GlaxoSmithKline, Prosensa's muscular dystrophy drug drisapersen misses goal of late-stage study

GlaxoSmithKline and Prosensa said Friday that a Phase III trial of drisapersen failed to meet its main goal of a significant improvement in the 6-minute walking distance (6MWD) test compared to placebo in patients with Duchenne muscular dystrophy (DMD). Shares in Prosensa, which licensed global rights to the drug to GlaxoSmithKline in 2009, fell as much as 71 percent on the news.

The study randomised 186 boys with DMD to receive drisapersen or placebo via subcutaneous injection over 48 weeks. The companies noted that the difference in 6MWD of 10.33 metres seen between those given drisapersen and placebo was not significant. In addition, results showed that there was no treatment difference in key secondary assessments of motor function using the 10-metre walk/run test, 4-stair climb and the North Star Ambulatory Assessment.

Carlo Russo, head of GlaxoSmithKline's Rare Diseases Research & Development unit, said "we are committed to evaluating the outcome of this study in the context of the overall development programme...and we expect such evaluation to help inform our next steps for drisapersen." GlaxoSmithKline and Prosensa indicated that "full evaluation of the benefit-to-risk profile of drisapersen treatment across all studies is anticipated to be completed by year end." The companies added that results of the Phase III trial will be presented at a future scientific meeting and published in a peer-reviewed journal.

Drisapersen, which was granted FDA breakthrough therapy designation in June for DMD, is an antisense oligonucleotide designed to induce exon skipping of exon 51. Sarepta Therapeutics is developing a similar treatment called eteplirsen and in July said it will seek FDA approval in the first half of 2014.

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