Rare Disease Report

FDA Accepts PTC's Duchenne Drug Application

MARCH 06, 2017
James Radke
It’s been a long and winding road for PTC Therapeutics to get their Duchenne drug reviewed by the FDA.
In February 2016, PTC Therapeutics received a ‘Refuse to File’ letter from the FDA regarding their drug Translarna (ataluren) to treat nonsense mutation Duchenne muscular dystrophy (nmDMD). The letter received meant the application was not sufficiently complete for the FDA to properly review the application.  Finally, a year later, the FDA has now accepted the drug application.
A PDUFA date is set for October 24, 2017.

Clinical Data

The Refuse to File letter was not the only uphill climb PTC Therapeutics has faced with this drug’s approval process.  In October 2015, the company announced that their Phase 3 clinical trial testing ataluren for the treatment of nmDMD failed to meet its primary endpoint (the 6 minute walk test).
In the overall intent-to-treat study population, the primary endpoint of change from baseline in the 6-minute walk test (6MWT) demonstrated a 15 meter benefit that was not statistically significant (P = .213).
While those results are disappointing and raise the question of it getting approval by the FDA, the trial did find that in a pre-specified patient population of boys who had baseline 6-minute walk test results of 300-400 meters, there was a highly significant benefit of 47 meters (P = .007). The company also reported that no patients in the treatment group lost ambulation (0/47) versus 4 patients in the placebo group (4/52). 
Whether or not the FDA approves the drug based on this post-hoc analysis remains to be seen.
Last fall, we talked with Craig Campbell, MD, of the Department of Pediatric Neurology at Western University about a recent meta-analysis that was performed on the two phase 3 studies involving ataluren to treat children with Duchenne muscular dystrophy.

Translarna (ataluren)

Translarna (ataluren) is a protein restoration therapy designed to enable the formation of a functioning protein in patients with genetic disorders caused by a nonsense mutation. Last week, PTC Therapeutics announced that its program to test the use of ataluren to treat cystic fibrosis patients with nonsense mutations was being halted based on a failed Phase 3 study.

Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a progressive muscle disorder caused by the lack of functional dystrophin protein. Patients with Duchenne muscular dystrophy lose the ability to walk as early as age 10 and experience life-threatening lung and heart complications in their late teens and twenties.

There are an estimated 35,000 patients with Duchenne muscular dystrophy in the United States and Europe but the population has many subsets based on mutations of the dystrophin gene. Approximately 13% of those patients have a nonsense mutation.

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