Vertex Pharmaceuticals (VRTX) presented phase 3 data showing Casgevy delivered durable benefits in children aged 5 to 11 with severe sickle cell disease or transfusion-dependent beta thalassemia, the company said Thursday.

In the late stage study, all 11 treated patients remained free of vaso-occlusive crises, while all eight patients with sufficient follow-up achieved the primary endpoint of at least 12 consecutive months without a crisis, Vertex said.

In the transfusion-dependent beta thalassemia study, all eight patients with sufficient follow-up achieved at least 12 consecutive months of transfusion independence, the company said.

The safety profile was consistent with previous studies in older patients, Vertex said.

The US Food and Drug Administration is reviewing Vertex Pharmaceuticals' application to expand Casgevy's use to younger children.