Wellcovorin Approved as First Treatment for Cerebral Folate Deficiency

The FDA has approved expanded use of GSK’s leucovorin calcium tablets (Wellcovorin) for the treatment of cerebral folate deficiency in adult and pediatric patients with a confirmed variant in the folate receptor 1 (FOLR1) gene.

The approval provides the first FDA-approved treatment for this rare genetic condition, which affects the transport of folate — a vitamin essential for brain health — into the brain.

Cerebral folate deficiency is a neurological disorder caused by impaired transport of folate into the central nervous system. Children with the condition often develop normally during infancy but may begin losing motor and cognitive skills around early childhood. 

People with FOLR1-related cerebral folate deficiency often experience severe developmental delays, movement disorders, seizures and other neurological complications. 

The FDA said the approval was based on a systematic review of published literature, including case reports with patient-level data and mechanistic evidence.

The expanded indication was approved through a Supplemental New Drug Application (sNDA) submitted by GSK. The sNDAt provides a new indication for Wellcovorin for the treatment of cerebral folate transport deficiency in adult and pediatric patients who have a confirmed variant in the folate receptor 1 gene.

The FDA said it worked with GSK to update the drug’s labeling with the scientific and safety information needed for its use in patients with FOLR1-related cerebral folate deficiency.

Possible side effects associated with leucovorin include pruritus, rash, urticaria, dyspnea, rigors and impaired thermoregulation. Anaphylaxis, a severe allergic reaction requiring immediate medical attention, is also a potential risk.

The FDA approval letter also noted that commercial marketing of Wellcovorin tablets was discontinued in 1997. If GSK decides to restart selling the drug, the company would need to submit updated information showing that the product meets current regulatory and manufacturing standards.

Recent Firsts in Ultra-Rare Disease Treatment

In the ultra-rare disease space, where extremely small patient populations can complicate traditional clinical trials, latest developments have produced notable firsts.

In February 2026, the FDA released a draft guidance outlining a framework for developing individualized therapies for ultra-rare genetic conditions. The guidance describes how sponsors may generate evidence of effectiveness and safety when randomized trials are not feasible. It focuses on therapies that target specific genetic or molecular abnormalities, including genome editing and RNA-based treatments. The guidance highlights the role of natural history data and biologically supported mechanisms in evaluating potential benefit.

In another recent regulatory development, the FDA approved Kygevvi (doxecitine and doxribtimine) for TK2 deficiency, the first approved treatment for the life-threatening mitochondrial disorder, which is characterized by progressive muscle weakness. The therapy reduced the risk of death by approximately 86% compared with historical outcomes. TK2 deficiency previously had no approved treatment options.

Another milestone came in September 2025, when Forzinity (elamipretide) received accelerated FDA approval as the first treatment for Barth syndrome, a rare mitochondrial disease that weakens heart and skeletal muscle. The therapy is designed to improve muscle strength.

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