The FDA says it does not have sufficient data to show leucovorin is effective for treating autism, walking back earlier signals that suggested the drug could help many children.

•? ?The agency instead approved leucovorin for a rare genetic condition, cerebral folate deficiency linked to the FOLR1 gene.

•? ?Interest in the drug surged after a September White House briefing, when officials suggested it could help large numbers of children with autism, causing prescriptions to spike.