Prosensa heralds new hope for once-failed muscular dystrophy drug

Prosensa's ($RNA) Duchenne muscular dystrophy treatment endured a Phase III setback that led partner GlaxoSmithKline ($GSK) to head for the exit, but the Dutch biotech is back with a new analysis of drisapersen's data that could spell a path forward, sending its shares up 25%.

According to Prosensa, a deeper dive into drisapersen's results suggests that administering the drug earlier in the disease and treating longer can delay the progression of DMD. For example, in 96-week extension data from a Phase III study, patients on continual treatment could walk 49 meters farther in a 6-minute walking test than those who took placebo for 48 weeks before switching to drisapersen, the company said.

"These data encourage us to engage patient groups, clinical experts and regulators to explore a path forward for drisapersen, which includes the possibility of re-dosing," CEO Hans Schikan said in a statement.

But that new way of looking at drisapersen apparently wasn't enough to sway GSK, which announced this week that it was handing the once-breakthrough-designated drug back to its partner. Investors tell a different story, however, and Prosensa leapt 25% on the news, trading at around $6.90.

Whether Prosensa's rehabilitation project can give drisapersen another shot at treating the muscle-deteriorating disease is anyone's guess, but it'll be a long climb up from what seemed like drug development oblivion just a few months ago.

Back in September, the partners revealed that drisapersen had failed to beat out placebo in improving 6-minute walk distance in boys with DMD, slashing about 70% off the top of Prosensa's recently IPO'd shares and casting doubt on the drug's mechanism of action. Like Sarepta's ($SRPT) competing eteplirsen, drisapersen works by spurring the body to ignore faulty dystrophin proteins that cause DMD in a technique called exon skipping.

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