Sarepta gets creative in bolstering its case for quick eteplirsen approval

Sarepta Interim CEO Ed Kaye

Facing an expert panel showdown at the FDA next month, Sarepta Therapeutics cobbled together a new set of positive data for its Duchenne muscular dystrophy drug eteplirsen, aiming to overcome persistent doubts about the tiny size of its key trial. Pulling together a control arm by selecting patients who had been enrolled in other studies--a rare maneuver--the biotech sought to reassure doubters that its drug provided a significant, long-lasting benefit with clear biomarker evidence that the drug usually worked as expected.

By any standard of professional drug development, the idea of creating a post hoc comparison arm presents some messy data issues that Sarepta almost certainly will be questioned closely on by regulators. But this application is also coming at a time that the agency has shown repeatedly that it is willing to take chances and approve new therapies that may not have passed muster just a few years ago. And in this case a large group of families and patient advocates--as well as more than a few investors--have been pushing hard to gain approvals for new drugs to treat a ruthless disease.

The problem with Sarepta's case has always centered closely on the small size of its key study. Only 12 patients were enrolled. For several years now the company has tracked a much higher likelihood that these patients could continue to do much better than historical data would indicate. Now they've assembled their post hoc comparison arm to give regulators an idea of what that positive difference would look like.

"We are encouraged by the positive clinical outcomes, such as the statistically significant difference in the 6MWT (6 minute walk test) in eteplirsen-treated patients compared to a control, especially since we see them accompanied by data that continues to demonstrate exon skipping and dystrophin production (the biomarker) in most patients," said Ed Kaye, Sarepta's interim chief executive officer and chief medical officer, in a statement.

Kaye presented an expert panel at a London conference to back him up, including some of the investigators involved in making a case for eteplirsen. As might be expected, they endorsed Kaye's contention that new safety data from more patients would help augment their case for a quick approval, backed up by evidence of a slower decline in the boys with better ambulatory and pulmonary outcomes than could be expected otherwise.

The case helped bolster investor confidence for the company, which has been on a roller-coaster ride of dramatic ups and downs as the company pursued an approval based on the small study. Shares were up 17% in premarket trading today.

The FDA's Peripheral and Central Nervous System Drugs Advisory Committee is expected to pick up the matter on November 24, a day after experts grill BioMarin on drisapersen, a rival DMD drug that was acquired in the acquisition of Prosensa.

- here's the release

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