CAMBRIDGE, Mass. ( TheStreet) -- Citibank biotech analyst Yaron Werber is a Prosensa (RNA) bull and a Sarepta Therapeutics (SRPT) bear. Well, he was a Prosensa bull until its Duchenne muscular dystrophy drug drisapersen blew up in a failed phase III study last week.
Werber remains a Sarepta skeptic. He created a minor dust-up Thursday after publishing a research note in which he claimed noted DMD expert Dr. Jerry Mendell is now raising doubts about Sarepta's chances of gaining FDA approval for eteplirsen based on the existing phase II study.
Mendell is the principal investigator in Sarepta's phase II study and has been publicly supportive of eteplirsen in the past, so it would be big news if he suddenly changed his mind about the drug. Mandell spoke this week at the DIA/FDA Oligonucleotide-based Therapeutics Conference in Washington, DC.
Here's what Werber wrote to clients about Mandell on Thursday:While Sarepta's stock has been making steady gains upwards as investors view Prosensa's ph 3 failure as a big win for Sarepta, the DMD field is less convinced, as this highlights the difficulty in showing a clinical outcome benefit in this disease. More concerning, there were clear statements from Sarepta's own principal investigator highlighting dystrophin should not be used as a primary measure to support approval since it's not a good marker of clinical activity.
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