GlaxoSmithKline plc (ADR) (GSK), Sarepta Therapeutics Inc (SRPT): The Good and Bad of a Competitor’s Failure

GlaxoSmithKline plc (ADR) (NYSE:GSK) measured walking ability as well, and only the boys that received continuous dosing increased the distance they could walk in six minutes after 25 weeks in the study by 31.5 meters on average. The group that got intermittent dosing — mean decrease of 0.1 meter — looked similar to the mean decrease of 3.6 meters for the placebo group.

It’s very curious that having 72% of patients increase dystrophin levels creates a statistically significant increase in walking ability, but having 59% of patients increase dystrophin produces no noticeable increase. If dystrophin levels were an indication of walking ability, you’d expect the intermittent group to walk at a level in between the continuous group and the placebo group.

It could be that there’s some unknown threshold where dystrophin increases becomes clinically meaningful. Or maybe an increase in dystrophin levels just isn’t predictive of an increase in walking ability and the data is all over the place — some patients with dystrophin increases walked further, while others that were positive were at the other spectrum. Either way, a lack of correlation would be bad for Sarepta Therapeutics Inc (NASDAQ:SRPT) if the FDA isn’t willing to give a full approval with walking data.

Of course, it’s hard to draw definitive conclusions with pooled data. What we’d really like to see is the dystrophin and walk data on an individualized basis. Do individual patients who increase dystophin walk further while those who don’t increase dystrophin walk less?

Unfortunately, GlaxoSmithKline plc (ADR) (NYSE:GSK) didn’t provide that level of detail, so the speculation on the likelihood that Sarepta gains FDA approval continues.

The article The Good and Bad of a Competitor’s Failure originally appeared on Fool.com and is written by Brian Orelli.

Fool contributor Brian Orelli and The Motley Fool have no position in any of the stocks mentioned.

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