GlaxoSmithKline (GSK) has withdrawn its application with the Food and Drug Administration for leucovorin, a drug recently promoted by federal health officials as a potential autism treatment, after regulators declined to support its broader use.

Leucovorin, a derivative of Vitamin B9 long used in cancer care, drew national attention last fall when Health and Human Services Secretary Robert F. Kennedy Jr. and FDA Commissioner Marty Makary pointed to it as a promising therapy for some individuals with autism. The endorsements led to a surge in prescriptions, with some families reporting difficulty obtaining the drug.

Despite the initial push, federal regulators later clarified that available data do not support leucovorin as a general treatment for autism. FDA officials said the evidence reviewed was only sufficient to justify approval for a rare genetic condition known as cerebral folate transport deficiency tied to a specific receptor 1 gene variant.

“Right now, we don’t have sufficient data to say that we can establish efficacy for autism more broadly,” one senior FDA official said, noting that the agency’s review was limited to a narrower medical indication.

GSK’s decision to pull the application was described as procedural. The company has not marketed leucovorin since 1999 and indicated it had no plans to reintroduce the drug commercially. A company spokeswoman said generic versions are already available and can now include labeling for the rare genetic condition approved by the FDA.

The episode highlights ongoing debate over experimental and off-label treatments for autism, as well as the challenges regulators face in balancing patient demand with scientific evidence. While some officials had framed leucovorin as a potentially “exciting” option for broader use, the FDA ultimately limited its position to a narrowly defined group of patients with a confirmed genetic disorder.

The development leaves families and providers navigating a more constrained regulatory landscape, with no new federally endorsed pharmaceutical treatment for autism emerging from the review.