Prosensa: One Duchenne Therapy Down

Includes: GSK, RNA, SRPT
by: Derek Lowe

In the post here the other day about Duchenne Muscular Dystrophy [DMD] I mentioned two other companies that are looking at transcriptional approaches: Prosensa (with GSK) and Sarepta. They've got antisense-driven exon-skipping mechanisms, rather than PTC's direct read-through one.

Well, Sarepta still does, anyway. Prosensa and GSK just announced clinical data on their agent, drisapersen, and it appears to have missed completely. The primary endpoint was a pretty direct one, total distance walked over six minutes, and they didn't make statistical significance versus placebo. This was over 48 weeks of treatment, and none of the secondary measures showed any signs either, from what I can see. I can't think of any way to spin this in any positive direction at all.

So drisapersen is presumably done. What does this say about Sarepta's candidate, eteplirsen? On the one hand, its major competitor has just been removed from the board. But on the other, their complete failure with such a closely related therapy can't help but raise doubts. I don't know enough about the differences between the two (PK?) to speculate, but it'll be interesting to see if Sarepta's stock zips up today, sells off, or (perhaps) fights to a draw between two groups of investors who are taking this news in very different ways.

That's the delirious fun of biotech investing. And that's just for the shareholders - you can imagine what it feels like to bet your whole company on this sort of thing.