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.