Visual acuity after retinal gene therapy for choroideremia

To the Editor: Two recent clinical reports of retinal gene therapy with adeno-associated virus (AAV) vectors in patients with Leber's congenital amaurosis showed initial gains in visual function that subsequently declined.(1),(2) We previously reported early improvement in visual acuity in two of six patients who received retinal gene therapy in one eye (the study eye) to treat choroideremia,(3) a disease that is characterized by atrophy of the choriocapillaris and retinal pigment epithelium and involves vision loss that leads to blindness. Choroideremia is caused by loss-of-function mutations in the gene CHM. We delivered nonmutated CHM in an AAV vector (AAV.REP1) . .