Vertex Pharmaceuticals has presented new Phase 3 data showing positive outcomes for CASGEVY in children aged 5–11 years with severe sickle cell disease and transfusion-dependent beta thalassaemia, while confirming it has completed a UK regulatory submission to expand the therapy’s use to younger patients.

The results, presented at the European Hematology Association Congress and published simultaneously in the New England Journal of Medicine, support ongoing efforts to extend access to the CRISPR/Cas9 gene-edited therapy beyond its current approval for eligible patients aged 12 years and older.

In the Phase 3 Climb-151 study, all 11 children with severe sickle cell disease who received CASGEVY remained free from vaso-occlusive crises at the time of analysis, while all eight patients with sufficient follow-up achieved at least 12 consecutive months without a vaso-occlusive crisis.

In the Phase 3 Climb-141 study in transfusion-dependent beta thalassaemia, all eight evaluable children achieved the primary endpoint of at least 12 consecutive months of transfusion independence while maintaining the required haemoglobin level. The company said those patients remained transfusion independent throughout follow-up.

Vertex reported that the safety profile in younger children was consistent with previous studies in older patients receiving myeloablative conditioning and autologous stem cell transplantation. One death occurred in a child with transfusion-dependent beta thalassaemia following severe veno-occlusive disease related to busulfan conditioning and was reported as unrelated to CASGEVY.

Alongside the clinical update, Vertex announced that regulatory review is under way in the US to extend CASGEVY’s indication to younger children and that it has recently completed submissions in both the UK and Saudi Arabia seeking approval for use in patients aged 5–11 years.

Carmen Bozic, executive vice president of global medicines development and medical affairs and chief medical officer at Vertex, said: “The data presented at EHA and published in NEJM underscore the consistent, durable and transformative benefits CASGEVY can provide to people living with sickle cell disease or transfusion-dependent beta thalassemia from early in life.”

Franco Locatelli, professor of paediatrics and presenting author of the paediatric data, said: “These data represent a profoundly important step forward, and I look forward to the possibility of providing earlier intervention to prevent complications in children and for families who have had limited potentially curative options to date.”

CASGEVY is an autologous CRISPR/Cas9 gene-edited cell therapy designed to increase production of fetal haemoglobin. The treatment is currently approved in multiple countries for eligible patients aged 12 years and older with severe sickle cell disease or transfusion-dependent beta thalassaemia.