PTC Therapeutics’ amyotrophic lateral sclerosis (ALS) prospect has flunked a phase 2 trial, prompting the biotech to drop plans for further development of the drug candidate.
The study randomized more than 300 people to receive utreloxastat or placebo. Utreloxastat, also known as PTC857, targets a pathway of oxidative stress and cell death that PTC identified as an important driver of ALS. Talking at a Morgan Stanley event in September, PTC CEO Matthew Klein, M.D., said hitting the pathway could “affect a lot of the different important aspects of ALS.”
But utreloxastat had little effect on ALS in the phase 2 trial. PTC powered the study to show whether twice-daily oral dosing of utreloxastat could achieve a two-point difference on ALSFRS, an instrument for evaluating the functional status of ALS patients. The drug candidate fell short of that bar.
PTC said it saw a “modest numerical benefit” on the ALSFRS primary endpoint, but the result fell short of statistical significance. The study also missed its secondary efficacy endpoints.
The biotech reported a “correlation of favorable clinical effect with lowering of” a biomarker of neuronal damage. But, with PTC concluding there was a lack of efficacy and biomarker signals, management axed plans for further development.
William Blair analysts said in a note to investors that the result is “unfortunate” but has no effect on their take on PTC. The analysts never included the program in their assessment of the biotech's value, which instead focuses on the phenylketonuria candidate sepiapterin that is under review at the FDA alongside a Huntington’s program that could soon board a pathway toward accelerated approval.
Investors were similarly unmoved by the failure. PTC’s share price slipped 2.2% to $45 in after-hours trading Tuesday. But the dip came after the stock hit its highest level since mid-2023 and against the backdrop of a more than 60% rise in share price over the course of the year.