PTC Therapeutics Inc. CEO Matthew Klein said the firm “achieved all we set out to [achieve] in phase II” with PTC-518 in Huntington’s disease (HD), but it wasn’t enough to excite Wall Street, as some questioned whether the level of associations between trial findings and efficacy would appease the U.S. FDA. Shares (NASDAQ:PTCT) ended May 5 at $40.65, down $9.30, or 18.6%. Warren, N.J.-based PTC rolled out the most recent data from the Pivot-HD effort in stage 2 and stage 3 HD with PTC-518, an oral, centrally as well as peripherally distributed huntingtin (HTT) pre-mRNA splicing modifier.

PTC Therapeutics Inc. said a “highly competitive process with several parties involved” led to the deal centered on the firm’s Huntington’s disease program with Novartis AG, an arrangement that brings $1 billion up front along with as much as $1.9 billion in development, regulatory, and sales milestone rewards.

A nearly two-year-old partial clinical hold has been lifted by the U.S. FDA on PTC Therapeutics Inc.’s pivotal phase II study in Huntington’s disease. The agency had paused enrollment in October 2022, saying it wanted more data on PTC-518, an orally bioavailable small-molecule splicing modifier, before enrollment could continue.

The U.S. FDA wants more data on PTC-518 before PTC Therapeutics Inc.'s phase II study of Huntington’s disease can continue enrollment. While stopped in the U.S., the study of the oral, small-molecule splicing modifier still is enrolling participants at sites in several European countries and in Australia.

Researchers at PTC Biotherapeutics Inc. have identified orally available small-molecule compounds that broadly lowered the levels of mutant huntingtin protein in both the brain and the periphery by affecting its splicing. One of those compounds, PTC-518, is currently in phase I trials as a therapy for Huntington's disease.