(HealthDay News) – For patients with a hereditary form of blindness previously treated with gene therapy in one eye, a second dose of gene therapy in the other eye is safe and improves vision even further, according to a study published in the Feb. 8 issue of Science Translational Medicine.

Jean Bennett, M.D., Ph.D., from the University of Pennsylvania in Philadelphia, and colleagues treated three patients with Leber congenital amaurosis due to mutations in the RPE65 gene. These patients had already received gene therapy in one eye as part of a larger gene therapy study 1.7 to 3.3 years earlier. The patients now received gene therapy in the second eye via subretinal injection of a virus carrying a correct RPE65 gene.

Six months later, the researchers found that the patients became far more sensitive to dim light, and two patients were able to navigate in dim light. Vision also improved in the previously treated eye. Functional magnetic resonance imaging showed changes in retinal and cortical activation. The treatment was safe and no adverse responses were observed.

“In summary, this study provides the first demonstration of improved retinal and visual function after gene therapy readministration in a genetic disease and also the first demonstration of efficacy after readministration to the contralateral eye,” Bennett and colleagues conclude.

Several authors disclosed financial relationships with pharmaceutical companies and/or involvement with patents related to the study subject matter.

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