Mixed results for PTC Duchenne drug put spotlight on EU approval

Dive Brief:

• A Duchenne muscular dystrophy drug missed its main goal in an important study but showed benefits on most other measures, potentially positioning the treatment’s maker, PTC Therapeutics, to maintain its approval in Europe.
• PTC’s drug, called Translarna, was approved in Europe in 2014 on the condition the company carry out a confirmatory study to prove its ability to help people with Duchenne, a debilitating genetic disease that erodes muscle strength and leads eventually to organ failure. PTC disclosed results from the trial Tuesday.
• While Translarna fell short in a certain group of Duchenne patients PTC had specified ahead of time, treatment appeared to slow declines in walking and other functional abilities versus placebo across the entire population studied. On a conference call Tuesday, PTC CEO Stuart Peltz said his company expects the data will support full approval in Europe, and indicated they will meet with the Food and Drug Administration in the U.S.

Dive Insight:

For the past seven years, PTC has sold Translarna in Europe under a conditional authorization that, so far, has been renewed by regulators there each year. Since 2017, the New Jersey-based biotech company has been running a Phase 3 study in more than 350 patients with Duchenne that’s meant to confirm the drug can help slow the disease’s steady progression. 

The results released Tuesday are mixed. Among the specific group of patients that PTC selected to assess Translarna’s impact — boys aged 7 to 16 years old who have a certain level of baseline walking function, but aren’t considered stable — treatment did not result in a statistically greater effect than placebo on a measure called the six-minute walk test. 

But, including all 359 patients enrolled into the study, Translarna did seem to slow declines in walk test scores and on a composite measure of other functional tasks like climbing a box or standing. (A statistical model favored by the FDA did not show similarly statistically significant results, however.)

“Translarna is the first disease-modifying treatment for DMD to show statistically significant treatment benefit across the entire [intent-to-treat] population,” said Peltz on Tuesday’s conference call. “In the primary analysis,” he added, “while we demonstrated a positive trend across all endpoints, statistical significance was not achieved.” 

PTC also presented data pooled from its confirmatory study and prior testing that it claims show a substantial treatment benefit on the six-minute walk test and functional scores. It did not disclose specific safety data from the confirmatory trial, but noted treatment was “well-tolerated” and no patients discontinued as a result of side effects. 

PTC plans to take the data to the European Medicines Agency for full approval, an outcome that analysts at RBC Capital Markets and Cantor Fitzgerald regard as a real possibility. 

“The totality of the data .. should very likely be good enough to keep the drug on and reimbursed in the European market,” wrote RBC’s Brian Abrahams in a June 21 note to clients. 

The FDA, which previously rejected Translarna, could be a different story, although PTC plans to try. “We remain fully committed to bringing Translarna to DMD boys in the United States and we look forward to discussing these results and potential path forward for approval with the FDA,” said Peltz. 

Shares in PTC rose 15% in value by mid-morning Tuesday. 

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