Vertex Pharmaceuticals (VRTX) said late Wednesday the US Food and Drug Administration has expanded its approval of Casgevy to treat children aged two years and older with sickle cell disease and recurrent vaso-occlusive crises or transfusion-dependent beta thalassemia.

The expanded label lowers the minimum eligible age from 12 years and makes about 5,500 additional children in the US eligible for the one-time therapy, the company said.

Vertex Pharmaceuticals added regulatory reviews for label expansion are currently underway in the UK and Saudi Arabia.