8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): June 21, 2023

PTC THERAPEUTICS, INC.

(Exact Name of Company as Specified in Charter)

Delaware	001-35969	04-3416587
(State or Other Jurisdiction	(Commission	(IRS Employer
of Incorporation)	File Number)	Identification No.)

100 Corporate Court
South Plainfield, NJ	07080
(Address of Principal Executive Offices)	(Zip Code)

Registrant’s telephone number, including area code: (908) 222-7000

Not applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, $0.001 par value per share	PTCT	Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

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 13(a) of the Exchange Act. ☐

Item 7.01. Regulation FD Disclosure.

PTC Therapeutics, Inc. (the “Company”) will host a conference call on June 21, 2023 at 8:00 a.m. eastern time. During this conference call, the Company expects to discuss interim data from the initial 12-week portion of its Phase 2 study of PTC518 for the treatment of Huntington’s disease. Directions on how to access the conference call are included in the press release furnished as Exhibit 99.1 hereto. A copy of the slide deck that will be presented during the conference call is furnished as Exhibit 99.2 hereto.

The information in this Item 7.01 of this Current Report on Form 8-K (“Report”), including Exhibits 99.1 and 99.2, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing. All website addresses given in this Report or incorporated herein by reference are for information only and are not intended to be an active link or to incorporate any website information into this Report.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

Exhibit No.	Description
99.1	Press Release, dated June 21, 2023 issued by PTC Therapeutics, Inc.
99.2	Corporate Presentation – PIVOT-HD Interim Data Update
104	The cover page from this Current Report on Form 8-K, formatted in Inline XBRL

Signature

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this Report to be signed on its behalf by the undersigned hereunto duly authorized.

	PTC Therapeutics, Inc.
Date: June 21, 2023	By:	/s/ Mark E. Boulding
	Name:	Mark E. Boulding
	Title:	Executive Vice President and Chief Legal Officer

EX-99.1

Exhibit 99.1

PTC Therapeutics Shares Positive Interim Data from

PIVOT-HD Clinical Trial in Huntington’s Disease Patients

- Dose-dependent lowering of blood Huntingtin (HTT) protein levels at 12 weeks -

- Favorable tolerability profile with no treatment-related serious adverse events or NfL spikes -

- Conference call and webcast to be held June 21^st at 8:00 am EDT -

SOUTH PLAINFIELD, N.J., June 21, 2023 -- PTC Therapeutics, Inc. (NASDAQ: PTCT) today shared interim data from the 12-week portion of the PIVOT-HD Phase 2 study of PTC518 in Huntington’s disease (HD) patients. The study demonstrated dose-dependent lowering of Huntingtin (HTT) protein levels in peripheral blood cells, reaching a mean 30% reduction in mutant HTT levels at the 10mg dose level. In addition, PTC518 exposure in the cerebrospinal fluid (CSF) was consistent with or higher than plasma unbound drug levels.

PTC518 treatment was also demonstrated to be well tolerated, with no treatment-related serious adverse events, no reports of peripheral neuropathy or dose-limiting toxicities. Furthermore, there were no CSF neurofilament light chain protein (NfL) treatment-related spikes, with an overall trend towards lowering of CSF NfL levels following 12 weeks of PTC518 treatment.

"We are very pleased with the encouraging data from the PIVOT-HD interim analysis demonstrating dose-dependent HTT lowering, desired CSF exposure and a favorable tolerability profile without evidence of treatment-related serious adverse events or CSF NfL spikes," said Dr. Matthew Klein, Chief Executive Officer, PTC Therapeutics, Inc.

PIVOT-HD is a global, placebo-controlled study and consists of two parts: an initial 12-week placebo-controlled phase focused on PTC518 pharmacology and pharmacodynamic effect, followed by a 9-month placebo-controlled portion. The study will initially include two dose levels, 5 milligrams and 10 milligrams, with the ability to include a third dose level of up to 20 milligrams.

Today's Conference Call and Webcast PTC will hold a conference call at 8:00 am EDT today to discuss this news. To access the call by phone, please click here to register and you will be provided with dial-in details. To avoid delays, we recommend participants dial in to the conference call 15 minutes prior to the start of the call. The webcast conference call can be accessed on the Investor section of the PTC website at https://ir.ptcbio.com/events-presentations. A replay of the call will be available approximately two hours after completion of the call and will be archived on the company's website for 30 days following the call.

About PTC518

PTC is developing a potential treatment for Huntington’s disease based on our splicing platform technology. PTC518, a small molecule that can be taken orally, reduces the production of the mutated Huntingtin protein that leads to injury and death of the neuron, which results in disease progression. The orally bioavailable small molecule penetrates the blood brain barrier, is selective, titratable, and not effluxed – which are key differentiation properties.

About Huntington’s Disease

Huntington’s disease (HD) is a rare, hereditary, genetic disorder of the central nervous system.¹ It is caused by a defective gene. This gene produces a protein, called Huntingtin, which is involved in the functioning of the nerve cells in the brain (neurons). When the gene is defective, it produces an abnormal (or mutated) Huntingtin protein that is toxic and causes neuron damage and neuron death.² HD usually presents in people who are in their 30s or 40s. Symptoms can present earlier in life, and this is called the Juvenile HD.^2,3 There are also cases of infantile HD, when symptoms develop in children who are younger than 10 years old.² While symptoms vary from person to person, the disease primarily affects the brain and results in abnormal movements, difficulties with speech, swallowing and walking, as well as a number of other symptoms including behavioral, cognitive and motor symptoms. ^4,5 While there are

therapies approved for specific disease symptoms, currently, there is no cure for HD and there are no approved drugs that delay the onset or slow disease progression.

About PTC Therapeutics, Inc.

PTC is a global biopharmaceutical company focused on the discovery, development and commercialization of clinically differentiated medicines that provide benefits to patients with rare disorders. PTC's ability to innovate to identify new therapies and to globally commercialize products is the foundation that drives investment in a robust and diversified pipeline of transformative medicines. PTC's mission is to provide access to best-in-class treatments for patients who have little to no treatment options. PTC's strategy is to leverage its strong scientific and clinical expertise and global commercial infrastructure to bring therapies to patients. PTC believes this allows it to maximize value for all its stakeholders. To learn more about PTC, please visit us at www.ptcbio.com and follow us on Facebook, Instagram, LinkedIn and Twitter at @PTCBio.

For More Information:

Investors:

Kylie O'Keefe

+1 (908) 300-0691

kokeefe@ptcbio.com

Media:

Jeanine Clemente

+1 (908) 912-9406

jclemente@ptcbio.com

Forward-Looking Statement

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. All statements contained in this press release, other than statements of historic fact, are forward-looking statements, including statements with respect to the future expectations, plans and prospects for PTC, PTC's strategy, including with respect to the expected timing of clinical trials and studies, availability of data, regulatory submissions and responses and other matters, future operations, future financial position, future revenues, projected costs; and the objectives of management. Other forward-looking statements may be identified by the words, "guidance", "plan," "anticipate," "believe," "estimate," "expect," "intend," "may," "target," "potential," "will," "would," "could," "should," "continue," and similar expressions.

PTC's actual results, performance or achievements could differ materially from those expressed or implied by forward -looking statements it makes as a result of a variety of risks and uncertainties, including those related to: the outcome of pricing, coverage and reimbursement negotiations with third party payors for PTC's products or product candidates that PTC commercializes or may commercialize in the future; significant business effects, including the effects of industry, market, economic, political or regulatory conditions; changes in tax and other laws, regulations, rates and policies; the eligible patient base and commercial potential of PTC's products and product candidates; PTC's scientific approach and general development progress; the sufficiency of PTC's cash resources and its ability to obtain adequate financing in the future for its foreseeable and unforeseeable operating expenses and capital expenditures; and the factors discussed in the "Risk Factors" section of PTC's most recent Annual Report on Form 10-K, as well as any updates to these risk factors filed from time to time in PTC's other filings with the SEC. You are urged to carefully consider all such factors.

As with any pharmaceutical under development, there are significant risks in the development, regulatory approval and commercialization of new products. There are no guarantees that any product will receive or maintain regulatory approval in any territory, or prove to be commercially successful.

The forward-looking statements contained herein represent PTC's views only as of the date of this press release and PTC does not undertake or plan to update or revise any such forward-looking statements to reflect actual results or changes in plans, prospects, assumptions, estimates or projections, or other circumstances occurring after the date of this press release except as required by law.

References:

1. World Health Organization, 2020. 8A01.10 Huntington disease. Available at: https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/2132180242 Accessed October 2021.

2. Gatto EM, González Rojas N, Persi G, et al. Clin Parkinsonism Rel Disord 2020;3:100056.

3. Tabrizi SJ, Flower MD, Ross CA, et al. Nat Rev Neurol 2020;16(10):529–546.

4. Roos RAC. Orphanet J Rare Dis 2010;5:40.

5. Kirkwood SC, Su JL, Conneally P, et al. Arch Neurol 2001;58(2):273–278.

EX-99.2

Exhibit 99.2

Patient Living with HD Matthew Klein, M.D. CEO June 2023 PIVOT -HD Interim Data Update

2 PIVOT-HD Interim Data Update Forward-Looking Statements This presentation contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. All statements contained in this presentation, other than statements of historic fact, are forward-looking statements, including statements with respect to the future expectations, plans and prospects for PTC, PTC's strategy, including with respect to the expected timing of clinical trials and studies, availability of data, regulatory submissions and responses and other matters, future operations, future financial position, future revenues, projected costs; and the objectives of management. Other forward-looking statements may be identified by the words, "guidance", "plan," "anticipate," "believe," "estimate," "expect," "intend," "may," "target," "potential," "will," "would," "could," "should," "continue," and similar expressions. PTC's actual results, performance or achievements could differ materially from those expressed or implied by forward-looking statements it makes as a result of a variety of risks and uncertainties, including those related to: the outcome of pricing, coverage and reimbursement negotiations with third party payors for PTC's products or product candidates that PTC commercializes or may commercialize in the future; significant business effects, including the effects of industry, market, economic, political or regulatory conditions; changes in tax and other laws, regulations, rates and policies; the eligible patient base and commercial potential of PTC's products and product candidates; PTC's scientific approach and general development progress; the sufficiency of PTC's cash resources and its ability to obtain adequate financing in the future for its foreseeable and unforeseeable operating expenses and capital expenditures; and the factors discussed in the "Risk Factors" section of PTC's most recent Annual Report on Form 10-K, as well as any updates to these risk factors filed from time to time in PTC's other filings with the SEC. You are urged to carefully consider all such factors. As with any pharmaceutical under development, there are significant risks in the development, regulatory approval and commercialization of new products. There are no guarantees that any product will receive or maintain regulatory approval in any territory, or prove to be commercially successful. The forward-looking statements contained herein represent PTC's views only as of the date of this presentation and PTC does not undertake or plan to update or revise any such forward-looking statements to reflect actual results or changes in plans, prospects, assumptions, estimates or projections, or other circumstances occurring after the date of this presentation except as required by law.

Novel Chemical Library HTSpliceseq Databases of Splicing Targets PTC518 developed from PTC's validated splicing platform PTC518 Program Developed from PTCs Validated Splicing Platform PTC518 Program Leveraged Learnings from Successful Development of Evrysdi 3 PIVOT-HD Interim Data Update • Importance of molecule selectivity and specificity • CNS bioavailability with broad brain biodistribution • Leverage systemic exposure to confirm target engagement and splicing activity and inform dose selection Key learnings from successful development of Evrysdi Expert Team

4 PIVOT-HD Interim Data Update Key Objectives for 12-Week Interim Data Readout Confirm the relationship of HTT mRNA to protein lowering at steady state Define CSF/plasma drug exposure in Huntington’s disease patients Determine HTT protein lowering after 12 weeks of treatment with PTC518 at 5mg and 10mg Evaluate PTC518 safety and tolerability

12-Week Interim Data Met Key Objectives 5 PIVOT-HD Interim Data Update PTC518 treatment resulted in dose-dependent lowering of HTT mRNA and protein levels in blood cells PTC518 demonstrated desired CSF exposure with higher concentrations of free drug in the CSF than plasma PTC518 was well tolerated with no treatment-related serious adverse events and no reports of peripheral neuropathy CSF NfL levels remained stable after 12 weeks of treatment with no treatment-related spikes

PIVOT-HD Study Design 6 PIVOT-HD Interim Data Update 12 weeks 9 months PTC518 5mg PTC518 10mg PTC518 20mg R Part 1 Part 2 Placebo PTC518 5mg PTC518 10mg PTC518 20mg Primary Endpoints • Safety and tolerability of PTC518 • Percent reduction in HTT mRNA and protein in blood Secondary Endpoints • Percent reduction in mHTT protein in CSF • Changes in neurofilament light chain (NfL) in plasma and CSF • Change in brain volume on volumetric MRI imaging Optional Dose Optional Dose

PIVOT-HD Trial Populations 7 PIVOT-HD Interim Data Update • Ambulatory Huntington’s patients age 25 and older • CAG repeats 40-50 inclusive • Motor and Cognitive Function: - UHDRS-IS score of 100 - UHDRS TFC score of 13 • PINHD score of 0.18 - 4.93 - Multivariate calculation including SDMT, TMS, age, CAG Inclusion Criteria Stage 2 Inclusion Criteria Early Stage 3 • Ambulatory Huntington’s patients age 25 and older • CAG repeats 40-50 inclusive • Motor and Cognitive Function: - UHDRS-IS score of less than 100 and/or - UHDRS TFC score of 11 or 12

PIVOT-HD Interim Analysis Patient Characteristics 8 PIVOT-HD Interim Data Update Category PTC518 5mg (N=13) PTC518 10mg (N=11) Placebo (N=9) Overall (N=33) Age (years) mean 46.2 47.4 46.9 46.8 Gender, n (%) Male 5 (38.5%) 6 (54.5%) 6 (66.7%) 17 (51.5%) Female 8 (61.5%) 5 (45.5%) 3 (33.3%) 16 (48.5%) CAG length Mean (SD) 44.08 (1.9) 43.73 (2.4) 44.11 (2.0) 43.97 (2.1) Min – Max 42 - 49 42 - 50 42 - 47 42 – 50 TFC (Total Functional Capacity) Score Mean 13 13 13 13

PTC518 Treatment Resulted in Dose-Dependent Blood HTT Protein Lowering at Week 12 9 PIVOT-HD Interim Data Update -40% -30% -20% -10% 0% 10% 20% Placebo PT518 5mg PTC518 10mg Mean % change from baseline blood mHTT (Week 12) +12% Mean % change from baseline mRNA (Week 12) -27% -29% -21% -30% Dose-dependent lowering of HTT protein mRNA and protein lowering ~1:1 PTC518 5mg Note: Error bars represent the standard error of the mean.

PTC518 CSF Drug Levels Confirm Targeted CNS Exposure at Week 12 10 PIVOT-HD Interim Data Update Ratio of CSF to Free Plasma Treatment Concentration Group Mean CSF Concentration (ng/mL) Mean Free Plasma Concentration (ng/mL) 5mg 0.923 0.917 10mg 2.037 1.402 5mg 1.1 to 1 10mg 1.5 to 1

PTC518 Treatment Demonstrated to Be Well Tolerated 11 PIVOT-HD Interim Data Update Most common adverse events were upper respiratory tract infection and headache PTC518 was well tolerated, with no treatment-related serious adverse events and no adverse events leading to discontinuation Similar adverse event profile across treatment groups, including placebo group

PTC518 Treatment Demonstrated to Be Well Tolerated 12 PIVOT-HD Interim Data Update Category PTC518 5mg (N = 13) PTC518 10mg (N=11) Placebo (N=9) Overall (N=33) Subjects with at least one TEAE 9 (69.2) 7 (63.6) 6 (66.7) 22 (66.7) Subjects with at least one serious TEAE 0 0 0 0 Subjects with at least one TEAEs leading to study treatment discontinuation 0 0 0 0 Subjects with at least one TEAE leading to death 0 0 0 0 Subjects with at least one treatment related AE# 3 (23.1) 4 (36.4) 1 (11.1) 8 (24.2) Subjects with at least one TEAEs by maximum severity N (%) 9 (69.2) 7 (63.6) 6 (66.7) 22 (66.7) Grade 1 4 2 5 11 Grade 2 4 5 1 10 Grade 3 1* 0 0 1 Grade 4/5 0 0 0 0 * Unrelated to drug # Judged by the investigator to be probably or possibly related to treatment

CSF NfL Levels Trended Lower in Subjects Treated with PTC518 13 PIVOT-HD Interim Data Update Mean Change in CSF NfL Levels from Baseline to Week 12 Note: One patient excluded due to non-treatment related viral syndrome. Note: Error bars represent the standard error of the mean. -20 -15 -10 -5 0 5 10 Placebo PTC518 5mg PTC518 10mg CSF NfL % change from baseline (Week 12) 6,000 5,000 4,000 3,000 2,000 1,000 0 Individual Subject CSF NfL Trajectories Baseline CSF NfL Levels (pg/ml) Week 12

Summary and Next Steps 14 PIVOT-HD Interim Data Update Dose-dependent lowering of HTT protein levels, safety, and CNS biodistribution objectives achieved Share safety data with FDA to support US enrollment in PIVOT-HD Continue enrollment in Stage 2 and early Stage 3 patient cohorts

XML

Document and Entity Information	Jun. 21, 2023
Document and Entity Information [Abstract]
Document Type	8-K
Document Period End Date	Jun. 21, 2023
Entity File Number	001-35969
Entity Registrant Name	PTC THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3416587
Entity Address, Address Line One	100 Corporate Court
Entity Address, City or Town	South Plainfield
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	07080
City Area Code	908
Local Phone Number	222-7000
Written Communications	false
Soliciting Material	false
Pre-commencement Tender Offer	false
Pre-commencement Issuer Tender Offer	false
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	PTCT
Security Exchange Name	NASDAQ
Entity Emerging Growth Company	false
Entity Central Index Key	0001070081
Amendment Flag	false