As filed with the Securities and Exchange Commission on April 11, 2025

Registration No. 333-278829

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-1

ON FORM S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Q32 BIO INC.

(Exact name of registrant as specified in its charter)

Delaware	47-3468154
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification Number)

830 Winter Street

Waltham, MA 02451

(781) 999-0232

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Jodie Morrison

Chief Executive Officer

Q32 Bio Inc.

830 Winter Street

Waltham, MA 02451

(781) 999-0232

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Sarah Ashfaq, Esq.

Jacqueline Mercier, Esq.

Alicia M. Tschirhart, Esq.

Goodwin Procter LLP

100 Northern Avenue

Boston, MA 02210

(617) 570-1000

Approximate Date of Commencement of Proposed Sale to the Public: From time to time after the effective date of this registration statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box. ☐

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, other than securities offered only in connection with dividend or interest reinvestment plans, 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 registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box. ☐

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box. ☐

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 pursuant 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 this registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

Explanatory Note

On April 19, 2024, Q32 Bio Inc., or the Company, filed a registration statement with the U.S. Securities and Exchange Commission, or the SEC, on Form S-1 (File No. 333-278829), or the Registration Statement. The Registration Statement was initially declared effective by the SEC on April 29, 2024 and registered the offer and sale from time to time by the selling stockholders (including their transferees, donees, assignees, pledgees and other successors-in-interest) named in this prospectus of up to an aggregate of 1,682,045 shares of common stock, par value $0.0001 per share, of the Company, or the common stock.

This Post-Effective Amendment No. 1 to Form S-1 on Form S-3, or the Post-Effective Amendment No. 1, is being filed by the Company to convert the registration statement on Form S-1 into a registration statement on Form S-3.

The information included in this Post-Effective Amendment No. 1 amends the Registration Statement and the prospectus contained therein. No additional securities are being registered under this Post-Effective Amendment No. 1. All applicable fees were paid at the time of the original filing of the Registration Statement on April 19, 2024.

The information in this preliminary prospectus is not complete and may be changed. Neither we nor the selling stockholders may sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED APRIL 11, 2025

PRELIMINARY PROSPECTUS

Up to 1,682,045 Shares of Common Stock

This prospectus relates to the proposed offer and resale or other disposition from time to time by the selling stockholders identified in this prospectus of up to an aggregate of 1,682,045 shares of common stock.

We are registering the resale of the shares of common stock pursuant to the selling stockholders’ registration rights under a registration rights agreement between us and the selling stockholders. Our registration of the resale of the shares of common stock covered by this prospectus does not mean that the selling stockholders will offer or sell all or any of the shares of common stock. The selling stockholders may offer, sell or distribute all or a portion of their shares of common stock from time to time directly or indirectly through one or more underwriters, broker-dealers or agents, and in one or more public or private transactions. The shares of common stock may be sold in one or more transactions at fixed prices, at prevailing market prices at the time of the sale, at varying prices determined at the time of sale or at negotiated prices. These sales may be effected in transactions, which may involve crosses or block transactions. See the section entitled “Plan of Distribution” for more information.

We will not receive any proceeds from any sale of common stock by the selling stockholders pursuant to this prospectus. We have agreed to bear the expenses in connection with the registration of the resale of the shares of common stock to be offered by this prospectus by the selling stockholders other than any underwriting discounts and commissions or transfer taxes relating to the sale of common stock, which will be borne by the selling stockholders.

Our common stock is listed on the Nasdaq Capital Market, or Nasdaq, under the symbol “QTTB.” On April 10, 2025, the closing price for our common stock, as reported on Nasdaq, was $1.68 per share.

As of the date of this prospectus, we are a smaller reporting company as defined under Rule 405 of the Securities Act of 1933, as amended, or the Securities Act, and, as such, are subject to certain reduced public company reporting requirements. See “Prospectus Summary—Implications of Being a Smaller Reporting Company” on page 5 of this prospectus.

Investing in our securities involves certain risks. See the section entitled “Risk Factors” beginning on page 7 of this prospectus, in any applicable prospectus supplement and any related free writing prospectus, and in our SEC filings that are incorporated by reference herein. You should read the entire prospectus carefully before you make your investment decision.

Neither the SEC 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 date of this prospectus is    , 2025.

TABLE OF CONTENTS

	Page
ABOUT THIS PROSPECTUS		1
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS		2
PROSPECTUS SUMMARY		4
THE OFFERING		6
RISK FACTORS		7
USE OF PROCEEDS		8
SELLING STOCKHOLDERS		9
DESCRIPTION OF CAPITAL STOCK		12
MATERIAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS		16
PLAN OF DISTRIBUTION		21
LEGAL MATTERS		23
EXPERTS		23
WHERE YOU CAN FIND MORE INFORMATION		23
INCORPORATION BY REFERENCE		23

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the SEC, utilizing a “shelf” registration process. Under this shelf registration process, the selling stockholders identified in this prospectus under the caption “Selling Stockholders” may, from time to time, sell up to an aggregate of 1,682,045 shares of common stock described in this prospectus, in one or more offerings. We are not selling any shares of common stock under this prospectus, and we will not receive any proceeds from the sale of shares of common stock offered hereby by the selling stockholders.

You should rely only on the information provided in this prospectus as well as the information incorporated by reference herein and any applicable prospectus supplement or amendment. Neither we, nor the selling stockholders, have authorized anyone to give any information or to make any representation other than those contained or incorporated by reference in this prospectus. You must not rely upon any information or representation not contained or incorporated by reference in this prospectus. The selling stockholders are offering to sell, and seeking offers to buy, shares of our common stock only in jurisdictions where it is lawful to do so. This prospectus does not constitute an offer to sell or the solicitation of an offer to buy any shares other than the registered shares to which it relates, nor does this prospectus constitute an offer to sell or the solicitation of an offer to buy shares in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction. You should not assume that the information contained in this prospectus is accurate on any date subsequent to the date set forth on the front of the document or that any information we have incorporated by reference is correct on any date subsequent to the date of the document incorporated by reference, even though this prospectus is delivered or shares are sold on a later date. Our business, financial condition, results of operations and prospects may have changed since those dates.

This prospectus incorporates by reference market data and industry statistics and forecasts that are based on independent industry publications and other publicly available information. Although we believe these sources are reliable, we do not guarantee the accuracy or completeness of this information and we have not independently verified this information. In addition, the market and industry data and forecasts that may be included or incorporated by reference in this prospectus may involve estimates, assumptions and other risks and uncertainties and are subject to change based on various factors, including those discussed under the heading “Risk Factors” contained in this prospectus and under similar headings in other documents that are incorporated by reference into this prospectus. Accordingly, investors should not place undue reliance on this information.

A prospectus supplement may add to, update or change the information contained in this prospectus. You should read both this prospectus and any applicable prospectus supplement together with additional information described below under the heading “Where You Can Find Additional Information” or incorporated by reference herein as described under the heading “Incorporation of Certain Information by Reference.”

Unless the context otherwise indicates, references in this prospectus to “Company,” “we,” “our” and “us” refer, collectively to Q32 Bio Inc., a Delaware corporation, and its consolidated subsidiaries (including Legacy Q32 (as defined herein)).

We use various trademarks and trade names in our business, including without limitation our corporate name and logo. All other trademarks or trade names referred to in this prospectus are the property of their respective owners. Solely for convenience, the trademarks and trade names in this prospectus may be referred to without the ^® and ^™ symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus contains and/or incorporates by reference statements that are not historical facts and are considered forward-looking within the meaning of Section 27A of the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. Our forward-looking statements include, but are not limited to, statements regarding our or our management team’s expectations, hopes, beliefs, intentions or strategies regarding the future. In addition, any statements that refer to projections, forecasts or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking statements. The words “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intends,” “may,” “might,” “plan,” “possible,” “potential,” “predict,” “project,” “should,” “will,” “would” and similar expressions may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking. Forward looking statements in this prospectus may include, for example, statements about:

• our ability to achieve and sustain profitability in the future;

• our strategies, prospects, plans, expectations or objectives of management for our future operations;

• estimates of our future expenses, revenues, capital requirements, and our needs for additional financing;

• our estimates of and anticipated use of our existing cash, cash equivalents and marketable securities;

• the progress, scope or timing of the development of our product candidates;

• our expectations surrounding the potential safety, efficacy, and regulatory and clinical progress of our product candidates, including bempikibart, and our anticipated milestones and timing therefor;

• our ability to obtain and maintain regulatory approval of our product candidates;

• our ability to achieve and maintain market acceptance and adoption of our product candidates;

• the benefits that may be derived from any of our future products or the commercial or market opportunity with respect to any of our future products;

• our ability to maintain patent protection for our product candidates and protect our intellectual property rights;

• our ability to successfully compete against other companies developing similar products to ours;

• our anticipated operations, financial position, ability to raise capital to fund our operations, revenues, costs or expenses;

• our ability to evaluate and execute on strategic options for our tissue-targeted complement inhibitor platform, inclusive of ADX-097 and early-stage assets;

• our ability to implement and achieve cost savings in connection with the strategic restructuring plan, including the reduction in force;

• our ability to retain our key executives and to attract and retain highly qualified personnel;

• our ability to successfully protect against cyber-attacks, security breaches and other disruptions to our information technology systems;

• our ability to establish and maintain an effective system of internal controls over financial reporting;

• the effect of uncertainties related to economic downturns, public health crises, and other macroeconomic conditions;

• our reliance on third parties in the supply and manufacture of our product candidates;

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• the impact of applicable laws and regulations, whether in the U.S. or foreign jurisdictions, and any changes thereto;

• the statements regarding our future economic conditions or performance, statements of belief and any statement of assumptions underlying any of the foregoing; and

• other risks and uncertainties, including those listed under the caption “Risk Factors.”

These forward-looking statements are based on information available to us at the time of this prospectus or the documents incorporated by reference herein and current expectations, forecasts and assumptions, and involve a number of judgments, risks and uncertainties. Accordingly, forward-looking statements should not be relied upon as representing our views as of any subsequent date, and we do not undertake any obligation to update forward-looking statements to reflect events or circumstances after the date they were made, whether as a result of new information, future events or otherwise, except as may be required under applicable securities laws.

The outcome of the events described in these forward-looking statements is subject to known and unknown risks, uncertainties, and other factors. As a result of a number of known and unknown risks and uncertainties, our actual results or performance may be materially different from those expressed or implied by these forward-looking statements, including those set forth in this prospectus in the section entitled “Risk Factors” and in our periodic filings with the SEC. Our SEC filings are available publicly on the SEC’s website at www.sec.gov. Given these risks and uncertainties, you should not place undue reliance on these forward-looking statements. Additional cautionary statements or discussions of risks and uncertainties that could affect our results or the achievement of the expectations described in forward-looking statements may also be contained in any accompanying prospectus supplement. Should one or more of the risks or uncertainties described in this prospectus, or should underlying assumptions prove incorrect, actual results and plans could differ materially from those expressed in any forward-looking statements.

You should read this prospectus and any accompanying prospectus supplement completely and with the understanding that our actual future results, levels of activity and performance as well as other events and circumstances may be materially different from what we expect. Except as otherwise required by applicable law, we disclaim any duty to update any forward-looking statements, all of which are expressly qualified by the statements in this section, to reflect events or circumstances after the date of this prospectus. We qualify all of our forward-looking statements by these cautionary statements.

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PROSPECTUS SUMMARY

Our Company

We are a clinical stage biotechnology company focused on developing novel biologics to effectively and safely restore healthy immune balance in patients with autoimmune and inflammatory diseases driven by pathological immune dysfunction. To achieve this goal of restoring homeostasis to a dysregulated immune system, we are advancing antibody-based therapeutic candidates designed to target two central pathways of adaptive and innate immunity. The adaptive immune system is largely composed of T- and B-cell mediated cellular and antibody responses; while the innate immune system is a first line of defense employing leukocytes such as monocytes, macrophages, neutrophils, dendritic cells and natural killer cells that are responsible for clearing pathogens and cellular debris, and modulating T- and B-cell function. We believe that targeting these key pathways of immune dysregulation in autoimmune and inflammatory diseases will deliver therapeutics for indications with clear unmet medical need in the near term, while enabling us to build a broad and diverse pipeline in the long term. We have multiple product candidates across a variety of autoimmune and inflammatory diseases.

Bempikibart (ADX-914), our most advanced product candidate, is a fully human anti–interleukin-7 receptor alpha, or IL-7Rα, antagonist monoclonal antibody designed to re-regulate adaptive immune function by blocking signaling mediated by interleukin-7, or IL-7, and thymic stromal lymphopoietin, or TSLP. We have completed two Phase 2a clinical trials evaluating bempikibart: SIGNAL-AA for the treatment of alopecia areata, or AA, and SIGNAL-AD for the treatment of atopic dermatitis, or AD. We are focused on the advancement of bempikibart for the treatment in AA.

ADX-097, a Phase 2 asset and the lead product candidate from our complement inhibitor platform, is a humanized anti-C3d monoclonal antibody, or mAb, fusion protein. ADX-097 is designed to restore complement regulation—an integral part of the innate immune system—through a tissue-targeted mechanism. ADX-097 is designed to inhibit alternative pathway complement activation locally in diseased tissues where complement-mediated pathology is actively manifest. We believe ADX-097 has the potential to drive improved clinical activity and address the limitations of the currently available systemic approaches to complement inhibition, including infection risk and the need for high drug doses and frequent administration, to achieve therapeutic levels of inhibition.

Additional discovery and earlier development efforts from our complement inhibitor platform include ADX-096, a C3d mAb—CR1 fusion protein which demonstrated preclinical data supportive of its use in ophthalmologic indications, as well as other C3d mAb fusions and nanobodies designed for tissue-targeted complement inhibition.

In February 2025, we announced a corporate restructuring to focus on the advancement of bempikibart for the treatment of patients with AA. As part of the restructuring, we discontinued the Phase 2 renal basket clinical trial of ADX-097 and are evaluating strategic options for our tissue-targeted complement inhibitor platform, inclusive of ADX-097 and early-stage assets, to prioritize the clinical development of bempikibart.

Corporate Information

We were incorporated under the laws of the State of Delaware on April 10, 2017. Our principal executive office is located at 830 Winter Street, Waltham, Massachusetts 02451, and our telephone number is (781) 999-0232. Our website address is https://www.q32bio.com. We do not incorporate the information on or accessible through our website into this prospectus, and you should not consider any information on, or that can be accessed through, our website as part of this prospectus. Our common stock is listed on Nasdaq under the symbol “QTTB.”

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On March 25, 2024, Kenobi Merger Sub, Inc., or Merger Sub, a wholly-owned subsidiary of Homology Medicines, Inc., or Homology, completed its merger with and into Q32 Bio Operations Inc. (previously named Q32 Bio Inc. and referred to herein as Legacy Q32), with Legacy Q32 continuing as the surviving entity as a wholly-owned subsidiary of Homology. This transaction is referred to herein as the Merger. Homology changed its name to Q32 Bio Inc., and Legacy Q32, which remains as a wholly-owned subsidiary of ours, changed its name to Q32 Bio Operations, Inc. The Merger was effected pursuant to an Agreement and Plan of Merger, or the Merger Agreement, dated as of November 16, 2023, by and among Homology, Legacy Q32, and Merger Sub. Effective March 26, 2024, our common stock began trading on the Nasdaq Global Market under the trading symbol “QTTB.”

Implications of Being a Smaller Reporting Company

We are a “smaller reporting company” as defined in the Exchange Act. We may take advantage of certain of the scaled disclosures available to smaller reporting companies and will be able to take advantage of these scaled disclosures for so long as the market value of the common stock held by non-affiliates is less than $250.0 million measured on the last business day of our second fiscal quarter, or our annual revenue is less than $100.0 million during the most recently completed fiscal year and the market value of the common stock held by non-affiliates is less than $700.0 million measured on the last business day of our second fiscal quarter. As a result, the information in this prospectus and that we provide to our investors in the future may be different than what you might receive from other public reporting companies.

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THE OFFERING

Issuer Q32 Bio Inc.

Common stock Offered by the Selling Stockholders 1,682,045 shares of common stock

Use of Proceeds We will not receive any proceeds from the sale of the shares of common stock covered by this prospectus. See the section titled “Use of Proceeds” appearing elsewhere in this prospectus for more information.

Nasdaq Symbol QTTB

Offering Price The selling stockholders will offer the shares of common stock offered by this prospectus at the prevailing market prices or at privately negotiated prices.

Risk Factors You should read the “Risk Factors” section of this prospectus and other information included and incorporated by reference in this prospectus for a discussion of factors to consider carefully before deciding to invest in shares of our common stock.

For additional information concerning the offering, see “Plan of Distribution” beginning on page 21.

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RISK FACTORS

Investing in our securities involves risks. Before you make a decision to buy our securities, in addition to the risks and uncertainties discussed above under “Cautionary Note Regarding Forward-Looking Statements,” you should carefully consider the risks factors incorporated herein by reference to our most recent Annual Report on Form 10-K and in any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K we file after the date of this prospectus, all other information contained or incorporated by reference into this prospectus, as updated by our subsequent filings under the Exchange Act, and the risk factors and other information contained in any applicable prospectus supplement. We operate in a dynamic and rapidly changing industry that involves numerous risks and uncertainties. If any of these risks actually occur, it may materially harm our business, financial condition, liquidity and results of operations. As a result, the market price of our securities could decline, and you could lose all or part of your investment. Additionally, the risks and uncertainties described in this prospectus or any prospectus supplement are not the only risks and uncertainties that we face. Additional risks and uncertainties not presently known to us or that we currently believe to be immaterial may become material and adversely affect our business.

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USE OF PROCEEDS

This prospectus relates to the potential resale from time to time of some or all of 1,682,045 shares of our common stock. The selling stockholders will receive all of the proceeds from any sale of such shares. We will not receive any proceeds from any sales of shares of our common stock by the selling stockholders.

We have agreed to bear the expenses in connection with the registration of the shares of common stock to be offered by this prospectus by the selling stockholders other than any underwriting discounts and commissions or transfer taxes relating to the sale of common stock, which will be borne by the selling stockholders.

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SELLING STOCKHOLDERS

The selling stockholders acquired shares of common stock from us in the Merger upon exchange of shares of Legacy Q32 acquired from Legacy Q32 immediately prior to the Merger pursuant to an exemption from registration under Section 4(a)(2) of the Securities Act. Pursuant to the registration rights agreement that we assumed in the Merger, we filed a registration statement with the SEC for the purposes of registering for resale from time to time the shares of common stock.

Except for the ownership of shares of common stock received in the Merger, the selling stockholders have not had any material relationship with our company within the past three years.

The table below lists the selling stockholders and other information regarding their ownership of the shares of common stock offered hereby. The second column lists the number of shares of common stock beneficially owned by the selling stockholders as of March 27, 2025 based on information obtained from the Selling Stockholders. The selling stockholders may have sold or transferred some or all of the common stock indicated below and may in the future sell or transfer some or all of the common stock indicated below in transactions exempt from the registration requirements of the Securities Act rather than under this prospectus. The third column lists the shares of common stock being offered by this prospectus by the selling stockholders. The fourth column assumes the sale of all of the shares of common stock offered by the selling stockholders pursuant to this prospectus. The selling stockholders may sell all, some or none of their shares of common stock in this offering. See “Plan of Distribution.”

Except as indicated by the footnotes below, we believe, based on the information furnished to us, that the selling stockholders have sole voting and investment power with respect to all shares of common stock that they own, subject to applicable community property laws. Beneficial ownership for the purposes of the table below is determined in accordance with the rules and regulations of the SEC. These rules generally provide that a person is the beneficial owner of securities if such person has or shares the power to vote or direct the voting thereof, or to dispose or direct the disposition thereof or has the right to acquire such powers within 60 days. Percentage of beneficial ownership is based on 12,197,615 shares of common stock outstanding as of March 27, 2025.

Name and Address of Selling Stockholders	Number of Shares Beneficially Owned Before the Offering		Number of Shares that May Be Offered Hereby(10)		Shares Beneficially Owned After the Offering
					Number		Percentage
Abingworth Bioventures VII LP(1)		1,102,741		208,031		894,710		7.34
Acorn Bioventures, L.P.(2)		803,425		151,565		651,860		5.34
Entities Affiliated with Atlas Venture(3)		2,092,106		394,674		1,697,432		13.92
Aventis Inc.(4)		244,083		46,046		198,037		1.62
Bristol-Myers Squibb Company(5)		200,244		200,244		—		—
CU Healthcare Innovation Fund, L.P.(6)		139,550		50,061		89,489		*
OrbiMed Private Investments VII, LP(7)		2,252,987		425,024		1,827,963		14.99
The Trustees of Columbia University in the City of New York(8)		133,903		25,260		108,643		*
Agent Capital Fund III LP(9)		60,097		60,097		—		—

* Less than 1%

(1) Shares listed under “Number of Shares Beneficially Owned Before Offering” consists of (i) 1,102,741 shares of our common stock held of record by Abingworth Bioventures VII LP, or ABV VII. The Carlyle Group Inc., which is a publicly traded entity listed on the Nasdaq Global Select Market, is the sole shareholder of Carlyle Holdings I GP Inc., which is the sole member of Carlyle Holdings I GP Sub L.L.C., which is the general partner of Carlyle Holdings I L.P., which, with respect to the securities reported herein,

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is the managing member of GG Subsidiary Holdings L.L.C., which is the managing member of TC Group, L.L.C., which is the managing member of Carlyle Investment Management, L.L.C., which is the sole member of Carlyle Genesis UK LLC, which is the principal member of Abingworth LLP. ABV VII has delegated to Abingworth LLP all investment and dispositive power over the securities held of record by ABV VII. As a result, each of the foregoing entities may be deemed to share beneficial ownership of the securities held of record by ABV VII, but each disclaims any such beneficial ownership. Voting and investment determinations with respect to the securities held by ABV VII are made by an investment committee of Abingworth LLP, which is comprised of Timothy Haines, Kurt von Emster, Bali Muralidhar and Andrew Sinclair. Each member of the investment committee disclaims beneficial ownership of the securities held of record by ABV VII. The address for each of Abingworth LLP and ABV VII is c/o Abingworth LLP, 38 Jermyn Street, London, England SW1Y 6DN. The address for each of the other entities named in this footnote is c/o The Carlyle Group, 1001 Pennsylvania Ave. NW, Suite 220 South, Washington, DC 20004-2505.

(2) Shares listed under “Number of Shares Beneficially Owned Before Offering” consists of (i) 803,425 shares held by Acorn Bioventures, L.P. The general partner of Acorn is Acorn Capital Advisors GP, LLC. Isaac Manke is a General Partner at Acorn and a member of Q32’s board of directors. The address for Acorn and Acorn Capital Advisors GP, LLC is 410 Lexington Ave, Suite 2626, New York, NY 10170.

(3) Shares listed under “Number of Shares Beneficially Owned Before Offering” consists of (i) 864,261 shares of our common stock held by Atlas Venture Fund X, L.P., or Atlas X, (ii) 503,296 shares of our common stock held by Atlas Venture Opportunity Fund I, L.P., or Atlas Opportunity I, and (iii) 724,549 shares of our common stock held by Atlas Venture Opportunity Fund II, L.P., or Atlas Opportunity II. The general partner of Atlas X is Atlas Venture Associates X, L.P., or AVA X, and the general partner of AVA X is Atlas Ventures Associates X, LLC, or AVA X LLC. The general partner of Atlas Opportunity I is Atlas Venture Associates Opportunity I, L.P., or AVAO I, and the general partner of AVAO I is Atlas Venture Associates Opportunity I, LLC, or AVAO I LLC. The general partner of Atlas Opportunity II is Atlas Venture Associates Opportunity II, L.P., or AVAO II, and the general partner of AVAO II is Atlas Venture Associates Opportunity II, LLC, or AVAO II LLC. David Grayzel is a member of AVA X LLC, AVAO I LLC, and AVAO II LLC, and is a member of Q32’s board of directors. Each of AVA X, AVA X LLC, AVAO I, AVAO I LLC, AVAO II, AVAO II LLC, and Mr. Grayzel may be deemed to beneficially own the shares held by Atlas X, Atlas Opportunity I, and Atlas Opportunity II. Each of AVA X, AVA X LLC, AVAO I, AVAO I LLC, AVAO II, AVAO II LLC, and Mr. Grayzel expressly disclaim beneficial ownership of the securities owned by Atlas X, Atlas Opportunity I, and Atlas Opportunity II, except to the extent of its pecuniary interest therein, if any. The address for Atlas X, AVA X, AVA X LLC, Atlas Opportunity I, AVAO I, AVAO I LLC, Atlas Opportunity II, AVAO II, AVAO II LLC is 300 Technology Sq., 8th Floor, Cambridge, MA 02139.

(4) Shares listed under “Number of Shares Beneficially Owned Before Offering” consists of 244,083 shares held by Aventis, Inc, or Aventis. Aventis is an indirect, wholly owned subsidiary of Sanofi, a French société anonyme (limited liability company), which may be deemed to have sole voting and dispositive power over the securities held by Aventis. The address for Aventis is 100 Morris Ave, Morristown, NJ 07960.

(5) Shares listed under “Number of Shares Beneficially Owned Before Offering” consists of 200,244 shares of our common stock held by Bristol-Myers Squibb Company, or BMS. The address for BMS is Route 206 & Province Line Road, Princeton, NJ 08543-4000.

(6) Shares listed under “Number of Shares Beneficially Owned Before Offering” consists of 139,550 shares held by CU Healthcare Innovation Fund L.P., or CU Healthcare. The natural persons that have power to vote or dispose of the shares are Steven Lindseth and Kimberly Muller, each of whom disclaim beneficial ownership of the shares held by CU Healthcare. The address for CU Healthcare is 12635 East Montview Blvd., Suite 100, Aurora, Colorado 80045.

(7) Shares listed under “Number of Shares Beneficially Owned Before Offering” consists of 2,252,987 shares held by OrbiMed Private Investments VII, LP. Securities are held of record by OrbiMed Private Investments VII, LP, or OPI VII. OrbiMed Capital GP VII LLC, or GP VII, is the general partner of OPI VII, and OrbiMed Advisors LLC, or OrbiMed Advisors, is the managing member of GP VII. By virtue of such relationships, GP VII and Advisors may be deemed to have voting power and investment power over the

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securities held by OPI VII and as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Advisors exercises voting and investment power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the shares held by OPI VII. Diyong Xu, a member of Q32’s board of directors, is an employee of OrbiMed Advisors. The address for the OrbiMed entities is c/o OrbiMed Advisors LLC, 601 Lexington Avenue, 54th Floor, New York, NY 10022.

(8) Shares listed under “Number of Shares Beneficially Owned Before Offering” consists of 133,903 shares held by the Trustees of Columbia University in the City of New York. The Trustees of Columbia University in the City of New York may be deemed to have voting and dispositive power over the securities held by the selling stockholder. The address for the Trustees of Columbia University in the City of New York is 1177 Avenue of the Americas, 34^th Floor, New York, NY 10036.

(9) Shares listed under “Number of Shares Beneficially Owned Before Offering” consists of 60,097 shares held by Agent Capital Fund III LP. Agent Capital Fund III LP is a Delaware limited partnership whose general partner is Agent Capital Fund III GP, LLC, or Agent GP, a Delaware limited liability company. Geeta Vemuri is the managing member of Agent GP and exercises voting and investment power with respect to the shares owned by Agent Capital Fund III LP. Agent GP and Ms. Vemuri disclaim beneficial ownership of all shares held by Agent Capital Fund III LP, except to the extent of their respective pecuniary interests therein. The principal business address of Agent Capital Fund III LP is 1400 Main Street, Floor 1, Waltham MA 02451.

(10) No other shares of common stock, including, without limitation, shares of common stock acquired in the open market are being offered under this prospectus.

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DESCRIPTION OF CAPITAL STOCK

The following description summarizes some of the terms of our restated certificate of incorporation and amended and restated bylaws and of the Delaware General Corporation Law. This description is summarized from, and qualified in its entirety by reference to, our restated certificate of incorporation and amended and restated bylaws, each of which has been publicly filed with the SEC.

Our authorized capital stock consists of:

• 400,000,000 shares of common stock, par value $0.0001 per share; and

• 10,000,000 shares of preferred stock, par value $0.0001 per share

Common Stock

Our common stock is listed on Nasdaq under the symbol “QTTB.”

Voting Rights. Holders of our common stock are entitled to one vote for each share held on all matters submitted to a vote of stockholders and do not have cumulative voting rights. An election of directors by our stockholders shall be determined by a plurality of the votes cast by the stockholders entitled to vote on the election. Subject to the supermajority votes for some matters, other matters shall be decided by the affirmative vote of our stockholders having a majority in voting power of the votes cast by the stockholders present or represented and voting on such matter. Our restated certificate of incorporation and amended and restated bylaws also provide that our directors may be removed only for cause and only by the affirmative vote of the holders of at least two-thirds in voting power of the outstanding shares of capital stock entitled to vote thereon. In addition, the affirmative vote of the holders of at least two-thirds in voting power of the outstanding shares of capital stock entitled to vote thereon is required to amend or repeal, or to adopt any provision inconsistent with, several of the provisions of our restated certificate of incorporation. See below under “-Anti-Takeover Effects of Delaware Law and Our Certificate of Incorporation and Bylaws-Amendment of Charter Provisions.”

Rights Upon Liquidation. In the event of our liquidation or dissolution, the holders of common stock are entitled to receive proportionately our net assets available for distribution to stockholders after the payment of all debts and other liabilities and subject to the prior rights of any outstanding preferred stock.

Other Rights. Holders of common stock have no preemptive, subscription, redemption or conversion rights. Our outstanding shares of common stock are, when issued and paid for, validly issued, fully paid and nonassessable. The rights, preferences and privileges of holders of common stock are subject to and may be adversely affected by the rights of the holders of shares of any series of preferred stock that we may designate and issue in the future.

Transfer Agent

The transfer agent and registrar for our common stock is Equiniti Trust Company, LLC.

Dividend

Holders of common stock are entitled to receive proportionately any dividends as may be declared by our board of directors, subject to any preferential dividend rights of outstanding preferred stock. We have never declared or paid any cash dividends on our common stock. We do not intend to declare or pay cash dividends for the foreseeable future. We currently expect to retain all future earnings, if any, for use in the development, operation and expansion of our business. Any determination to pay cash dividends in the future will depend upon, among other things, our results of operations, plans for expansion, tax considerations, available net profits and reserves, limitations under law, financial condition, capital requirements and other factors that our board of directors considers to be relevant.

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Preferred Stock

Under the terms of our restated certificate of incorporation, our board of directors is authorized to issue shares of preferred stock in one or more series without stockholder approval. Our board of directors have the discretion to determine the rights, preferences, privileges and restrictions, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences, of each series of preferred stock.

The purpose of authorizing the board of directors to issue preferred stock and determine its rights and preferences is to eliminate delays associated with a stockholder vote on specific issuances. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions, future financings and other corporate purposes, could have the effect of making it more difficult for a third party to acquire, or could discourage a third party from seeking to acquire, a majority of Homology’s outstanding voting stock.

Registration Rights

In connection with the Merger Agreement, Legacy Q32 entered into a subscription agreement in November 2023, or the Subscription Agreement, with certain investors to consummate their purchase of shares of Legacy Q32’s common stock for an aggregate purchase price of $42.0 million, or the Pre-Closing Financing. Pursuant to the Subscription Agreement, on March 25, 2024, we entered into a registration rights agreement, or the Registration Rights Agreement, with the investors in the Pre-Closing Financing. Under the Registration Rights Agreement, among other things, we agreed to register for resale certain shares of our common stock held by such investors from time to time, including shares of our common stock issued in the Merger in exchange for the shares of Legacy Q32 common stock issued in the Pre-Closing Financing.

Pursuant to the Registration Rights Agreement, we are obligated to prepare and file a shelf registration statement covering the resale of covered shares of our common stock within forty-five (45) calendar days following the closing of the Merger, subject to certain exceptions, pursuant to Rule 415 of the Securities Act. We also agreed to use our reasonable best efforts to keep such registration statement continuously effective under the Securities Act until the earlier of the date that all registrable securities covered by such registration statement (a) have been sold, thereunder or pursuant to Rule 144 of the Securities Act, or Rule 144, or (b) may be sold without volume or manner-of-sale restrictions pursuant to Rule 144 and without the requirement for us to be in compliance with the current public information requirement under Rule 144. The registration rights agreement also provides that we will pay certain expenses of the securityholders and indemnify the applicable securityholders against certain liabilities.

Anti-Takeover Effects of Delaware Law and Our Certificate of Incorporation and Bylaws

Some provisions of the Delaware law, our restated certificate of incorporation and amended and restated bylaws could make the following transactions more difficult: an acquisition by means of a tender offer; an acquisition by means of a proxy contest or otherwise; or the removal incumbent officers and directors. It is possible that these provisions could make it more difficult to accomplish or could deter transactions that stockholders may otherwise consider to be in their best interest or in our best interests, including transactions which provide for payment of a premium over the market price for our shares.

These provisions, summarized below, are intended to discourage coercive takeover practices and inadequate takeover bids. These provisions are also designed to encourage persons seeking to acquire control of our company to first negotiate with our board of directors. We believe that the benefits of the increased protection of our potential ability to negotiate with the proponent of an unfriendly or unsolicited proposal to acquire or restructure Homology outweigh the disadvantages of discouraging these proposals because negotiation of these proposals could result in an improvement of their terms.

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Undesignated Preferred Stock

The ability of our board of directors, without action by the stockholders, to issue up to 10,000,000 shares of undesignated preferred stock with voting or other rights or preferences as designated by our board of directors could impede the success of any attempt to change control of it. These and other provisions may have the effect of deferring hostile takeovers or delaying changes in control or management.

Stockholder Meetings

Our amended and restated bylaws provide that a special meeting of stockholders may be called only by our chairman of the board, chief executive officer or president (in the absence of a chief executive officer), or by a resolution adopted by a majority of our board of directors.

Requirements for Advance Notification of Stockholder Nominations and Proposals

Our amended and restated bylaws establish advance notice procedures with respect to stockholder proposals to be brought before a stockholder meeting and the nomination of candidates for election as directors, other than nominations made by or at the direction of the board of directors or a committee of the board of directors.

Elimination of Stockholder Action by Written Consent

Our restated certificate of incorporation eliminates the right of stockholders to act by written consent without a meeting.

Staggered Board

Our board of directors is divided into three classes. The directors in each class will serve for a three-year term, one class being elected each year by our stockholders. This system of electing and removing directors may tend to discourage a third party from making a tender offer or otherwise attempting to obtain control of our company, because it generally makes it more difficult for stockholders to replace a majority of the directors.

Removal of Directors

Our restated certificate of incorporation and amended and restated bylaws provide that, subject to the rights of holders of any series of preferred stock, no member of our board of directors may be removed from office by our stockholders except for cause and, in addition to any other vote required by law, upon the approval of the holders of at least two-thirds in voting power of the outstanding shares of capital stock entitled to vote in the election of directors. Subject to the rights of holders of any series of preferred stock, any vacancy on our board of directors, including a vacancy resulting from an enlargement of our board of directors, may be filled only by vote of a majority of directors then in office, unless our board of directors determines by resolution that any such vacancy or newly created directorship shall be filled by our stockholders.

Stockholders Not Entitled to Cumulative Voting

Our restated certificate of incorporation does not permit stockholders to cumulate their votes in the election of directors. Accordingly, the holders of a majority of the outstanding shares of our common stock entitled to vote in any election of directors can elect all of the directors standing for election, if they choose, other than any directors that holders of our preferred stock may be entitled to elect.

Delaware Anti-Takeover Statute

We are subject to Section 203 of the General Corporation Law of the State of Delaware, which prohibits persons deemed to be “interested stockholders” from engaging in a “business combination” with a publicly held Delaware corporation for three years following the date these persons become interested stockholders unless the

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business combination is, or the transaction in which the person became an interested stockholder was, approved in a prescribed manner or another prescribed exception applies. Generally, an “interested stockholder” is a person who, together with affiliates and associates, owns, or within three years prior to the determination of interested stockholder status did own, 15% or more of a corporation’s voting stock. Generally, a “business combination” includes a merger, asset or stock sale, or other transaction resulting in a financial benefit to the interested stockholder. The existence of this provision may have an anti-takeover effect with respect to transactions not approved in advance by the board of directors.

Choice of Forum

Our restated certificate of incorporation provides that, unless we consent in writing to an alternative forum, the Court of Chancery of the State of Delaware will be the sole and exclusive forum for: (1) any derivative action or proceeding brought on our behalf; (2) any action asserting a claim of breach of a fiduciary duty or other wrongdoing by any of our directors, officers, employees or agents to us or our stockholders; (3) any action asserting a claim against it arising pursuant to any provision of the General Corporation Law of the State of Delaware or our restated certificate of incorporation or amended and restated bylaws; or (4) any action asserting a claim governed by the internal affairs doctrine. Our restated certificate of incorporation also provides that any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock will be deemed to have notice of and to have consented to this choice of forum provision. It is possible that a court of law could rule that the choice of forum provision contained in our restated certificate of incorporation is inapplicable or unenforceable if it is challenged in a proceeding or otherwise.

In addition, our amended and restated bylaws provide that unless we consent in writing to the selection of an alternative forum, to the fullest extent permitted by law, the federal district courts of the United States of America shall be the exclusive forum for the resolution of any complaint asserting a cause of action arising under the Securities Act, and any person or entity purchasing or otherwise acquiring or holding any interest in our shares of capital stock shall be deemed to have notice of and consented to this choice of forum provision.

Amendment of Charter Provisions

The amendment of any of the above provisions, except for the provision making it possible for our board of directors to issue preferred stock and the provision prohibiting cumulative voting, would require approval by holders of at least two-thirds in voting power of the outstanding shares of capital stock entitled to vote thereon.

The provisions of Delaware law, our restated certificate of incorporation and amended and restated bylaws could have the effect of discouraging others from attempting hostile takeovers and, as a consequence, they may also inhibit temporary fluctuations in the market price of our common stock that often result from actual or rumored hostile takeover attempts. These provisions may also have the effect of preventing changes in the composition of our board and management. It is possible that these provisions could make it more difficult to accomplish transactions that stockholders may otherwise deem to be in their best interests.

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MATERIAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS

Material U.S. Federal Income Tax Consequences for Holders of Common Stock

The following is a discussion of certain material U.S. federal income tax consequences of the acquisition, ownership and disposition of our shares of common stock, which we refer to as our securities. This discussion applies only to securities that are held as capital assets for U.S. federal income tax purposes and is applicable only to holders who are receiving our securities in this offering.

This discussion is a summary only and does not describe all of the tax consequences that may be relevant to you in light of your particular circumstances, including but not limited to the alternative minimum tax, the Medicare tax on certain investment income and the different consequences that may apply if you are subject to special rules that apply to certain types of investors (such as the effects of Section 451 of the Code), including but not limited to:

• financial institutions or financial services entities;

• broker-dealers;

• governments or agencies or instrumentalities thereof;

• regulated investment companies;

• real estate investment trusts;

• expatriates or former long-term residents of the United States;

• persons that actually or constructively own 5% or more of our voting shares;

• insurance companies;

• dealers or traders subject to a mark-to-market method of accounting with respect to the securities;

• persons holding the securities as part of a “straddle,” hedge, integrated transaction or similar transaction;

• U.S. holders (as defined below) whose functional currency is not the U.S. dollar;

• partnerships or other pass-through entities for U.S. federal income tax purposes and any beneficial owners of such entities; and

• tax-exempt entities.

This discussion is based on the Code, and administrative pronouncements, judicial decisions and final, temporary and proposed Treasury regulations as of the date hereof, which are subject to change, possibly on a retroactive basis, and changes to any of which subsequent to the date of this prospectus may affect the tax consequences described herein. This discussion does not address any aspect of state, local or non-U.S. taxation, or any U.S. federal taxes other than income taxes (such as gift and estate taxes).

We have not sought, and will not seek, a ruling from the Internal Revenue Service, or the IRS, as to any U.S. federal income tax consequence described herein. The IRS may disagree with the discussion herein, and its determination may be upheld by a court. Moreover, there can be no assurance that future legislation, regulations, administrative rulings or court decisions will not adversely affect the accuracy of the statements in this discussion. You are urged to consult your tax advisor with respect to the application of U.S. federal tax laws to your particular situation, as well as any tax consequences arising under the laws of any state, local or foreign jurisdiction.

This discussion does not consider the tax treatment of partnerships or other pass-through entities or persons who hold our securities through such entities. If a partnership (or other entity or arrangement classified as a

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partnership or other pass-through entity for U.S. federal income tax purposes) is the beneficial owner of our securities, the U.S. federal income tax treatment of a partner or member in the partnership or other pass-through entity generally will depend on the status of the partner or member and the activities of the partnership or other pass-through entity. If you are a partner or member of a partnership or other pass-through entity holding our securities, we urge you to consult your tax advisor.

THIS DISCUSSION IS ONLY A SUMMARY OF CERTAIN UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS ASSOCIATED WITH THE ACQUISITION, OWNERSHIP AND DISPOSITION OF OUR SECURITIES. EACH PROSPECTIVE INVESTOR IN OUR SECURITIES IS URGED TO CONSULT ITS TAX ADVISOR WITH RESPECT TO THE PARTICULAR TAX CONSEQUENCES TO SUCH INVESTOR OF THE ACQUISITION, OWNERSHIP AND DISPOSITION OF OUR SECURITIES, INCLUDING THE APPLICABILITY AND EFFECT OF ANY UNITED STATES FEDERAL NON-INCOME, STATE AND LOCAL, AND NON-U.S. TAX LAWS.

Material U.S. Federal Income Tax Consequences for U.S. Holders

For purposes of this discussion, a “U.S. Holder” is any beneficial owner of our common stock that, for U.S. federal income tax purposes, is or is treated as:

• an individual who is a citizen or resident of the United States;

• a corporation created or organized in or under the laws of the United States, any state thereof, or the District of Columbia;

• an estate, the income of which is subject to U.S. federal income tax regardless of its source; or

• a trust that (1) is subject to the primary supervision of a U.S. court and all substantial decisions of which are subject to the control of one or more “United States persons” (within the meaning of Section 7701(a)(30) of the Code), or (2) has a valid election in effect to be treated as a United States person for U.S. federal income tax purposes.

Taxation of Distributions. If we pay distributions in cash or other property (other than certain distributions of our stock or rights to acquire our stock) to U.S. holders of shares of common stock, such distributions generally will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Distributions in excess of current and accumulated earnings and profits will constitute a return of capital that will be applied against and reduce (but not below zero) the U.S. holder’s adjusted tax basis in common stock. Any remaining excess will be treated as gain realized on the sale or other disposition of the common stock and will be treated as described under “U.S. Holders-Gain or Loss on Sale, Taxable Exchange or Other Taxable Disposition of common stock” below.

Dividends we pay to a U.S. holder that is a taxable corporation generally will qualify for the dividends received deduction if the requisite holding period is satisfied. With certain exceptions (including, but not limited to, dividends treated as investment income for purposes of investment interest deduction limitations), and provided certain holding period requirements are met, dividends we pay to a non-corporate U.S. holder may constitute “qualified dividends” that will be subject to tax at the maximum tax rate accorded to long-term capital gains. If the holding period requirements are not satisfied, then a corporation may not be able to qualify for the dividends received deduction and would have taxable income equal to the entire dividend amount, and non-corporate holders may be subject to tax on such dividend at regular ordinary income tax rates instead of the preferential rate that applies to qualified dividend income.

Gain or Loss on Sale, Taxable Exchange or Other Taxable Disposition of common stock. Upon a sale or other taxable disposition of common stock, a U.S. holder generally will recognize capital gain or loss in an amount equal to the difference between the amount realized and the U.S. holder’s adjusted tax basis in the

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common stock. Any such capital gain or loss generally will be long-term capital gain or loss if the U.S. holder’s holding period for the common stock so disposed of exceeds one year. If the holding period requirements are not satisfied, any gain on a sale or taxable disposition of the shares would be subject to short-term capital gain treatment and would be taxed at regular ordinary income tax rates. Long-term capital gains recognized by non-corporate U.S. holders will be eligible to be taxed at reduced rates. The deductibility of capital losses is subject to limitations.

Generally, the amount of gain or loss recognized by a U.S. holder is an amount equal to the difference between (i) the sum of the amount of cash and the fair market value of any property received in such disposition and (ii) the U.S. holder’s adjusted tax basis in its common stock so disposed of. A U.S. holder’s adjusted tax basis in its common stock generally will equal the U.S. holder’s acquisition cost for the common stock or less, in the case of a share of common stock, any prior distributions treated as a return of capital. In the case of any shares of common stock originally acquired as part of an investment unit, the acquisition cost for the share of common stock that were part of such unit would equal an allocable portion of the acquisition cost of the unit based on the relative fair market values of the components of the unit at the time of acquisition.

Information Reporting and Backup Withholding. In general, information reporting requirements may apply to dividends paid to a U.S. holder and to the proceeds of the sale or other disposition of our shares of common stock, unless the U.S. holder is an exempt recipient. Backup withholding may apply to such payments if the U.S. holder fails to provide a taxpayer identification number, a certification of exempt status or has been notified by the IRS that it is subject to backup withholding (and such notification has not been withdrawn).

Any amounts withheld under the backup withholding rules generally should be allowed as a refund or a credit against a U.S. holder’s U.S. federal income tax liability provided the required information is timely furnished to the IRS.

Material U.S. Federal Income Tax Consequences for Non-U.S. Holders

This section applies to you if you are a “Non-U.S. holder.” As used herein, the term “Non-U.S. holder” means a beneficial owner of common stock who or that is for U.S. federal income tax purposes:

• a non-resident alien individual (other than certain former citizens and residents of the U.S. subject to U.S. tax as expatriates);

• a foreign corporation or

• an estate or trust that is not a U.S. holder;

but generally does not include an individual who is present in the United States for 183 days or more in the taxable year of disposition. If you are such an individual, you should consult your tax advisor regarding the U.S. federal income tax consequences of the acquisition, ownership or sale or other disposition of our securities.

Taxation of Distributions. In general, any distributions we make to a Non-U.S. holder of shares of common stock, to the extent paid out of our current or accumulated earnings and profits (as determined under U.S. federal income tax principles), will constitute dividends for U.S. federal income tax purposes and, provided such dividends are not effectively connected with the Non-U.S. holder’s conduct of a trade or business within the United States, we will be required to withhold tax from the gross amount of the dividend at a rate of 30%, unless such Non-U.S. holder is eligible for a reduced rate of withholding tax under an applicable income tax treaty and provides proper certification of its eligibility for such reduced rate (usually on an IRS Form W-8BEN or W-8BEN-E). Any distribution not constituting a dividend will be treated first as reducing (but not below zero) the Non-U.S. holder’s adjusted tax basis in its shares of common stock and, to the extent such distribution exceeds the Non-U.S. holder’s adjusted tax basis, as gain realized from the sale or other disposition of the common stock, which will be treated as described under “Non-U.S. Holders-Gain on Sale, Taxable Exchange or Other Taxable Disposition of common stock” below.

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The withholding tax does not apply to dividends paid to a Non-U.S. holder who provides a Form W-8ECI, certifying that the dividends are effectively connected with the Non-U.S. holder’s conduct of a trade or business within the United States. Instead, the effectively connected dividends will be subject to regular U.S. income tax as if the Non-U.S. holder were a U.S. resident, subject to an applicable income tax treaty providing otherwise. A Non-U.S. corporation receiving effectively connected dividends may also be subject to an additional “branch profits tax” imposed at a rate of 30% (or a lower treaty rate).

Gain on Sale, Taxable Exchange or Other Taxable Disposition of common stock. A Non-U.S. holder generally will not be subject to U.S. federal income or withholding tax in respect of gain recognized on a sale, taxable exchange or other taxable disposition of common stock, unless:

• the gain is effectively connected with the conduct of a trade or business by the Non-U.S. holder within the United States (and, under certain income tax treaties, is attributable to a United States permanent establishment or fixed base maintained by the Non-U.S. holder); or

• we are or have been a “U.S. real property holding corporation” for U.S. federal income tax purposes at any time during the shorter of the five-year period ending on the date of disposition or the period that the Non-U.S. holder held common stock, and, in the case where shares of common stock are regularly traded on an established securities market, the Non-U.S. holder has owned, directly or constructively, more than 5% of common stock at any time within the shorter of the five-year period preceding the disposition or such Non-U.S. holder’s holding period for the shares of common stock. There can be no assurance that common stock will be treated as regularly traded on an established securities market for this purpose.

Unless an applicable treaty provides otherwise, gain described in the first bullet point above will be subject to tax at generally applicable U.S. federal income tax rates as if the Non-U.S. holder were a U.S. resident. Any gains described in the first bullet point above of a Non-U.S. holder that is a foreign corporation may also be subject to an additional “branch profits tax” at a 30% rate (or lower treaty rate).

If the second bullet point above applies to a Non-U.S. holder, gain recognized by such holder on the sale, exchange or other disposition of common stock will be subject to tax at generally applicable U.S. federal income tax rates.

Information Reporting and Backup Withholding. Information returns will be filed with the IRS in connection with payments of dividends and the proceeds from a sale or other disposition of our shares of common stock. A Non-U.S. holder may have to comply with certification procedures to establish that it is not a United States person in order to avoid information reporting and backup withholding requirements. The certification procedures required to claim a reduced rate of withholding under a treaty will satisfy the certification requirements necessary to avoid the backup withholding as well. The amount of any backup withholding from a payment to a Non-U.S. holder will be allowed as a credit against such holder’s U.S. federal income tax liability and may entitle such holder to a refund, provided that the required information is timely furnished to the IRS.

FATCA Withholding Taxes. Provisions commonly referred to as “FATCA” impose withholding of 30% on payments of dividends (including constructive dividends) on common stock to “foreign financial institutions” (which is broadly defined for this purpose and in general includes investment vehicles) and certain other Non-U.S. entities unless various U.S. information reporting and due diligence requirements (generally relating to ownership by U.S. persons of interests in or accounts with those entities) have been satisfied by, or an exemption applies to, the payee (typically certified as to by the delivery of a properly completed IRS Form W-8BEN-E). Pursuant to proposed Treasury Regulations, the U.S. Treasury Department has indicated its intent to eliminate the requirement under FATCA of withholding on gross proceeds from the sale or other disposition of property of a type which can produce U.S. source dividends or interest. The U.S. Treasury Department has indicated that taxpayers may rely on these proposed Treasury Regulations pending their finalization. Foreign financial

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institutions located in jurisdictions that have an intergovernmental agreement with the United States governing FATCA may be subject to different rules. Under certain circumstances, a Non-U.S. holder might be eligible for refunds or credits of such withholding taxes, and a Non-U.S. holder might be required to file a U.S. federal income tax return to claim such refunds or credits. Prospective investors should consult their tax advisers regarding the effects of FATCA on their investment in our securities.

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PLAN OF DISTRIBUTION

Each selling stockholder of the securities and any of their pledgees, assignees, donees, transferees or other successors-in-interest may, from time to time, sell, transfer or otherwise dispose of any or all of their securities covered hereby on the Nasdaq Global Select Market, the Nasdaq Global Market, the Nasdaq Capital Market, or the New York Stock Exchange or any other stock exchange, market or trading facility on which the securities are traded or in private transactions. These sales may be at fixed or negotiated prices. A selling stockholder may use any one or more of the following methods when selling securities:

• ordinary brokerage transactions and transactions in which the broker-dealer solicits purchasers;

• block trades in which the broker-dealer will attempt to sell the securities as agent but may position and resell a portion of the block as principal to facilitate the transaction;

• purchases by a broker-dealer as principal and resale by the broker-dealer for its account;

• an exchange distribution in accordance with the rules of the applicable exchange;

• privately negotiated transactions;

• settlement of short sales entered into after the effective date of the registration statement of which this prospectus is a part;

• in transactions through broker-dealers that agree with the selling stockholders to sell a specified number of such securities at a stipulated price per security;

• through the writing or settlement of options or other hedging transactions, whether through an options exchange or otherwise;

• a combination of any such methods of sale; or

• any other method permitted pursuant to applicable law.

The selling stockholders may also sell securities under Rule 144 or any other exemption from registration under the Securities Act, if available, rather than under this prospectus.

Broker-dealers engaged by the selling stockholders may arrange for other brokers-dealers to participate in sales. Broker-dealers may receive commissions or discounts from the selling stockholders (or, if any broker-dealer acts as agent for the purchaser of securities, from the purchaser) in amounts to be negotiated, but, except as set forth in a supplement to this prospectus, in the case of an agency transaction not in excess of a customary brokerage commission in compliance with FINRA Rule 2121; and in the case of a principal transaction a markup or markdown in compliance with FINRA Rule 2121.

In connection with the sale of the securities or interests therein, the selling stockholders may enter into hedging transactions with broker-dealers or other financial institutions, which may in turn engage in short sales of the securities in the course of hedging the positions they assume. The selling stockholders may also sell securities short and deliver these securities to close out their short positions, or loan or pledge the securities to broker-dealers that in turn may sell these securities. The selling stockholders may also enter into option or other transactions with broker-dealers or other financial institutions or create one or more derivative securities that require the delivery to such broker-dealer or other financial institution of securities offered by this prospectus, which securities such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction). The selling stockholders also may transfer the securities in other circumstances, in which case the transferees, pledgees, donees or other successors in interest will be the selling beneficial owners for purposes of this prospectus.

The selling stockholders and any broker-dealers or agents that are involved in selling the securities may be deemed to be “underwriters” within the meaning of the Securities Act in connection with such sales (it being

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understood that the selling stockholders shall not be deemed to be underwriters solely as a result of their participation in this offering). In such event, any commissions received by such broker-dealers or agents and any profit on the resale of the securities purchased by them may be deemed to be underwriting commissions or discounts under the Securities Act. Each selling stockholder has informed us that it does not have any written or oral agreement or understanding, directly or indirectly, with any person to distribute the securities.

We are required to pay certain fees and expenses incurred by us incident to the registration of the securities. We have agreed to indemnify the selling stockholders against certain losses, claims, damages and liabilities, including liabilities under the Securities Act.

We agreed to keep this prospectus effective until the earlier of the date that the securities (i) have been sold, pursuant to this prospectus or pursuant to Rule 144, or (ii) the date on which the securities may be resold by the selling stockholders without registration and without regard to any volume or manner-of-sale limitations by reason of Rule 144, and without the requirement for us to be in compliance with the current public information under Rule 144 under the Securities Act or any other rule of similar effect. The resale securities will be sold only through registered or licensed brokers or dealers if required under applicable state securities laws. In addition, in certain states, the resale securities covered hereby may not be sold unless they have been registered or qualified for sale in the applicable state or an exemption from the registration or qualification requirement is available and is complied with.

Under applicable rules and regulations under the Exchange Act, any person engaged in the distribution of the resale securities may not simultaneously engage in market making activities with respect to the common stock for the applicable restricted period, as defined in Regulation M, prior to the commencement of the distribution. In addition, the selling stockholders will be subject to applicable provisions of the Exchange Act and the rules and regulations thereunder, including Regulation M, which may limit the timing of purchases and sales of the common stock by the selling stockholders or any other person. We will make copies of this prospectus and any appliable prospectus supplement available to the selling stockholders and have informed them of the need to deliver a copy of this prospectus and any appliable prospectus supplement to each purchaser at or prior to the time of the sale (including by compliance with Rule 172 under the Securities Act).

We will not receive any proceeds from sales of any shares of common stock by the selling stockholders.

We cannot assure you that the selling stockholders will sell all or any portion of the shares of common stock offered hereby. We are registering the resale of shares of our common stock to provide the selling stockholders with freely tradable securities, but the registration of such shares does not necessarily mean that any of such shares will be offered or sold by the selling stockholders pursuant to this prospectus or at all.

To the extent required, this prospectus may be amended and/or supplemented from time to time to describe a specific plan of distribution.

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LEGAL MATTERS

The validity of the common stock being offered by this prospectus has been passed upon for us by Goodwin Procter LLP, Boston, Massachusetts.

EXPERTS

The consolidated financial statements of Q32 Bio Inc. appearing in Q32 Bio Inc.’s Annual Report (Form 10-K) for the year ended December 31, 2024, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon, included therein, and incorporated herein by reference. Such financial statements are, and audited financial statements to be included in subsequently filed documents will be, incorporated herein by reference in reliance upon the report of Ernst & Young LLP pertaining to such financial statements (to the extent covered by consents filed with the Securities and Exchange Commission) given on the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the informational requirements of the Exchange Act and in accordance therewith, file annual, quarterly and current reports, proxy statements and other information with the SEC electronically, and the SEC maintains a website that contains our filings as well as reports, proxy and information statements, and other information issuers file electronically with the SEC at www.sec.gov.

We also make available free of charge on or through our website at www.q32bio.com, our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act as soon as reasonably practicable after we electronically file such material with or otherwise furnishes it to the SEC. The website addresses are inactive textual references and except as specifically incorporated by reference into this prospectus, information on those websites is not part of this prospectus.

This prospectus and any prospectus supplement are part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. The full registration statement may be obtained from the SEC or us, as provided below. Other documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement or documents incorporated by reference in the registration statement. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may inspect a copy of the registration statement through the SEC’s website, as provided above.

INCORPORATION BY REFERENCE

The SEC allows us to incorporate by reference into this prospectus the information contained in other documents we file with the SEC, which means that we can disclose important information to you by referring you to those documents. Any statement contained in any document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded, for purposes of this prospectus, to the extent that a statement contained in or omitted from this prospectus, or in any other subsequently filed document that also is or is deemed to be incorporated by reference herein, modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus. We incorporate by reference the documents listed below which have been filed by us:

• Annual Report on  Form 10-K for the fiscal year ended December 31, 2024, filed with the SEC on March 11, 2025;

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• Current Reports on Form 8-K filed with the SEC on February 10, 2025 and March 10, 2025; and

• The description of the Registrant’s Common Stock contained in (i)  the Registration Statement on Form 8-A (File No. 001-38433), filed by the Registrant with the Commission under Section 12(b) of the Exchange Act on March 19, 2018, including any amendments or reports filed for the purpose of updating such description and (ii)  Exhibit 4.1—Description of Securities to Amendment No. 1 to our Annual Report on Form 10-K/A, as filed with the Commission on April 12, 2024.

All documents we file with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, except as to any portion of any report or documents that is not deemed filed under such provisions, (i) on or after the date of filing of the registration statement containing this prospectus and prior to the effectiveness of the registration statement and (ii) on or after the date of this prospectus until the earlier of the date on which all of the securities registered hereunder have been sold or the registration statement of which this prospectus is a part has been withdrawn, shall be deemed incorporated by reference in this prospectus and to be a part of this prospectus from the date of filing of those documents and will be automatically updated and, to the extent described above, supersede information contained or incorporated by reference in this prospectus and previously filed documents that are incorporated by reference in this prospectus.

Nothing in this prospectus shall be deemed to incorporate information furnished but not filed with the SEC pursuant to Item 2.02, 7.01 or 9.01 of Form 8-K. Upon written or oral request, we will provide without charge to each person, including any beneficial owner, to whom a copy of the prospectus is delivered a copy of any or all of the reports or documents incorporated by reference herein (other than exhibits to such documents, unless such exhibits are specifically incorporated by reference herein). You may request a copy of these filings, at no cost, by writing or telephoning us at the following address or phone number:

Q32 Bio Inc.

830 Winter Street

Waltham, MA 02451

Attn: Investor Relations

(781) 999-0232

Email: IR@q32bio.com

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Up to 1,682,045 Shares of Common Stock

PROSPECTUS

, 2025

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution.

The following is an estimate of the expenses (all of which are to be paid by the registrant) that we may incur in connection with the securities being registered hereby.

	Amount
SEC registration fee	$	6,479*
FINRA filing fee		**
Legal fees and expenses		**
Accounting fees and expenses		**
Miscellaneous		**
Total	$	**

* Previously paid.

** These fees are calculated based on the securities offered and the number of issuances and accordingly cannot be defined at this time.

Item 15. Indemnification of Directors and Officers.

Section 145 of the Delaware General Corporation Law, or the DGCL authorizes a corporation to indemnify its directors and officers against liabilities arising out of actions, suits and proceedings to which they are made or threatened to be made a party by reason of the fact that they have served or are currently serving as a director or officer to a corporation. The indemnity may cover expenses (including attorneys’ fees) judgments, fines and amounts paid in settlement actually and reasonably incurred by the director or officer in connection with any such action, suit or proceeding. Section 145 permits corporations to pay expenses (including attorneys’ fees) incurred by directors and officers in advance of the final disposition of such action, suit or proceeding. In addition, Section 145 provides that a corporation has the power to purchase and maintain insurance on behalf of its directors and officers against any liability asserted against them and incurred by them in their capacity as a director or officer, or arising out of their status as such, whether or not the corporation would have the power to indemnify the director or officer against such liability under Section 145.

Section 102(b)(7) of the DGCL provides that a corporation’s certificate of incorporation may contain a provision eliminating or limiting the personal liability of a director or officer to the corporation or its stockholders for monetary damages for breach of fiduciary duty, provided that such provision shall not eliminate or limit the liability (i) for any breach of the duty of loyalty to the corporation or its stockholders, (ii) for acts or omissions not in good faith or that involve intentional misconduct or a knowing violation of law, (iii) under Section 174 of the DGCL, or (iv) for any transaction from which an improper personal benefit was derived. The Bylaws provide that we will indemnify each person who was or is a party or threatened to be made a party to any threatened, pending or completed action, suit or proceeding (other than an action by or in the right of us) by reason of the fact that he or she is or was, or has agreed to become, a director or officer, or is or was serving, or has agreed to serve, at our request as a director, officer, partner, employee or trustee of, or in a similar capacity with, another corporation, partnership, joint venture, trust or other enterprise (all such persons being referred to as an “Indemnitee”), or by reason of any action alleged to have been taken or omitted in such capacity, against all expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred in connection with such action, suit or proceeding and any appeal therefrom, if such Indemnitee acted in good faith and in a manner he or she reasonably believed to be in, or not opposed to, our best interests, and, with respect to any criminal action or proceeding, he or she had no reasonable cause to believe his or her conduct was unlawful. The Bylaws provide that we will indemnify any Indemnitee who was or is a party to an action or suit

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by or in the right of us to procure a judgment in our favor by reason of the fact that the Indemnitee is or was, or has agreed to become, a director or officer, or is or was serving, or has agreed to serve, at our request as a director, officer, partner, employee or trustee of, or in a similar capacity with, another corporation, partnership, joint venture, trust or other enterprise, or by reason of any action alleged to have been taken or omitted in such capacity, against all expenses (including attorneys’ fees) and, to the extent permitted by law, amounts paid in settlement actually and reasonably incurred in connection with such action, suit or proceeding, and any appeal therefrom, if the Indemnitee acted in good faith and in a manner he or she reasonably believed to be in, or not opposed to, our best interests, except that no indemnification shall be made with respect to any claim, issue or matter as to which such person shall have been adjudged to be liable to us, unless a court determines that, despite such adjudication but in view of all of the circumstances, he or she is entitled to indemnification of such expenses. Notwithstanding the foregoing, to the extent that any Indemnitee has been successful, on the merits or otherwise, he or she will be indemnified by us against all expenses (including attorneys’ fees) actually and reasonably incurred in connection therewith. Expenses must be advanced to an Indemnitee under certain circumstances.

We have entered into indemnification agreements with each of our directors and officers. These indemnification agreements may require us, among other things, to indemnify our directors and officers for some expenses, including attorneys’ fees, judgments, fines and settlement amounts incurred by a director or officer in any action or proceeding arising out of his or her service as one of our directors or officers, or any of our subsidiaries or any other company or enterprise to which the person provides services at our request.

We also maintain general liability insurance that covers certain liabilities of our directors and officers arising out of claims based on acts or omissions in their capacities as directors or officers, including liabilities under the Securities Act.

Under the Merger Agreement, from the effective time of the Merger through the sixth anniversary of the date of the effective time, we agreed to indemnify and hold harmless each person who was, as of November 16, 2023, the signing date of the Merger Agreement, or had been at any time prior, or who becomes prior to the effective time of the Merger, a director or officer of our company or Legacy Q32, against all claims, losses, liabilities, damages, judgments, fines and reasonable fees, costs and expenses, including attorneys’ fees and disbursements, pertaining to claims arising out of the fact that such person was a director or officer of our company or Legacy Q32, at or prior to the effective time of the merger, to the fullest extent permitted under the DGCL.

Under the Merger Agreement, we agreed not to amend, modify or repeal provisions in the Restated Certificate of Incorporation and the Amended and Restated Bylaws that were in effect as of November 16, 2023, the date of the Merger Agreement, with respect to indemnification, advancement of expenses and exculpation of our present and former directors and officers for a period of six years from the effective time of the Merger in a manner that would adversely affect the rights of such individuals who at the effective time of the Merger were our officers or directors.

In connection with the Merger, we purchased an insurance policy in effect for six years from the effective time of the Merger, providing no less favorable coverage as the current directors’ and officers’ liability insurance policies maintained by us with respect to any actual or alleged error, misstatement, misleading statement, act, omission, neglect, breach of duty or any matter claimed against our current and former officers and directors.

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Item 16. Exhibits

		Incorporation by Reference
Exhibit Number	Description	Form		File No		Exhibit		Filing Date		Filed Herewith
2.1*	Agreement and Plan of Merger, dated as of November  16, 2023, by and among Homology Medicines, Inc., Kenobi Merger Sub, Inc. and Q32 Bio Inc.		S-4		333-276093		2.1		12/18/2023
3.1	Restated Certificate of Incorporation, as currently in effect.		8-K		001-38433		3.1		4/3/18
3.2	Certificate of Amendment to the Amended and Restated Certificate of Incorporation of the Company-reverse stock split and authorized share increase, dated March 25, 2024.		8-K		001-38433		3.1		3/26/2024
3.3	Certificate of Amendment to the Amended and Restated Certificate of Incorporation of the Company-name change, dated March 25, 2024.		8-K		001-38433		3.2		3/26/2024
3.4	Amended and Restated Bylaws, as currently in effect.		8-K		001-38433		3.1		12/18/20
4.1	Description of Registrant’s Securities.		10-K/A		001-38433		4.1		4/12/2024
5.1	Opinion of Goodwin Procter LLP		S-1		333-278829		5.1		4/19/2024
10.1*	Subscription Agreement, dated November  16, 2023, by and among Q32 Bio Operations Inc. (formerly Q32 Bio Inc.) and certain parties thereto.		8-K		001-38433		10.1		3/26/2024
10.2*	Registration Rights Agreement, dated March  25, 2024, by and among Q32 Bio Operations Inc. (formerly Q32 Bio Inc.) and certain parties thereto.		8-K		001-38433		10.2		3/26/2024
10.3	Form of Lock-Up Agreement.		8-K		001-38433		10.3		3/26/2024
10.4	Contingent Value Rights Agreement dated March 23, 2024, by and between Homology Medicines Inc. and Equiniti Trust Company, LLC.		8-K		001-38433		10.4		3/26/2024
10.5	Q32 Bio Inc. Warrant to Purchase Common Stock dated December 11, 2020.		8-K		001-38433		10.13		3/26/2024
10.6	Q32 Bio Inc. Warrant to Purchase Common Stock dated July 12, 2023.		8-K		001-38433		10.14		3/26/2024
23.1	Consent of Ernst & Young LLP, Independent Registered Public Accounting Firm.										X

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		Incorporation by Reference
Exhibit Number	Description	Form		File No		Exhibit		Filing Date		Filed Herewith
23.2	Consent of Goodwin Procter LLP (included in Exhibit 5.1 hereto).		S-1		333-278829		23.3		4/19/2024
24.1	Power of Attorney (included on signature page of the initial filing of this Registration Statement).		S-1		333-278829		24.1		4/19/2024
107	Filing Fee Table		S-1		333-278829		107		4/19/2024

* Annexes, schedules and exhibits have been omitted pursuant to Item 601(b)(2) or 601(a)(5), as applicable, of Regulation S-K. The registrant agrees to furnish supplementally a copy of any omitted attachment to the SEC on a confidential basis upon request.

Item 17. Undertakings.

(a) The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i) to include any prospectus required by Section 10(a)(3) of the Securities Act;

(ii) to reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the SEC pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than 20 percent change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and

(iii) to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement;

provided, however, that: Paragraphs (a)(1)(i), (a)(1)(ii) and (a)(1)(iii) of this section do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the registrant pursuant to Section 13 or Section 15(d) of the Exchange Act, that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

(2) That, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3) To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(4) That, for the purpose of determining liability under the Securities Act to any purchaser:

(i) Each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

(ii) Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5) or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii) or (x) for the purpose of providing the information required by Section 10(a) of the Securities Act shall

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be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(5) That, for the purpose of determining liability of the registrant under the Securities Act to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and

(iv) Any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(b) The undersigned Registrant hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the Registrant’s annual report pursuant to section 13(a) or section 15(d) of the Exchange Act (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to section 15(d) of the Exchange Act) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(c) Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

(d) The undersigned registrant hereby undertakes that:

(1) For purposes of determining any liability under the Securities Act, the information omitted from the form of prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in a

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form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part of this registration statement as of the time it was declared effective.

(2) For the purpose of determining any liability under the Securities Act, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this Post-Effective Amendment No. 1 to the Registration Statement to Form S-1 on Form S-3 to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Waltham, Commonwealth of Massachusetts, on April 11, 2025.

Q32 BIO INC.

/s/ Jodie Morrison

Name: Jodie Morrison

Title: Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this Post-Effective Amendment No. 1 to the Registration Statement to Form S-1 on Form S-3 has been signed below by the following persons in the capacities and on the date indicated.

Signature	Title	Date
/s/ Jodie Morrison Jodie Morrison	Chief Executive Officer and Director Principal Executive Officer	April 11, 2025
* Lee Kalowski	Chief Financial Officer and President Principal Financial Officer and Principal Accounting Officer	April 11, 2025
* David Grayzel	Director	April 11, 2025
* Diyong Xu	Director	April 11, 2025
* Isaac Manke	Director	April 11, 2025
* Arthur Tzianabos	Director	April 11, 2025
* Kathleen LaPorte	Director	April 11, 2025
* Mary Thistle	Director	April 11, 2025
* Mark Iwicki	Director	April 11, 2025
* Bill Lundberg	Director	April 11, 2025

*By:	/s/ Jodie Morrison
Name:	Jodie Morrison
Title:	Attorney-in-fact

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