The Food and Drug Administration is putting off a decision on whether to approve a controversial drug that patient advocates and some senators say is the only hope for children with a fatal rare disease.

Sarepta Therapeutics said Wednesday that the agency wouldn’t make a decision as expected on Thursday on the drug eteplirsen to treat Duchenne Muscular Dystrophy, a rare disease that mainly targets young boys. The decision comes as hundreds of lawmakers have pushed the agency to approve the treatment because there is no other for Duchenne.