PTC Therapeutics’ cystic fibrosis drug fails in phase 3 trial

Ataluren was generally well tolerated and ACT CF confirmed a favorable safety profile for ataluren, which has now been used by more than 1,000 patients across multiple indications. PTC plans to discontinue current clinical development of ataluren in cystic fibrosis, close ongoing extension studies and withdraw its application for marketing authorization in cystic fibrosis in Europe.

PTC Therapeutics CEO Stuart W. Peltz said: "We are disappointed with the outcome of this trial as there are no treatments that target the underlying cause of nonsense mutation cystic fibrosis, one of the most difficult forms to treat.

"We are particularly grateful to patients and investigators who participated in our trials. We remain committed to patients receiving ataluren in other indications."

ACT CF was a double-blind, placebo-controlled, 48-week clinical trial comparing ataluren to placebo in nmCF patients six years of age or older not receiving chronic inhaled aminoglycosides. The Phase 3 study, conducted in 16 countries, enrolled 279 patients who were randomized to receive either ataluren or placebo.

In the intent-to-treat population, the primary endpoint of lung function as measured by absolute change in percent-predicted FEV1 (forced expiratory volume in one second), over 48 weeks from baseline, there was a 0.6% difference in favor of ataluren versus placebo (-1.4% change on ataluren versus -2.0% change on placebo; p=0.534).

For the secondary endpoint of rate of pulmonary exacerbations, there was a trend in favor of ataluren, with the rate in the ataluren group being 14% lower than the placebo group (p=0.401). The results were not statistically significant. 

The safety profile of ataluren in the ACT CF study was consistent with previous studies and no new safety signals were identified.