Form 8-K

8-K — PTC THERAPEUTICS, INC.

Accession: 0001070081-26-000006

Filed: 2026-04-28

Period: 2026-04-28

CIK: 0001070081

SIC: 2834 (PHARMACEUTICAL PREPARATIONS)

Item: Regulation FD Disclosure

Item: Financial Statements and Exhibits

Documents

8-K — tmb-20260428x8k.htm (Primary)

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8-K

8-K (Primary)

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PTC THERAPEUTICS, INC._April 28, 2026

0001070081false00010700812026-04-282026-04-28

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): April 28, 2026

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.)

500 Warren Corporate Center Drive

Warren, NJ

07059

(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.

On April 28, 2026, PTC Therapeutics, Inc. (the “Company”) reported positive topline results from the 24-month interim analysis of the PIVOT-HD long-term extension study of votoplam. As previously announced, the Company will also provide a virtual presentation on the results on April 28, 2026 at 4:30 p.m. Eastern time. The presentation will be webcast live on the Events and Presentations page under the Investors section of the Company’s website.

The full text of the press release issued in connection with the announcement and the slide presentation are furnished as Exhibits 99.1 and 99.2 to this Current Report on Form 8-K (this “Report”), and are incorporated by reference into this Item 7.01.

The information in this Item 7.01 (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 April 28, 2026 issued by PTC Therapeutics, Inc.

99.2

Corporate Presentation – PIVOT-HD 24-month interim analysis

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: April 28, 2026

By:

/s/ Pierre Gravier

Name:

Pierre Gravier

Title:

Chief Financial Officer

EX-99.1

Filename: tmb-20260428xex99d1.htm · Sequence: 2

Exhibit 99.1

PTC Therapeutics Reports Positive Topline Results from Month 24 Interim Analysis of PIVOT-HD Extension Study of Votoplam

- Dose-dependent benefit on cUHDRS in Stage 2 participants compared to matched natural history cohort, with 52% slowing at 10 mg dose -

- Continued evidence of favorable safety profile -

- Novartis initiated global Phase 3 INVEST-HD study of votoplam -

- PTC will host a conference call to discuss results today, April 28, at 4:30 pm ET -

WARREN, N.J., April 28, 2026 - PTC Therapeutics, Inc. (NASDAQ: PTCT) today reported positive topline results from the 24-month interim analysis of the PIVOT-HD long-term extension study, with favorable dose-dependent effects on disease progression for Stage 2 Huntington’s disease (HD) patients following 24 months of votoplam treatment compared to an external natural history cohort.

“These results give us confidence in the potential for votoplam to deliver long-term meaningful effect on slowing Huntington’s disease progression," said Matthew B. Klein, M.D., Chief Executive Officer, PTC Therapeutics. “In particular, the evidence of dose-dependent slowing of progression on the cUHDRS disease rating scale in the Stage 2 study participants supports the Novartis-initiated Phase 3 INVEST-HD study. We look forward to continuing to review the data and aligning on potential regulatory interactions based on the results with our partner Novartis.”

The PIVOT-HD study was a 12-month placebo-controlled study of two dose levels of votoplam in participants with Stage 2 and Stage 3 HD. The study met the primary endpoint of blood Huntingtin (HTT) protein lowering at 12 weeks, with persistent dose-dependent lowering at Month 12. PIVOT-HD participants then enrolled in the PIVOT-HD extension study in which those originally randomized to receive 5 mg or 10 mg of votoplam remained on those dose levels. Participants initially randomized to receive placebo were randomized to receive 5 mg or 10 mg. All participants and investigators remain blinded to initial PIVOT-HD treatment assignment. The objectives of the long-term extension study are to assess the safety and efficacy of long-term votoplam treatment.

In the interim analysis following 24 months of votoplam treatment, there was evidence of dose-dependent benefit in slowing progression on the Composite Unified Huntington's Disease Rating Scale (cUHDRS) relative to a propensity weighted natural history cohort in Stage 2 participants, with 52% and 28% slowing for 10 mg and 5 mg participants, respectively. Signals of favorable treatment effects relative to natural history were recorded across the cUHDRS subscales for the 10 mg cohort. In addition, there were no treatment-related neurofilament light chain protein (NfL) increases and mean NfL levels remained below baseline at 24 months for both high and low dose cohorts – in contrast to the reported natural history that NfL levels increase over time in individuals with HD. In Stage 3 participants, potential signals of slowing of progression were observed at 24 months. Importantly, the safety data at Month 24 for both dose levels and both stages were consistent with the previously established evidence of favorable safety.

Exhibit 99.1

Novartis announced their initiation of the global Phase 3 INVEST-HD study on their First Quarter Earnings Call earlier today. This placebo-controlled study will enroll approximately 770 individuals with early-stage HD who will be randomized 3:2 to receive votoplam 10 mg or placebo. The primary endpoint will be the change from baseline up to month 36 in the cUHDRS. The INVEST-HD study is sponsored and funded by Novartis. Novartis and PTC will continue to review the data and discuss potential next steps including regulatory interactions.

Conference Call and Webcast Details:

PTC will hold a conference call at 4:30 pm ET today to discuss this news. The webcast conference call can be accessed on the Investors section of the PTC website at https://ir.ptcbio.com/events-presentations. To participate via phone, please register in advance here to receive dial-in details. 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 PIVOT-HD

PIVOT-HD was designed as a 12-month placebo-controlled trial to assess pharmacodynamic effect and safety of votoplam at two dose levels, 5 mg and 10 mg, relative to placebo. Initially, the study included only Stage 2 patients. A Stage 3 cohort of similar size was subsequently added to help identify the best study population for future studies. The primary endpoints of PIVOT-HD were total blood Huntingtin (HTT) lowering at 12 weeks and safety events. Secondary endpoints included 12-month blood HTT levels, and other blood-and central nervous system (CNS) biomarkers as well as changes in Composite Unified Huntington's Disease Rating Scale (cUHDRS).

Following 12 months, patients were eligible to enroll in a long-term extension study in which all subjects would receive votoplam. Those originally randomized to 5 mg and 10 mg would continue at that dose level; those initially randomized to placebo would be randomized 1:1 to 5 mg or 10 mg. All subjects and investigators remain blinded to initial treatment assignment.

About Votoplam

Votoplam (formerly PTC518) is a small molecule splicing modifier that acts via a unique mechanism to promote the inclusion of a novel pseudoexon containing a premature termination codon, thus triggering Huntingtin (HTT) mRNA degradation and subsequent reduction in HTT protein levels. Votoplam was discovered from PTC's validated splicing platform, following the successful discovery and development of Evrysdi® (risdiplam) for spinal muscular atrophy (SMA). Votoplam was partnered with Novartis in December 2024. Following the completion of the PIVOT-HD clinical trial, Novartis assumed responsibility for votoplam's development, manufacturing and commercialization.

About Huntington's Disease

Huntington's disease (HD) is a fatal, hereditary, genetic disorder of the central nervous system.1 It is caused by a defective gene. This gene produces a protein, called Huntingtin (HTT), 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) HTT 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 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,

Exhibit 99.1

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 dedicated to the discovery, development and commercialization of clinically differentiated medicines for children and adults living with rare disorders. PTC is advancing a robust and diversified pipeline of transformative medicines as part of its mission to provide access to best-in-class treatments for patients with unmet medical needs. The company's strategy is to leverage its scientific expertise and global commercial infrastructure to optimize value for patients and other stakeholders. To learn more about PTC, please visit www.ptcbio.com and follow us on LinkedIn, X, Instagram and Facebook.

For More Information:

Investors:

Ellen Cavaleri

+1 (615) 618-6228

ecavaleri@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; expectations with respect to PTC's license and collaboration agreement with Novartis Pharmaceuticals Corporation for votoplam for the treatment of Huntington’s disease including its right to receive development, regulatory and sales milestones, profit sharing and royalty payments from Novartis, the design and expected timing of clinical trials and studies, the availability of data, and regulatory submissions and responses, including potential accelerated approval;

Exhibit 99.1

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/browse10/2019/en#/G10. 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

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PTC Therapeutics

PIVOT

-HD LTE 24

-Month Interim Analysis Results

PTC Therapeutics

PIVOT

-HD LTE 24

-Month Interim Analysis Results

PIVOT

-HD

Extension Study

-Month Topline

Interim Analysis

Results

Matthew B. Klein, MD

CEO

April 2026

Patient living with HD

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

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; expectations with respect

to PTC's license and collaboration agreement with Novartis Pharmaceuticals Corporation for votoplam for the treatment of Huntington’s disease

including its right to receive development, regulatory and sales milestones, profit sharing and royalty payments from Novartis, the design and

expected timing of clinical trials and studies, the availability of data, and regulatory submissions and responses, including potential accelerated

approval; 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.

Forward Looking Statements

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

PIVOT-HD Study Design

*Placebo participants randomized 1:1

to 5 mg or 10 mg for LTE and all

participants remain blinded to initial

treatment assignment

Primary Endpoint: Reduction in

Blood HTT protein (Week 12)

12 Weeks

Placebo-Controlled Study

12 Months

Placebo

Votoplam 10 mg

Votoplam 5 mg

48 Months

Long-Term Extension Study*

Screening

R Votoplam 10 mg

Votoplam 5 mg

Votoplam 10 mg

Votoplam 5 mg

LTE Study is sponsored by Novartis

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

PIVOT-HD Met Primary Endpoint of Blood HTT Lowering

with Dose-Dependent Lowering Maintained at Month 12

Favorable safety

and tolerability profile with

no treatment-related

NfL increases

Favorable and dose-dependent trends on clinical

scales at Month 12

in Stage 2 subjects

PIVOT-HD study met primary

endpoint of blood HTT protein

lowering at Week 12 with

durable dose-dependent

lowering at Month 12

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results 5

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

24-Month Interim Analysis

Results

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

24-Month Interim Analysis Overview

Explore blood-based and

other disease associated

biomarkers

Assess long-term safety

and tolerability profile

of votoplam

Evaluate long-term clinical

efficacy of votoplam versus a

propensity score–matched

natural history cohort*

*Natural history comparison was prespecified

in the long-term extension protocol

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

Baseline Characteristics of 24-month Analysis Population

Baseline Characteristic

Stage 2 Stage 3

Votoplam 5 mg

(N=21)

Votoplam 10 mg

(N=24)

Votoplam 5 mg

(N=22)

Votoplam 10 mg

(N=24)

Age (years) Mean 45.6 46.7 53.2 49.2

Gender, n (%)

Male

Female

11 (52.4%)

10 (47.6%)

11 (45.8%)

13 (54.2%)

12 (54.5%)

10 (45.5%)

14 (58.3%)

10 (41.7%)

CAG length

Mean (SD)

Min – Max

44.1 (2.28)

41 – 49

43.8 (2.66)

41 – 50

43.0 (2.31)

40 – 50

44.3 (3.03)

40 – 50

TFC (Total Functional

Capacity) Score Mean 13.0 13.0 11.6 12.0

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

ENROLL-HD Registry Propensity Weighted Natural History

Comparator Group

ENROLL-HD is a large (>30,000 patient records), global, prospective, longitudinal observational

registry for Huntington’s disease designed to systematically collect standardized natural history data.

ENROLL-HD was used to create a comparator group based on key drivers of disease progression.

Variables Used for Identification of Natural History Cohort

Sex Total Functional Capacity (TFC)

Age Symbol Digit Modalities Test (SDMT)

CAG repeats Stroop Word Reading Test (SWRT)

Independence Score (IS) Total Motor Score (TMS)

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

Natural History Cohort Well Matched to Votoplam

Treated Population

Demographics and Baseline

Disease Characteristics

Stage 2 Stage 3

Votoplam

5 mg

(N=21)

Votoplam

10 mg

(N=24)

NH Cohort

(N=73)

Votoplam

5 mg

(N=22)

Votoplam

10 mg

(N=24)

NH Cohort

(N=67)

Sex (% Male) 52.4% 45.8% 54.9% 54.5% 58.3% 56.7%

Age 45.6 46.7 47.0 53.2 49.2 51.2

CAG repeats 44.1 43.8 43.8 43.0 44.3 43.6

cUHDRS 14.3 14.5 14.5 11.6 11.9 11.4

Total Functional Capacity (TFC) 13.0 13.0 13.0 11.6 11.9 11.6

SDMT 41.1 38.7 39.7 31.1 31.4 30.7

SWRT 80.0 86.4 84.4 70.3 72.6 69.9

Total Motor Score (TMS) 12.9 11.2 11.4 22.0 22.3 24.4

Independence Score (IS) 100.0 100.0 100.0 89.8 91.0 88.7

Groups well matched based on Standardized Mean Difference (SMD) < 0.05 for all matching variables

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

Dose-dependent Slowing of Disease Progression on

cUHDRS at 24 months in Stage 2 Participants

Worsening

Results based on observed data

Baseline 12 Month 24 Month

Mean (+/-SE) Change from

Baseline of Composite UHDRS

-0.5

-1.0

-1.5

NH Cohort

Votoplam

5 mg

Votoplam

10 mg

Mean difference in

cUHDRS progression of

52% (10mg) and 28% (5mg)

at Month 24

SE = Standard Error

Treatment Group Mean (SE) Mean (SE)

-1.20 (0.20)

-0.86 (0.24)

-0.57 (0.24)

-0.58 (0.15)

-0.42 (0.16)

-0.34 (0.21)

Natural History (N=73)

5 mg (N=21)

10 mg (N=24)

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

-4

-3

-2

-1

Evidence of Treatment Benefit Across cUHDRS Subscales

for Stage 2 Participants

-1.2

-1

-0.8

-0.6

-0.4

-0.2

Baseline 12 Month 24 Month

Mean Change from

Baseline (+/-SE)

TFC Subscale

Baseline 12 Month 24 Month

Mean Change from

Baseline (+/-SE)

SDMT Subscale

-1

Baseline 12 Month 24 Month

Mean Change from

Baseline (+/-SE)

TMS Subscale

-7.5

-5

-2.5

2.5

Baseline 12 Month 24 Month

Mean Change from

Baseline (+/-SE)

SWRT Subscale

NH Cohort Votoplam 5 mg Votoplam 10 mg Worsening

Worsening Worsening

Worsening

SE = Standard Error

Results based on observed data

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

No Evidence of Treatment-related NfL Spikes at Month 24,

with Mean Levels Below Baseline

-15%

-10%

-5%

Mean % Change from Baseline (SE)

in plasma NfL

-4.1% -2.4%

Votoplam

5 mg

Votoplam

10 mg

Plasma NfL reported to

increase over time based on

natural history*

*Parkin et al., 2024

5 mg

10 mg

NfL-plasma (pg/mL)

Month

BL 12 24

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

Benefit Signals Observed at Month 24 in Stage 3 Participants

-2.5

-2

-1.5

-1

-0.5

Baseline 12 Month 24 Month

cUHDRS

Worsening

-2

-1.5

-1

-0.5

Mean Change from Baseline (+/-SE)

Baseline 12 Month 24 Month

Mean Change from Baseline (+/-SE)

TFC Subscale

Worsening

NH Cohort Votoplam 5 mg Votoplam 10 mg

Results based on observed data

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

Safety profile consistent for

both dose levels and stages

No new AE signals

identified at 24 months

Votoplam safety profile

remains favorable after

24 months of treatment

Votoplam Treatment Continues to Show Favorable

Safety Profile at Month 24 in Stage 2 and 3 Participants

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results 15

AE Category

PIVOT-HD Long-Term Extension*

Placebo

N (%)

Votoplam 5 mg

N (%)

Votoplam 10 mg

N (%)

Votoplam 5 mg

N (%)

Votoplam 10 mg

N (%)

Any TEAEs 46 (86.8) 43 (82.7) 49 (90.7) 38 (86.4) 45 (91.8)

Any TESAEs 4 (7.5) 1 (1.9) 2 (3.7) 3 (6.8) 3 (6.1)

Any TEAEs resulting

in death 1 (1.9) 1 (1.9) 0 0 0

Any TEAEs leading to

treatment discontinuation 0 1 (1.9) 2 (3.7) 0 0

TEAEs by maximum severity

Grade 1

Grade 2

Grade 3

Grade 4

Grade 5

27 (50.9)

15 (28.3)

2 (3.8)

1 (1.9)

23 (44.2)

18 (34.6)

1 (1.9)

20 (37.0)

24 (44.4)

5 (9.3)

20 (45.5)

16 (36.4)

2 (4.5)

23 (46.9)

18 (36.7)

3 (6.1)

1 (2.0)

Votoplam Treatment Showed Favorable Safety

Profile at Month 24 in Stage 2 and 3 Participants

*Grade 3 and 4 AEs not treatment related

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results

INVEST-HD Global Phase 3 Trial Initiated by Novartis

INVEST-HD* Global Phase 3 Study Overview

• Individuals with early symptomatic disease

• 3:2 randomization of votoplam 10mg: placebo

• Target enrollment: ~770 participants in >30 countries

• Primary endpoint: Change from baseline in cUHDRS

• Treatment period up to 36 months

• Interim analysis planned for efficacy and futility

*Study sponsored and funded by Novartis; NCT#: NCT07326709

PTC Therapeutics

PIVOT-HD LTE 24-Month Interim Analysis Results 17

Align with partner Novartis on

plans for potential regulatory

interactions to discuss data

Continued evidence of

favorable safety profile with

no new AE signals identified

Evidence of dose-dependent

disease slowing on cUHDRS

in Stage 2 participants

Summary and Next Steps

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Document and Entity Information

Apr. 28, 2026

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Apr. 28, 2026

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PTC THERAPEUTICS, INC.

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500 Warren Corporate Center Drive

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Warren

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