Moreover, the long-term trend depicted in the regression analyses suggests that visual improvement in treated patients may continue to progress with time, in line with the improvement noted up to 7 years after treatment in a small cohort of MT-ND4 LHON patients treated with another gene therapy product, although the majority of patients in that study were younger than 15 years in age (16). This evidence concerns the gene MT-ND4 and Leber hereditary optic neuropathy.