I worry that the absolute 78-meter decline in 6MWT for the placebo group at 36 weeks seems unusually rapid. A 2010 study published in Muscle and Nerve suggests somewhat slower progression -- less than 60 meters of decline -- at 52 weeks. Although this difference could be due to normal disease variability or patient differences, the late acceleration of progression in the placebo group is a red flag.
Feuerstein, in his last column on Sarepta, wants, justifiably, to see a correlation between 48-week dystrophin levels and clinical outcomes. I do too. Those data could eliminate my concern about this issue.
4. Sarepta's patent situation seems shaky. Prosensa has rights to patents, both in the U.S. and Europe, which appear to cover Sarepta's eteplirsen. In fact, Sarepta tried and failed to overturn Prosensa's European patent related to treatment of DMD through skipping of dystrophin exons 51 and 46. That's a concern. Although a weak patent estate won't impact Sarepta's data, it might temper eteplirsen's commercial potential.
5. Corporate red flags are a concern. I'm not crazy about Sarepta's recent name change and one-for-six reverse stock split, but those are forgivable offenses given potentially groundbreaking data. I'm far less sanguine about the June 2012 resignation of Chief Scientific Officer Dr. Peter Linsley. Although Dr. Linsley informed the company of his intent in mid-April, this should be considered a concern for two reasons. First, high-ranking executives rarely resign without any apparent reason on the cusp of positive data. Second, Sarepta never issued a press release about the change, instead choosing to disclose the information in an SEC Form 8-K. Although management briefly mentioned the change on the company's Q1 2012 call, investors seem to have missed it.I'm not ready to declare eteplirsen a breakthrough, but it definitely appears promising. Given Sarepta's $230 million market capitalization and the obvious unmet medical need in DMD, I think the stock is a reasonable long position for biotech investors with a healthy appetite for risk. Nonetheless, I would keep the position on the smaller side since the roads of biotech can be unexpectedly bumpy. Caveat emptor. Disclosure: Sadeghi has no positions in any of the stocks mentioned in this article. Follow Nathan Sadeghi-Nejad on Twitter.