That leaves doctors who want more proof of the drug's efficacy to wait for a study in patients with kidney disease.

FORBES: Efficacy Questions Still Dog Vytorin

Sarepta, formerly known as AVI Biopharma, boomed because of data from an 8-patient study that shows unprecedented efficacy for its drug, eteplirsen, dramatically reduced the rate at which patients with Duchenne muscular dystrophy worsened.

FORBES: Sarepta Outperformed Biotechs In August Due To Muscular Dystrophy Drug

It doesn't stop ticking while a drugmaker does a five-year study to compare the drug, in safety and efficacy, with the alternatives.

FORBES: In Denial

But there were strings: The FDA demanded a fourth big study to confirm the drug's very modest efficacy before it would give final approval.

FORBES: Crisis in the Cabinet

More than 13, 000 patients have been enrolled in one study to test the drug's safety and efficacy for an application with the Food and Drug Administration.

FORBES: Magazine Article