The FDA approved the expansion of Casgevy, which had previously been greenlit for patients 12 and up, into a younger pediatric population under the agency’s Commissioner’s National Priority Voucher program.
The FDA has approved a pediatric expansion of Vertex Pharmaceuticals’ gene therapy Casgevy, allowing its use in children 2 years and up who have sickle cell disease and transfusion-dependent beta thalassemia.
Casgevy is the first genetic medicine for these indications that can be used in young children, according to Vertex’s news release of the approval on Wednesday. The regulatory win opens up a market of around 5,500 patients in the U.S. who can access the one-time therapy from more than 75 authorized treatment centers, the biotech added. The gene therapy had previously been approved for both indications in patients 12 years and older.
The FDA, for its part, touted the approval as a success of its Commissioner’s National Priority Voucher (CNPV) program. “The approval decision was granted just 53 days after filing,” the agency said in its own news release, “and represented the eighth approval” granted under the CNPV scheme. Casgevy was given the accelerated review ticket in November 2025, and Vertex announced that it had completed its submission for the therapy’s expansion on May 4, officially starting the 1- to 2-month review clock, down from traditional review times of 10–12 months.
Casgevy was assessed in a study of 11 patients with sickle cell disease (SCD) who were aged 5 years to less than 12 years, the FDA said on Wednesday. None of the eight evaluable patients experienced severe vaso-occlusive crises for at least 12 consecutive months within the first two years of Casgevy infusion—meeting the study’s primary endpoint.
In transfusion-dependent beta thalassemia, Casgevy was tested in a trial with 15 patients in the same age range. Nine participants had evaluable data, of whom eight no longer needed transfusions for 12 consecutive months, according to the agency.
The decision to approve for patients as young as 2 years of age was based on “extrapolation to the younger pediatric age population,” taking into account Casgevy’s clinical data and product characteristics, the FDA said. Vertex is running the Phase 3 open-label CLIMB-141 and CLIMB-151 studies to test Casgevy in this younger population, the biotech said Wednesday.
Casgevy, which Vertex developed in partnership with CRISPR Therapeutics, is a CRISPR-based medicine that in December 2023 became the industry’s first gene therapy for SCD, alongside bluebird bio’s Lyfgenia. But uptake has been slow, with the product making $43 million in the first quarter. In February, Vertex set a high revenue bar for the gene therapy, forecasting $500 million in combined revenue with its non-opioid painkiller Jourvnavx.
“With Casgevy, we had a strong year with 300 or so patients initiating—150 or so having first cell collections,” Vertex COO and CFO Charles Wagner told investors during the company’s fourth-quarter 2025 earnings call. “Given the length of the patient journey, that gives us great visibility into the [upcoming] year. So we’re very confident that Casgevy will ramp up nicely compared to 2025.”
Much of the investor attention on Vertex, however, has been focused on its potentially “iconic” showing in kidney disease later this year. Vertex is developing a fusion protein therapy called povetacicept for IgA nephropathy, which is currently under FDA review, with a target action date of Nov. 30. If approved, povetacicept could be a “new pillar of [Vertex’s] business,” BMO Capital Markets wrote in a March 9 note.
