Shares of Sarepta Therapeutics, which is developing a drug to treat Duchenne muscular dystrophy (DMD), are getting a boost today due to disappointing data from a clinical trial from Prosensa Holding, which is developing a competing drug for DMD.
Wall Street has given Sarepta (ticker: SRPT) the edge in developing a drug for DMD, which could generate over $1 billion in annual revenues, and the new data from Prosensa's partner, GlaxoSmithKline, probably will help Sarepta in its quest for approval from the Food and Drug Administration. Sarepta plans to file for approval for its DMD drug, eteplirsen, with the FDA early next year. There now is no effective treatment for DMD.
Sarepta shares are up $2.64 at $34.68 while Prosensa shares are down $2.77 at $25.77. GlaxoSmithKline released long-awaited data on the dystrophin production from a Phase II study of the drug, drisapersen, that concluded about a year ago. Dystrophin is the protein critical to muscle health that is missing in boys with DMD, a fatal muscle-wasting disease caused by a genetic mutation.
The data showed that drisapersen produced dystrophin in 72% of the boys who got a continuous dose of the drug, while just 59% of boys who got an intermittent dose of the drug in the Phase II trial showed dystrophin in their muscles. GSK didn't elaborate on the level of dystrophin as a percentage of normal in the boys who showed dystrophin production.
By contrast, all 12 boys in the Sarepta Phase II trial of its drug, eteplirsen, showed dystrophin production based on data released by the company. Both the Sarepta and Prosensa drugs are designed to work at the genetic level to stimulate production of dystrophin and halt the progression of the disease.
"GSK's newly released dystophin data indicates that a substantial number of patients treated with the targeted dose of drisapersen may not be getting a meaningful drug effect. We believe this introduces new clinical, regulatory, and commercial risk for this competitive dru
"GSK's newly released dystophin data indicates that a substantial number of patients treated with the targeted dose of drisapersen may not be getting a meaningful drug effect. We believe this introduces new clinical, regulatory, and commercial risk for this competitive drug, which should benefit Sarepta given the more favorable therapeutic index that eteplirsen appears to have," wrote Baird analyst Brian Skorney in a note published today. He carries an Outperform rating on Sarepta with a $63 price target.
Barron's has written favorably several times on Sarepta and the prospects for approval of its DMD drug.
GSK had released previously some data on the Phase II trial about the performance of the more than 50 boys on a six-minute walk test, which is a key clinical measure. The six-minute walk test data were mixed.
The new trial results deepen the skepticism among Sarepta supporters about drisapersen, which also has shown adverse side effects among patients in the clinical trial, a contrast with the clean record of eteplirsen. No boys in the drisapersen trial, however, dropped out. Sarepta backers note that eteplirsen is being dosed at a much higher level than drisapersen due to apparent safety issues with the Prosensa drug. This gives an edge to Sarepta.
The results of a Phase III trial for drisapersen are expected later this year. Sarepta plans to start a Phase III trial for eteplirsen next year.