Sarepta-Glaxo Duchenne's Rivalry Heats Up This Week

BOSTON ( TheStreet) -- The race between Sarepta Therapeutics ( SRPT) and GlaxoSmithKline ( GSK) to develop the first new therapy for Duchenne muscular dystrophy just took an interesting twist. Glaxo decided -- somewhat abruptly -- to present results from its randomized phase IIb study of drisapersen at a research conference on Thursday.

This is the first time Glaxo is sharing data from any placebo-controlled study of drisapersen in Duchenne muscular dystrophy (DMD) patients. The timing is odd for a couple of reasons: Glaxo and partner Prosensa have said several times in the past that no data from this drisapersen study would be announced until the third quarter (when the ongoing phase III study was expected to be completed.)

Glaxo also chose a somewhat obscure venue to present the phase IIb drisapersen data Thursday -- the RNA & Oligonucleotide Therapeutics conference at Cold Spring Harbor Laboratories. A more high-profile venue would have been the The Muscular Dystrophy Association's Scientific Conference, scheduled for April 21-24.

Here is where you can let your speculative juices flow. Is Glaxo trying to hide negative drisapersen data? Or, are the drisapersen data so positive that Glaxo is rushing to get the news out ahead of the expected announcement later this month by Sarepta about the possibility of an accelerated approval filing for eteplirsen?

This may sound paradoxical, but Sarepta supporters should be rooting for drisapersen since the two drugs are both designed to "skip over" the defective exon 51 in DMD patients and produce functional dystrophin. Sarepta's phase II study has already demonstrated eteplirsen's ability to 1) produce functional dystrophin; and 2) improve walking ability in DMD patients. But Sarepta's phase II study was only conducted in a small number of patients, which has made the findings controversial, as we all know.

The case Sarepta is making to FDA about eteplirsen based on a small number of patients would be strengthened if Glaxo's phase II study of drisapersen produces similar findings.

Safety may be the area where Sarepta has an edge over Glaxo, which has already disclosed hospitalizations and treatment discontinuations in drisapersen-treated DMD patients due to kidney toxicity and low platelet counts. It will be very interesting to see the drisapersen safety data presented by Glaxo on Thursday.

As a reminder, the phase IIb study enrolled 54 DMD patients, randomized to treatment with two doses of drisapersen (3 mg and 6 mg) or a placebo. The study's primary endpoint is the mean change in the six-minute walk test from baseline to 24 weeks. Measurement of dystrophin levels via biopsy is a key secondary endpoint.

Sarepta released positive 74-week results from its phase II eteplirsen study on Friday, while investors wait for the company to announce its FDA filing plans. That announcement is expected before the end of April.

-- Reported by Adam Feuerstein in Boston.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.