FDA Approves Leucovorin for Cerebral Folate Deficiency, Sparking Debate Over Off-Label Use in Autism

The U.S. Food and Drug Administration (FDA) approved leucovorin in 2025 for the treatment of cerebral folate deficiency (CFD), a rare condition that can co-occur with autism. However, the agency explicitly stated that the approval does not extend to autism itself. Despite this, leucovorin is increasingly being used off-label to address language symptoms in autistic individuals, fueling a contentious debate among clinicians, researchers, and families.

What Is Cerebral Folate Deficiency (CFD)?

CFD is a rare neurological disorder where the brain cannot properly transport folate, a B vitamin crucial for brain development and function. This results in low levels of 5-methyltetrahydrofolate (5-MTHF) in the cerebrospinal fluid, leading to symptoms like developmental delays, seizures, and movement disorders. Some autistic individuals have been found to have mutations in genes like FOLR1, DHFR, or MTHFR, which are involved in the folate pathway, though the prevalence and clinical significance of these mutations vary widely. For more on the genetics, see this Frontiers review.

What Is Leucovorin?

Leucovorin is a form of folate, commonly used to counteract the toxic effects of certain chemotherapy drugs. In CFD, it bypasses the impaired folate transport system, delivering folate directly to the brain. Its off-label use in autism stems from the hypothesis that some autistic individuals might benefit from increased folate availability, though this remains unproven.

The Evidence So Far

Small clinical trials and anecdotal reports suggest that leucovorin may improve language skills in some autistic individuals. For example, a pilot study (NCT02839915) found modest improvements in communication among a subset of participants, though the study was uncontrolled and industry-sponsored. However, these findings have not been replicated in large-scale, randomized controlled trials (RCTs), which are the gold standard for medical evidence. Two other RCTs referenced in this JHEOR article remain unpublished.

As Medical Xpress reported, the off-label use of leucovorin for autism has surged despite the lack of robust data. Some parents, like those featured in the JHEOR article, report dramatic improvements in their children's speech. Yet, experts urge caution, emphasizing that these anecdotal successes do not constitute scientific proof.

The Bigger Picture

The debate over leucovorin underscores a broader issue in autism treatment: the lack of FDA-approved medications for core traits like social communication differences and repetitive behaviors. Currently, the only FDA-approved drugs for autism are risperidone and aripiprazole, which target irritability and aggression, not core traits. Their approvals are based on 20-year-old trials, highlighting the slow pace of progress in this area.

Preclinical studies, such as those using zebrafish models or repurposing epilepsy drugs, show early promise but have yet to yield human-relevant results. The FDA's approval of leucovorin for CFD is a targeted regulatory action, not a breakthrough for autism treatment.

Autistic Perspectives and Ethical Considerations

Many autistic self-advocates emphasize that autism is a neurodevelopmental difference, not a disease to be cured. They argue for supports that address co-occurring challenges like anxiety or sensory issues, rather than medications aimed at altering core autistic traits. Any off-label use of leucovorin should be decided collaboratively with autistic individuals (or caregivers where appropriate), respecting informed consent and neurodiversity principles. For more on this perspective, see this Nature review.

What’s Next?

Researchers are calling for more rigorous studies to determine whether leucovorin can benefit autistic individuals, particularly those with folate pathway mutations. Until then, the drug's off-label use remains a contentious topic, with some families eager to try it and experts urging restraint. Families considering off-label use should discuss potential risks, such as folate masking B12 deficiency or interactions with seizure thresholds, with their healthcare providers. The drug's cost trajectory post-approval is also a concern, as price spikes could make off-label use prohibitive for many families.