Sarepta Therapeutics Inc (NASDAQ:SRPT) shot up by more than 70% after the Food and Drugs Administration gave it the greenlight to begin marketing its Duchenne muscular dystrophy drug Exondys 51. However, the drug maker will have to carry out two-year trials to determine just how effective the drug, is according to the agreement reached by the FDA.

 FDA Unusual Approval

 The accelerated approval by the FDA was highly unusual given that the agency had voted in April against approving the drug. Winning a regulatory approval has been an uphill task for Sarepta given that the drug’s efficacy levels have been hotly debated for months.

A 12-person study result filed early in the year evoked some questions, after Exondys 51 failed to boost dystrophin to levels that could suggest clinical benefit.  Given the limited number of treatments for the condition, the agency had no option other than to approve it pending further trials.

“Accelerated approval makes this drug available to patients based on initial data, but we eagerly await learning more about the efficacy of this drug through a confirmatory clinical trial that the company must conduct after approval.” FDA in a statement.

 Market Potential

 Duchene is a progressive crippling medical condition that affects mostly male children. It affects one in every 3,500 children worldwide by destroying muscles, leading to death by the time patients are in their 30’s.

 The approval of Exondys 51 was in one way necessitated by parents making a rallying call for its approval given the impact it has already had in children. The agency had initially indicated that it would be open to approving it given the lack of alternatives in the market for the devastating illness.

Sarepta Therapeutics Inc (NASDAQ:SRPT) has already started proceedings to market the drug, reiterating that the drug’s costs will be based on a patient’s weight. The annual cost for an average size child could reach highs of $300,000 according to initial estimates. It is still unclear the number of patients the drug will benefit to help gauge the amount of money the drug maker stands to make.