PTC Therapeutics said today it will halt development of its lead product candidate Translarna™ (ataluren) in cystic fibrosis, close ongoing extension studies, and withdraw its marketing application in that indication in Europe after the treatment failed a Phase III study.

Translarna missed its primary and secondary endpoints in the Ataluren Confirmatory Trial (ACT), a double-blind, placebo-controlled, 48-week clinical trial comparing Translarna to placebo in nonsense mutation cystic fibrosis (nmCF) patients 6 years of age or older not receiving chronic inhaled aminoglycosides.

The 16-country Phase II study enrolled 279 patients randomized to either Translarna or placebo. In the intent-to-treat population, the primary endpoint of lung function as measured by absolute change in percent-predicted forced expiratory volume in one second (FEV1) over 48 weeks from baseline saw a statistically insignificant 0.6% difference in favor of Translarna versus placebo, based on a –1.4% change on Translarna versus a –2.0% change on placebo.

For the secondary endpoint of rate of pulmonary exacerbations, the rate in the Translarna group was 14% lower than the placebo group. Those results were also not statistically significant, according to PTC.

“We are disappointed with the outcome of this trial as there are no treatments that target the underlying cause of nmCF, one of the most difficult forms to treat,” PTC CEO Stuart W. Peltz, Ph.D., said in a statement.

ACT CF also confirmed a favorable safety profile for Translarna and showed the candidate to be generally well tolerated, PTC said, adding that ataluren has been used by more than 1000 patients across multiple indications.

PTC’s scrapping its clinical program for Translarna in cystic fibrosis comes a year after the company eliminated approximately 18% of its workforce, or about 74 jobs. The layoffs were part of a cost-cutting program that followed the FDA’s issuing a Refuse to File letter in response to the company’s New Drug Application (NDA) for Translarna in nonsense mutation Duchenne muscular dystrophy (nmDMD). PTC has said it will re-file the NDA over protest with the FDA in the first quarter.

PTC won European Commission approval last year for Translarna in nmDMD in ambulatory patients aged 5 years and older. That approval was renewed in January; PTC is required to renew the approval each year following reassessment by the European Medicines Agency. The EC also required PTC to conduct an additional trial of Translarna in nmDMD.

Also in January, PTC issued guidance to investors projecting Translarna for nmDMD will achieve net sales of between $105 and $125 million outside the U.S.

Translarna is in Phase II development for mucopolysaccharidosis type I (MPS I), aniridia, and Dravet syndrome or cyclin-dependent kinase-like 5 (CDKL5) disorder.

Shares of PTC fell nearly 18% from yesterday’s close of $13.18, to $10.82 as of 9:54 a.m.

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