GTS-15 covers 11 of the 13 approved gene therapies, three cell therapy treatments, and one maintenance medication. Diseases covered under the GTS-15 program include Leber congenital amaurosis, spinal muscular atrophy types 1 and 2 for children ages 2 and under, beta thalassemia, cerebral adrenoleukodystrophy, hemophilia A, hemophilia B, Duchenne muscular dystrophy, sickle cell disease, transfusion-dependent beta thalassemia, metachromatic leukodystrophy, multiple myeloma, and congenital athymia.
