PTC Therapeutics Inc. (NASDAQ: PTCT) reported positive results from a 24-month interim analysis of its PIVOT-HD extension study evaluating votoplam for Huntington's disease treatment.

The study showed dose-dependent benefits on disease progression in Stage 2 Huntington's disease patients. Participants receiving the 10 mg dose demonstrated 52% slowing of disease progression compared to a natural history cohort, while those on the 5 mg dose showed 28% slowing, as measured by the Composite Unified Huntington's Disease Rating Scale.

The analysis included patients who had completed the initial 12-month PIVOT-HD placebo-controlled study and continued treatment in the extension phase. Participants originally receiving placebo were randomized to either 5 mg or 10 mg doses, with all participants and investigators remaining blinded to initial treatment assignments.

"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, Chief Executive Officer of PTC Therapeutics.

The company reported no treatment-related increases in neurofilament light chain protein levels, with mean levels remaining below baseline at 24 months for both dose groups. Safety data remained consistent with previously established profiles.

Novartis has initiated a global Phase 3 INVEST-HD study of votoplam, which will enroll approximately 770 individuals with early-stage Huntington's disease. The placebo-controlled study will randomize participants 3:2 to receive votoplam 10 mg or placebo, with the primary endpoint measuring change in disease rating scores over 36 months.

Votoplam is a small molecule that reduces Huntingtin protein levels through mRNA degradation. Novartis assumed responsibility for the drug's development, manufacturing and commercialization following completion of the PIVOT-HD trial under a partnership agreement established in December 2024.