus or any prospectus supplement is accurate only as of the date on the front of those documents only, regardless of the time of delivery of this prospectus or any applicable prospectus supplement, or any sale of a security. Our business, financial condition, results of operations and prospects may have changed since those dates.

We are not, and the underwriters are not, offering to sell or seeking offers to purchase these securities in any jurisdiction where the offer or sale is not permitted. We and the underwriters have not done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the securities as to distribution of the prospectus outside of the United States.

The industry and market data and certain other statistical information used throughout this prospectus are from our own research, surveys or studies conducted by third parties and industry or general publications. Industry publications and third-party research, surveys, and studies generally indicate that their information has been obtained from sources believed to be reliable, although they do not guarantee the accuracy or completeness of such information. We are responsible for all of the disclosure contained in this prospectus, and we believe that these sources are reliable; however, we have not independently verified the information contained in such publications. While we are not aware of any misstatements regarding any third-party information presented in this prospectus, their estimates, in particular, as they relate to projections, involve numerous assumptions, are subject to risks and uncertainties, and are subject to change based on various factors, including those discussed under the section entitled “Risk Factors” and elsewhere in this prospectus. Some data are also based on our good faith estimates.

SiLinkers™, CAPs™ and other common law trade names, trademarks or service marks of our company appearing in this prospectus are the property of OS Therapies Incorporated. This prospectus contains additional trade names, trademarks and service marks of other companies that are the property of their respective owners. Solely for convenience, trademarks and trade names referred to in this prospectus appear without ™symbol, but those references are not intended to indicate that we will not assert, to the fullest extent under applicable law, our rights, or that the applicable owners will not assert their rights, to these trademarks and trade names. We do not intend our use or display of other companies’ trade names, trademarks or service marks to imply a relationship with, or endorsement or sponsorship by us of, these other companies.

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PROSPECTUS SUMMARY

This summary highlights information contained in greater detail elsewhere in this prospectus. This summary is not complete and does not contain all of the information you should consider in making your investment decision. You should read the entire prospectus carefully before making an investment in our common stock. You should carefully consider, among other things, our financial statements and the related notes and the sections entitled “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” included elsewhere in this prospectus. Unless the context otherwise requires, the terms “OS Therapies,” “OST,” the “Company,” “we,” “us” and “our” refer to OS Therapies Incorporated.

Our Company and Mission

OS Therapies Incorporated is a clinical stage biopharmaceutical company focused on the identification, development and commercialization of treatments for Osteosarcoma (OS) and other solid tumors. Our mission is to address the significant need for new treatments in cancers of the bone in children and young adults. Osteosarcoma is an extremely challenging and often aggressive cancer that has particular treatment challenges due to its location, changing genotypes and high recurrence rates. We are currently seeking to answer the call for new treatments with our lead core product candidate OST-HER2 (also known as OST31-164). We intend to expand our pipeline beyond Osteosarcoma with this product candidate into other solid tumors with the same recurrence mechanism of action, including breast, esophageal and lung cancers. With the addition of our OST-Tunable Drug Conjugate (OST-TDC) platform, which we consider to be a next generation antibody-drug conjugate (ADC) technology, we will be targeting ovarian, lung and pancreatic cancers. “Tunable” is a term used in drug development that refers to the properties that can be influenced by chemical modifications, and “antibody-drug conjugate” or ADC is a term used to describe a drug made up of a monoclonal antibody attached to a cytotoxic payload, or a highly active and toxic pharmaceutical molecule, through chemical linkers. The ADC links an antibody that can home in on a targeted tumor and deploy the cytotoxic payload or toxic agent against the tumor. Furthering our founding mission, we also intend to investigate clinical indications for OST-TDC in Osteosarcoma.

There have not been any new treatments approved by the U.S. Food and Drug Administration (FDA) for Osteosarcoma for more than 40 years. In humans, Osteosarcoma is an extremely rare cancer that primarily affects children, teenagers and young adults generally under 40 years of age. We are not aware of any competing adjuvant therapy for Osteosarcoma to be tested in children that is further along in the development process than OST-HER2. This disease is difficult to diagnose. The standard of care following first line therapies is simply to screen and wait for possible recurrence/metastasis, or the development of secondary malignant growths at a distance from a primary site of cancer. Studies published in the Journal of Clinical Oncology, “Osteosarcoma relapse after combined modality therapy: an analysis of unselected patients in the Cooperative Osteosarcoma Study Group (COSS),” by Bempf-Bielack B., et al. (January 2005), reported that recurrence/metastasis happens in approximately half of all patients within 12 to 18 months following initial remittance. For those patients that experience recurrence, metastasis is typically to the lungs and brain, with survival rates of approximately 13% over the next year, according to these studies.

Our Pipeline of Product Candidates

We have built a pipeline of product candidates targeting multiple indications for solid cancers. Our pipeline includes two drug technologies: (i) OST-HER2, an off-the-shelf immunotherapy, which is a type of cancer treatment that helps one’s immune system fight cancer, comprised of a genetically weakened and modified strain of Listeria monocytogenes, or a species of bacteria that causes the infection listeriosis, that expresses HER2 peptides, and (ii) OST-TDC, a next generation tunable ADC with a plug-and-play platform that features tunable pH sensitive silicone linkers (SiLinkers™). The payloads can include antibodies, chemotherapeutics, cytotoxins and potentially mRNA treatments directly into and in the vicinity of solid tumors.

OST-HER2 (OST31-164).    Our most advanced product candidate, OST-HER2, is a genetically engineered strain of Listeria monocytogenes, attenuated for reduced virulence, increased antibiotic susceptibility and the expression of three HER2 protein epitopes fused to immune-enhancing peptides on the membrane of the bacteria.

OST-HER2 has received an orphan drug designation in the United States. The FDA may designate a biologic product as an orphan product if it is intended to treat a rare disease or condition, which generally is defined as having a patient population of fewer than 200,000 individuals in the United States. Osteosarcoma has an incidence rate of approximately 1,000 individuals affected per year in the United States. Orphan product designation, subject to limited exceptions, can provide a period of market exclusivity for a product that is the first to receive marketing

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approval for the designated indication. Other potential indications may include breast, esophageal, lung and other solid tumors. In August 2021, OST-HER2 was awarded rare pediatric disease designation and previously received fast track designation by the FDA. Such designations by the FDA do not convey any advantages in, or shorten the duration of, the regulatory review or approval process.

OST-TDC.    Our tunable drug conjugate (TDC) platform is currently in preclinical development. Each TDC contains four main components: ligand, payload cassette adaptor, linker and payload. In addition, TDCs contain units to optimize physicochemical properties. The ligands are selected to bind to receptors overexpressed on cancer cells. Upon binding, the TDC construct gets internalized into the cancer cell, where the payload is released, to cause cell death. The payload cassette adaptors enable the stoichiometrical attachments of linkers and payloads. The SiLinkers represent a novel and pH-sensitive linker system. The SiLinker release profile can be tuned with proximal functional groups, resulting in payload release in the endosome, lysosome or the slightly acidic tumor microenvironment. The SiLinker system is compatible with a variety of payloads and not limited to the employment of cytotoxic drug delivery. The first set of internal programs focus on the use of SiLinker and conditionally active payloads (CAPs™) drug products. CAPs are cytotoxic drugs which on their own, due to their functional groups, cannot readily permeate cells at physiological pH; however, at the slightly acidic pH of the tumor-microenvironment, after some linker cleavage, these payloads readily permeate into cancer cells, resulting in an enhanced bystander effect. Our lead program targets folate receptor alpha, a protein expressed on the surface of cells that participates in cell signaling, as well as cellular replication and division, and is overexpressed in multiple cancers such as ovarian and endometrial cancers. The lead compound employs folic acid, a small molecule, as the targeting ligands and contains six exatecan-silanols, which is a type of silanol-based cytotoxic payload. This discovery work is being carried out at Syngene International Limited, an integrated contract research organization (CRO) based in Bangalore, India.

From time to time, we may evaluate collaboration opportunities for our product candidates. We expect to work opportunistically with pharmaceutical and biotechnology companies, as we have done with BlinkBio, Inc. by in-licensing the OST-TDC technology, seeking to utilize our technology and know-how for developing additional oncologic drug products. The following table summarizes information regarding our product candidates and development programs.

In addition to our development of OST-HER2 for multiple indications of solid cancers in humans, OST-HER2 is a product candidate for veterinary use in canines. We hold a conditional license for OST-HER2 granted by the U.S. Department of Agriculture (USDA), which allows OST-HER2 to be commercialized but its use is limited to the treatment of dogs diagnosed with Osteosarcoma that are one year of age or older. As part of our growth strategies following this offering, we intend to consider potentially out-licensing OST-HER2 to animal health companies for such use. See “OS-Focused Clinical Trials and Studies – Preclinical Animal Study” for more information.

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Our OS-Focused Clinical Trials and Studies

We and our licensors have conducted a number of clinical trials and studies in the field of Osteosarcoma and Tunable Drug Conjugates to date.

Phase IIb Clinical Trial.In July 2021, we commenced and are sponsoring a Phase IIb clinical trial to treat Osteosarcoma in humans, which is being conducted by George Clinical, Inc., our clinical research services provider, utilizing our OST-HER2 product candidate. The course of the trial involves a regimen of 16 infusions of OST-HER2 administered over 48 weeks to eligible patients from ages 12 to 39 years, of which 36 of 45 patients have already been enrolled. Enrollment remains ongoing and the Phase IIb trial is being conducted at major hospitals across 21 sites in 18 states. The primary outcome measures are the relative proportion of patients experiencing event-free (recurrence-free) survival at 12 months compared to historical controls by evaluating the patients for recurrence every 3 months, consistent with the standard of care. The secondary outcome measures are overall survival of patients for three years compared to the three-year overall survival of historical controls, which will be evaluated by assessing patients every three months over the course of three years, and the incidence of treatment-emergent adverse events as assessed by Common Terminology Criteria for Adverse Events (CTCAE) Grade5, the safety of which will be assessed throughout the treatment period of 48 weeks with assessments of potential persistence of the vector every three months and continuing for three years after treatment. CTCAE is a method to categorize adverse events across all clinical trials of five grades, with Grade 5 being death. The expected completion date of OST-HER2’s Phase IIb clinical trial is late 2024. We plan to submit a new drug application (NDA) with the FDA for approval to market the drug candidate following the completion of the Phase IIb clinical trial if there is sufficiently positive endpoint data from such trial supporting the safety and efficacy of the drug candidate. We expect that it will take six to eight months from the completion of the Phase IIb clinical trial, subject to the receipt of sufficiently positive endpoint data, to compile and file the NDA with the FDA for marketing approval. The FDA generally takes six to ten months to complete its review of an NDA, subject to any FDA request for additional information.

Phase Ib Clinical Trial.From September 2015 to May 2017, a Phase Ib trial to treat Osteosarcoma in humans was sponsored and conducted by Advaxis, Inc. (now Ayala Pharmaceuticals, Inc.) (“Advaxis”) utilizing ADXS-HER2 (also known as ADXS31-164), the patents of which we in-license to develop and commercialize our lead core product candidate, OST-HER2. The trial was conducted at hospitals in Colorado, Michigan, North Carolina, Pennsylvania and Texas. The course of the trial involved injecting 12 adult patients with HER2 expressing solid tumors with escalating doses of ADXS-HER2 every three weeks during a 12-week treatment cycle. Following the last dose of study treatment, all 12 patients participated in a three-year Listeria monocytogenes surveillance period. The primary outcome measures were the number of patients with dose-limiting toxicities for each dose level as assessed by the CTCAE Grade 4 (time frame: four months), with Grade 4 being life threatening, and the frequency and severity of adverse effects as assessed by CTCAE Grade 4 (time frame: three years). The secondary outcome measures were proportion of patients who have objective tumor response (complete or partial) evaluated by the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 and RECIST-based immune criteria (ir-RECIST), as well as changes in clinical immunology based upon serum, which were measured and evaluated by collection of peripheral blood for preparation of peripheral blood mononuclear cells and serum at baseline, prior to each treatment and post-treatment in the first treatment cycle only. The data presented from the Phase Ib trial demonstrated that ADXS-HER2 IV infusion at the dose of 1×109 CFU was well tolerated. See “Business — Our OS-Focused Clinical Trials and Studies — Phase Ib Clinical Trial” for more information.

Preclinical Animal Study.From July 2012 to September 2015, a preclinical study to treat Osteosarcoma in 18 companion canines (sometimes referred to as a Phase I animal trial) was sponsored and conducted by a previous licensee of Advaxis utilizing ADXS-HER2, the product candidate of Advaxis, from whom we in-license patents for ADXS-HER2 constructs that enable us to develop OST-HER2. The results showed, in the setting of minimal residual disease where there is a very small number of cancer cells remaining in the body during or after initial treatment, significant improvements in overall survival and metastatic disease progression when compared to an historical control group with Human Epidermal Growth Factor Receptor 2-positive (HER2) appendicular Osteosarcoma, a well-recognized spontaneous model for pediatric Osteosarcoma, treated with amputation and chemotherapy alone. In September 2016, the study results, published in the journal, Clinical Cancer Research, “Immunotherapy with a HER2-Targeting Listeria Induces HER2-Specific Immunity and Demonstrates Potential Therapeutic Effects in a Phase I Trial in Canine Osteosarcoma,” by Mason, N. et al. (https://pubmed.ncbi.nlm.nih.gov/26994144/), indicated that ADXS-HER2 significantly increased the duration of survival time and one-, two- and three-year survival rates and significantly reduced the incidence of metastatic disease (the spread of cancer cells from an initial or primary site

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to a different or secondary site within the host’s body) when compared with the historical control group. The overall survival rates at one, two and three years for dogs treated with ADXS-HER2 were 77.8%, 67% and 56%, respectively, compared to 55%, 28% and 22%, respectively, for the historical control group. The median survival time (MST) for the historical control group was 423 days, which was significantly shorter than the 956 days for ADXS-HER2 — treated dogs (p=0.014, HR 0.33; 95% confidence intervals; CI, 0.136 – 0.802). The study also noted the important translational relevance of the findings for children with Osteosarcoma. This study for canine Osteosarcoma indications constituted preclinical work as it relates to our development of OST-HER2 to treat Osteosarcoma in humans.

In analyzing preclinical study results, a p-value is used to determine the probability as to whether the difference between two data sets is due to chance. The smaller the p-value, the more likely the differences are not due to chance alone. In general, if the p-value is less than or equal to 0.05, the outcome is considered statistically significant. The FDA’s evidentiary standard of efficacy generally relies on a p-value of less than or equal to 0.05. A p-value greater than 0.05 is considered statistically non-significant. As shown above, the results of this preclinical study were statistically significant compared to the historical control group.

Following the study, an application for the use of ADXS-HER2, our OST-HER2, in the treatment of canine Osteosarcoma was submitted to the USDA. In December 2017, ADXS-HER2 was granted a conditional license by the USDA. Because we are the current licensee of ADXS-HER2 constructs, we hold the conditional license previously granted to ADXS-HER2 for OST-HER2. The conditional license allows for commercialization but limits the use of OST-HER2 to treat dogs, one year of age and older, diagnosed with Osteosarcoma. To receive full licensure, the USDA requires the submission of additional data that further describes the effects of OST-HER2 on metabolism and shedding in canines and provides substantial evidence of the safety, purity, potency and effectiveness of OST-HER2. We do not intend to pursue full licensure from the USDA at this time. We are considering potentially out-licensing OST-HER2 to animal health companies for the treatment of dogs diagnosed with Osteosarcoma, one year of age and older. In the event that we determine to out-license OST-HER2 to animal health companies, the animal health companies will be responsible for obtaining full licensure from the USDA for OST-HER2 in order to market and sell the product candidate for use in dogs with Osteosarcoma without any limitation.

Preclinical Development.Our OST-HER2 product candidate for breast, esophageal, lung and other solid tumor indications is currently in preclinical development. Whether additional preclinical trials will be required will depend on several factors, including the outcome of our ongoing Phase IIb clinical trial, the inclusion or exclusion of breast, esophageal, lung or other solid tumor indications in any follow-on study, or master protocol, to the Phase IIb clinical trial and the FDA’s determination of whether the preclinical data is sufficient to support the safety and efficacy of the drug. Although we cannot be certain, we believe that OST-HER2 may not require additional preclinical development before progressing to human clinical trials for breast, esophageal, lung and other solid tumor indications if the results of our ongoing Phase IIb clinical trial have sufficiently positive endpoint data as determined by the FDA.

Our OST-TDC product candidate for all indications is also currently in preclinical development. We will need to conduct further preclinical trials for OST-TDC prior to the submission of an investigational new drug application (IND) in order to pursue clinical trials with these candidates. Such preclinical trials are expected to include pharmacokinetics and pharmacodynamics, two-week dose finding toxicology studies in vivo (on living cell lines or in living animals), as well as good laboratory practice (GLP) trials ensuring stability, potency and purity of the IND product candidate.

Our Platform Technology

We are in the process of building a fully integrated platform technology to accelerate the development of a range of product candidates across multiple therapeutic areas. Our platform technology is intended to leverage our management’s in-depth experience in immunotherapy research, development and manufacturing to enable us to pursue multiple therapeutic targets. Our scientists and scientific advisors have accumulated decades of collective experience in the field of immunotherapy, oncology and small-molecule drug production, contributing key insights and significant achievement in our clinical development process.

Our Management Team

We have assembled a management team of biopharmaceutical industry professionals with extensive experience in developing novel products and therapies from initial research through commercialization. Our team is led by our President and Chief Executive Officer, Paul A. Romness, MPH, who has more than 25 years of experience in the biopharmaceutical industry, and our Chief Financial Officer, Alan A. Musso. Our Chief Medical and Scientific Officer,

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Robert G. Petit, Ph.D., is an accomplished biopharmaceutical executive and medical scientist. Our management team is assisted by Colin Goddard, Ph.D., our Chairman of the Board, whose in-depth knowledge of the biotechnology market and experience leading OSI Pharmaceuticals make his input invaluable to our company.

Our Growth Strategies

Our goal is to enrich and lengthen the lives of patients by being a leading, fully integrated biotechnology company. We are seeking to develop, manufacture and commercialize multiple product candidates targeting orphan and non-orphan oncologic diseases across multiple tissue types and therapeutic areas. To achieve our goal, we are pursuing the following growth strategies:

•Consider potentially out-licensing OST-HER2 to animal health companies for veterinary use to treat dogs diagnosed with Osteosarcoma, one year of age or older.

•Obtain marketing approval for OST-HER2 in Osteosarcoma, then quickly pivot to a master protocol within breast, esophageal, lung and other solid tumors where metastases express HER2 that could be targeted by immune cells.

•Conclude pre-clinical and toxicology trials with the lead drug candidate for OST-TDC (OST-TDC-A, Exatecan-silanol-FRa), and file for an investigational new drug application (IND) to initiate a Phase I trial in ovarian cancer and other folate receptor alpha overexpressing cancers like endometrial cancer and some osteosarcomas. We believe that positive results from preclinical two-week and good laboratory practice (GLP) toxicology studies may also stimulate potential out-licensing activity of SiLinker and CAPs drug products, while not limiting therapeutic development.

•Establish global commercial and medical affairs capabilities for OST-HER2 based therapies.

Expansion Opportunities

We believe opportunities may exist from time to time to expand our current business through acquisitions or in-licenses of complementary products or technologies or acquisitions of companies with complementary products or technologies. While we have current collaborative agreements in place, we believe in an opportunistic approach to collaboration and licensing; thus, we expect to operate in a manner that is customary in the pharmaceutical industry, including potential acquisitions and partnerships.

We are also aware of increased acquisition and licensing interest from large pharmaceutical firms in biotechnology companies developing antibody-drug conjugate, or ADC, technology as a relatively new kind of cancer therapy. In the article, “Seagen Cancer Therapy Draws Suitors” (March 7, 2023), The Wall Street Journal reported that driving this interest, according to analysts, is the potential for ADCs to capture a chunk of the worldwide cancer market. Technical advances by combining the ADCs with widely used cancer agents like immunotherapies have also opened up exploring various potential cancer applications, according to the article.

The expected use of the net proceeds from this offering for development of our current product candidates represents our intentions based upon our current plans and business conditions, which could change in the future as our plans and business conditions evolve. The amounts and timing of our actual expenditures may vary significantly depending on numerous factors, including the progress of our development, the status of, and results from, clinical trials and the potential need to conduct additional clinical trials to obtain approval of our product candidates for all intended indications, as well as any additional collaborations that we may enter into with third parties for our product candidates and any unforeseen cash needs. As a result, our management will retain broad discretion over the allocation of the net proceeds from this offering.

Based on our planned use of the net proceeds from this offering and our existing cash, we estimate that such funds will be sufficient to enable us to fund our operating expenses and capital expenditure requirements over the next 12 to 18 months. We have based this estimate on assumptions that may prove to be wrong, and we could use our available capital resources sooner than we currently expect.

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Recapitalization and Private Placements

Recapitalization Transactions

Unless otherwise indicated, this prospectus gives effect to the following transactions (referred to as the “Recapitalization”), which will be completed before the effectiveness of this offering:

•the automatic conversion of all of our outstanding convertible notes, including accrued interest, totaling approximately $14.2 million as of March31, 2023, into 8,728,737shares of our common stock (based on the initial public offering price of $5.00 per share), as described below;

•the issuance of an additional 325,000shares of our common stock to the noteholders in our private placement commenced in November 2022 upon the automatic conversion of their outstanding convertible notes, as described below;

•the automatic conversion of all of our outstanding shares of Series A preferred stock into an aggregate of 1,302,082shares of our common stock; and

•the elimination of our authorized shares of Class B common stock (none of which were outstanding) and renaming our Class A common stock as “common stock.”

The financial statements of our company in this prospectus do not reflect the Recapitalization transactions. The effect of the transactions on the financial statements will essentially be to increase our outstanding shares of common stock by an additional 8,728,737shares, reduce our long-term liabilities by approximately $10.4 million as of December 31, 2022, as a result of the extinguishment of all outstanding convertible notes payable by us, and to eliminate our senior class of Series A preferred stock as a result of converting such shares into an equal number of shares of common stock. Following this offering, our common stock will be our only outstanding class of capital stock and we will have no outstanding indebtedness. See “Capitalization,” “Dilution” and “Certain Relationships and Related Party Transactions.”

Private Placements

We have completed five separate private placement transactions from July 2018 to March 2023, in which we raised total gross proceeds of $15,253,020 from accredited investors. A summary of each private placement is set forth below.

From July 2018 through November 2021, we issued convertible notes with an aggregate principal amount of $1,154,000 (the “Group A Convertible Notes”) to accredited investors, including related parties, in exchange for cash in an aggregate amount of $1,154,000. The Group A Convertible Notes bear interest at a rate of 10% per annum and mature on March 31, 2024. The Group A Convertible Notes will automatically convert into common stock at 80% to 87.5% of the price per share in our Next Equity Financing (which is this initial public offering), subject to valuation ceilings that range from $5 million to $25 million. The Group A Convertible Notes will have a conversion price that ranges from $0.40 to $1.98 per share, depending on the applicable valuation ceiling of each note (based on the initial public offering price of $5.00 per share).

From April 2020 through June 2021, we issued convertible notes with an aggregate principal amount of $5,154,000 (the “Group B Convertible Notes”) to accredited investors in exchange for cash in an aggregate amount of $5,154,000. The Group B Convertible Notes bear interest at a rate of 6% per annum and mature on March 31, 2024. The Group B Convertible Notes will automatically convert into common stock at 80% of the price per share in our Next Equity Financing (which is this initial public offering), subject to a valuation ceiling of $19 million. As a result of the valuation ceiling, the Group B Convertible Notes will have a conversion price of $1.34 per share (based on the initial public offering price of $5.00 per share).

In connection with the private placement of Group B Convertible Notes, we issued to Noble Life Science Partners, a division of Noble Capital Markets, the placement agent for the offering, warrants to purchase 384,082shares of common stock at an exercise price of $1.34 per share (the “Group B Warrants”), based on the initial public offering price of $5.00 per share. The Group B Warrants may, at the option of the holder, be exercised in whole or part on a cashless basis. The Group B Warrants expire five years after the effective date of this offering.

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On August 19, 2020, we issued a convertible note with a principal amount of $2,400,000 (the “BlinkBio Convertible Note”) to BlinkBio, Inc., which is a related party based on Dr. Goddard being our Chairman and as the Chairman and Chief Executive Officer of BlinkBio, in exchange for the entry into the license agreement to utilize a group of patents described as silicon based drug conjugates and methods, along with silanol based therapeutic payloads. The BlinkBio Convertible Note bears interest at a rate of 10% per annum. On March 15, 2021, we issued 1,302,082shares of Series A preferred stock to BlinkBio in exchange for the BlinkBio Convertible Note.

From June 2021 through January 2023, we issued convertible notes with an aggregate principal amount of $3,945,020 (the “Group C Convertible Notes”) to accredited investors in exchange for cash in an aggregate amount of $3,945,020. The Group C Convertible Notes bear interest at a rate of 6% per annum and mature on May 31, 2024. The Group C Convertible Notes will automatically convert into common stock at 80% of the price per share in our Next Equity Financing (which is this initial public offering), subject to a valuation ceiling of $50 million. As a result of the valuation ceiling, the Group C Convertible Notes will have a conversion price of $2.70 per share (based on the initial public offering price of $5.00 per share).

In connection with the private placement of Group C Convertible Notes, we issued to Noble Life Science Partners, a division of Noble Capital Markets, the placement agent for the offering, warrants to purchase 110,486shares of common stock at an exercise price of $2.70 per share (the “Group C Warrants”), based on the initial public offering price of $5.00 per share. The Group C Warrants may, at the option of the holder, be exercised in whole or part on a cashless basis. The Group C Warrants expire five years after the effective date of this offering.

In November 2022, we issued convertible notes with an aggregate principal amount of $2,000,000 (the “November 2022 Convertible Notes”) to accredited investors in exchange for cash in an aggregate amount of $2,000,000. In March 2023, we issued two convertible notes in the aggregate principal amount of $600,000 on the same terms as the November 2022 Convertible Notes (the “March 2023 Convertible Notes” and, together with the November 2022 Convertible Notes, the “Group D Convertible Notes”) to a holder of November 2022 Convertible Notes and a holder of the Group C Convertible Notes in exchange for cash in an amount of $600,000. The Group D Convertible Notes bear interest at a rate of 6% per annum and mature on November15, 2023. The Group D Convertible Notes automatically convert into common stock at 50% of the price per share in our Next Equity Financing (which is this initial public offering), subject to a valuation ceiling of $50million. As a result of the valuation ceiling, the Group D Convertible Notes will have a conversion price of $2.47 per share (based on the initial public offering price of $5.00 per share).

In connection with the Group D Convertible Notes, we agreed to issue an additional 325,000shares of Class A common stock to the Group D investors, pro-rated based on such investor’s investment amount, as an inducement for their investment in the Group D Convertible Notes. We will issue such shares upon the automatic conversion of the Group D Convertible Notes. Additionally, we issued to Noble Life Science Partners, a division of Noble Capital Markets, the placement agent for the offering, warrants to purchase 81,116shares of common stock at an exercise price of $2.47 per share (the “Group D Warrants”), based on the initial public offering price of $5.00 per share. The Group D Warrants may, at the option of the holder, be exercised in whole or part on a cashless basis. The Group D Warrants expire five years after the effective date of this offering.

We have used the net proceeds of our private placements to develop our pipeline of product candidates and fund our working capital requirements.

Summary of Risks Associated with Our Business

An investment in our common stock involves substantial risk. Our ability to execute on our strategy is also subject to certain risks. The risks described under the heading “Risk Factors” immediately following this prospectus summary may have an adverse effect on our business, cash flows, financial condition and results of operations or may cause us to be unable to successfully execute all or part of our strategy. Below are the principal factors that make an investment in our company speculative or risky:

Risks Related to Our Financial Position and Need for Additional Capital

•We are a clinical stage biopharmaceutical company and have not generated any revenue to date from drug sales, and may never become profitable.

•We have incurred significant operating losses in recent periods and anticipate that we will incur continued losses for the foreseeable future.

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•Even if we consummate this offering, we will need to raise substantial additional funding, and if we are unable to raise capital when needed or on attractive terms, we would be forced to delay, scale back or discontinue some of our product candidate development programs or commercialization efforts.

•We have identified conditions and events that raise substantial doubt about our ability to continue as a going concern.

•Our ability to utilize our net operating loss carryforwards and certain other tax attributes may be limited.

Risks Related to Drug Development and Regulatory Approval

•We depend heavily on the success of our core product candidates OST-HER2 and OST-TDC. We may not be able to obtain regulatory permission to conduct future clinical studies, or may not be able to obtain regulatory approval for, or successfully commercialize, any of our current or future product candidates.

•If we experience delays or difficulties in the enrollment of patients in clinical trials, our receipt of necessary regulatory approvals could be delayed or prevented.

•If we are not able to obtain, or if there are delays in obtaining, required regulatory approvals both for our current or future product candidates, we will not be able to commercialize, or will be delayed in commercializing, our current or future product candidates, and our ability to generate revenue will be materially impaired.

•Our current or future product candidates may cause adverse or other undesirable side effects that could delay or prevent their future testing in clinical studies or delay or prevent regulatory approval, limit the commercial profile of an approved label, or result in significant negative consequences following marketing approval, if any.

•We may not be able to obtain or maintain Orphan Drug Designation or exclusivity for any product candidates and, even if we do, that exclusivity may not prevent the FDA or the EMA from approving other competing products.

•Even if we receive regulatory approval for any of our current or future product candidates, we will be subject to ongoing obligations and continued regulatory review, which may result in significant additional expense. Additionally, our current or future product candidates, if approved, could be subject to labeling and other restrictions and market withdrawal, and we may be subject to penalties if we fail to comply with regulatory requirements or experience unanticipated problems with our drugs.

•Even if we receive marketing approval for our current or future product candidates in the U.S., we may never receive regulatory approval to market our current or future product candidates outside of the U.S.

•Manufacturing our current or future product candidates is complex and we may encounter difficulties in production. If we encounter such difficulties, our ability to provide supply of our current or future product candidates for preclinical studies and clinical trials or for commercial purposes could be delayed or stopped.

•Our future growth may depend, in part, on our ability to penetrate foreign markets, where we would be subject to additional regulatory burdens and other risks and uncertainties that could materially adversely affect our business.

Risks Related to Intellectual Property

•If we or those from whom we in-license patents are unable to obtain and maintain patent and other intellectual property protection for our technology and product candidates or if the scope of the intellectual property protection obtained is not sufficiently broad, our competitors could develop and commercialize technology and drugs similar or identical to ours, and our ability to successfully commercialize our technology and drugs may be impaired.

•If our trademarks and trade names for our products or company name are not adequately protected in one or more countries where we intend to market our products, we may delay the launch of product brand names, use different trademarks or tradenames in different countries, or face other potentially adverse consequences to building our product brand recognition.

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•If we are unable to adequately protect and enforce our trade secrets, our business and competitive position would be harmed.

•We may initiate, become a defendant in, or otherwise become party to lawsuits to protect or enforce our intellectual property rights, which could be expensive, time-consuming and unsuccessful.

•We may not obtain or grant licenses or sublicenses to intellectual property rights in all markets on equally or sufficiently favorable terms with third parties.

•If we fail to comply with our obligations in any agreements under which we may license intellectual property rights from third parties or otherwise experience disruptions to our business relationships with our licensors, we could lose license rights that are important to our business.

•Any in-license patent covering our current or future product candidates or other valuable technology could be narrowed or found invalid or unenforceable if challenged in court or before administrative bodies in the U.S. or abroad, including the USPTO and the EPO.

Risks Related to Management and our Operations

•In our industry in particular, our future success depends on our ability to retain key scientific employees and to attract, retain and motivate qualified personnel.

•Our internal computer systems, or those of our third-party clinical research organizations, or CROs, or other contractors or consultants, may fail or suffer security breaches, which could result in a material disruption of our current or future product candidates’ development programs.

•We will incur increased costs as a result of operating as a public company, and our management will be required to devote substantial time to new compliance initiatives.

Implications of Being an Emerging Growth Company and a Smaller Reporting Company

We qualify as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). For as long as we remain an emerging growth company, we may take advantage of specified reduced reporting requirements and other burdens that are otherwise applicable generally to other public companies. These provisions include, but are not limited to:

•reduced obligations with respect to financial data, including presenting only two years of audited financial statements and selected financial data, and only two years of related Management’s Discussion and Analysis of Financial Condition and Results of Operations disclosure in our initial registration statement;

•an exemption from the auditor attestation requirement in the assessment of our internal control over financial reporting pursuant to the Sarbanes-Oxley Act of 2002, as amended;

•reduced disclosure about executive compensation arrangements in our periodic reports, registration statements and proxy statements; and

•exemptions from the requirements to seek non-binding advisory votes on executive compensation or stockholder approval of any golden parachute arrangements.

We may take advantage of some or all of these provisions until we are no longer an emerging growth company. We will remain an emerging growth company until the earliest of (i) the last day the fiscal year following the fifth anniversary of the completion of this offering, (ii) the last day of the first fiscal year in which our annual gross revenues exceed $1.235 billion, (iii) the date on which we have, during the immediately preceding three-year period, issued more than $1.0 billion in non-convertible debt securities and (iv) the date on which we are deemed to be a large accelerated filer under the rules of the SEC. We may choose to take advantage of some but not all of these reduced burdens. For example, we have taken advantage of the reduced reporting requirements with respect to disclosure regarding our executive compensation arrangements, have presented only two years of audited financial statements and only two years of related “Management’s Discussion and Analysis of Financial Condition and Results of Operations”

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disclosure in this prospectus, and have taken advantage of the exemption from auditor attestation on the effectiveness of our internal control over financial reporting. To the extent that we take advantage of these reduced burdens, the information that we provide stockholders may be different than you might obtain from other public companies in which you hold shares.

In addition, the JOBS Act permits emerging growth companies to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies. We have elected to use this extended transition period. As a result of this election, our timeline to comply with new or revised accounting standards will in many cases be delayed as compared to other public companies that are not eligible to take advantage of this election or have not made this election. Therefore, our financial statements may not be comparable to those of companies that comply with the public company effective dates for these accounting standards.

We are also a “smaller reporting company” as defined in the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and have elected to take advantage of certain of the scaled disclosures available to smaller reporting companies. To the extent that we continue to qualify as a “smaller reporting company” as such term is defined in Rule 12b-2 under the Exchange Act, after we cease to qualify as an emerging growth company, certain of the exemptions available to us as an “emerging growth company” may continue to be available to us, including exemption from compliance with the auditor attestation requirements pursuant to the Sarbanes-Oxley Act and reduced disclosure about our executive compensation arrangements. We will continue to be a “smaller reporting company” until we have $250 million or more in public float (based on our common stock) measured as of the last business day of our most recently completed second fiscal quarter or, in the event we have no public float (based on our common stock) or a public float (based on our common stock) that is less than $700 million, annual revenues of $100 million or more during the most recently completed fiscal year.

Corporate History and Information

We were formed as a Delaware limited liability company on April 12, 2018 under the name OS Therapies, LLC. On June 24, 2019, we converted from a limited liability company to a Delaware corporation and changed our name to OS Therapies Incorporated.

Our principal executive office is located at 15825 Shady Grove Road, Suite 135, Rockville, Maryland 20850, and our telephone number is (410) 297-7793. Our website address is www.ostherapies.com. The information contained on, or that can be accessed through, our website is not incorporated by reference into this prospectus, and you should not consider any information contained on, or that can be accessed through, our website as part of this prospectus or in deciding whether to purchase our common stock.

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Summary of the Offering

Common stock offered	2,000,000shares.
Common stock outstanding immediately before this offering	10,745,000shares.(1)
Common stock to be outstanding immediately after this offering	23,100,819shares (23,400,819shares if the underwriters exercise their option to purchase additional shares in full).(1)
Underwriters’ option to purchase additional shares	We have granted a 45-day option to the underwriters to purchase up to an aggregate of 300,000 additional shares of common stock from us at the public offering price, less underwriting discounts and commissions on the same terms as set forth in this prospectus.
Use of proceeds	We estimate that our net proceeds from the sale of shares of our common stock in this offering will be approximately $8,560,000, or $9,940,000 if the underwriters exercise in full their option to purchase additional shares, based on the initial public offering price of $5.00 per share, and after deducting underwriting discounts and commissions and estimated offering expenses payable by us. We expect to use the net proceeds from this offering as follows: (i) approximately $4.2 million to advance the clinical development of OST-HER2 for Osteosarcoma, (ii) approximately $2.0 million to advance the development of OST-TDC for ovarian cancer and (iii) the remainder of the net proceeds of approximately $2.36 million for the discovery and development of new product candidates and for working capital and other general corporate purposes.
Representative’s warrants	We have agreed to issue warrants to Boustead Securities, LLC, as the representative of the underwriters named in this prospectus, to purchase a number of shares of common stock equal to 7% of the total number of shares sold in this offering at an exercise price equal to 100% of the public offering price of the shares sold in this offering. The representative’s warrants will be exercisable upon issuance, will have a cashless exercise provision and will terminate on the fifth anniversary of the commencement date of sales in this offering. The representative’s warrants are not exercisable or convertible for more than five years from the commencement date of sales in this offering. See the section entitled “Underwriting” beginning on page 105 of this prospectus for additional information regarding compensation payable to the underwriters.
Risk Factors	You should carefully read the “Risk Factors” section of this prospectus for a discussion of factors that you should consider before deciding to invest in our common stock.
Proposed ticker symbol	“OSTX”

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(1)The number of shares of common stock outstanding immediately before this offering (as of March 31, 2023) excludes, and the number of shares of common stock to be outstanding immediately after this offering includes, the issuance of the following shares which will occur before the effectiveness of this offering:

(i)8,728,737shares of common stock upon the automatic conversion of all outstanding convertible notes, including accrued interest, totaling approximately $14.2 million as of March 31, 2023 (based on the initial public offering price of $5.00 per share);

(ii)325,000 additional shares of common stock issuable to the noteholders in our private placement commenced in November 2022 upon the automatic conversion of their outstanding convertible notes; and

(iii)1,302,082shares of common stock upon the automatic conversion of all outstanding shares of Series A preferred stock.

Additionally, we currently have outstanding warrants to purchase up to 575,684shares of common stock and expect to issue warrants to purchase up to 140,000shares of common stock to the representative of the underwriters (up to 161,000shares if the underwriters exercise their over-allotment option in full) in connection with this offering. These shares are not included in the common stock figures above.

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Summary Financial Data

The following table summarizes the relevant financial data for our business and should be read with our financial statements, which are included at the end of this prospectus. We have derived the summary financial data for the years ended December 31, 2022 and 2021 from our audited financial statements and related notes included at the end of this prospectus. Our historical results are not necessarily indicative of results that may be expected in the future. You should read the following summary financial data together with our audited financial statements and related notes thereto and the information in the section titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations.”

Statements of Operations Data:

	Year Ended December 31,
	2022			2021
Operating expenses:
Research and development	$	3,291,417		$	2,174,179
General and administrative	$	1,153,672		$	1,503,534
Licensing	$	1,210		$	1,159,642
Total operating expenses	$	4,446,299		$	4,837,355
Loss from operations	$	(4,446,299	)	$	(4,837,355	)
Other income (expenses):
Other income (expense)	$	(1,808,386	)	$	(2,582,893	)
Total other income (expense)	$	(1,808,386	)	$	(2,582,893	)
Net income (loss)	$	(6,254,685	)	$	(7,420,248	)
Cumulative Series A preferred stock dividend requirement	$	(125,000	)	$	(93,750	)
Net loss available to common shareholders	$	(6,379,685	)	$	(7,513,998	)
Weighted average number of shares – Class A		9,980,000			9,980,000
Basic and diluted loss per common share – Class A	$	(0.64	)	$	(0.75	)

Balance Sheet Data:

	As of December 31, 2022
	Actual			Pro Forma(1)			Pro Forma, As Adjusted(2)
Total current assets	$	496,835		$	772,625		$	10,072,625
Working capital(deficit)	$	(5,650,957	)	$	(1,112,270	)	$	8,187,730
Total assets	$	509,105		$	784,895		$	10,084,895
Total liabilities	$	18,066,333		$	2,675,804		$	2,675,804
Total stockholders’ (deficit) equity	$	(17,557,228	)	$	(1,859,658	)	$	7,440,342

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(1)The pro forma balance sheet data gives effect to (i) the renaming of our Class A common stock as “common stock” and the issuances of shares of our common stock in connection with the Recapitalization transactions, (ii) the issuance of 740,000shares of our common stock that we previously agreed to issue to certain directors, officers, key employees and key advisors in consideration for accrued services rendered to our company and (iii) the grant of 25,000shares of our common stock to our Chief Financial Officer in March 2023.

(2)The pro forma, as adjusted balance sheet data gives effect to the pro forma adjustments described in footnote (1) above and the sale of 2,000,000shares of our common stock in this offering at the initial public offering price of $5.00 per share after deducting the underwriting discount and estimated offering expenses payable by us. The pro forma, as adjusted information discussed above is illustrative only and will be adjusted based on the actual public offering price and other terms of this offering determined at pricing.

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RISK FACTORS

You should carefully review and consider the risk factors described below and described under the heading “Risk Factors” in the accompanying prospectus and the other information contained in this prospectus, including the financial statements and notes to the financial statements, matters addressed in the sections entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and “Risk Factor Summary” included in this prospectus. The occurrence of one or more of the events or circumstances described in these risk factors, alone or in combination with other events or circumstances, may have an adverse effect on our business, cash flows, financial condition and results of operations. We may face additional risks and uncertainties that are not presently known to us, or, or that we currently deem immaterial, which may also harm our business, financial condition, results of operations and prospects.

Risks Related to Our Financial Position and Need for Additional Capital

We are a clinical stage biopharmaceutical company, and have not generated any revenue to date from drug sales, and may never become profitable.

Our ability to become profitable depends upon our ability to generate revenue. To date, while we have generated significant interest in various research collaboration revenue, we have not generated any commercial revenue from our current core product candidates, including our lead core product candidate OST-HER2 and our other core product candidate OST-TDC, and we do not know and do not expect to generate any revenue from the sale of drugs in the near future. We do not expect to generate revenue unless and until we complete the development of, obtain marketing approval for, and begin to sell, OST-HER2, which is being evaluated in a Phase IIb clinical trial, or OST-TDC, which is still being evaluated at the preclinical stage. We are also unable to predict when, if ever, we will be able to generate revenue from such product candidates due to the numerous risks and uncertainties associated with drug development, including the uncertainty of:

•our ability to add and retain key research and development personnel;

•our ability to successfully develop, obtain regulatory approval for, and then successfully commercialize, OST-HER2 and OST-TDC;

•our successful enrollment in and completion of clinical trials, including our ability to generate positive data from any such clinical trials;

•our ability to establish an appropriate safety profile with IND-enabling toxicology and other preclinical studies for OST-TDC;

•the costs associated with the development of any additional development programs we identify in-house or acquire through collaborations or other arrangements;

•our ability to discover, develop and utilize biomarkers to demonstrate target engagement, pathway engagement and the impact on disease progression, as applicable, of our product candidates;

•our ability to establish and maintain agreements with third-party manufacturers for clinical supply for our clinical trials and commercial manufacturing;

•our ability to forecast and meet supply requirements for clinical trials and commercialized products using third-party manufacturers;

•the terms and timing of any additional collaboration, license or other arrangement, including the terms and timing of any payments thereunder;

•obtaining any necessary licenses to manufacture and distribute OST-HER2 and/or OST-TDC and/or contractual arrangements with third party logistics providers and/or distributors to distribute our products in the United States;

•obtaining and maintaining third-party coverage and adequate reimbursement, if OST-HER2 and/or OST-TDC is approved;

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•acceptance of our core product candidates, if and when approved, by patients, the medical community and third-party payors;

•effectively competing with other therapies, if OST-HER2 and/or OST-TDC are approved;

•our ability and the ability or third parties from which we in-license patents to obtain and maintain patent, trade secret and other intellectual property protection, OST-HER2 and/or OST-TDC and regulatory exclusivity for OST-HER2 and/or OST-TDC if and when approved;

•our receipt of marketing approvals for OST-HER2 and/or OST-TDC from applicable regulatory authorities; and

•the continued acceptable safety profiles of our core product candidates following approval.

We have incurred significant operating losses in recent periods and anticipate that we will incur continued losses for the foreseeable future.

Since inception, we have focused substantially all of our efforts on the development of OST-HER2 and OST-TDC and our other clinical developments. To date, we have financed our operations primarily through the sale of convertible notes to outside investors. From inception through March31, 2023, we have raised an aggregate of approximately $15.2 million in gross proceeds from sales of our convertible notes. As of December 31, 2022, we had cash of $171,480. Due to our significant research and development expenditures, we have experienced negative cash flows from operations, even in periods of operating income. For each of the fiscal years ended December 31, 2021 and 2022, we incurred a loss from operations and negative cash flows from operations. We expect to continue to incur significant expenses and operating losses over the next several years and for the foreseeable future. Our prior losses, combined with expected future losses, have had and will continue to have an adverse effect on our stockholders’ equity and working capital. We expect our expenses to significantly increase in connection with our ongoing activities, as we:

•complete preclinical studies, initiate and complete clinical trials for product candidates;

•consult with the FDA at each stage of development;

•seek toxicology success of OST-TDC;

•contract to manufacture our product candidates;

•advance research and development related activities to expand our product pipeline;

•seek regulatory approval for our core product candidates that successfully complete clinical development;

•develop and scale up our capabilities to support our ongoing preclinical activities and clinical trials for our drug candidates and commercialization of any of our drug candidates for which we obtain marketing approval;

•maintain, expand, enforce, defend and protect our intellectual property portfolio;

•hire additional staff, including clinical, scientific and management personnel;

•secure facilities to support continued growth in our research, development and commercialization efforts; and

•incur additional costs associated with operating as a public company upon the completion of this offering.

Even if we consummate this offering, we will need to raise substantial additional funding. If we are unable to raise capital when needed or on attractive terms, we would be forced to delay, scale back or discontinue some of our product candidate development programs or commercialization efforts.

The development of pharmaceutical drugs is capital intensive. We are currently advancing OST-HER2 through clinical development and OST-TDC through preclinical development. The FDA allowed our OST31-164-01 study to be conducted in July 2021, and we initiated a Phase IIb clinical trial in 2022. We expect our expenses to increase in connection with our ongoing activities, particularly as we continue the research and development of, advance the

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preclinical and clinical activities of, and seek marketing approval for, our current or future product candidates. In addition, depending on the status of regulatory approval or, if we obtain marketing approval for any of our current or future product candidates, we expect to incur significant commercialization expenses related to sales, marketing, product manufacturing and distribution to the extent that such sales, marketing, product manufacturing and distribution are not the responsibility of our collaborators. We may also need to raise additional funds sooner if we choose to pursue additional indications and/or geographies for our current or future product candidates or otherwise expand more rapidly than we presently anticipate. Further, upon the closing of this offering, we expect to incur additional costs associated with operating as a public company. Although we expect that the net proceeds from this offering, together with our existing cash, will be sufficient to fund our operations for the next 12 to 18 months, we will need to obtain substantial additional funding in connection with our continuing operations. If we are unable to raise capital on a timely basis or on favorable terms, we would be forced to delay, scale back or discontinue the development and commercialization of one or more of our product candidates or delay our pursuit of potential in-licenses or acquisitions, which could materially affect our business, financial condition and results of operations.

Raising additional capital may cause dilution to our existing shareholders, restrict our operations or require us to relinquish rights to our technologies or product candidates.

We may seek additional capital through a combination of public and private equity offerings, debt financings, strategic collaborations and alliances and licensing arrangements. The terms of any financing may adversely affect the holdings or the rights of our stockholders and the issuance of additional securities, whether equity or debt, by us, or the possibility of such issuance, may cause the market price of our shares to decline. The sale of additional equity or convertible securities would dilute all of our stockholders. The incurrence of indebtedness would result in increased fixed payment obligations and we may be required to agree to certain restrictive covenants, such as limitations on our ability to incur additional debt, limitations on our ability to acquire, sell or license intellectual property rights and other operating restrictions that could adversely impact our ability to conduct our business. We could also be required to seek funds through arrangements with collaborators or otherwise at an earlier stage than otherwise would be desirable and we may be required to relinquish rights to some of our technologies or current or future product candidates or otherwise agree to terms unfavorable to us, any of which may have a material adverse effect on our business, operating results and prospects.

Our independent registered public accounting firm has expressed substantial doubt about our ability to continue as a going concern.

As of December 31, 2022, we had cash of $171,480. We have primarily financed our operations through proceeds from the sale of convertible notes to accredited investors. We have experienced significant negative cash flows from operations in each year since our inception. We do not expect to experience any significant positive cash flows from our existing collaboration agreements and do not expect to have any product revenue in the near term. We expect to incur substantial operating losses and negative cash flows from operations for the foreseeable future as we continue to invest significantly in research and development of our programs. As a result, our independent registered public accounting firm has issued a going concern opinion on our financial statements, expressing substantial doubt that we can continue as an ongoing business for the next 12 months after issuance of their report based on us having suffered recurring losses from operations and having a net capital deficiency.

Our financial statements do not include any adjustments that might result from the outcome of this uncertainty. We will need to raise additional capital in this offering and/or otherwise to fund our future operations and remain as a going concern. However, we cannot guarantee that we will be able to obtain sufficient additional funding in this offering or otherwise or that such funding, if available, will be obtainable on terms favorable to us. In the event that we are unable to obtain sufficient additional funding, there can be no assurance that we will be able to continue as a going concern.

Our ability to utilize our net operating loss carryforwards and certain other tax attributes in the future may be limited.

Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, or the Code, if a corporation undergoes an “ownership change” (generally defined as a greater than 50 percentage points (by value) in the ownership of its equity over a three-year period), the corporation’s ability to use its pre-change tax attributes to offset its post-change income may be limited. We have experienced such ownership changes in the past, and we may experience ownership

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changes in the future as a result of this offering or subsequent shifts in our stock ownership, some of which are outside our control. As of December 31, 2022 and 2021, we had federal and state NOLs of approximately $16,453,174 and $11,509,196, respectively, and we had federal and state research and development tax credit and general business credit carryforwards of approximately $292,144 and $320,120, respectively. Our ability to utilize these NOLs and tax credit carryforwards may be limited by an “ownership change.” If we undergo future ownership changes, many of which may be outside of our control, our ability to utilize our NOLs and tax credit carryforwards could be further limited by Sections 382 and 383 of the Code. There is also a risk that due to regulatory changes, such as suspensions on the use of NOLs, or other unforeseen reasons, our existing NOLs could expire or otherwise become unavailable to offset future income tax liabilities. Additionally, our NOLs and tax credit carryforwards could be limited under state law. For these reasons, even if we attain profitability, we may be unable to use a material portion of our NOLs and other tax attributes.

Risks Related to Drug Development and Regulatory Approval

We depend heavily on the success of our lead product candidates, OST-HER2 and OST-TDC. We may not be able to obtain regulatory approval for, or successfully commercialize, any of our current or future product candidates.

We currently have no product candidates approved for sale and may never be able to develop marketable product candidates. Our business depends heavily on the successful development, regulatory approval and commercialization of the current or future immunotherapy for Osteosarcoma product candidates, of which our lead product candidate, OST-HER2, is in Phase IIb clinical development. OST-TDC will require additional preclinical development and substantial clinical development, testing and regulatory approval before we are permitted to commence its commercialization. The preclinical studies and clinical trials of our current or future product candidates are, and the manufacturing and marketing of our current or future product candidates will be, subject to extensive and rigorous review and regulation by numerous government authorities in the United States and in other countries where we intend to test or, if approved, market any of our current or future product candidates. Before obtaining regulatory approvals for the commercial sale of any of our current or future product candidates, we must demonstrate through preclinical studies and clinical trials that each product candidate is safe and effective for use in each target indication. Drug development is a long, expensive and uncertain process, and delay or failure can occur at any stage of any of our clinical trials. This process can take many years and may include post-marketing studies and surveillance, which will require the expenditure of substantial resources beyond the proceeds we raise in this offering. Of the large number of drugs in development in the United States, only a small percentage will successfully complete the FDA regulatory approval process and will be commercialized, with similarly low rates of success for drugs in development in the European Union obtaining regulatory approval from the European Medicines Agency (EMA). Accordingly, even if we are able to obtain the requisite financing to continue to fund our development and preclinical studies and clinical trials, we cannot assure you that any of our current or future product candidates will be successfully developed and commercialized.

We are not permitted to market our current or future product candidates in the United States until we receive approval of a new drug application (NDA) from the FDA, in the European Economic Area (EEA) until we receive approval of a marketing authorization applications (MAA) from the EMA, or in any other foreign countries until we receive the requisite approval from such countries. Obtaining approval of an NDA or MAA is a complex, lengthy, expensive and uncertain process, and the FDA or EMA may delay, limit or deny approval of any of our current or future product candidates for many reasons, including, among others:

•we may not be able to demonstrate that our current or future product candidates are safe and effective in treating their target indications to the satisfaction of the FDA or applicable foreign regulatory agencies;

•the results of our preclinical studies and clinical trials may not meet the level of statistical or clinical significance required by the FDA or applicable foreign regulatory agencies for marketing approval;

•the FDA or applicable foreign regulatory agencies may disagree with the number, design, size, conduct or implementation of our preclinical studies and clinical trials;

•the FDA or applicable foreign regulatory agencies may require that we conduct additional preclinical studies and clinical trials;

•the FDA or applicable foreign regulatory agencies may not approve the formulation, labeling or specifications of any of our current or future product candidates;

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•the contract research organizations (CROs) that we retain to conduct our preclinical studies and clinical trials may take actions that materially adversely impact our preclinical studies and clinical trials;

•the FDA or applicable foreign regulatory agencies may find the data from preclinical studies and clinical trials insufficient to demonstrate that our current or future product candidates’ clinical and other benefits outweigh their safety risks;

•the FDA or applicable foreign regulatory agencies may disagree with our interpretation of data from our preclinical studies and clinical trials;

•the FDA or applicable foreign regulatory agencies may not accept data generated at our preclinical studies and clinical trial sites;

•if our NDA, if and when submitted, is reviewed by an advisory committee, the FDA may have difficulties scheduling an advisory committee meeting in a timely manner or the advisory committee may recommend against approval of our application or may recommend that the FDA require, as a condition of approval, additional preclinical studies or clinical trials, limitations on approved labeling or distribution and use restrictions;

•the FDA may require development of a risk evaluation and mitigation strategy (REMS) as a condition of approval or post-approval;

•the FDA or an applicable foreign regulatory agency may determine that the manufacturing processes or facilities of third-party manufacturers with which we contract do not conform to applicable requirements, including current good manufacturing practices (GMPs); or

•the FDA or applicable foreign regulatory agencies may change their approval requirements or policies or adopt new regulations.

Any of these factors, many of which are beyond our control, could jeopardize our ability to obtain regulatory approval for and successfully market our current or future product candidates. Any such setback in our pursuit of regulatory approval would have a material adverse effect on our business and prospects.

If we experience delays or difficulties in the enrollment of patients in clinical trials, our receipt of necessary regulatory approvals could be delayed or prevented.

We may not be able to initiate or continue clinical trials for our current or future product candidates if we are unable to locate and enroll a sufficient number of eligible patients to participate in these trials as required by the FDA or similar regulatory authorities outside the United States. In particular, because we are focused on patients with rare Osteosarcoma, our ability to enroll eligible patients may be limited or may result in slower enrollment than we anticipate. Some of our competitors have ongoing clinical trials for current or future product candidates that treat the same patient populations as our current or future product candidates, and patients who would otherwise be eligible for our clinical trials may instead enroll in clinical trials of our competitors’ current or future product candidates.

Patient enrollment may be affected by other factors that we may not be able to control including:

•the willingness of participants to enroll in our clinical trials and available support in our countries of interest;

•the obtaining of informed consent from parents or guardians of pediatric patients which meet evolving regulatory requirements in the United States and other countries;

•the severity of the disease under investigation;

•the eligibility criteria for the clinical trial in question;

•the availability of an appropriate screening test;

•the perceived risks and benefits of the product candidate under study;

•the efforts to facilitate timely enrollment in clinical trials;

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•the patient referral practices of physicians;

•the ability to monitor patients adequately during and after treatment; and

•the proximity and availability of clinical trial sites for prospective patients.

Rare Osteosarcoma may have relatively low prevalence and it may be difficult to identify patients with driver genes of the disease, which may lead to delays in enrollment for our trials.

Osteosarcoma has relatively low prevalence and it may be difficult to identify patients with the eligibility criteria we are targeting. Osteosarcoma has an incident rate of approximately 1,000 individuals affected per year in the United States. Our inability to enroll a sufficient number of patients with the target indication for our clinical trials would result in significant delays and could require us to abandon one or more clinical trials altogether. Enrollment delays in our clinical trials may result in increased development costs for our current or future product candidates, which would cause the value of our company to decline and limit our ability to obtain additional financing. If we are unable to include patients with the target indication, this could compromise our ability to seek participation in the FDA’s expedited review and approval programs, or otherwise to seek to accelerate clinical development and regulatory timelines for our other product candidates.

If we are not able to obtain, or if there are delays in obtaining, required regulatory approvals both for our current or future product candidates, we will not be able to commercialize, or will be delayed in commercializing, our current or future product candidates, and our ability to generate revenue will be materially impaired.

Our current or future product candidates and the activities associated with their development and commercialization, including their design, testing, manufacture, safety, efficacy, recordkeeping, labeling, storage, approval, advertising, promotion, sale, distribution, import and export are subject to comprehensive regulation by the FDA and other regulatory agencies in the United States and by comparable authorities in other countries. Before we can commercialize any of our current or future product candidates, we must obtain marketing approval. We have not received approval to market any of our current product candidates and may not obtain regulatory approvals for our future product candidates, if any, from regulatory authorities in any jurisdiction and it is possible that none of our current or future product candidates or any current or future product candidates we may seek to develop in the future will ever obtain regulatory approval. We have only limited experience in filing and supporting the applications necessary to gain regulatory approvals and expect to rely on third-party CROs and/or regulatory consultants to assist us in this process. Securing regulatory approval requires the submission of extensive preclinical and clinical data and supporting information to the various regulatory authorities for each therapeutic indication and line of treatment to establish the product candidate’s safety and efficacy. Securing regulatory approval also requires the submission of information about the drug manufacturing process to, and inspection of manufacturing facilities by, the relevant regulatory authority. Our current or future product candidates may not be effective, may be only moderately effective or may prove to have undesirable or unintended side effects, toxicities or other characteristics that may preclude our obtaining marketing approval or prevent or limit commercial use.

The process of obtaining regulatory approvals, both in the United States and abroad, is expensive, may take many years if additional clinical trials are required, if approval is obtained at all, and can vary substantially based upon a variety of factors, including the type, complexity and novelty of the current or future product candidates involved. Changes in marketing approval requirements or policies during the development period, changes in or the enactment of additional statutes or regulations, or changes in regulatory review for each submitted NDA. The FDA and comparable authorities in other countries have substantial discretion in the approval process and may refuse to accept any application or may decide that our data are insufficient for approval and require additional preclinical, clinical or other studies. Our current or future product candidates could be delayed in receiving, or fail to receive, regulatory approval for many reasons, including the following:

•the FDA or comparable foreign regulatory authorities may disagree with the design or implementation of our clinical trials;

•we may be unable to demonstrate to the satisfaction of the FDA or comparable foreign regulatory authorities that a product candidate is safe and effective for its proposed indication or that it is suitable to identify appropriate patient populations;

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•the results of clinical trials may not meet the level of statistical significance required by the FDA or comparable foreign regulatory authorities for approval;

•we may be unable to demonstrate that a product candidate’s clinical and other benefits outweigh its safety risks;

•the FDA or comparable foreign regulatory authorities may disagree with our interpretation of data from preclinical studies or clinical trials;

•the data collected from clinical trials of our current or future product candidates may not be sufficient to support the submission of an NDA or other submission or to obtain regulatory approval in the United States or elsewhere;

•the FDA or comparable foreign regulatory authorities may fail to approve the manufacturing processes or facilities of third-party manufacturers with which we contract for clinical and commercial supplies; and

•the approval requirements or policies or regulations of the FDA or comparable foreign regulatory authorities may significantly change in a manner rendering our clinical data insufficient for approval.

In addition, even if we were to obtain approval, regulatory authorities may approve any of our current or future product candidates for fewer or more limited indications than we request, may not approve the price we intend to charge for our drugs, may grant approval contingent on the performance of costly post-marketing clinical trials, or may approve a product candidate with a label that does not include the labeling claims necessary or desirable for the successful commercialization of that product candidate. Any of the foregoing scenarios could materially harm the commercial prospects for our current or future product candidates, and our ability to generate revenues will be materially impaired.

Our current or future product candidates may cause adverse or other undesirable side effects that could delay or prevent their regulatory approval, limit the commercial profile of an approved label, or result in significant negative consequences following marketing approval, if any.

Undesirable side effects caused by our current or future product candidates could cause us to interrupt, delay or halt preclinical studies or could cause us or regulatory authorities to interrupt, delay or halt clinical trials and could result in a more restrictive label or the delay or denial of regulatory approval by the FDA or other regulatory authorities. While we have initiated clinical trials for OST-HER2, and although there have been limited side effects with this therapy to date, it is likely that there may be adverse side effects associated with its use. Results of our trials could reveal a high and unacceptable severity and prevalence of these or other side effects. In such an event, our trials could be suspended or terminated and the FDA or comparable foreign regulatory authorities could order us to cease further development of or deny approval of our current or future product candidates for any or all targeted indications. The drug-related side effects could affect patient recruitment or the ability of enrolled patients to complete the trial or result in potential product liability claims. Any of these occurrences may significantly harm our business, financial condition and prospects.

Further, our current or future product candidates could cause undesirable side effects in clinical trials related to on-target toxicity, or exaggerated and adverse pharmacologic effects at the target of interest in the test system. If on-target toxicity is observed, or if our current or future product candidates have characteristics that are unexpected, we may need to abandon their development or limit development to more narrow uses or subpopulations in which the undesirable side effects or other characteristics are less prevalent, less severe or more acceptable from a risk-benefit perspective. In our industry, many compounds that initially showed promise in early stage testing for treating cancer have later been found to cause side effects that prevented further development of the compound.

Clinical trials by their nature utilize a sample of the potential patient population. For example, 39 to 45 patients in our Phase IIb trial of OST-HER2 may include a limited number of patients with side effects. With a limited number of patients and limited duration of exposure, rare and severe side effects of our current or future product candidates may only be uncovered with a significantly larger number of patients exposed to the product candidate. If our current

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or future product candidates are tested in large numbers of patients or if they receive marketing approval and we or others identify undesirable side effects caused by such current or future product candidates after such approval, a number of potentially significant negative consequences could result, including:

•regulatory authorities may place a hold on an ongoing clinical trial or may refuse to allow a future clinical trial to be conducted;

•regulatory authorities may withdraw or limit their approval of current or future product candidates;

•we may or a regulatory authority might require that the product or products be recalled;

•regulatory authorities may require the addition of labeling statements, such as a “boxed” warning or a contraindication;

•we may be required to create a medication guide outlining the risks of such side effects for distribution to patients;

•we may be required to change the way such current or future product candidates are distributed or administered, conduct additional clinical trials or change the labeling of the current or future product candidates;

•regulatory authorities may require a REMS plan to mitigate risks, which could include medication guides, physician communication plans, or elements to assure safe use, such as restricted distribution methods, patient registries and other risk minimization tools;

•we may be subject to regulatory investigations and government enforcement actions;

•we may decide to remove such current or future product candidates from the marketplace; and

•we could be sued and held liable for injury caused to individuals exposed to or taking our current or future product candidates.

We believe that any of these events could prevent us from achieving or maintaining market acceptance of the affected current or future product candidates and could substantially increase the costs of commercializing our current or future product candidates, if approved, and significantly impact our ability to successfully commercialize our current or future product candidates and generate revenues.

A Breakthrough Therapy Designation by the FDA for our current or future product candidate does not convey any advantage in, or shorten the duration of, the regulatory review or approval process, and it does not increase the likelihood that our current or future product candidates will receive marketing approval.

We may seek a Breakthrough Therapy Designation for some of our current or future product candidates. A breakthrough therapy is defined as a drug that is intended, alone or in combination with one or more other drugs, to treat a serious or life-threatening disease or condition, and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. For drugs that have been designated as breakthrough therapies, interaction and communication between the FDA and the sponsor of the trial can help to identify the most efficient path for clinical development while minimizing the number of patients placed in ineffective control regimens. Drugs designated as breakthrough therapies by the FDA are also eligible for accelerated approval.

Designation as a breakthrough therapy is within the discretion of the FDA. Accordingly, even if we believe that one of our current or future product candidates meets the criteria for designation as a breakthrough therapy, the FDA may disagree and instead determine not to make such designation. In any event, the receipt of a Breakthrough Therapy Designation for a product candidate does not convey any advantage in, or shorten the duration of, regulatory review or approval compared to drugs considered for approval under conventional FDA procedures and does not assure ultimate approval by the FDA. In addition, even if one or more of our current or future product candidates qualify as breakthrough therapies, the FDA may later decide that the drugs no longer meet the conditions for qualification.

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A Fast Track Designation by the FDA does not convey any advantage in, or shorten the duration of, the regulatory review regulatory review or approval process.

If a drug is intended for the treatment of a serious or life-threatening condition and the drug demonstrates the potential to address unmet medical needs for this condition, the drug sponsor may apply for Fast Track Designation. The FDA has broad discretion whether or not to grant this designation, so even if we believe that a particular product candidate is eligible for this designation, we cannot assure you that the FDA would decide to grant it. Even though we have received Fast Track Designation for OST-HER2 and may receive Fast Track Designation again in the future for certain current or future product candidates, this designation does not convey any advantage in, or shorten the duration of, regulatory review or approval compared to conventional FDA procedures. The FDA may withdraw Fast Track Designation if it believes that the designation is no longer supported by data from our clinical development program.

We may not be able to obtain or maintain orphan drug designation or exclusivity for any product candidates and, even if we do, that exclusivity may not prevent the FDA or EMA from approving other competing products.

We received orphan drug designation for OST-HER2 for Osteosarcoma in the United States, and we may seek Orphan Drug Designation for other current or future product candidates. Regulatory authorities in some jurisdictions, including the United States and the European Union, may designate drugs for relatively small patient populations as orphan drugs. Under the Orphan Drug Act of 1983, the FDA may designate a product as an orphan drug if it is a drug intended to treat a rare disease or condition, which is generally defined as a patient population of fewer than 200,000 individuals in the United States.

Generally, if a product with an orphan drug designation subsequently receives the first marketing approval for the indication for which it has such designation, the product is entitled to a period of marketing exclusivity, which precludes the FDA or EMA from approving another marketing application for the same drug for that time period. The applicable period is seven years in the United States and ten years in the European Union. The exclusivity period in the European Union can be reduced to six years if a drug no longer meets the criteria for Orphan Drug Designation or if the drug is sufficiently profitable so that market exclusivity is no longer justified. Orphan drug exclusivity may be lost if the FDA or EMA determines that the request for designation was materially defective or if the manufacturer is unable to assure sufficient quantity of the drug to meet the needs of patients with the rare disease or condition.

Even if we obtain orphan drug exclusivity for a product, that exclusivity may not effectively protect the product from competition because competing drugs containing a different active ingredient can be approved for the same condition. In addition, even after an orphan drug is approved, the FDA can subsequently approve the same drug for the same condition if the FDA concludes that the later drug is clinically superior in that it is shown to be safer, more effective or makes a major contribution to patient care. Further, we may not be the first to obtain marketing approval for any particular orphan indication due to the uncertainties associated with developing pharmaceutical products, and thus, for example, approval of our product candidates could be blocked for seven years if another company previously obtained approval and orphan drug exclusivity in the United States for the same drug and same condition.

On August 3, 2017, the U.S. Congress passed the FDA Reauthorization Act of 2017. This act, among other things, codified the FDA’s pre-existing regulatory interpretation to require that a drug sponsor demonstrate the clinical superiority of an orphan drug that is otherwise the same as a previously approved drug for the same rare disease in order to receive orphan drug exclusivity. The new legislation reverses prior precedent holding that the Orphan Drug Act unambiguously requires that the FDA recognize the orphan exclusivity period regardless of a showing of clinical superiority. The FDA may further reevaluate the Orphan Drug Act and its regulations and policies. We do not know if, when or how the FDA may change the orphan drug regulations and policies in the future, and it is uncertain how any changes might affect our business. Depending on what changes the FDA may make to its Orphan Drug regulations and policies, our business could be adversely impacted.

Although we have obtained Rare Pediatric Disease Designation for OST-HER2 for Osteosarcoma patients, we may not be eligible to receive a priority review voucher in the event that FDA approval does not occur prior to September 30, 2026.

The Rare Pediatric Disease Priority Review Voucher Program (“PRV Program”) is intended to incentivize pharmaceutical sponsors to develop drugs for rare diseases. A sponsor who obtains approval of an NDA or biological license application for a rare disease may be eligible for a Priority Review Voucher (“PRV”) under this program,

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which may be redeemed by the owner of such PRV to obtain priority review for a marketing application. A PRV is fully transferrable and can be sold to any sponsor, who in turn can redeem the PRV for priority review of a marketing application in six months, compared to the standard timeframe of approximately ten months. Under the 21st Century Cures Act, a drug that receives Rare Disease Designation before September 30, 2024, will continue to be eligible for a PRV if the drug is approved before September 30, 2026. If we do not obtain approval of an NDA for OST-HER2 in patients with Osteosarcoma, and if the PRV Program is not extended by Congressional action, we may not receive a PRV.

Even if we receive regulatory approval for any of our current or future product candidates, we will be subject to ongoing obligations and continued regulatory review, which may result in significant additional expense. Additionally, our current or future product candidates, if approved, could be subject to labeling and other restrictions and market withdrawal and we may be subject to penalties if we fail to comply with regulatory requirements or experience unanticipated problems with our drugs.

If the FDA or a comparable foreign regulatory authority approves any of our current or future product candidates, the manufacturing processes, labeling, packaging, distribution, adverse event reporting, storage, advertising, promotion and recordkeeping for the drug will be subject to extensive and ongoing regulatory requirements. These requirements include submissions of safety and other post-marketing information and reports, registration, as well as continued compliance with cGMPs and Good Clinical Practices, or GCPs, for any clinical trials that we conduct post-approval. Any regulatory approvals that we receive for our current or future product candidates may also be subject to limitations on the approved indicated uses for which the drug may be marketed or to the conditions of approval, or contain requirements for potentially costly post-marketing testing, including Phase IV clinical trials, and surveillance to monitor the safety and efficacy of the drug. Later discovery of previously unknown problems with a drug, including adverse events of unanticipated severity or frequency, or with our third-party manufacturers or manufacturing processes, or failure to comply with regulatory requirements, may result in, among other things:

•restrictions on the marketing or manufacturing of the drug, withdrawal of the drug from the market, or drug recalls;

•fines, warning or other letters or holds on clinical trials;

•refusal by the FDA to approve pending applications or supplements to approved applications filed by us, or suspension or revocation of drug license approvals;

•drug seizure or detention, or refusal to permit the import or export of drugs; and

•injunctions or the imposition of civil or criminal penalties.

The FDA’s policies may change and additional government regulations may be enacted that could prevent, limit or delay regulatory approval of our current or future product candidates. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may lose any marketing approval that we may have obtained, which would adversely affect our business, prospects and ability to achieve or sustain profitability.

Positive results from early preclinical studies and clinical trials of our current or future product candidates are not necessarily predictive of the results of later preclinical studies and clinical trials of our current or future product candidates. If we cannot replicate the positive results from our earlier preclinical studies and clinical trials of our current or future product candidates in our later preclinical studies and clinical trials, we may be unable to successfully develop, obtain regulatory approval for and commercialize our current or future product candidates.

Positive results from our preclinical studies of our current or future product candidates, and any positive results we may obtain from our early clinical trials of our current or future product candidates, may not necessarily be predictive of the results from required later preclinical studies and clinical trials. Similarly, even if we are able to complete our planned preclinical studies or clinical trials of our current or future product candidates according to our current development timeline, the positive results from our preclinical studies and clinical trials of our current or future product candidates may not be replicated in subsequent preclinical studies or clinical trial results. For example, our later-stage clinical trials could differ in significant ways from our ongoing Phase IIb clinical trial of OST-HER2, which could cause the outcome of these later-stage trials to differ from our earlier-stage clinical trials. For example, these differences may

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include changes to inclusion and exclusion criteria, final dosage formulation, efficacy endpoints and statistical design. Many companies in the pharmaceutical and biotechnology industries have suffered significant setbacks in late-stage clinical trials after achieving positive results in early-stage development, and we cannot be certain that we will not face similar setbacks. These setbacks have been caused by, among other things, preclinical findings made while clinical trials were underway or safety or efficacy observations made in preclinical studies and clinical trials, including previously unreported adverse events. Moreover, preclinical and clinical data are often susceptible to varying interpretations and analyses, and many companies that believed their product candidates performed satisfactorily in preclinical studies and clinical trials nonetheless failed to obtain FDA approval. If we fail to produce positive results in our planned preclinical studies or clinical trials of any of our current or future product candidates, the development timeline and regulatory approval and commercialization prospects for our current or future product candidates, and, correspondingly, our business and financial prospects, would be materially adversely affected.

Manufacturing our current or future product candidates is complex and we may encounter difficulties in production. If we encounter such difficulties, our ability to provide our current or future product candidates for preclinical studies and clinical trials or for commercial purposes could be delayed or stopped.

The process of manufacturing of our current or future product candidates is complex and highly regulated. We do not have our own manufacturing facilities or personnel and currently rely, and expect to continue to rely, on third parties based in the United States, Europe and Asia for the manufacture of our current or future product candidates. These third-party manufacturing providers may not be able to provide adequate resources or capacity to meet our needs and may incorporate their own proprietary processes into our product candidate manufacturing processes. We have limited control and oversight of a third-party’s proprietary process, and a third-party may elect to modify its process without our consent or knowledge. These modifications could negatively impact our manufacturing, including product loss or failure that requires additional manufacturing runs or a change in manufacturer, both of which could significantly increase the cost of and significantly delay the manufacture of our current or future product candidates. As our current or future product candidates progress through preclinical studies and clinical trials towards approval and commercialization, it is expected that various aspects of the manufacturing process will be altered in an effort to optimize processes and results. Such changes may require amendments to be made to regulatory applications which may further delay the timeframes under which modified manufacturing processes can be used for any of our current or future product candidates and additional bridging studies or trials may be required.

Our future growth may depend, in part, on our ability to penetrate foreign markets, where we would be subject to additional regulatory burdens and other risks and uncertainties that could materially adversely affect our business.

We are not permitted to market or promote any of our current or future product candidates in foreign markets before we receive regulatory approval from the applicable regulatory authority in that foreign market, and we may never receive such regulatory approval for any of our current or future product candidates. To obtain separate regulatory approval in many other countries we must comply with numerous and varying regulatory requirements of such countries regarding safety and efficacy and governing, among other things, clinical trials and commercial sales, pricing and distribution of our current or future product candidates, and we cannot predict success in these jurisdictions. If we obtain approval of our current or future product candidates and ultimately commercialize our current or future product candidates in foreign markets, we would be subject to additional risks and uncertainties, including:

•differing regulatory requirements in foreign countries, which may cause obtaining regulatory approvals outside of the United States to take longer and be more costly than obtaining approval in the United States;

•the burden of complying with complex and changing foreign regulatory, tax, accounting and legal requirements;

•different medical practices and customs in foreign countries affecting acceptance in the marketplace;

•import or export licensing requirements;

•reduced protection of intellectual property rights and the existence of additional potentially relevant third-party intellectual property rights;

•economic weakness, including inflation, or political instability in particular foreign economies and markets;

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•compliance with tax, employment, immigration and labor laws for employees living or traveling abroad;

•foreign currency fluctuations, which could result in increased operating expenses and reduced revenue, and other obligations incident to doing business in another country;

•workforce uncertainty in countries where labor unrest is more common than in the United States;

•potential liability under the Foreign Corrupt Practices Act of 1977 or comparable foreign regulations;

•production shortages resulting from any events affecting raw material supply or manufacturing capabilities abroad; and

•business interruptions resulting from geopolitical actions, including war and terrorism.

Foreign sales of our current or future product candidates could also be adversely affected by the imposition of governmental controls, political and economic instability, trade restrictions and changes in tariffs.

We may in the future conduct clinical trials for current or future product candidates outside the United States, and the FDA and comparable foreign regulatory authorities may not accept data from such trials.

We may in the future choose to conduct one or more clinical trials outside the United States, including in Europe. The acceptance of study data from clinical trials conducted outside the United States or another jurisdiction by the FDA or comparable foreign regulatory authority may be subject to certain conditions or may not be accepted at all. In cases where data from foreign clinical trials are intended to serve as the basis for marketing approval in the United States, the FDA will generally not approve the application on the basis of foreign data alone unless (i) the data are applicable to the United States population and United States medical practice and (ii) the trials were performed by clinical investigators of recognized competence and pursuant to GCP regulations. Additionally, the FDA’s clinical trial requirements, including sufficient size of patient populations and statistical powering, must be met. Many foreign regulatory authorities have similar approval requirements. In addition, such foreign trials would be subject to the applicable doctrines or local laws of the foreign jurisdictions where the trials are conducted. There can be no assurance that the FDA or any comparable foreign regulatory authority will accept data from trials conducted outside of the United States or the applicable jurisdiction. If the FDA or any comparable foreign regulatory authority does not accept such data, it would result in the need for additional trials, which could be costly and time-consuming, and which may result in current or future product candidates that we may develop not receiving approval for commercialization in the applicable jurisdiction.

We may not be successful in our efforts to identify or discover additional product candidates or we may expend our limited resources to pursue a particular product candidate or indication and fail to capitalize on product candidates or indications that may be more profitable or for which there is a greater likelihood of success.

The success of our business depends primarily upon our ability to identify, develop and commercialize our product candidates. Although some of our current product candidates are in preclinical and clinical development, our scientific hypotheses may be incorrect or our research programs may fail to identify other potential product candidates for clinical development for a number of reasons. Our research methodologies may be unsuccessful in identifying potential product candidates, or our potential product candidates may be shown to have harmful side effects or may have other characteristics that may make the products unmarketable or unlikely to receive marketing approval.

Because we have limited financial and management resources, we focus on a limited number of research programs and product candidates and are currently focused on our core programs, including our lead core product candidate OST-HER2 for the treatment of Osteosarcoma and our other core product candidate OST-TDC for the treatment of Osteosarcoma. As a result, we may forego or delay pursuit of opportunities with other current or future product candidates or for other indications that later prove to have greater commercial potential. Our resource allocation decisions may cause us to fail to capitalize on viable commercial drugs or profitable market opportunities. Our spending on current and future research and development programs and current or future product candidates for specific indications may not yield any commercially viable drugs. If we do not accurately evaluate the commercial potential or target market for a particular product candidate, we may relinquish valuable rights to that product candidate through future collaboration, licensing or other royalty arrangements in cases in which it would have been more advantageous for us to retain sole development and commercialization rights to such product candidate.

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If any of these events occur, we may be forced to abandon our development efforts for a program, which would have a material adverse effect on our business and could potentially cause us to cease operations. Research programs to identify new product candidates require substantial technical, financial and human resources. We may focus our efforts and resources on potential programs or current or future product candidates that ultimately prove to be unsuccessful.

In light of the larger population of patients with Osteosarcoma who reside in foreign countries, our ability to generate meaningful revenues in those jurisdictions may be limited due to the strict price controls and reimbursement limitations imposed by governments outside of the United States.

The incidence of new cases of Osteosarcoma is approximately 1,000 individuals in the United States annually and approximately 20,000 individuals globally. In some countries, particularly in the European Union, the pricing of prescription pharmaceuticals is subject to governmental control. In these countries, pricing negotiations with governmental authorities can take considerable time after the receipt of marketing approval for a drug. To obtain coverage and reimbursement or pricing approval in some countries, we may be required to conduct a clinical trial that compares the cost-effectiveness of our product candidate to other available therapies. In addition, many countries outside the United States have limited government support programs that provide for reimbursement of drugs such as are product candidates, with an emphasis on private payors for access to commercial products. If reimbursement of our product candidates is unavailable or limited in scope or amount, or if pricing is set at unsatisfactory levels, our business could be harmed, possibly materially, based, in part, on the larger population of patients with Osteosarcoma who reside in foreign countries. In parts of Africa and certain countries in the Middle East, the lack of healthcare infrastructure to help adequately diagnose and treat patients may limit our business potential in those otherwise viable markets.

Business interruptions resulting from the Covid-19 outbreak or similar public health crises could cause a disruption to the development of our product candidates and adversely impact our business.

Public health crises such as pandemics or similar outbreaks could adversely impact our business. The continued spread of Covid-19 globally could adversely impact our preclinical or clinical trial operations in the United States (and outside of the United States), including our ability to recruit and retain patients and principal investigators and site staff who, as healthcare providers, may have heightened exposure to Covid-19 if an outbreak occurs in their geography. For example, similar to other biopharmaceutical companies, we are experiencing delays in the dosing of patients in our clinical trials as well as in activating new trial sites. Covid-19 may also affect employees of third-party CROs located in affected geographies that we rely upon to carry out our clinical trials. In addition, as a result of medical complications associated with Osteosarcoma, the patient populations that our lead core and other core product candidates target may be particularly susceptible to Covid-19, which may make it more difficult for us to identify patients able to enroll in our current and future clinical trials and may impact the ability of enrolled patients to complete any such trials. Any negative impact Covid-19 has to patient enrollment or treatment or the execution of our product candidates could cause costly delays to clinical trial activities, which could adversely affect our ability to obtain regulatory approval for and to commercialize our product candidates, increase our operating expenses, and have a material adverse effect on our financial results.

Additionally, timely enrollment in planned clinical trials is dependent upon clinical trial sites which will be adversely affected by global health matters, such as pandemics. We plan to conduct clinical trials for our product candidates in geographies which are currently being affected by the Covid-19. Some factors from the coronavirus outbreak that will delay or otherwise adversely affect enrollment in the clinical trials of our product candidates, as well as our business generally, include:

•the potential diversion of healthcare resources away from the conduct of clinical trials to focus on pandemic concerns, including the attention of physicians serving as our clinical trial investigators, hospitals serving as our clinical trial sites and hospital staff supporting the conduct of our prospective clinical trials;

•limitations on travel that could interrupt key trial and business activities, such as clinical trial site initiations and monitoring, domestic and international travel by employees, contractors or patients to clinical trial sites, including any government-imposed travel restrictions or quarantines that will impact the ability or willingness of patients, employees or contractors to travel to our clinical trial sites or secure visas or entry permissions, a loss of face-to-face meetings and other interactions with potential partners, any of which could delay or adversely impact the conduct or progress of our prospective clinical trials;

•the potential negative effect on the operations of our third-party manufacturers;

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•interruption in global shipping affecting the transport of ingredients used in our product candidates and clinical trial materials, such as patient samples, investigational drug product and conditioning drugs, or drugs that are designed to prepare the body for a certain treatment or procedure, and other supplies used in our prospective clinical trials; and

•business disruptions caused by potential workplace, laboratory and office closures and an increased reliance on employees working from home, disruptions to or delays in ongoing laboratory experiments and operations, staffing shortages, travel limitations or mass transit disruptions, any of which could adversely impact our business operations or delay necessary interactions with local regulators, ethics committees and other important agencies and contractors.

These and other factors arising from the coronavirus could worsen in countries that are already afflicted with the coronavirus or could continue to spread to additional countries. Any of these factors, and other factors related to any such disruptions that are unforeseen, could have a material adverse effect on our business and our results of operations and financial condition. Further, uncertainty around these and related issues could lead to adverse effects on the economy of the United States and other economies, which could impact our ability to raise the necessary capital needed to develop and commercialize our product candidates.

Risks Related to Commercialization

Even if we receive marketing approval for our current or future product candidates, our current or future product candidates may not achieve broad market acceptance, which would limit the revenue that we generate from their sales.

The commercial success of our current or future product candidates, if approved by the FDA or other applicable regulatory authorities, will depend upon the awareness and acceptance of our current or future product candidates among the medical community, including physicians and patients, as well as reimbursement and coverage by third party payors including Medicare and Medicaid. Market acceptance of our current or future product candidates, if approved, will depend on a number of factors, including, among others:

•the efficacy of our current or future product candidates as demonstrated in clinical trials, and, if required by any applicable regulatory authority in connection with the approval for the applicable indications, to provide patients with incremental health benefits, as compared with other available medicines;

•limitations or warnings contained in the labeling approved for our current or future product candidates by the FDA or other applicable regulatory authorities;

•the clinical indications for which our current or future product candidates are approved;

•availability of alternative treatments already approved or expected to be commercially launched in the near future;

•the potential and perceived advantages of our current or future product candidates over current treatment options or alternative treatments, including future alternative treatments;

•the willingness of the target patient population to try new therapies or treatment methods and of physicians to prescribe these therapies or methods;

•the need to dose such product candidates in combination with other therapeutic agents, and related costs;

•the strength of marketing and distribution support and timing of market introduction of competitive products;

•pricing and cost effectiveness;

•the effectiveness of our sales and marketing strategies;

•our ability to increase awareness of our current or future product candidates;

•our ability to obtain sufficient third-party coverage and reimbursement, including from federal healthcare programs such as Medicare and Medicaid; or

•the ability or willingness of patients to pay out-of-pocket in the absence of third-party coverage.

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If our current or future product candidates are approved but do not achieve an adequate level of acceptance by patients, physicians and payors, we may not generate sufficient revenue from our current or future product candidates to become or remain profitable. Before agreeing to cover and reimburse our products, third party payors may require us to demonstrate that our current or future product candidates, in addition to treating these target indications, are not only safe but cost effective compared to alternative therapies. Our efforts to educate the medical community, patient organizations and third-party payors about the benefits of our current or future product candidates may require significant resources and may never be successful.

We face substantial competition, which may result in others discovering, developing or commercializing drugs before or more successfully than we do.

The development and commercialization of new drugs is highly competitive. We face competition with respect to our current product candidates and will face competition with respect to any product candidates that we may seek to develop or commercialize in the future from major pharmaceutical companies, specialty pharmaceutical companies and biotechnology companies worldwide. There are a number of large pharmaceutical and biotechnology companies that currently market and sell drugs or are pursuing the development of therapies for rare diseases and cancers, including Osteosarcoma. Some of these competitive drugs and therapies are based on scientific approaches that are similar to our approach, and others are based on entirely different approaches. Potential competitors also include academic institutions, government agencies and other public and private research organizations that conduct research, seek patent protection and establish collaborative arrangements for research, development, manufacturing and commercialization.

Specifically, there are a large number of companies developing or marketing treatments for rare diseases and cancers, including many major pharmaceutical and biotechnology companies. If OST-HER2 receives marketing approval for the treatment of Osteosarcoma, it may face competition from other product candidates in development for these indications, including product candidates in development from AstraZeneca, Y-mAbs Therapeutics and MD Anderson Cancer Center, among others.

Many of the companies against which we are competing or against which we may compete in the future have significantly greater financial resources and expertise in research and development, manufacturing, preclinical testing, conducting clinical trials, obtaining regulatory approvals and reimbursement and marketing approved drugs than we do. Mergers and acquisitions in the pharmaceutical and biotechnology industries may result in even more resources being concentrated among a smaller number of our competitors. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies. These competitors also compete with us in recruiting and retaining qualified scientific, sales, marketing and management personnel and establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs.

Our commercial opportunity could be reduced or eliminated if our competitors develop and commercialize drugs that are safer, more effective, have fewer or less severe side effects, are more convenient or are less expensive than any drugs that we or our collaborators may develop. Our competitors also may obtain FDA or other regulatory approval for their drugs more rapidly than we may obtain approval for ours, which could result in our competitors establishing a strong market position before we or our collaborators are able to enter the market. The key competitive factors affecting the success of all of our current or future product candidates, if approved, are likely to be their efficacy, safety, convenience, price, the level of generic competition and the availability of reimbursement from government and other third-party payors.

Product liability lawsuits against us could cause us to incur substantial liabilities and could limit commercialization of any current or future product candidates that we may develop.

We will face an inherent risk of product liability exposure related to the testing of our current or future product candidates in human clinical trials and will face an even greater risk if we commercially sell any current or future product candidates that we may develop. If we cannot successfully defend ourselves against claims that our current or future product candidates caused injuries, we could incur substantial liabilities. Regardless of merit or eventual outcome, liability claims may result in:

•decreased demand for any current or future product candidates that we may develop;

•injury to our reputation and significant negative media attention;

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•withdrawal of clinical trial participants;

•significant costs and resources to defend the related litigation;

•substantial monetary awards to trial participants or patients; and

•the inability to commercialize any current or future product candidates that we may develop.

Although we maintain product liability insurance coverage, it may not be adequate to cover all liabilities that we may incur. We anticipate that we will need to increase our insurance coverage when we initiate a large global trial and if we successfully commercialize any product candidate. Insurance coverage is increasingly expensive. We may not be able to maintain product liability insurance coverage at a reasonable cost or in an amount adequate to satisfy any liability that may arise.

Even if we are able to commercialize any current or future product candidates, such drugs may become subject to unfavorable pricing regulations or third-party coverage and reimbursement policies, which would harm our business.

The regulations that govern regulatory approvals, pricing and reimbursement for new drugs vary widely from country to country. Some countries require approval of the sale price of a drug before it can be marketed. In many countries, the pricing review period begins after marketing approval is granted. In some foreign markets, prescription pharmaceutical pricing remains subject to continuing governmental control even after initial approval is granted. As a result, we might obtain marketing approval for a product candidate in a particular country, but then be subject to price regulations that delay our commercial launch of the product candidate, possibly for lengthy time periods, and negatively impact the revenues we are able to generate from the sale of the product candidate in that country. Adverse pricing limitations may hinder our ability to recoup our investment in one or more current or future product candidates, even if our current or future product candidates obtain marketing approval.

Our ability to commercialize any current or future product candidates successfully also will depend in part on the extent to which coverage and reimbursement for these current or future product candidates and related treatments will be available from government authorities, private health insurers and other organizations. Government authorities and other third-party payors, such as private health insurers and health maintenance organizations, decide which medications they will pay for (i.e., cover) and establish reimbursement levels. Factors payors consider in determining reimbursement are based on whether the product is:

•a covered benefit under its health plan;

•safe, effective and medically necessary;

•appropriate for the specific patient;

•cost-effective; and

•neither experimental nor investigational.

A primary trend in the U.S. healthcare industry and elsewhere is cost containment. Government authorities and other third-party payors have attempted to control costs by limiting coverage and the amount of reimbursement for particular drugs. Increasingly, third-party payors are requiring that drug companies provide them with predetermined discounts from list prices and are challenging the prices charged for drugs. We cannot be sure that coverage will be available for any product candidate that we commercialize and, if coverage is available, the level of reimbursement. Reimbursement may impact the demand for, or the price of, any product candidate for which we obtain marketing approval. If reimbursement is not available or is available only to limited levels, we may not be able to successfully commercialize any product candidate for which we obtain marketing approval.

There may be significant delays in obtaining reimbursement for newly approved drugs, and coverage may be more limited than the purposes for which the drug is approved by the FDA or similar regulatory authorities outside the United States. Moreover, eligibility for reimbursement does not imply that any drug will be paid for in all cases or at a rate that covers our costs, including research, development, manufacture, sale and distribution. Interim reimbursement levels for new drugs, if applicable, may also not be sufficient to cover our costs and may not be made permanent. Reimbursement rates may vary according to the use of the drug and the clinical setting in which it is used, may be based on reimbursement levels already set for lower cost drugs and may be incorporated into existing payments for other services. Net prices for

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drugs may be reduced by mandatory discounts or rebates required by government healthcare programs or private payors and by any future relaxation of laws that presently restrict imports of drugs from countries where they may be sold at lower prices than in the United States. In the United States, decisions as to coverage and reimbursement by the Medicare program are typically made by the Centers for Medicare & Medicaid Services, or CMS, an agency within the U.S. Department of Health and Human Services, or HHS. CMS decides whether and to what extent a new medicine will be covered and reimbursed under Medicare. Third-party payors often rely upon Medicare coverage policy and payment limitations in setting their own reimbursement policies. Our inability to promptly obtain coverage and profitable payment rates from both government-funded and private payors for any approved drugs that we develop could have a material adverse effect on our operating results, our ability to raise capital needed to commercialize drugs and our overall financial condition.

Healthcare reform measures may have a material adverse effect on our business and results of operations.

The United States and many foreign jurisdictions have enacted or proposed legislative and regulatory changes affecting the healthcare system that could prevent or delay marketing approval of our current or future product candidates or any future product candidates, restrict or regulate post-approval activities and affect our ability to profitably sell a product for which we obtain marketing approval. Changes in regulations, statutes or the interpretation of existing regulations could impact our business in the future by requiring, for example: (i) changes to our manufacturing arrangements, (ii) additions or modifications to product labeling, (iii) the recall or discontinuation of our products or (iv) additional record-keeping requirements. If any such changes were to be imposed, they could adversely affect the operation of our business.

Our revenue prospects could be affected by changes in healthcare spending and policy in the United States and abroad. We operate in a highly regulated industry and new laws, regulations or judicial decisions, or new interpretations of existing laws, regulations or decisions, related to healthcare availability, the method of delivery or payment for healthcare products and services could negatively impact our business, operations and financial condition. We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative action in the United States or any other jurisdiction. It is possible that additional governmental action is taken to address the Covid-19 pandemic. If we or any third parties we may engage are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we or such third parties are not able to maintain regulatory compliance, our product candidates may lose any regulatory approval that may have been obtained and we may not achieve or sustain profitability.

If, in the future, we are unable to establish sales and marketing and patient support capabilities or enter into agreements with third parties to sell and market our current or future product candidates, we may not be successful in commercializing our current or future product candidates if and when they are approved, and we may not be able to generate any revenue.

We do not currently have a sales or marketing infrastructure and have limited experience in the sales, marketing, patient support or distribution of drugs. To achieve commercial success for any approved product candidate for which we retain sales and marketing responsibilities, we must build our sales, marketing, patient support, managerial and other non-technical capabilities or make arrangements with third parties to perform these services. In the future, we may choose to build a focused sales and marketing infrastructure to sell, or participate in sales activities with our collaborators for, some of our current or future product candidates if and when they are approved.

There are risks involved with both establishing our own sales and marketing and patient support capabilities and entering into arrangements with third parties to perform these services. For example, recruiting and training a sales force is expensive and time consuming and could delay any drug launch. If the commercial launch of a product candidate for which we recruit a sales force and establish marketing capabilities is delayed or does not occur for any reason, we would have prematurely or unnecessarily incurred these commercialization expenses. This may be costly, and our investment would be lost if we cannot retain or reposition our sales and marketing personnel.

Factors that may inhibit our efforts to commercialize our current or future product candidates on our own include:

•our inability to recruit and retain adequate numbers of effective sales and marketing personnel;

•the inability of sales personnel to obtain access to physicians or persuade adequate numbers of physicians to prescribe any future drugs;

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•the lack of complementary drugs to be offered by sales personnel, which may put us at a competitive disadvantage relative to companies with more extensive product lines; and

•unforeseen costs and expenses associated with creating an independent sales and marketing organization.

If we enter into arrangements with third parties to perform sales, marketing, patient support and distribution services, our drug revenues or the profitability of these drug revenues to us are likely to be lower than if we were to market and sell any current or future product candidates that we develop ourselves. In addition, we may not be successful in entering into arrangements with third parties to sell and market our current or future product candidates or may be unable to do so on terms that are favorable to us. We likely will have little control over such third parties, and any of them may fail to devote the necessary resources and attention to sell and market our current or future product candidates effectively, or they may engage in practices that pose legal risks to us under applicable anti-kickback, fraud and abuse and other healthcare laws and regulations. If we do not establish sales and marketing capabilities successfully, either on our own or in collaboration with third parties, we will not be successful in commercializing our current or future product candidates.

Our relationships with prescribers, customers and third-party payors will be subject to applicable anti-kickback, fraud and abuse and other healthcare laws and regulations, which could expose us to criminal sanctions, civil penalties, exclusion from government healthcare programs, contractual damages, reputational harm and diminished profits and future earnings.

Although we do not currently have any drugs on the market, if we begin commercializing our current or future product candidates, we will be subject to additional healthcare statutory and regulatory requirements and enforcement by the federal government and the states and foreign governments in which we conduct our business. Healthcare providers, including physicians, play a primary role in the recommendation and prescription of any current or future product candidates for which we obtain marketing approval. Our future arrangements with healthcare providers, as well as third-party payors and customers, will expose us to broadly applicable fraud and abuse and other healthcare laws and regulations will constrain the business and/or financial arrangements and relationships through which we market, sell and distribute our current or future product candidates for which we obtain marketing approval. Restrictions under applicable federal and state healthcare laws and regulations, include the following:

•the federal Anti-Kickback Statute prohibits, among other things, persons from knowingly and willfully soliciting, offering, receiving or providing remuneration, directly or indirectly, in cash or in kind, to induce or reward either the referral of an individual for, or the purchase, order or recommendation of, any good or service, for which payment may be made under federal and state healthcare programs such as Medicare, Medicaid and TRICARE. The Anti-Kickback Statute has been interpreted to apply to arrangements between pharmaceutical manufacturers on the one hand and prescribers, purchasers, and formulary managers on the other hand. The term remuneration has been interpreted broadly to include anything of value. A person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation

•the federal False Claims Act imposes criminal and civil penalties, including through civil whistleblower or qui tam actions, against individuals or entities for knowingly presenting, or causing to be presented, to the federal government, claims for payment that are false or fraudulent or making a false statement to avoid, decrease or conceal an obligation to pay money to the federal government. In addition, manufacturers can be held liable under the False Claims Act even when they do not submit claims directly to government payors if they are deemed to “cause” the submission of false or fraudulent claims. False Claims Act liability is potentially significant in the healthcare industry because the statute provides for treble damages and mandatory per claim penalties. Government enforcement agencies and private whistleblowers have investigated pharmaceutical companies for or asserted liability under the False Claims Act for a variety of alleged promotional and marketing activities, such as providing free products to customers with the expectation that the customers would bill federal programs for the products; providing consulting fees and other benefits to physicians to induce them to prescribe products; engaging in promotion for “off-label” uses; and submitting inflated best price information to the Medicaid Drug Rebate Program. In addition, the government may assert that a claim including items and services resulting from a violation of the federal Anti-Kickback Statute constitutes a false of fraudulent claim for purposes of the False Claims Act;

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•the federal Health Insurance Portability and Accountability Act of 1996, or HIPAA, imposes criminal and civil liability for executing a scheme to defraud any healthcare benefit program, or knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false statement in connection with the delivery of or payment for healthcare benefits, items or services; similar to the federal Anti-Kickback Statute, a person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation;

•the federal physician payment transparency requirements, sometimes referred to as the “Sunshine Act” under the Affordable Care Act (ACA) require manufacturers of drugs, devices, biologics and medical supplies that are reimbursable under Medicare, Medicaid, or the Children’s Health Insurance Program to report to the Department of Health and Human Services information related transfers of value to certain covered recipients (defined to include doctors, dentists, optometrists, podiatrists and chiropractors, as well as physicians assistants, nurse practitioners, clinical nurse specialists, certified nurse anesthetists and certified nurse-midwives) and their immediate family members, and teaching hospitals. Effective January1, 2022, these reporting obligations will extend to include transfers of value made to certain non-physician providers such as physician assistants and nurse practitioners;

•HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act of 2009, or HITECH, and its implementing regulations, which also imposes obligations on certain covered entity healthcare providers, health plans, and healthcare clearinghouses as well as their business associates that perform certain services involving the use or disclosure of individually identifiable health information, including mandatory contractual terms, with respect to safeguarding the privacy, security and transmission of individually identifiable health information. HITECH also created new tiers of civil monetary penalties, amended HIPAA to make civil and criminal penalties directly applicable to business associates, and gave state attorneys general new authority to file civil actions for damages or injunctions in federal courts to enforce the federal HIPAA laws and seek attorneys’ fees and costs associated with pursuing federal civil actions; and

•analogous state laws and regulations, such as state anti-kickback and false claims laws that may apply to sales or marketing arrangements and claims involving healthcare items or services reimbursed by non-governmental third-party payors, including private insurers; and some state laws require pharmaceutical companies to comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government in addition to requiring drug manufacturers to report information related to payments to physicians and other health care providers or marketing expenditures, and state laws governing the privacy and security of health information in certain circumstances, many of which differ from each other in significant ways and often are not preempted by HIPAA, thus complicating compliance efforts.

Ensuring that our future business arrangements with third parties comply with applicable healthcare laws and regulations could involve substantial costs. It is possible that governmental authorities will conclude that our business practices do not comply with current or future statutes, regulations or case law involving applicable fraud and abuse or other healthcare laws and regulations. If our operations were to be found to be in violation of any of these laws or any other governmental regulations that may apply to us, we may be subject to significant civil, criminal and administrative penalties, damages, fines, exclusion from government funded healthcare programs, such as Medicare and Medicaid, and the curtailment or restructuring of our operations. If any of the physicians or other providers or entities with whom we expect to do business is found to be not in compliance with applicable laws, they may be subject to criminal, civil or administrative sanctions, including exclusions from government funded healthcare programs.

We may face potential liability if we obtain identifiable patient health information from clinical trials sponsored by us.

Most healthcare providers, including certain research institutions from which we may obtain patient health information, are subject to privacy and security regulations promulgated under HIPAA, as amended by the HITECH. We are not currently classified as a covered entity or business associate under HIPAA and thus are not directly subject to its requirements or penalties. However, any person may be prosecuted under HIPAA’s criminal provisions either directly or under aiding-and-abetting or conspiracy principles. Consequently, depending on the facts and circumstances, we could face substantial criminal penalties if we knowingly receive individually identifiable

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health information from a HIPAA-covered healthcare provider or research institution that has not satisfied HIPAA’s requirements for disclosure of individually identifiable health information. In addition, in the future, we may maintain sensitive personally identifiable information, including health information, that we receive throughout the clinical trial process, in the course of our research collaborations, and directly from individuals (or their healthcare providers) who may enroll in patient assistance programs if we choose to implement such programs. As such, we may be subject to state laws requiring notification of affected individuals and state regulators in the event of a breach of personal information, which is a broader class of information than the health information protected by HIPAA.

Further, certain health privacy laws, data breach notification laws, consumer protection laws and genetic testing laws may apply directly to our operations and/or those of our collaborators and may impose restrictions on our collection, use and dissemination of individuals’ health information. Patients about whom we or our collaborators may obtain health information, as well as the providers who may share this information with us, may have statutory or contractual rights that limit our ability to use and disclose the information. We may be required to expend significant capital and other resources to ensure ongoing compliance with applicable privacy and data security laws. Claims that we have violated individuals’ privacy rights or breached our contractual obligations, even if we are not found liable, could be expensive and time- consuming to defend and could result in adverse publicity that could harm our business.

If we or third-party CMOs, CROs or other contractors or consultants fail to comply with applicable federal, state/provincial or local regulatory requirements, we could be subject to a range of regulatory actions that could affect our or our contractors’ ability to develop and commercialize our therapeutic candidates and could harm or prevent sales of any affected therapeutics that we are able to commercialize, or could substantially increase the costs and expenses of developing, commercializing and marketing our therapeutics. Any threatened or actual government enforcement action could also generate adverse publicity and require that we devote substantial resources that could otherwise be used in other aspects of our business. Increasing use of social media could give rise to liability, breaches of data security or reputational damage.

If we fail to comply with environmental, health and safety laws and regulations, we could become subject to fines or penalties or incur costs that could have a material adverse effect on the success of our business.

We are subject to numerous environmental, health and safety laws and regulations, including those governing laboratory procedures and the handling, use, storage, treatment and disposal of hazardous materials and wastes. Our operations involve the use of hazardous and flammable materials, including chemicals and biological and radioactive materials. Our operations also produce hazardous waste products. We generally contract with third parties for the disposal of these materials and wastes. We cannot eliminate the risk of contamination or injury from these materials. In the event of contamination or injury resulting from our use of hazardous materials, we could be held liable for any resulting damages, and any liability could exceed our resources. We also could incur significant costs associated with civil or criminal fines and penalties. Although we maintain workers’ compensation insurance to cover us for costs and expenses we may incur due to injuries to our employees resulting from the use of hazardous materials, this insurance may not provide adequate coverage against potential liabilities. We do not maintain insurance for environmental liability or toxic tort claims that may be asserted against us in connection with our storage or disposal of biological, hazardous or radioactive materials.

If the market opportunities for OST-HER2 and our other current and future product candidates are smaller than we believe they are, our revenue may be adversely affected and our business may suffer. Moreover, because the target patient populations we are seeking to treat are small, we must be able to successfully identify patients and capture a significant market share to achieve profitability and growth.

We focus our research and product development on treatments for Osteosarcoma. The incidence of new cases of Osteosarcoma is approximately 1,000 individuals in the United States annually and approximately 20,000 individuals globally. Given the smaller number of patients who have the diseases that we are targeting, it is critical to our ability to grow and become profitable that we continue to successfully identify patients with these rare diseases. Our projections of both the number of people who have these diseases, are based on our beliefs and estimates. These estimates have been derived from a variety of sources, including the scientific literature, surveys of clinics, patient foundations or market research that we conducted, and may prove to be incorrect or contain errors. New studies may change the estimated incidence or prevalence of these diseases. The number of patients may turn out to be lower than expected. The effort to identify patients with diseases we seek to treat is in early stages, and we cannot accurately predict the

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number of patients for whom treatment might be possible. Further, even if we obtain significant market share for OST-HER2 and any of our other current or future product candidates, because the potential target populations are very small, we may never achieve profitability despite obtaining such significant market share.

Our target patient populations are relatively small, and there are currently limited standard of care treatments directed at Osteosarcoma. As a result, the pricing and reimbursement of OST-HER2 and any other product candidates we may develop, if approved, is uncertain, but must be adequate to support commercial infrastructure. If we are unable to obtain adequate levels of reimbursement, our ability to successfully market and sell OST-HER2 and any of our other current or future product candidates will be adversely affected.

Risks Related to Our Dependence on Third Parties

We rely, and expect to continue to rely, on third parties to conduct our ongoing and planned clinical trials for our current and future product candidates. If these third parties do not successfully carry out their contractual duties, comply with regulatory requirements or meet expected deadlines, we may not be able to obtain marketing approval for or commercialize our current and potential future product candidates and our business could be substantially harmed.

We do not have the ability to independently conduct clinical trials. We rely on medical institutions, clinical investigators, contract laboratories, and other third parties, including collaboration partners, to conduct or otherwise support our clinical trials for OST-HER2 and expect to rely on them when we begin clinical trials for OST-TDC and other current or future product candidates. We rely heavily on these parties for execution of clinical trials and control only certain aspects of their activities. Nevertheless, we are responsible for ensuring that each of our clinical trials is conducted in accordance with the applicable protocol, legal and regulatory requirements and scientific standards, and our reliance on CROs will not relieve us of our regulatory responsibilities. For any violations of laws and regulations during the conduct of our clinical trials, we could be subject to untitled and warning letters or enforcement action that may include civil penalties up to and including criminal prosecution.

We and any third parties that we contract with are required to comply with regulations and requirements, including GCP, for conducting, monitoring, recording and reporting the results of clinical trials to ensure that the data and results are scientifically credible and accurate, and that the trial patients are adequately informed of the potential risks of participating in clinical trials and their rights are protected. These regulations are enforced by the FDA, the Competent Authorities of the Member States of the European Economic Area and comparable foreign regulatory authorities for any drugs in clinical development. The FDA enforces GCP requirements through periodic inspections of clinical trial sponsors, principal investigators and trial sites. If we or the third parties we contract with fail to comply with applicable GCP, the clinical data generated in our clinical trials may be deemed unreliable and the FDA or comparable foreign regulatory authorities may require us to perform additional clinical trials before approving our marketing applications. We cannot assure you that, upon inspection, the FDA will determine that any of our current or future clinical trials will comply with GCP. In addition, our clinical trials must be conducted with current or future product candidates produced under cGMP regulations. Our failure or the failure of third parties that we contract with to comply with these regulations may require us to repeat some aspects of a specific, or an entire, clinical trial, which would delay the marketing approval process and could also subject us to enforcement action. We also are required to register certain ongoing clinical trials and provide certain information, including information relating to the trial’s protocol, on a government-sponsored database, ClinicalTrials.gov, within specific timeframes. Failure to do so can result in fines, adverse publicity and civil and criminal sanctions.

Although we intend to design the clinical trials for our current or future product candidates, or be involved in the design when other parties sponsor the trials, we anticipate that third parties will conduct all of our clinical trials. As a result, many important aspects of our clinical development, including their conduct, timing and response to the ongoing COVID-19 pandemic, will be outside of our direct control. Our reliance on third parties to conduct future clinical trials will also result in less direct control over the management of data developed through clinical trials than would be the case if we were relying entirely upon our own staff. Communicating with outside parties can also be challenging, potentially leading to mistakes as well as difficulties in coordinating activities.

These factors may materially adversely affect the willingness or ability of third parties to conduct our clinical trials and may subject us to unexpected cost increases that are beyond our control. If our CROs do not perform clinical trials in a satisfactory manner, breach their obligations to us or fail to comply with regulatory requirements, the development, marketing approval and commercialization of our current or future product candidates may be delayed,

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we may not be able to obtain marketing approval and commercialize our current or future product candidates, or our development programs may be materially and irreversibly harmed. If we are unable to rely on clinical data collected by our CROs, we could be required to repeat, extend the duration of, or increase the size of any clinical trials we conduct and this could significantly delay commercialization and require significantly greater expenditures.

If any of our relationships with these third-party CROs terminate, we may not be able to enter into arrangements with alternative CROs on commercially reasonable terms, or at all. If our CROs do not successfully carry out their contractual duties or obligations or meet expected deadlines, if they need to be replaced or if the quality or accuracy of the clinical data they obtain are compromised due to the failure to adhere to our clinical protocols, regulatory requirements or for other reasons, any clinical trials such CROs are associated with may be extended, delayed or terminated, and we may not be able to obtain marketing approval for or successfully commercialize our current or future product candidates. As a result, we believe that our financial results and the commercial prospects for our current or future product candidates in the subject indication would be harmed, our costs could increase and our ability to generate revenue could be delayed.

The third parties upon whom we rely for the supply of the active pharmaceutical ingredient, or API, drug product and drug substance used in our core product candidates are limited in number, and the loss of any of these suppliers could significantly harm our business.

The API drug product and drug substance used in our core product candidates are supplied to us from a small number of suppliers, and in some cases sole source suppliers. Our ability to successfully develop our current or future product candidates, and to ultimately supply our commercial drugs in quantities sufficient to meet the market demand, depends in part on our ability to obtain the API, drug product and drug substance for these drugs in accordance with regulatory requirements and in sufficient quantities for commercialization and clinical testing. We do not currently have arrangements in place for a redundant or second-source supply of all API, drug product or drug substance in the event any of our current suppliers of such API, drug product and drug substance cease their operations for any reason.

For all of our current or future product candidates, we intend to identify and qualify additional manufacturers to provide such API, drug product and drug substance prior to submission of an NDA to the FDA and/or an MAA to the EMA. We are not certain, however, that our single-source and dual source suppliers will be able to meet our demand for their products, either because of the nature of our agreements with those suppliers, our limited experience with those suppliers or our relative importance as a customer to those suppliers. It may be difficult for us to assess their ability to timely meet our demand in the future based on past performance. While our suppliers have generally met our demand for their products on a timely basis in the past, they may subordinate our needs in the future to their other customers.

Establishing additional or replacement suppliers for the API, drug product and drug substance used in our current or future product candidates, if required, may not be accomplished quickly. If we are able to find a replacement supplier, such replacement supplier would need to be qualified and may require additional regulatory approval, which could result in further delay. While we seek to maintain adequate inventory of the API, drug product and drug substance used in our current or future product candidates, any interruption or delay in the supply of components or materials, or our inability to obtain such API, drug product and drug substance from alternate sources at acceptable prices in a timely manner could impede, delay, limit or prevent our development efforts, which could harm our business, results of operations, financial condition and prospects.

Our success is dependent on our executive management team’s ability to successfully pursue business development, strategic partnerships and investment opportunities as our company matures. We may also form or seek strategic alliances or acquisitions or enter into additional collaboration and licensing arrangements in the future, and we may not realize the benefits of such collaborations, alliances, acquisitions or licensing arrangements.

We have entered into licensing arrangements with Advaxis, Inc. (now Ayala Pharmaceuticals, Inc.) and BlinkBio, Inc. and a Research Service Agreement with George Clinical, Inc., and may in the future form or seek strategic alliances or acquisitions, create joint ventures, or enter into additional collaboration and licensing arrangements with third parties that we believe will complement or augment our development and commercialization efforts with respect to our current product candidates and any future product candidates that we may develop.

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Going forward, we are seeking strategic partners for the further development and potential commercialization of our non-core and out-licensed programs, including OST-TDC. Any of these relationships may require us to incur non-recurring and other charges, increase our near and long-term expenditures, issue securities that dilute our existing stockholders or disrupt our management and business.

In addition, we face significant competition in seeking appropriate strategic partners and the negotiation process is time-consuming and complex. We may not be successful in our efforts to establish a strategic partnership or acquisition or other alternative arrangements for our current or future non-core product candidates because they may be deemed to be at too early of a stage of development for collaborative effort and third parties may not view our current or future product candidates as having the requisite potential to demonstrate safety, potency, purity and efficacy and obtain marketing approval.

As a result, we may not be able to realize the benefit of our existing collaboration and licensing arrangements or any future strategic partnerships or acquisitions, license arrangements we may enter, if we are unable to successfully integrate them with our existing operations and company culture, which could delay our timelines or otherwise adversely affect our business. We also cannot be certain that, following a strategic transaction, license, collaboration or other business development partnership, we will achieve the revenue or specific net income that justifies such transaction. Any delays in entering into new collaborations or strategic partnership agreements related to our current or future product candidates could delay the development and commercialization of our current or future product candidates in certain geographies for certain indications, which would harm our business prospects, financial condition and results of operations.

Our manufacturing process needs to comply with FDA regulations relating to the quality and reliability of such processes. Any failure to comply with relevant regulations could result in delays in or termination of our clinical programs and suspension or withdrawal of any regulatory approvals.

In order to produce our product candidates for clinical trials and our products, if any, for commercial purposes, either at our own facility or at a third-party’s facility, we and our third party vendors will need to comply with the FDA’s cGMP regulations and guidelines. As part of our ongoing quality and process improvement efforts, we conducted a gap analysis of our cGMP quality system and it identified certain key areas for necessary remediation, including with regard to documentation requirements. We may encounter difficulties in achieving compliance with quality control and quality assurance requirements and may experience shortages in qualified personnel. We are subject to inspections by the FDA and comparable foreign regulatory authorities to confirm compliance with applicable regulatory requirements. Any failure to follow cGMP or other regulatory requirements, including any failure to remedy the issues identified in the cGMP gap analysis, or delay, interruption or other issues that arise in the manufacture, fill-finish, packaging, or storage of our product candidate as a result of a failure of our facilities or the facilities or operations of third parties to comply with regulatory requirements or pass any regulatory authority inspection could significantly impair our ability to develop and commercialize our current or future product candidates, including leading to significant delays in the availability of our product candidates for our clinical trials or the termination of or suspension of a clinical trial, or the delay or prevention of a filing or approval of marketing applications for our current or future product candidates. Significant non-compliance could also result in the imposition of sanctions, including warning or untitled letters, fines, injunctions, civil penalties, failure of regulatory authorities to grant marketing approvals for our current or future product candidates, delays, suspension or withdrawal of approvals, license revocation, seizures or recalls of products, operating restrictions and criminal prosecutions, any of which could damage our reputation and our business.

If our third-party manufacturers use hazardous and biological materials in a manner that causes injury or violates applicable law, we may be liable for damages.

Our research and development activities involve the controlled use of potentially hazardous substances, including chemical materials, by our third-party manufacturers. Our manufacturers are subject to federal, state and local laws and regulations in the United States governing the use, manufacture, storage, handling and disposal of medical and hazardous materials. Although we believe that our manufacturers’ procedures for using, handling, storing and disposing of these materials comply with legally prescribed standards, we cannot completely eliminate the risk of contamination or injury resulting from medical or hazardous materials. As a result of any such contamination or injury, we may incur liability or local, city, state or federal authorities may curtail the use of these materials and interrupt our business operations. In the event of an accident, we could be held liable for damages or penalized with fines, and the liability could exceed our

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resources. We do not have any insurance for liabilities arising from medical or hazardous materials. Compliance with applicable laws and regulations is expensive, and current or future regulations may impair our research, development and production efforts, which could harm our business, prospects, financial condition or results of operations.

Risks Related to Intellectual Property

If we and those third parties from whom we in-license patents are unable to obtain and maintain patent and other intellectual property protection for our technology and product candidates or if the scope of the intellectual property protection obtained is not sufficiently broad, our competitors could develop and commercialize technology and drugs similar or identical to ours, and our ability to successfully commercialize our technology and drugs may be impaired.

The patent position of biotechnology and pharmaceutical companies generally is highly uncertain, involves complex legal and factual questions and has in recent years been the subject of much litigation. Our commercial success depends in part on our ability and the ability of those third parties from whom we in-license patents to obtain and maintain intellectual property protection in the United States and other countries for our current or future product candidates, including our lead core product candidate OST-HER2, our other core product candidate OST-TDC, our non-core product candidates, our proprietary compound library and other know-how. We seek to protect our proprietary and intellectual property position by, among other methods, in-licensing patents and patent applications in the United States and abroad related to our proprietary technology, inventions and improvements that are important to the development and implementation of our business.

We do not currently own any issued patents. We in-license patents and patent applications related to our lead core product candidate OST-HER2 and our other core product candidate OST-TDC. The OST-HER2 product candidate and methods of use are covered by three granted U.S. utility patents and one granted Japanese patent, which is directed to non-human indications. The patents are expected to expire between 2030 and 2031, not including any patent term extension. There are 37 pending foreign patent applications in various jurisdictions, including without limitation China, the European Union, India, Hong Kong, Mexico, New Zealand and South Korea, which are expected to expire in 2035 if granted, not including any patent term extension. The OST-TDC product candidate is covered by five granted U.S. utility patents, one granted Australian patent and one granted Japanese patent. Of these granted patents, one U.S. utility patent, the Australian patent and the Japanese patent are for methods of use of silicon based drug conjugates. The other four U.S. utility patents are for silanol based therapeutic payloads. The patents are expected to expire between 2036 and 2037, not including any patent term extension. There are 16 pending foreign patent applications in various jurisdictions, including without limitation Australia, Canada, China, the European Union and Japan, that are expected to expire between 2036 and 2037, if granted, not including any patent term extension. These foreign patent applications are a combination of composition of matter patents for novel products and method of use patents for new uses of known products. For additional information about our patents, see “Business — Our Intellectual Property.”

The degree of patent protection we require to successfully commercialize our current or future product candidates may be unavailable or severely limited in some cases and may not adequately protect our rights or permit us to gain or keep any competitive advantage. We cannot provide any assurances that any of the patents that we in-license have, or that any of such pending patent applications that mature into issued patents will include, claims with a scope sufficient to protect OST-HER2 and OST-TDC or our other current or future product candidates. In addition, if the breadth or strength of protection provided by such patent applications or any patents we may in-license is threatened, it could dissuade companies from collaborating with us to license, develop or commercialize current or future product candidates.

Other parties have developed technologies that may be related or competitive to our own or those covered by our in-licensed patents, and such parties may have filed or may file patent applications, or may have received or may receive patents, claiming inventions that may overlap or conflict with those claimed in such patent applications or issued patents, with respect to either the same compounds, methods, formulations or other subject matter. Publications of discoveries in the scientific literature often lag behind the actual discoveries, and patent applications in the United States and other jurisdictions are typically not published until at least 18 months after the earliest priority date of patent filing, or in some cases not at all. Therefore, we cannot know with certainty whether the holder of our in-licensed patents was the first to make the inventions claimed in such patents or pending patent applications. As a result, the issuance, scope, validity, enforceability and commercial value of these in-licensed patent rights cannot be predicted with any certainty.

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The issuance of a patent is not conclusive as to its inventorship, scope, validity, or enforceability, and our in-licensed patents or patents we may own in the future may be challenged in the courts or patent offices in the United States and abroad. Such challenges may result in loss of patent or product exclusivity or freedom to operate or in patent claims being narrowed, invalidated or held unenforceable, in whole or in part, which could limit our ability to stop others from using or commercializing similar or identical technology and product candidates, or limit the duration of the patent protection of our technology and product candidates. In addition, given the amount of time required for the development, testing, and regulatory review of new product candidates, patents protecting such candidates might expire before or shortly after such candidates are commercialized. Any impairment of our intellectual property rights, or our failure to protect our intellectual property rights adequately, could give third parties access to our technology and product candidates and could materially and adversely impact our business, financial condition, results of operations, and prospects.

If our trademarks and trade names for our products or company name are not adequately protected in one or more countries where we intend to market our products, we may delay the launch of product brand names, use different trademarks or tradenames in different countries, or face other potentially adverse consequences to building our product brand recognition.

Our trademarks or trade names may be challenged, infringed, diluted, circumvented or declared generic or determined to be infringing on other marks. We intend to rely on both registration and common law protection for our trademarks. We may not be able to protect our rights to these trademarks and trade names or may be forced to stop using these names, which we need for name recognition by potential partners or customers in our markets of interest. During the trademark registration process, we may receive Office Actions from the USPTO or from comparable agencies in foreign jurisdictions objecting to the registration of our trademark. Although we would be given an opportunity to respond to those objections, we may be unable to overcome such rejections. In addition, in the USPTO and in comparable agencies in many foreign jurisdictions, third parties are given an opportunity to oppose pending trademark applications and/or to seek the cancellation of registered trademarks. Opposition or cancellation proceedings may be filed against our trademark applications or registrations, and our trademark applications or registrations may not survive such proceedings. If we are unable to obtain a registered trademark or establish name recognition based on our trademarks and trade names, we may not be able to compete effectively and our business may be adversely affected.

If we are unable to adequately protect and enforce our trade secrets, our business and competitive position would be harmed.

In addition to the protection afforded by patents we may own or in-license, we seek to rely on trade secret protection, confidentiality agreements, and license agreements to protect proprietary know-how that may not be patentable, processes for which patents are difficult to enforce and any other elements of our product discovery and development processes that involve proprietary know-how, information, or technology that may not be covered by patents. Although it is our policy to require all of our employees, consultants, advisors and any third parties who have access to our proprietary know-how, information or technology to enter into confidentiality and assignment of inventions agreements, trade secrets can be difficult to protect and we have limited control over the protection of trade secrets used by our collaborators and suppliers. We cannot be certain that we have or will obtain these agreements in all circumstances and we cannot guarantee that we have entered into such agreements with each party that may have or have had access to our trade secrets or proprietary information.

Moreover, any of these parties might breach the agreements and intentionally or inadvertently disclose our trade secret information and we may not be able to obtain adequate remedies for such breaches. In addition, competitors may otherwise gain access to our trade secrets or independently develop substantially equivalent information and techniques. Further, the laws of some foreign countries do not protect proprietary rights and trade secrets to the same extent or in the same manner as the laws of the United States. As a result, we may encounter significant problems in protecting and defending our intellectual property both in the United States and abroad. If we are unable to prevent unauthorized material disclosure of our intellectual property to third parties, we will not be able to establish or maintain a competitive advantage in our market, which could materially adversely affect our business, financial condition, results of operations and future prospects.

Enforcing a claim that a party illegally disclosed or misappropriated a trade secret is difficult, expensive and time-consuming, and the outcome is unpredictable. If we choose to go to court to stop a third-party from using any of our trade secrets, we may incur substantial costs. These lawsuits may consume our time and other resources even if we are successful. Although we take steps to protect our proprietary information and trade secrets, including through

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contractual means with our employees and consultants, third parties may independently develop substantially equivalent proprietary information and techniques or otherwise gain access to our trade secrets or disclose our technology. If any of our trade secrets were to be lawfully obtained or independently developed by a competitor or other third-party, we would have no right to prevent them from using that technology or information to compete with us.

We may initiate, become a defendant in, or otherwise become party to lawsuits to protect or enforce our intellectual property rights, which could be expensive, time-consuming and unsuccessful.

Competitors may infringe any patents we may own or in-license. In addition, any patents we may own or in-license also may become involved in inventorship, priority, validity or unenforceability disputes. To counter infringement or unauthorized use, we may be required to file infringement claims, which can be expensive and time-consuming. We may not prevail in any lawsuits that we initiate, and the damages or other remedies awarded, if any, may not be commercially meaningful. In addition, in an infringement proceeding, a court may decide that one or more of any patents we may own or in-license is not valid or is unenforceable or that the other party’s use of our technology that may be patented falls under the safe harbor to patent infringement under 35 U.S.C. §271(e)(1). There is also the risk that, even if the validity of these patents is upheld, the court may refuse to stop the other party from using the technology at issue on the grounds that any patents we may own or in-license do not cover the technology in question or that such third-party’s activities do not infringe the patent applications or any patents we in-license or may in the future own. An adverse result in any litigation or defense proceedings could put one or more of any patents we may own or in-license at risk of being invalidated, held unenforceable, or interpreted narrowly and could put those patent applications at risk of not issuing. Such litigation or proceedings could substantially increase our operating losses and reduce the resources available for development activities or any future sales, marketing, patient support or distribution activities. We may not have sufficient financial or other resources to conduct such litigation or proceedings adequately. Some of our competitors may be able to sustain the costs of such litigation or proceedings more effectively than we can because of their greater financial resources and more mature and developed intellectual property portfolios. Uncertainties resulting from the initiation and continuation of patent litigation or other proceedings could have a material adverse effect on our ability to compete in the marketplace.

Post-grant proceedings provoked by third parties or brought by the USPTO may be necessary to determine the validity or priority of inventions with respect to the patent applications or any patents we in-license or may in the future own. These proceedings are expensive and an unfavorable outcome could result in a loss of our current patent rights and could require us to cease using the related technology or to attempt to license rights to it from the prevailing party. Our business could be harmed if the prevailing party does not offer us a license on commercially reasonable terms. In addition to potential USPTO post-grant proceedings, we may become a party to patent opposition proceedings in the EPO, or similar proceedings in other foreign patent offices or courts where these patents may be challenged. The costs of these proceedings could be substantial, and may result in a loss of scope of some claims or a loss of the entire patent. An unfavorable result in a post-grant challenge proceeding may result in the loss of our right to exclude others from practicing one or more of our inventions in the relevant country or jurisdiction, which could have a material adverse effect on our business. Litigation or post-grant proceedings within patent offices may result in a decision adverse to our interests and, even if we are successful, may result in substantial costs and distract our management and other employees. We may not be able to prevent, misappropriation of our trade secrets or confidential information, particularly in countries where the laws may not protect those rights as fully as in the United States.

We may not be able to detect infringement against any patents we may own or in-license. Even if we detect infringement by a third-party of any patents we may own or in-license, we may choose not to pursue litigation against or settlement with the third-party. If we later sue such third-party for patent infringement, the third-party may have certain legal defenses available to it, which otherwise would not be available except for the delay between when the infringement was first detected and when the suit was brought. Such legal defenses may make it impossible for us to enforce any patents we may own or in-license against such third-party.

Intellectual property litigation and administrative patent office patent validity challenges in one or more countries could cause us to spend substantial resources and distract our personnel from their normal responsibilities.

Even if resolved in our favor, litigation or other legal proceedings relating to intellectual property claims may cause us to incur significant expenses, and could distract our technical and management personnel from their normal responsibilities. In addition, there could be public announcements of the results of hearings, motions or other interim proceedings or developments and if securities analysts or investors perceive these results to be negative, it could have a

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substantial adverse effect on the price of our common stock. Such litigation or proceedings could substantially increase our operating losses and reduce the resources available for development activities or any future sales, marketing, patient support or distribution activities. We may not have sufficient financial or other resources to conduct such litigation or proceedings adequately. As noted above, some of our competitors may be able to sustain the costs of such litigation or proceedings more effectively than we can because of their greater financial resources. Uncertainties resulting from the initiation and continuation of patent litigation or other proceedings could compromise our ability to compete in the marketplace, including compromising our ability to raise the funds necessary to continue our clinical trials, continue our research programs, license necessary technology from third parties, or enter into development collaborations that would help us commercialize our current or future product candidates, if approved. Any of the foregoing events would harm our business, financial condition, results of operations and prospects.

We may be unable to obtain patent or other intellectual property protection for our current or future product candidates or our future products, if any, in all jurisdictions throughout the world, and we may not be able to adequately enforce our intellectual property rights even in the jurisdictions where we seek protection.

We may not be able to pursue patent coverage of our current or future product candidates in all countries. Filing, prosecuting and defending patents on current or future product candidates in all countries throughout the world would be prohibitively expensive, and intellectual property rights in some countries outside the United States can be less extensive than those in the United States. In addition, the laws of some foreign countries do not protect intellectual property rights to the same extent as federal and state laws in the United States. Consequently, we may not be able to prevent third parties from practicing our inventions in all countries outside the United States, or from selling or importing products made using our inventions in and into the United States or other jurisdictions. Competitors may use our technologies in jurisdictions where we have not obtained patent protection to develop their own products and further, may export otherwise infringing products to territories where we have patent protection, but where enforcement is not as strong as that in the United States. These products may compete with our current or future product candidates and our current intellectual property rights may not be effective or sufficient to prevent them from competing.

Many companies have encountered significant problems in protecting and defending intellectual property rights in foreign jurisdictions. The legal systems of certain countries, particularly certain developing countries, do not favor the enforcement of patents, trade secrets and other intellectual property protection, particularly those relating to pharmaceutical products, which could make it difficult for us to stop the infringement of any patents we may own or in-license or marketing of competing products in violation of our proprietary rights generally.

Many countries have compulsory licensing laws under which a patent owner may be compelled to grant licenses to third parties. In addition, many countries limit the enforceability of patents against government agencies or government contractors. In these countries, the patent owner may have limited remedies, which could materially diminish the value of such patent. If we are forced to grant a license to third parties with respect to any patents we may own or license that are relevant to our business, our competitive position may be impaired, and our business, financial condition, results of operations, and prospects may be adversely affected.

We may not obtain or grant licenses or sublicenses to intellectual property rights in all markets on equally or sufficiently favorable terms with third parties.

It may be necessary for us to use the patented or proprietary technology of third parties to commercialize our products, in which case we would be required to obtain a license from these third parties. The licensing of third-party intellectual property rights is a competitive area, and more established companies may pursue strategies to license or acquire third-party intellectual property rights that we may consider attractive or necessary. More established companies may have a competitive advantage over us due to their size, capital resources and greater clinical development and commercialization capabilities. In addition, companies that perceive us to be a competitor may be unwilling to assign or license rights to us. We also may be unable to license or acquire third-party intellectual property rights on terms that would allow us to make an appropriate return on our investment or at all. If we are unable to license such technology, or if we are forced to license such technology on unfavorable terms, our business could be materially harmed. If we are unable to obtain a necessary license, we may be unable to develop or commercialize the affected current or future product candidates, which could materially harm our business, and the third parties owning such intellectual property rights could seek either an injunction prohibiting our sales, or, with respect to our sales, an obligation on our part to

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pay royalties or other forms of compensation. Even if we are able to obtain a license, it may be non-exclusive, thereby giving our competitors access to the same technologies licensed to us. Any of the foregoing could harm our competitive position, business, financial condition, results of operations and prospects.

If we fail to comply with our obligations in any agreements under which we may license intellectual property rights from third parties or otherwise experience disruptions to our business relationships with our licensors, we could lose license rights that are important to our business.

We may from time to time be party to license and collaboration agreements with third parties to advance our research or allow commercialization of current or future product candidates. Such agreements may impose numerous obligations, such as development, diligence, payment, commercialization, funding, milestone, royalty, sublicensing, insurance, patent prosecution, enforcement and other obligations on us and may require us to meet development timelines, or to exercise commercially reasonable efforts to develop and commercialize licensed products, in order to maintain the licenses. In spite of our best efforts, our licensors might conclude that we have materially breached our license agreements and might therefore terminate the license agreements, thereby removing or limiting our ability to develop and commercialize products and technologies covered by these license agreements.

Any termination of these licenses, or if the underlying patents fail to provide the intended exclusivity, could result in the loss of significant rights and could harm our ability to commercialize our current or future product candidates, and competitors or other third parties would have the freedom to seek regulatory approval of, and to market, products identical to ours and we may be required to cease our development and commercialization of certain of our current or future product candidates. Any of the foregoing could have a material adverse effect on our competitive position, business, financial conditions, results of operations, and prospects.

In addition, the agreements under which we may license intellectual property or technology from third parties are likely to be complex, and certain provisions in such agreements may be susceptible to multiple interpretations. The resolution of any contract interpretation disagreement that may arise could narrow what we believe to be the scope of our rights to the relevant intellectual property or technology, or increase what we believe to be our financial or other obligations under the relevant agreement, either of which could have a material adverse effect on our business, financial condition, results of operations and prospects. Moreover, if disputes over intellectual property that we may license prevent or impair our ability to maintain future licensing arrangements on acceptable terms, we may be unable to successfully develop and commercialize the affected current or future product candidates, which could have a material adverse effect on our business, financial conditions, results of operations and prospects.

Changes in patent law could diminish the value of patents in general, thereby impairing our ability to protect our current or future product candidates.

As is the case with other biopharmaceutical companies, our success is heavily dependent on intellectual property, particularly patents. Obtaining and enforcing patents in the biopharmaceutical industry involve both technological and legal complexity and is therefore costly, time consuming and inherently uncertain. Recent patent reform legislation in the United States and other countries, including the Leahy-Smith America Invents Act, or Leahy-Smith Act, signed into law on September 16, 2011, could increase those uncertainties and costs. The Leahy-Smith Act includes a number of significant changes to U.S. patent law. These include provisions that affect the way patent applications are prosecuted, redefine prior art and provide more efficient and cost-effective avenues for competitors to challenge the validity of patents. In addition, the Leahy-Smith Act has transformed the U.S. patent system into a “first inventor to file” system. The first-inventor-to-file provisions, however, only became effective on March 16, 2013. Accordingly, it is not yet clear what, if any, impact the Leahy-Smith Act will have on the operation of our business. However, the Leahy-Smith Act and its implementation could make it more difficult to obtain patent protection for our inventions and increase the uncertainties and costs surrounding the prosecution of the patent applications that we have in-licensed and the enforcement or defense of such issued patents, all of which could harm our business, results of operations and financial condition.

The U.S. Supreme Court has and other courts have ruled on several patent cases in recent years, either narrowing the scope of patent protection available in certain circumstances or weakening the rights of patent owners in certain situations. Additionally, there have been recent proposals for additional changes to the patent laws of the United States and other countries that, if adopted, could impact our ability to obtain patent protection for our proprietary technology or our ability to enforce our proprietary technology. Depending on future actions by the U.S. Congress,

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the U.S. courts, the USPTO and the relevant law-making bodies in other countries, the laws and regulations governing patents could change in unpredictable ways that would weaken our ability to obtain new patents or to enforce our existing patents and patents that we might obtain in the future.

Intellectual property rights do not guarantee commercial success of current or future product candidates or other business activities. Numerous factors may limit any potential competitive advantage provided by our intellectual property rights.

The degree of future protection afforded by our intellectual property rights, whether owned or in-licensed, is uncertain because intellectual property rights have limitations, and may not adequately protect our business, provide a barrier to entry against our competitors or potential competitors, or permit us to maintain our competitive advantage. Moreover, if a third party has intellectual property rights that cover the practice of our technology, we may not be able to fully exercise or extract value from our intellectual property rights. The following examples are illustrative:

•patent applications that we own or may in-license may not lead to issued patents;

•patents, should they issue, that we may own or in-license, may not provide us with any competitive advantages, may be narrowed in scope, or may be challenged and held invalid or unenforceable;

•others may be able to develop and/or practice technology, including compounds that are similar to the chemical compositions of our current or future product candidates, that is similar to our technology or aspects of our technology but that is not covered by the claims of any patents we may own or in-license, should any patents issue;

•third parties may compete with us in jurisdictions where we do not pursue and obtain patent protection;

•we, or our future licensors or collaborators, might not have been the first to make the inventions covered by a patent application that we own or may in-license;

•we, or our future licensors or collaborators, might not have been the first to file patent applications covering a particular invention;

•others may independently develop similar or alternative technologies without infringing, misappropriating or otherwise violating our intellectual property rights;

•our competitors might conduct research and development activities in the United States and other countries that provide a safe harbor from patent infringement claims for certain research and development activities, as well as in countries where we do not have patent rights, and may then use the information learned from such activities to develop competitive products for sale in our major commercial markets;

•we may not be able to obtain and/or maintain necessary licenses on reasonable terms or at all;

•third parties may assert an ownership interest in our intellectual property and, if successful, such disputes may preclude us from exercising exclusive rights, or any rights at all, over that intellectual property;

•we may choose not to file a patent in order to maintain certain trade secrets or know-how, and a third-party may subsequently file a patent covering such trade secrets or know-how;

•we may not be able to maintain the confidentiality of our trade secrets or other proprietary information; and

•we may not develop or in-license additional proprietary technologies that are patentable.

Should any of these events occur, they could significantly harm our business, financial condition, results of operations and prospects.

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Risks Related to Employee Matters, Managing Growth and Other Risks Related to Our Business

Our current operations are located in Maryland; and we or the third parties upon whom we depend may be adversely affected by natural disasters and our business continuity and disaster recovery plans may not adequately protect us from a serious disaster.

Our current operations are located in Maryland. Any unplanned event, such as flood, fire, explosion, earthquake, extreme weather condition, medical epidemics, including any potential effects from the current global spread of Covid-19, power shortage, telecommunication failure or other natural or man-made accidents or incidents that result in us being unable to fully utilize our facilities, or the manufacturing facilities of our third-party contract manufacturers, may have a material and adverse effect on our ability to operate our business, particularly on a daily basis, and have significant negative consequences on our financial and operating conditions. Loss of access to these facilities may result in increased costs, delays in the development of our product candidates or interruption of our business operations. Natural disasters or pandemics such as the Covid-19 outbreak could further disrupt our operations, and have a material and adverse effect on our business, financial condition, results of operations and prospects. If a natural disaster, power outage or other event occurred that prevented us from using all or a significant portion of our headquarters, that damaged critical infrastructure, such as the manufacturing facilities of our third-party contract manufacturers, or that otherwise disrupted operations, it may be difficult or, in certain cases, impossible, for us to continue our business for a substantial period of time. The disaster recovery and business continuity plans we have in place may prove inadequate in the event of a serious disaster or similar event. We may incur substantial expenses as a result of the limited nature of our disaster recovery and business continuity plans, which could have a material adverse effect on our business. As part of our risk management policy, we maintain insurance coverage at levels that we believe are appropriate for our business. However, in the event of an accident or incident at these facilities, we cannot assure our investors that the amounts of insurance will be sufficient to satisfy any damages and losses. If the manufacturing facilities of our third-party contract manufacturers are unable to operate because of an accident or incident or for any other reason, even for a short period of time, any or all of our research and development programs may be harmed. Any business interruption may have a material and adverse effect on our business, financial condition, results of operations and prospects.

Our future success depends on our ability to retain key executives and to attract, retain and motivate qualified personnel.

We are highly dependent on the research and development, clinical and business development expertise of Paul A. Romness, MPH, our President and Chief Executive Officer, and Robert G. Petit, Ph.D., our Chief Medical Officer and Chief Scientific Officer, as well as the other principal members of our management, scientific and clinical teams. Although we have entered into employment agreements or arrangements with our executive officers, each of them may terminate their employment with us at any time. We do not maintain “key person” insurance for any of our executives or other employees. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in formulating our research and development and commercialization strategy. Our consultants and advisors may be employed by employers other than us and may have commitments under consulting or advisory contracts with other entities that may limit their availability to us. If we are unable to continue to attract and retain high quality personnel, our ability to pursue our growth strategy will be limited.

Recruiting and retaining qualified scientific, clinical, manufacturing and sales and marketing personnel will also be critical to our success. The loss of the services of our executive officers or other key employees could impede the achievement of our research, development and commercialization objectives and seriously harm our ability to successfully implement our growth strategy. Further, replacing executive officers and key employees may be difficult and may take an extended period of time because of the limited number of individuals in our industry with the breadth of skills and experience required to successfully develop, gain regulatory approval of and commercialize drugs. Competition to hire from this limited pool is intense, and we may be unable to hire, train, retain or motivate these key personnel on acceptable terms given the competition among numerous pharmaceutical and biotechnology companies for similar personnel. We also experience competition for the hiring of scientific and clinical personnel from universities and research institutions. Failure to succeed in clinical trials may make it more challenging to recruit and retain qualified scientific personnel.

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We will need to develop and expand our company, and we may encounter difficulties in managing this development and expansion, which could disrupt our operations.

As of March31, 2023, we had three full-time employees, one part-time employee, an executive consultant and a limited number of regulatory and other consultants. In connection with becoming a public company, we expect to increase our number of employees and the scope of our operations. To manage our anticipated growth and expansion, we must continue to implement and improve our managerial, operational and financial systems, expand our facilities and continue to recruit and train additional qualified personnel. Also, our management may need to divert a disproportionate amount of its attention away from its day-to-day activities and devote a substantial amount of time to managing these growth-oriented activities. Due to our limited resources, we may not be able to effectively manage the expansion of our operations or recruit and train additional qualified personnel. This may result in weaknesses in our infrastructure, give rise to operational mistakes, loss of business opportunities, loss of employees and reduced productivity among remaining employees. The physical expansion of our operations may lead to significant costs and may divert financial resources from other projects, such as the development of our current or future product candidates. If our management is unable to effectively manage our expected growth and expansion, our expenses may increase more than expected, our ability to generate or increase our revenue could be reduced and we may not be able to implement our growth strategy. Our future financial performance and our ability to commercialize our current or future product candidates, if approved, and compete effectively will depend, in part, on our ability to effectively manage the future growth and expansion of our company.

Failure to maintain effective internal controls in accordance with Section 404 of the Sarbanes-Oxley Act could have a material adverse effect on our business, results of operation or financial condition. In addition, current and potential shareholders could lose confidence in our financial reporting, which could have a material adverse effect on the price of the common stock.

Effective internal controls are necessary for us to provide reliable financial reports and effectively prevent fraud. We are required to document and test our internal control procedures in order to satisfy the requirements of Section 404 of the Sarbanes-Oxley Act, which requires annual management assessments of the effectiveness of our internal control over financial reporting. In addition, if we fail to maintain the adequacy of our internal controls, as such standards are modified, supplemented or amended from time to time, we may not be able to ensure that we can conclude on an ongoing basis that we have effective internal controls over financial reporting in accordance with Section 404. Disclosing deficiencies or weaknesses in our internal controls, failing to remediate these deficiencies or weaknesses in a timely fashion or failing to achieve and maintain an effective internal control environment may cause investors to lose confidence in our reported financial information, which could have a material adverse effect on the price of the common stock. If we cannot provide reliable financial reports or prevent fraud, our operating results could be harmed.

Unstable market and economic conditions may have serious adverse consequences on our business, financial condition and stock price.

Global financial markets have experienced extreme volatility and disruptions in the past several years, including severely diminished liquidity and credit availability, declines in consumer confidence, declines in economic growth, increases in inflation and unemployment rates and uncertainty about economic stability. There can be no assurance that further deterioration in financial markets and confidence in economic conditions will not occur. Our general growth strategy may be adversely affected by any such economic downturn, volatile business environment or continued unpredictable and unstable market conditions. If the current equity and credit markets deteriorate, or do not improve, it may make any necessary debt or equity financing more difficult, more costly and more dilutive. Failure to secure any necessary financing in a timely manner and on favorable terms could have a material adverse effect on our growth strategy, financial performance and stock price and could require us to delay, scale back or discontinue the development and commercialization of one or more of our product candidates or delay our pursuit of potential in-licenses or acquisitions. In addition, there is a risk that one or more of our current service providers, manufacturers and other partners may not survive these difficult economic times, which could directly affect our ability to attain our operating goals on schedule and on budget.

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Our internal computer systems, or those of our third-party CROs or other contractors or consultants, may fail or suffer security breaches, which could result in a material disruption of our current or future product candidates’ development programs.

Despite the implementation of security measures, our internal computer systems and those of our third-party CROs and other contractors and consultants are vulnerable to damage from computer viruses, unauthorized access, natural disasters, terrorism, war and telecommunication and electrical failures. While we have not experienced any such system failure, accident, or security breach to date, if such an event were to occur and cause interruptions in our operations, it could result in a material disruption of our programs. For example, the loss of clinical trial data for our current or future product candidates could result in delays in our regulatory approval efforts and significantly increase our costs to recover or reproduce the data. To the extent that any disruption or security breach results in a loss of or damage to our data or applications or other data or applications relating to our technology or current or future product candidates, or inappropriate disclosure of confidential or proprietary information, we could incur liabilities and the further development of our current or future product candidates could be delayed.

We may be unable to adequately protect our information systems from cyberattacks, which could result in the disclosure of confidential or proprietary information, including personal data, damage our reputation, and subject us to significant financial and legal exposure.

We rely on information technology systems that we or our third-party providers operate to process, transmit and store electronic information in our day-to-day operations. In connection with our product discovery efforts, we may collect and use a variety of personal data, such as name, mailing address, email addresses, phone number and clinical trial information. A successful cyberattack could result in the theft or destruction of intellectual property, data or other misappropriation of assets, or otherwise compromise our confidential or proprietary information and disrupt our operations. Cyberattacks are increasing in their frequency, sophistication and intensity, and have become increasingly difficult to detect. Cyberattacks could include wrongful conduct by hostile foreign governments, industrial espionage, wire fraud and other forms of cyber fraud, the deployment of harmful malware, denial-of-service, social engineering fraud or other means to threaten data security, confidentiality, integrity and availability. A successful cyberattack could cause serious negative consequences for us, including, without limitation, the disruption of operations, the misappropriation of confidential business information, including financial information, trade secrets, financial loss and the disclosure of corporate strategic plans. Although we devote resources to protect our information systems, we realize that cyberattacks are a threat, and there can be no assurance that our efforts will prevent information security breaches that would result in business, legal, financial or reputational harm to us, or would have a material adverse effect on our results of operations and financial condition. Any failure to prevent or mitigate security breaches or improper access to, use of, or disclosure of our clinical data or patients’ personal data could result in significant liability under state (e.g., state breach notification laws), federal (e.g., HIPAA, as amended by HITECH), and international law (e.g., the EU General Data Protection Regulation, or GDPR) and may cause a material adverse impact to our reputation, affect our ability to use collected data, conduct new studies and potentially disrupt our business.

We rely on our third-party providers to implement effective security measures and identify and correct for any such failures, deficiencies or breaches. We also rely on our employees and consultants to safeguard their security credentials and follow our policies and procedures regarding use and access of computers and other devices that may contain our sensitive information. If we or our third-party providers fail to maintain or protect our information technology systems and data integrity effectively or fail to anticipate, plan for or manage significant disruptions to our information technology systems, we or our third-party providers could have difficulty preventing, detecting and controlling such cyber-attacks and any such attacks could result in losses described above as well as disputes with physicians, patients and our partners, regulatory sanctions or penalties, increases in operating expenses, expenses or lost revenues or other adverse consequences, any of which could have a material adverse effect on our business, results of operations, financial condition, prospects and cash flows. Any failure by such third parties to prevent or mitigate security breaches or improper access to or disclosure of such information could have similarly adverse consequences for us. If we are unable to prevent or mitigate the impact of such security or data privacy breaches, we could be exposed to litigation and governmental investigations, which could lead to a potential disruption to our business.

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Our employees, principal investigators, CROs and consultants may engage in misconduct or other improper activities, including non-compliance with regulatory standards and requirements and insider trading.

We are exposed to the risk that our employees, principal investigators, CROs and consultants may engage in fraudulent conduct or other illegal activity. Misconduct by these parties could include intentional, reckless and/or negligent conduct or disclosure of unauthorized activities to us that violate the regulations of the FDA and other regulatory authorities, including those laws requiring the reporting of true, complete and accurate information to such authorities; healthcare fraud and abuse laws and regulations in the United States and abroad; or laws that require the reporting of financial information or data accurately. In particular, sales, marketing, patient support and business arrangements in the healthcare industry are subject to extensive laws and regulations intended to prevent fraud, misconduct, kickbacks, self-dealing and other abusive practices. These laws and regulations may restrict or prohibit a wide range of pricing, discounting, marketing and promotion, sales commission, customer incentive programs and other business arrangements. Activities subject to these laws also involve the improper use of information obtained in the course of clinical trials or creating fraudulent data in our preclinical studies or clinical trials, which could result in regulatory sanctions and cause serious harm to our reputation. We intend to adopt, prior to the completion of this offering, a code of conduct applicable to all of our employees, but it is not always possible to identify and deter misconduct by employees and other third parties, and the precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to comply with these laws or regulations. Additionally, we are subject to the risk that a person could allege such fraud or other misconduct, even if none occurred. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business, including the imposition of civil, criminal and administrative penalties, damages, monetary fines, possible exclusion from participation in Medicare, Medicaid and other federal and state healthcare programs, debarment from participation in any FDA-related activities, contractual damages, reputational harm, diminished profits and future earnings, and curtailment of our operations, any of which could adversely affect our ability to operate our business and our results of operations.

Efforts to ensure that our business arrangements with third parties will comply with applicable healthcare laws and regulations will involve substantial costs. Because of the breadth of these laws and the narrowness of the statutory exceptions and safe harbors available, it is possible that some of our business activities could be subject to challenge under one or more of such laws. It is possible that governmental authorities will conclude that our business practices may not comply with current or future statutes, regulations or case law involving applicable fraud and abuse or other healthcare laws and regulations. If our operations are found to be in violation of any of these laws or any other governmental regulations that may apply to us, we may be subject to significant criminal, civil and administrative sanctions including monetary penalties, damages, fines, disgorgement, individual imprisonment, and exclusion from participation in government funded healthcare programs, such as Medicare and Medicaid, debarment from participation in any FDA-related activities, additional reporting requirements and oversight if we become subject to a corporate integrity agreement or similar agreement to resolve allegations of non-compliance with these laws, reputational harm, and we may be required to curtail or restructure our operations, any of which could adversely affect our ability to operate our business and our results of operations.

Risks Related to Our Common Stock and This Offering

Paul A. Romness, MPH, and our other executive officers, directors and their affiliates will continue to exercise significant influence over our company after this offering, which will limit your ability to influence corporate matters and could delay or prevent a change in corporate control.

Paul A. Romness, MPH, our President and Chief Executive Officer, beneficially owns approximately 34% of the outstanding shares of common stock of our company, and other executive officers and directors beneficially own another approximately 6.6% of our outstanding shares. Immediately following completion of this offering, and disregarding any shares of common stock that they purchase in this offering, the existing holdings of Mr. Romness and other executive officers, directors and their affiliates will represent beneficial ownership in the aggregate of approximately 37% of our outstanding common stock, assuming no exercise of the underwriters’ over-allotment option in this offering. As a result, these stockholders will be able to influence our management and affairs and the outcome of matters submitted to our stockholders for approval, including the election of directors and any sale, merger, consolidation or sale of all or substantially all of our assets. These stockholders acquired their shares of common stock for substantially less than the price of the shares of common stock being acquired in this offering, and these

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stockholders may have interests, with respect to their common stock, that are different from those of investors in this offering and the concentration of voting power among these stockholders may have an adverse effect on the price of our common stock. In addition, this concentration of ownership might adversely affect the market price of our common stock by:

•delaying, deferring or preventing a change of control our company;

•impeding a merger, consolidation, takeover or other business combination involving our company; or

•discouraging a potential acquirer from making a tender offer or otherwise attempting to obtain control of our company.

We will incur increased costs as a result of operating as a public company, and our management will be required to devote substantial time to new compliance initiatives.

As a public company, we will incur significant legal, accounting and other expenses that we did not incur as a private company. We will be subject to the reporting requirements of the Securities Exchange Act of 1934, which will require, among other things, that we file with the SEC annual, quarterly and current reports with respect to our business and financial condition. In addition, the Sarbanes-Oxley Act of 2002, as well as rules subsequently adopted by the SEC and the NYSE American to implement provisions of the Sarbanes-Oxley Act, impose significant requirements on public companies, including requiring establishment and maintenance of effective disclosure and financial controls and changes in corporate governance practices. Further, in July 2010, the Dodd-Frank Wall Street Reform and Consumer Protection Act was enacted. There are significant corporate governance and executive compensation related provisions in the Dodd-Frank Act under which the SEC adopted additional rules and regulations in these areas, such as “say on pay” and proxy access. Recent legislation permits emerging growth companies to implement many of these requirements over a longer period and up to five years from the pricing of this offering. We intend to take advantage of this new legislation but cannot guarantee that we will not be required to implement these requirements sooner than budgeted or planned and thereby incur unexpected expenses. Stockholder activism, the current political environment and the current high level of government intervention and regulatory reform may lead to substantial new regulations and disclosure obligations, which may lead to additional compliance costs and impact the manner in which we operate our business in ways we cannot currently anticipate.

We expect the rules and regulations applicable to public companies to substantially increase our legal and financial compliance costs and to make some activities more time-consuming and costly. If these requirements divert the attention of our management and personnel from other business concerns, they could have a material adverse effect on our business, financial condition and results of operations. The increased costs will increase our net loss and may require us to reduce costs in other areas of our business or increase the prices of our products or services. For example, we expect these rules and regulations to make it more difficult and more expensive for us to obtain director and officer liability insurance and we may be required to incur substantial costs to maintain the same or similar coverage. We cannot predict or estimate the amount or timing of additional costs we may incur to respond to these requirements. The impact of these requirements could also make it more difficult for us to attract and retain qualified persons to serve on our board of directors, our board committees or as executive officers.

The price of our common stock may be volatile and fluctuate substantially, which could result in substantial losses for purchasers of our common stock in this offering.

Our stock price is likely to be volatile. The stock market in general and the market for biopharmaceutical companies in particular have experienced extreme volatility that has often been unrelated to the operating performance of particular companies. As a result of this volatility, you may not be able to sell your common stock at or above the initial public offering price. The market price for our common stock may be influenced by many factors, including:

•the success of competitive drugs or technologies;

•results of clinical trials of our current or future product candidates or those of our competitors;

•regulatory or legal developments in the United States and other countries;

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•developments or disputes concerning patent applications, issued patents or other proprietary rights;

•the recruitment or departure of key personnel;

•the level of expenses related to any of our current or future product candidates or clinical development programs;

•the results of our efforts to discover, develop, acquire or in-license additional current or future product candidates or drugs;

•actual or anticipated changes in estimates as to financial results, development timelines or recommendations by securities analysts;

•changes in the structure of healthcare payment systems;

•market conditions in the pharmaceutical and biotechnology sectors;

•general economic, industry and market conditions; and

•the other factors described in this “Risk Factors” section.

An active trading market for our common stock may not develop, and you may not be able to resell your shares at or above the initial public offering price.

Prior to this offering, there has been no public market for shares of our common stock. Although we have applied to list our common stock for trading on the NYSE American, an active trading market for our common stock may never develop or be sustained following this offering. The initial public offering price of our common stock was determined through negotiations between us and the underwriters. This initial public offering price may not be indicative of the market price of our common stock after this offering. In the absence of an active trading market for our common stock, investors may not be able to sell their common stock at or above the initial public offering price or at the time that they would like to sell.

If you purchase our common stock in this offering, you will incur immediate and substantial dilution in the book value of your shares.

You will suffer immediate and substantial dilution in the net tangible book value of the common stock you purchase in this offering. Based on the initial public offering price of $5.00 per share, purchasers of common stock in this offering will experience immediate dilution of $4.68 per share in net tangible book value of the common stock. In addition, investors purchasing common stock in this offering will contribute approximately 29.1% of the total amount invested by stockholders since inception but will only own approximately 8.7% of the shares of common stock outstanding. In the past, we issued securities to acquire common stock at prices significantly below the initial public offering price. To the extent these outstanding securities are ultimately exercised, investors purchasing common stock in this offering will sustain further dilution. See the section of this prospectus titled “Dilution” for a more detailed description of the dilution to new investors in the offering.

Resales by the selling stockholders under our resale prospectus may have an adverse effect on the market price of our common stock.

The 536,336shares of common stock being offered under the resale prospectus for the account of the selling stockholders equals approximately 5.0% of the 10,745,000shares of our common stock outstanding as of March31, 2023, and approximately 5.2% of the “public float,” or the shares held by non-affiliates which are not subject to restrictions on sale, prior to this offering. Sales of the shares offered under the resale prospectus, or the potential of such sales, may have an adverse effect on the market price of our common stock and such sales could also affect our company’s ability to raise additional capital in the equity markets in the future.

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Raising additional capital may cause dilution to our stockholders, including purchasers of common stock in this offering, restrict our operations or require us to relinquish rights to our technologies or current or future product candidates.

Until such time, if ever, as we can generate substantial drug revenues, we expect to finance our cash needs through a combination of private and public equity offerings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. We do not currently have any committed external source of funds. To the extent that we raise additional capital through the sale of common stock or securities convertible, exercisable or exchangeable into common stock, your ownership interest will be diluted, and the terms of these securities may include liquidation or other preferences that materially adversely affect your rights as a common stockholder. Debt financing, if available, would increase our fixed payment obligations and may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends.

If we raise funds through additional collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our intellectual property, future revenue streams, research programs or current or future product candidates or to grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings when needed, we may be required to delay, scale back or discontinue the development and commercialization of one or more of our product candidates, delay our pursuit of potential in-licenses or acquisitions or grant rights to develop and market current or future product candidates that we would otherwise prefer to develop and market ourselves.

We have not paid, and do not intend to pay, dividends on our shares of common stock and, therefore, unless our common stock appreciates in value, our investors may not benefit from holding our shares.

We have not paid any cash dividends on our shares of common stock, and we do not anticipate paying any cash dividends on our common stock in the foreseeable future. As a result, investors in our common stock will not be able to benefit from owning these shares unless their market price becomes greater than the price paid by such investors and they are able to sell such shares. We cannot assure you that you will ever be able to resell our common stock at a price in excess of the price paid.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

Information set forth in this prospectus may contain various “forward-looking statements.” All information relative to future markets for our product candidates and trends in, and anticipated levels of, revenue, and expenses, as well as other statements containing words such as “anticipate,” “believe,” “estimate,” “expect,” “intend,” “may,” “plan,” “project,” “target,” “should” and “will” and other similar expressions constitute forward-looking statements. These forward-looking statements are subject to business, economic and other risks and uncertainties, both known and unknown, and actual results may differ materially from those contained in the forward-looking statements. Examples of risks and uncertainties that could cause actual results to differ materially from historical performance and any forward-looking statements include, but are not limited to, the risks described under the section below titled “Risk Factors,” as well as any subsequent filings with the Securities and Exchange Commission.

Given these risks, uncertainties and other factors, you should not place undue reliance on these forward-looking statements. Also, these forward-looking statements represent our estimates and assumptions only as of the date such forward-looking statements are made. You should read carefully this prospectus and any related free writing prospectuses that we have authorized for use in connection with this offering, together with the information incorporated herein or therein by reference as described under the heading “Where You Can Find More Information,” completely and with the understanding that our actual future results may be materially different from what we expect. We hereby qualify all of our forward-looking statements by these cautionary statements. Except as required by U.S. federal law, we assume no obligation to update these forward-looking statements publicly or to update the reasons actual results could differ materially from those anticipated in these forward-looking statements, even if new information becomes available in the future.

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USE OF PROCEEDS

We estimate that our net proceeds from the sale of 2,000,000shares of our common stock in this offering will be approximately $8,560,000, or $9,940,000 if the underwriters exercise in full their option to purchase additional shares, based on the initial public offering price of $5.00 per share, and after deducting underwriting discounts and commissions and estimated offering expenses payable by us.

We expect to use the net proceeds from this offering as follows:

•approximately $4,200,000 to advance the clinical development of OST-HER2 for Osteosarcoma;

•approximately $2,000,000 to advance development of OST-TDC for ovarian cancer; and

•the remainder of the net proceeds of approximately $2,360,000 for the discovery and development of new product candidates and for working capital and other general corporate purposes.

The net proceeds for the clinical development of OST 31-164 will be used to support the remainder of our current Phase IIb clinical trial in recurred, resected Osteosarcoma in eligible patients from ages 12 to 39 years, of which 36 of 45 patients have already been enrolled. These proceeds provide the funds to pay vendors for the trial, hire critical new employees to prepare for commercialization and cover professional fees for advancing regulatory discussions with the FDA. Funding should carry us through to completion of the Phase IIb clinical trial for OST-HER2, which is expected to be in late 2024. We plan to submit a new drug application (NDA) with the FDA for approval to market the drug candidate following the completion of the Phase IIb clinical trial if there is sufficiently positive endpoint data from such trial supporting the FDA’s determination of safety and efficacy of the drug candidate. We expect that it will take six to eight months from the completion of the Phase IIb clinical trial, subject to the receipt of sufficiently positive endpoint data, to compile and file the NDA with the FDA for marketing approval. The FDA generally takes six to ten months to complete its review of an NDA, subject to any FDA request for additional information.

We believe that it remains uncertain whether a Phase III clinical trial will be necessary for the advancement of OST-HER2 through the regulatory approval process. We will not know whether a Phase III trial will be required until we receive a determination from the FDA following the filing of an NDA for marketing approval as to whether the results of our ongoing Phase IIb trial provided sufficiently positive endpoint data. We do, however, plan to conduct a master protocol in other HER2-positive adult cancers, such as breast and esophageal cancers, to evaluate the potential possibility for FDA approval of OST-HER2 in solid tumor indications other than Osteosarcoma. Net proceeds from this offering should carry us into (but not beyond) our proposed master protocol.

The net proceeds for the development of OST-TDC will be used to fund the continued development costs associated with our preclinical trials, including pharmacokinetics and pharmacodynamics, two-week dose finding toxicology studies in vivo (on living cell lines or in living animals), as well as GLP trials. Additionally, funds will be used for preparing and submitting an application for an investigational new drug application (IND) with the FDA following the completion of GLP trials, as well as development of a Phase I clinical trial of OST-TDC for ovarian cancer indications. In addition to the Phase I trial, we expect that post completion GLP will lead to licensing opportunities for our silicon SiLinkers and CAPs. Funding should carry us into (but not beyond) our proposed Phase I clinical trial.

The remaining net proceeds from this offering will be available for the discovery and development of new product candidates and for working capital and other general corporate purposes, including enhancing our corporate infrastructure and systems to assist in creating a more robust means of tracking data, automating back office functions, improving our financial reporting system and making improvements to our principal executive offices in Rockville, Maryland to accommodate our growth and expansion strategies. We may allocate funds from our existing cash and other sources to fund some of these activities.

Our expected use of the net proceeds from this offering represents our intentions based upon our current plans and business conditions. As of the date of this prospectus, we cannot predict with certainty all of the particular uses for the net proceeds to be received upon the completion of this offering or the amounts that we will actually spend on the uses set forth above. We believe that the net proceeds from this offering, together with our existing cash, will enable us to fund our operating expenses and capital expenditure requirements for the next 12 to 18 months. We expect that we will require additional funds in order to fully accomplish the specified uses of the proceeds of this offering. We may

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also use a portion of the net proceeds to in-license, acquire or invest in complementary businesses or technologies to continue to build our pipeline, research and development capabilities and our intellectual property position, although we currently have no agreements, commitments or understandings with respect to any such transaction.

Due to the many inherent uncertainties in the development of our product candidates, the amounts and timing of our actual expenditures may vary significantly depending on numerous factors, including the progress of our research and development, the timing of patient enrollment and evolving regulatory requirements, the timing and success of preclinical studies, our ongoing clinical studies or clinical studies we may commence in the future, the timing of regulatory submissions, any strategic alliances that we may enter into with third parties for our product candidates or strategic opportunities that become available to us, and any unforeseen cash needs.

Pending our use of the net proceeds from this offering, we intend to invest the net proceeds in a variety of capital preservation instruments, including short-term and long-term interest-bearing instruments, investment-grade securities, and direct or guaranteed obligations of the U.S. government. We cannot predict whether the proceeds invested will yield a favorable return. Our management will retain broad discretion in the application of the net proceeds we receive from our initial public offering, and investors will be relying on the judgment of our management regarding the application of the net proceeds.

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DIVIDEND POLICY

We currently intend to retain all available funds and any future earnings to fund the growth and development of our business. We do not intend to pay cash dividends to our stockholders in the foreseeable future. Any future determination to declare dividends will be made at the discretion of our board of directors and will depend on our financial condition, operating results, capital requirements, contractual restrictions, general business conditions, and other factors that our board of directors may deem relevant.

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CAPITALIZATION

The following table sets forth our cash and our capitalization as of December 31, 2022:

•on an actual basis;

•on a pro forma basis to give effect to:

•the elimination of our authorized shares of Class B common stock (none of which were outstanding), the renaming of our Class A common stock as “common stock” and the issuances of shares of our common stock in connection with the Recapitalization transactions;

•the issuance of 740,000shares of our common stock that we previously agreed to issue to certain directors, officers, key employees and key advisors in consideration for accrued services rendered to our company; and

•the grant of 25,000shares of our common stock to our Chief Financial Officer in March 2023; and

•on a pro forma, as adjusted basis to give further effect to:

•the pro forma transactions listed above and our issuance and sale of 2,000,000shares of our common stock in this offering at the initial public offering price of $5.00 per share, after deducting underwriting discounts and commissions and estimated offering expenses payable by us.

The pro forma, as adjusted information below is illustrative only, and our capitalization following the completion of this offering will be adjusted based on the actual initial public offering price and other terms of this offering determined at pricing. You should read this table together with our financial statements and the related notes appearing elsewhere in this prospectus and the section of this prospectus titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations.” We currently intend to retain all available funds and any future earnings to fund the growth and development of our business. We do not intend to pay cash dividends to our stockholders in the foreseeable future. Any future determination to declare dividends will be made at the discretion of our board of directors and will depend on our financial condition, operating results, capital requirements, contractual restrictions, general business conditions, and other factors that our board of directors may deem relevant.

	As of December 31, 2022
(In thousands, except share and per share data)	Actual			Pro forma			Pro forma,as adjusted
Cash	$	171		$	886		$	10,166
Group A Convertible Notes	$	1,154		$	—		$	—
Group B Convertible Notes		5,154			—			—
Group C Convertible Notes		3,820			—			—
Group D Convertible Notes		2,000			—			—
Stockholders’ equity (deficit):
Series A preferred stock, par value $0.001, 1,400,000 shares authorized, 1,302,082 issued and outstanding, actual; no amounts issued and outstanding pro forma and pro forma, as adjusted		1			—			—
Common stock, par value $0.001, 50,000,000 shares authorized, 9,980,000 shares issued and outstanding, actual; 21,100,819 shares issued and outstanding, pro forma; 23,100,819 shares issued and outstanding, pro forma, as adjusted		10			21			23
Additional paid-in capital		4,033			22,907			32,205
Accumulated deficit		(21,602	)		(24,724	)		(24,724	)
Total stockholders’ equity (deficit)		(17,557	)		(1,796	)		7,504
Total capitalization	$	(5,429	)	$	(1,796	)	$	7,504

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DILUTION

If you invest in our common stock in this offering, your ownership interest will be diluted immediately to the extent of the difference between the initial public offering price per share of our common stock and the pro forma, as adjusted net tangible book value per share of our common stock immediately after this offering.

Our historical net tangible book value (deficit), as of December 31, 2022, was $(17.6) million, or $(1.76) per share of our common stock. Our historical net tangible book value (deficit) is the amount of our total tangible assets less our total liabilities and shares of Series A convertible preferred stock, which is not included within our stockholders’ equity (deficit). Historical net tangible book value per share represents historical net tangible book value (deficit) divided by the shares of our common stock outstanding as of December 31, 2022.

Our pro forma net tangible book value, as of December 31, 2022, was $(1.9) million, or $(0.09) per share of our common stock. Pro forma net tangible book value represents the amount of our total tangible assets less our total liabilities, after giving effect to (i) the issuances of shares of our common stock in connection with the Recapitalization transactions, (ii) the issuance of 740,000shares of our common stock that we previously agreed to issue to certain directors, officers, key employees and key advisors in consideration for accrued services rendered to our company and (iii) the grant of 25,000shares of our common stock to our Chief Financial Officer in March 2023. Pro forma net tangible book value per share represents pro forma net tangible book value divided by the total number of shares outstanding, as of December 31, 2022, after giving effect to the pro forma adjustments described above.

Unless otherwise noted, all per share amounts include only common stock. After giving further effect to our issuance and sale of 2,000,000shares of our common stock in this offering at the initial public offering price of $5.00 per share, after deducting underwriting discounts and commissions and estimated offering expenses payable by us, our pro forma, as adjusted net tangible book value as of December 31, 2022 would have been approximately $7.4million, or approximately $0.32 per share. This represents an immediate increase in pro forma, as adjusted net tangible book value per share of $0.41 to existing stockholders and immediate dilution of $4.68 per share in pro forma, as adjusted net tangible book value per share to investors purchasing shares of common stock in this offering. Dilution per share to investors purchasing shares of common stock in this offering is determined by subtracting pro forma, as adjusted net tangible book value per share after this offering from the initial public offering price per share paid by investors purchasing shares of common stock in this offering. The following table illustrates this dilution on a per share basis (without giving effect to any exercise by the underwriters of their option to purchase up to 300,000 additional shares of common stock in this offering):

Initial public offering price per share of common stock				$	5.00
Historical net tangible book value (deficit) per share as of December 31, 2022	$	(1.76	)
Increase per share attributable to the pro forma adjustments described above	$	1.67
Pro forma net tangible book value per share as of December 31, 2022				$	(0.09	)
Increase in pro forma, as adjusted net tangible book value per share attributable to investors purchasing shares of common stock in this offering	$	0.41
Pro forma, as adjusted net tangible book value per share after this offering				$	0.32
Dilution per share to investors purchasing shares of common stock in this offering				$	4.68

If the underwriters fully exercise their option to purchase 300,000 additional shares of common stock in this offering, our pro forma, as adjusted, net tangible book value per share after this offering would be $0.38 and the dilution in pro forma, as adjusted net tangible book value per share to investors purchasing common stock in this offering would be $4.62, assuming no change in the initial public offering price per share and after deducting underwriting discounts and commissions and estimated offering expenses payable by us.

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The following table summarizes, as of December 31, 2022, on the pro forma, as adjusted basis described above, the total number of shares of our common stock purchased from us on an as converted to common stock basis, the total consideration paid, or to be paid, and the average price per share paid or to be paid by existing stockholders and by investors in this offering at the initial public offering price of $5.00 per share of common stock, before deducting underwriting discounts and commissions and estimated offering expenses payable by us. As the table shows, investors purchasing shares of common stock in this offering will pay an average price per share substantially higher than our existing stockholders paid.

	Shares purchased			Total consideration				Average priceper share
	Number	Percent		Amount		Percentage
Existing stockholders	9,980,000	43.2	%	$	2,625,000	7.7	%	$	0.26
Recapitalization issuances	10,355,819	44.8