Less than five weeks after granting a highly controversial approval for the Alzheimer’s drug Aduhelm, the Food and Drug Administration has updated its recommendation for who should receive the drug. The update narrows the recommended patient pool from all those with Alzheimer’s disease to only those with mild forms of the disease.

The FDA’s initial sweeping recommendation was a highly contentious aspect of the drug’s approval, because it wasn’t backed by any data. Aduhelm’s developer, Biogen, had only included people with mild disease in its clinical trials. The numerous critics of the approval raised immediate questions as to why the drug would be open to all.

But those critics—including researchers and industry experts—aimed most of their ire at the approval itself, given that Biogen’s clinical trials failed to convincingly show that the drug works at treating mild Alzheimer’s. In fact, Biogen had halted two identically designed Phase III trials in 2019 after Aduhelm flunked a “futility analysis.”