8. Ampyra
Acorda Therapeutics
2013 Revenue:
$303 million

Ampyra was approved by the FDA in January 2010 as a treatment to help people with multiple sclerosis to improve their walking and is the only drug approved for that use. It has been used by more than 90,000 patients since then. The drug is marketed outside the U.S. as Fampyra by Biogen Idec ($BIIB).

The drug faltered in a postmarketing study completed in 2012 at the behest of the FDA, which wanted to see how patients responded to a 5-mg dose compared to the approved 10-mg dose. The problem was that while the 10-mg dose improved walking speed in a 25-foot walk after 4 weeks of treatment at more than the 5-mg dose, neither dose was statistically better than placebo. The company was quick to point out that that endpoint was a different measure of efficacy than the original evaluations of the drug.

Acorda ($ACOR) announced in June that Actavis ($ACT) is seeking approval of a generic and that it intends to vigorously defend its patents. -- Eric Palmer (email | Twitter)

For more:
Acorda MS drug falters in new walking study
Acorda CEO Cohen throws his weight behind new biotech trailblazer
MS drugs get yeas, nays and price increases
Acorda MS drug approval sparks buyout buzz