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PTC518

Phase 2

Huntington Disease | Small molecule | Neurology |PTC Therapeutics, Inc.|Last Updated: Jun 16, 2026

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLED
Total Trials1
Total Enrollment159

FDA Designations

FAST_TRACK

Clinical trial landscape

PTC518 · 1 trial · 1 indication

Phase 2 1
NCT05358717A Study to Evaluate the Safety and Efficacy of PTC518 in Participants With Huntington's Disease (HD)Huntington Disease
COMPLETED159 Analytics
PHASE2COMPLETED
A Study to Evaluate the Safety and Efficacy of PTC518 in Participants With Huntington's Disease (HD)
Huntington DiseaseUnlock trial analytics

Study Endpoints

Primary Endpoints

Number of Participants With Treatment-emergent Adverse Events (TEAEs)
Baseline up to Month 18

An adverse event (AE) was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. A TEAE was defined as an AE that had an onset date or date of worsening on or after the first dose of study drug. A summary of other non-serious AEs and all serious adverse events (SAEs), regardless of causality is located in the 'Reported AE section'.

Percent Change From Baseline in Geometric Mean Blood tHTT Protein at Month 3
Baseline, Month 3

Least square (LS) mean and 95% confidence interval (CI) were calculated using mixed-model repeated measures (MMRM). The blood tHTT protein value was log-transformed before fitting the MMRM model. The LS means from MMRM model were back-transformed to present geometric mean percent changes.

Secondary Endpoints

Percent Change From Baseline in Caudate Volume as Assessed Via Volumetric Magnetic Resonance Imaging (vMRI) at Month 12
Baseline, Month 12
Change From Baseline in Composite Unified Huntington's Disease Rating Scale (cUHDRS) Scores at Month 12
Baseline, Month 12
Percent Change From Baseline in Geometric Mean Blood tHTT Protein at Month 12
Baseline, Month 12
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Study Design & Arms

AllocationRANDOMIZED
MaskingDOUBLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
PTC518 5 mgEXPERIMENTALParticipants will receive PTC518 5 milligrams (mg) tablets once daily orally for 12 months.
PTC518 10 mgEXPERIMENTALParticipants will receive PTC518 10 mg tablets once daily orally for 12 months.
PTC518 20 mgEXPERIMENTALParticipants will receive PTC518 20 mg tablets once daily orally for 12 months.
PlaceboPLACEBO_COMPARATORParticipants will receive placebo matching to PTC518 tablets once daily orally for 12 months.

Interventions

NameTypeDescription
PTC518DRUGPTC518 will be administered per dose and schedule specified in the arm.
PlaceboDRUGPlacebo matching to PTC518 will be administered per schedule specified in the arm.
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Eligibility Criteria

Age Range25 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites28

Key Inclusion Criteria: * Genetically confirmed HD diagnosis with a cytosine-adenine-guanine (CAG) repeat length from 40 to 50, inclusive Eligibility for HD-ISS Stage 2 Group (Parts A, B, and C): * A Unified Huntington's Disease Rating Scale (UHDRS)-Independence Scale (IS) score of 100 * A UHDRS ...

Countries:United StatesAustraliaAustriaCanadaFranceGermanyItalyNetherlandsNew ZealandSpainUnited Kingdom
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Competitive Landscape -Huntington's Disease 8 trials (matched to "Huntington Disease")

Recent Changes (Last 90 Days)

MEDIUMJul 17, 2026NCT05358717TRIAL_REMOVED: changed
MEDIUMJul 17, 2026NCT05358717TRIAL_REMOVED: changed
MEDIUMJul 17, 2026NCT05358717TRIAL_REMOVED: changed

Frequently asked questions about PTC518

What is PTC518 used for?

PTC518 is an investigational small molecule being developed for Huntington's disease, a neurodegenerative disorder. It is currently in Phase 2 clinical development and has not been approved by the FDA. The drug is being studied to evaluate its safety and efficacy in participants with Huntington's disease.

What does PTC518 target?

PTC518 is a small molecule designed to target the underlying cause of Huntington's disease by modulating the expression of the huntingtin protein. It is being developed to potentially reduce the levels of this protein, which is central to the disease's pathology. The drug is in Phase 2 clinical trials.

Who makes PTC518?

PTC518 is being developed by PTC Therapeutics, Inc., a biopharmaceutical company listed on NASDAQ under the ticker symbol PTCT. The company is conducting clinical trials to evaluate the drug's safety and efficacy in patients with Huntington's disease.

What phase is PTC518 in?

PTC518 is in Phase 2 clinical development. It has completed one Phase 2 trial (NCT05358717) with 159 participants. The drug is not FDA approved and remains investigational. It has received Fast Track designation from the FDA for the treatment of Huntington's disease.

What clinical trials is PTC518 in?

PTC518 has been studied in a Phase 2 clinical trial (NCT05358717) titled 'A Study to Evaluate the Safety and Efficacy of PTC518 in Participants With Huntington's Disease (HD)'. This randomized, double-blind, placebo-controlled trial enrolled 159 participants across multiple countries including the United States, Australia, and several European nations.

Is PTC518 the same as other Huntington's disease treatments?

PTC518 is a distinct investigational small molecule being developed by PTC Therapeutics for Huntington's disease. It is not known to be the same as any other approved or investigational treatment. Its mechanism involves targeting the huntingtin protein, which differentiates it from other therapies in development.