PTC’s Novartis-partnered Huntington’s drug disappoints in mid-stage data reveal

# PTC518 for Huntington's Disease:
Mixed Results in PIVOT-HD Study

Study Outcomes

PTC Therapeutics recently announced that its experimental drug PTC518, designed to treat Huntington's disease, has met the primary endpoint in its Phase 2 PIVOT-HD study1 3. The drug demonstrated dose-dependent lowering of huntingtin (HTT) protein levels at 12 weeks, which was the main goal of the trial3. Results from the full 12-month cohort showed that PTC518 reduced blood HTT protein levels by 23% at the 5mg dose level for both Stage 2 and 3 patients1 2.

Despite achieving its primary endpoint, the market response has been negative. PTC Therapeutics' shares fell approximately 20% to $40 in premarket trading following the announcement5. This negative reaction suggests investors were hoping for more impressive results from the study.

Efficacy Concerns

The 23% reduction in HTT protein levels achieved by PTC518 appears to have disappointed investors who may have been expecting more substantial efficacy2. RBC Capital analysts commented that "some may have been looking for indisputable results," indicating that the data failed to provide the clear and convincing evidence of efficacy that stakeholders had anticipated5.

While PTC Therapeutics emphasized the positive aspects of meeting the primary endpoint, the market response suggests concerns about whether this level of protein reduction would translate to meaningful clinical benefits for patients with Huntington's disease, a rare neurological condition that impairs a person's ability to think, feel, and move5.

Future Outlook

The path forward for PTC518 remains uncertain. Although previous interim PIVOT-HD results had demonstrated "evidence of favorable CNS biomarker and clinical effects at Month 12"4, the recent data reveal has raised questions about the potential for accelerated approval3.

Despite the market's negative reaction, RBC Capital analysts maintained a somewhat positive outlook, stating that "the initial data looks to maintain the promise of the program, which over time we believe should be a win"5. This suggests that while the current data may be disappointing, there could still be long-term potential for PTC518 in the treatment of Huntington's disease.

The collaboration between PTC Therapeutics and Novartis, announced in late 2024, will likely continue to evaluate the potential of this drug in the treatment landscape for this debilitating neurological disease4.