I wrote here about Ampyra, the multiple sclerosis drug from Acorda Therapeutics, one that came close to the record for "simplest chemical matter in a marketed drug". (As it happens, Biogen Idec is making sure that it doesn't even have the title of "simplest drug for multiple sclerosis", and the shadow of valproic acid looms over this entire competition).

That post mentioned some doubts that had been expressed about how effective Ampyra is for its target: improving gait in MS patients. And now those doubts are increasing, because the company has been asked to conduct a trial of a lower 5 mg dose of the drug along with the approved 10 mg one (which was associated with seizures in some patients). And neither one of them met the primary endpoint. As that link shows, the company has several explanations - different endpoint than used before, higher placebo response than usual, wider variety of patients - but those are all ex post facto. Acorda wouldn't have set up the trial like this in the first place if they didn't think that the approved dose would work, and it didn't.

For a drug with a rather narrow symptomatic indication, that's not good news. And it comes as Acorda is still trying to get the compound approved in Europe. The cost/benefit ratio usually can't stand a big hit to the "benefit" term.