June 11, 2026 —
Vertex Pharmaceuticals announced new data showing that CASGEVY® demonstrated clinical benefit in children ages 5–11 with severe sickle cell disease, or SCD, and transfusion-dependent beta thalassemia, or TDT. The data were presented at the European Hematology Association Congress and simultaneously published in The New England Journal of Medicine.
CASGEVY, also known as exagamglogene autotemcel, is a non-viral, ex vivo CRISPR/Cas9 gene-edited cell therapy. The treatment uses a patient’s own hematopoietic stem and progenitor cells, which are edited at the erythroid-specific enhancer region of the BCL11A gene. This edit increases production of fetal hemoglobin, or HbF, which can reduce vaso-occlusive crises in SCD and eliminate or reduce transfusion dependence in TDT.
The new pediatric data come from the pivotal CLIMB-151 and CLIMB-141 studies, which are evaluating CASGEVY in younger children. Results were consistent with the durable clinical benefits previously established in patients ages 12 and older.
In the Phase 3 CLIMB-151 study of children with severe SCD, all 11 dosed patients were free from vaso-occlusive crises. Among the eight children with sufficient follow-up, all eight achieved the primary endpoint of being free from VOCs for at least 12 consecutive months. The mean duration of VOC-free response among these patients was 19.0 months, with follow-up ranging from 13.2 to 30.1 months.
In the Phase 3 CLIMB-141 study of children with TDT, 15 patients have been dosed with CASGEVY. Among the eight children with sufficient follow-up, all eight achieved the primary endpoint of transfusion independence for at least 12 consecutive months while maintaining a weighted average hemoglobin level of at least 9 g/dL. All children who achieved this endpoint remained transfusion independent throughout follow-up, with a mean duration of transfusion independence of 23.4 months.
The safety profile in younger children was consistent with myeloablative conditioning and autologous transplant, as previously observed in older patients with SCD and TDT. Vertex previously disclosed one death in a child with TDT who developed severe veno-occlusive disease from busulfan conditioning; the death was reported as not related to CASGEVY.
The data also showed durable and clinically relevant increases in fetal hemoglobin and stable allelic editing, consistent with results in older patient populations. These findings support the potential value of earlier intervention, as both SCD and TDT can cause progressive complications beginning in childhood, including organ damage and long-term disease burden.
CASGEVY is currently approved in multiple countries for eligible patients ages 12 and older with SCD and recurrent VOCs or TDT. Regulatory review is underway in the United States to expand use to younger children, and Vertex has recently completed submissions in the United Kingdom and the Kingdom of Saudi Arabia. Use of CASGEVY in children ages 5–11 remains investigational.
