Upbeat review of PhII DMD trial earns Prosensa a big boost to shares

Hans Schikan, CEO of Prosensa

After the markets closed last night, Prosensa issued an upbeat self-assessment of its 48-week extension data from a Phase II study of its lead drug drisapersen for Duchenne muscular dystrophy. The study had already failed to achieve statistical significance for the primary endpoint in the 6-minute walk test after 24 weeks. But Prosensa's ($RNA) emphasis on a "clinically meaningful" improvement seen for DMD patients at 48 weeks was enough to earn a big spike in its share price--more than 20%--in a field that has been plagued by one setback after the next.

Here's the core assertion: "The results of this study indicate that, compared to placebo, boys in the higher-dose drisapersen group (6 mg/kg once weekly) experienced stabilization and even improvements in their muscle function and physical activity as measured by the six-minute walk test (6MWT) for the 24-week treatment phase and maintained this improvement during the 24-week follow-up period. Additionally, when evaluating the percent-predicted six-minute walk distance (6MWD), a clinically meaningful treatment difference of 5.2% was observed at week 24 and 4.8% at week 48."

Words like "indicate" and "clinically meaningful" imply that the study was a success. But it wasn't--at least not by commonly accepted biotech standards requiring statistical significance. In a message to FierceBiotech, a Prosensa spokesperson says that the study wasn't powered to demonstrate statistical significance.

"We had previously reported (on Sept 25, 2013) the 24 week data (which was the primary endpoint) for this study (DEMAND V/DMD114876)," says Prosensa CEO Hans Schikan in an email to FierceBiotech. "At that time, we had reported that a non-statistically significant but clinically meaningful treatment benefit was seen."

Prosensa was hammered to the ropes last fall when a closely watched Phase III study of drisapersen conducted by GlaxoSmithKline ($GSK) failed to demonstrate a statistically significant benefit for patients. And things didn't get any better for the Dutch biotech when GSK subsequently opted out of their collaboration in January, leaving Prosensa to carry on by itself.

Since then, though, the share price has risen dramatically as the biotech refocuses on a group of patients who the company believes can be helped by drisapersen. Investigators now are working on the belief that giving the drug earlier to patients and providing it more consistently can spur a major benefit for patients, and they're backing up the theory with 96-week extension data from the failed Phase III study.

Prosensa isn't alone in maintaining a sunny attitude in the face of repeated setbacks. PTC Therapeutics ($PTCT) has suffered back-to-back clinical failures for its DMD drug, ataluren, recently acknowledging that European regulators had stiff-armed a move to get their therapy on the market ahead of an ongoing Phase III trial. And Sarepta ($SRPT) last year was hit hard after the biotech told investors that the FDA was raising serious doubts about the positive data it had garnered from a tiny study of its drug eteplirsen.

Despite the setbacks, all three biotechs have managed to raise funds from investors over the past year, many driven by the view that any drug that can demonstrate an improvement could make a big impact in a field where patients face a lethal condition with no therapies available to treat the disease. And Prosensa's shares are up 40% for the past three months.

Prosensa also announced today that the company ended 2013 with 82.2 million euros in reserves. Prosensa was named a 2012 Fierce 15 company.

Update: At the end of the day Tuesday, Prosensa gave up most of the day's gains. The stock closed up 6%.

- here's the release

Special Report: 2012 Fierce 15 - Prosensa

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