FDA Rescinds Broad Autism Claims, Approves Leucovorin Only for Rare Genetic Disorder

On March 10, 2026, the U.S. Food and Drug Administration (FDA) officially updated the labeling for leucovorin calcium (Wellcovorin), marking a significant pivot from the high-profile administration claims made just months prior. While federal officials had previously touted the drug as a potential “breakthrough” for hundreds of thousands of children on the autism spectrum, the final regulatory decision limits its approved use to a specific, ultra-rare condition: Cerebral Folate Transport Deficiency caused by mutations in the FOLR1 gene (CFD-FOLR1).

The “Bait and Switch”: From Autism to Ultra-Rare Disease

The FDA’s decision represents a major scaling back of the vision presented by Commissioner Marty Makary and Health Secretary Robert F. Kennedy Jr. in September 2025. At that time, officials suggested that leucovorin—a decades-old drug typically used to manage chemotherapy side effects—could treat the “root cause” of autism in a significant portion of the population.

However, following a “systematic review” of available data, the FDA concluded that there was insufficient evidence to support a broad indication for Autism Spectrum Disorder (ASD). Instead, the agency focused on the FOLR1 variant, a genetic disorder so rare that it is estimated to affect fewer than 50 to 100 people worldwide.

Understanding the Rare Disease: CFD-FOLR1

Cerebral Folate Transport Deficiency is a condition where folate—a form of Vitamin B9 essential for brain development—cannot be effectively transported across the blood-brain barrier. This leads to low levels of folate in the central nervous system, resulting in:

• Severe developmental delays
• Seizures and movement disorders
• Autistic features (which led to the initial confusion regarding its use as a general autism treatment)

Leucovorin bypasses the defective transport mechanism to restore brain folate levels. In 27 cases reviewed by the FDA in which patients were treated with oral leucovorin, 89% showed clinical improvement in neurological symptoms.

The Science Behind the Reversal

The FDA’s retreat from a broad autism approval was catalyzed by two major factors:

1. Retraction of Key Research: In early 2026, the European Journal of Pediatrics retracted the largest study supporting the use of leucovorin in autism. The journal cited “errors” and “concerns with statistical analyses,” effectively removing the strongest piece of evidence the administration had relied upon.
2. Lack of Clinical Trials: Despite the administration’s enthusiasm, the American Academy of Pediatrics (AAP) and other medical societies warned that the evidence for the general use of autism was “too limited.” Most existing studies were small, open-label, or failed to meet the rigorous standards of Phase 3 clinical trials.

Impact on Families and the Healthcare System

The discrepancy between the initial White House rhetoric and the final FDA label has created a “whimper” after a “bang.” Following the September announcement, outpatient prescriptions for leucovorin surged by 71% as parents sought the drug off-label. This spike led to localized supply issues and confusion among pediatricians who were inundated with requests for a drug they were not yet comfortable recommending.

While the new label provides a formal pathway for those with the ultra-rare FOLR1 mutation, it leaves the vast majority of the autism community without the “cure” that was once signaled. The FDA continues to encourage manufacturers to conduct formal, large-scale trials to determine if a broader subset of the autism population could truly benefit.

Sources

• FDA Approves First Treatment for Patients with Cerebral Folate Transport Deficiency | FDA News Release
• FDA scales back vision for drug it touted as possible treatment for autism | The Washington Post
• Bait and Switch? RFK Jr.’s FDA Pivots on ‘Promising’ Autism Treatment Leucovorin | Gizmodo
• FDA approves leucovorin for ultra-rare cerebral folate deficiency subset without clinical trial | Fierce Pharma
• FDA finds little evidence that the generic drug leucovorin can help people with autism | PBS NewsHour
• Largest leucovorin-autism trial retracted | The Transmitter
• Leucovorin Use in Autism and Cerebral Folate Deficiency FAQ | American Academy of Pediatrics