UK regulator extends Casgevy gene‑editing therapy to children aged 5 and over

Britain’s medicines regulator has widened access to Casgevy, extending the gene-editing treatment’s UK authorization to eligible children aged 5 and over with severe sickle-cell disease or transfusion-dependent β-thalassemia. The decision expands an existing approval rather than clearing a new drug for the first time.

The Medicines and Healthcare products Regulatory Agency, or MHRA, said on Friday that the marketing authorization extension was granted on Oct. 29 to Vertex Pharmaceuticals (Europe) Ltd. Casgevy, whose nonproprietary name is exagamglogene autotemcel and which is also known as exa-cel, had previously been authorized in the UK only for patients ages 12 and older.

Casgevy is one of the first approved medicines to use CRISPR gene editing in clinical practice. It is an autologous, ex vivo stem-cell therapy, meaning a patient’s own blood-forming stem cells are collected, edited outside the body and then reinfused. The treatment uses CRISPR/Cas9 to target a DNA control region linked to the BCL11A gene in order to raise levels of fetal hemoglobin, a form of hemoglobin that can help offset the effects of these inherited blood disorders.

That matters because severe sickle-cell disease and transfusion-dependent β-thalassemia are serious lifelong conditions caused by inherited problems in hemoglobin, the protein in red blood cells that carries oxygen. People with sickle-cell disease can face painful vaso-occlusive crises, while patients with transfusion-dependent β-thalassemia may need regular blood transfusions.

The pediatric expansion was supported by phase 3 open-label CLIMB studies in children ages 5 to 11: 15 with transfusion-dependent β-thalassemia and 11 with sickle-cell disease. Reported median follow-up was about 16 months. In children with evaluable follow-up of at least 16 months, those with β-thalassemia achieved transfusion independence, and those with sickle-cell disease had no severe vaso-occlusive crises, according to results reported in The New England Journal of Medicine.

Safety, however, remains central to the treatment’s use. All children in the pediatric study had at least one grade 3 or 4 adverse event. Two children with β-thalassemia developed severe veno-occlusive disease, a potentially serious liver complication, linked to busulfan conditioning chemotherapy given before the edited cells were returned. One of those children died; investigators said the death was attributed to the conditioning regimen rather than directly to the gene-edited cells.

In announcing the extension, the MHRA said its decision followed a review of the treatment’s safety, quality and effectiveness and that it would continue monitoring Casgevy after approval. “Severe sickle cell disease and β‑thalassemia are serious, lifelong conditions that in some cases can be fatal. This approval means this innovative gene‑editing treatment can now be used in eligible children from the age of five, extending this treatment option to younger patients,” Julian Beach, MHRA executive director of operations, said in a statement. “It is based on careful assessment of the available evidence on the treatment’s safety, quality and effectiveness. As with all medicines, we will continue to closely monitor the safety and effectiveness of Casgevy.”

The treatment also remains far more involved than a standard infusion. Patients must first undergo stem-cell collection, then individualized manufacturing of the edited cells, followed by high-intensity myeloablative conditioning with busulfan and hospital monitoring. That means Casgevy must be delivered in specialized transplant or advanced cellular therapy centers.

The MHRA first authorized Casgevy in November 2023, calling it the first licensed medicine using CRISPR gene editing. Internationally, the U.S. Food and Drug Administration expanded the therapy’s use to patients ages 2 and older in July 2026, while the European Medicines Agency granted a conditional marketing authorization for people 12 and older in February 2024. Britain’s latest move broadens eligibility for younger children, but the treatment will still require specialist-center care and continued safety follow-up.