FDA Expands Casgevy Gene Therapy Approval to Children as Young as Two with Sickle Cell Disease and Beta Thalassemia

Jul 2, 2026

The FDA has expanded its approval of Vertex and CRISPR Therapeutics' gene therapy Casgevy to children as young as two with sickle cell disease and transfusion-dependent beta thalassemia. This decision lowers the previous age limit of 12, opening access to an estimated 5,500 eligible U.S. patients. The accelerated 53-day review was granted under the FDA's priority voucher program, supported by clinical trials showing high rates of crisis prevention and transfusion independence.

Casgevy pediatric expansion approval

▪The FDA approved a pediatric expansion of Vertex Pharmaceuticals and CRISPR Therapeutics' gene therapy Casgevy for children aged two years and older.
▪The pediatric expansion of Casgevy opens up a market of approximately 5,500 eligible patients in the United States.
▪The expanded approval of Casgevy covers patients with sickle cell disease and transfusion-dependent beta thalassemia, lowering the previous age threshold from 12 years.

FDA priority voucher program

▪Vertex Pharmaceuticals completed its submission for the pediatric expansion of Casgevy on May 4, 2026.
▪The FDA approved the pediatric expansion of Casgevy 53 days after filing under the Commissioner’s National Priority Voucher program.

Clinical trial results

▪The FDA extrapolated clinical data from ongoing Phase 3 open-label CLIMB-141 and CLIMB-151 studies to approve Casgevy for patients as young as two.
▪In a study of 11 patients with sickle cell disease aged 5 to less than 12 years, none of the eight evaluable patients experienced severe vaso-occlusive crises for at least 12 consecutive months.
▪In a trial of 15 patients with transfusion-dependent beta thalassemia, eight of the nine evaluable participants no longer needed transfusions for 12 consecutive months.

Casgevy commercial uptake challenges

▪Casgevy generated $43 million in revenue in the first quarter of 2026, following a total of $114 million in sales for the full year of 2025.
▪Vertex Pharmaceuticals forecasted $500 million in combined revenue for Casgevy and its non-opioid painkiller Jourvnavx.

Vertex povetacicept kidney therapy

▪BMO Capital Markets wrote in a March 9, 2026 note that povetacicept could become a new pillar of Vertex Pharmaceuticals' business if approved.
▪Vertex Pharmaceuticals is developing povetacicept, a fusion protein therapy for IgA nephropathy, which has an FDA target action date of November 30, 2026.

CRISPR gene therapy market

▪There are an estimated 37,000 people living with sickle cell disease and transfusion-dependent beta thalassemia across the United States and Europe combined.
▪Casgevy became the first approved CRISPR-based gene therapy for sickle cell disease in December 2023, alongside bluebird bio's Lyfgenia.