Highly anticipated phase III clinical trial results of Spark Therapeutics's gene therapy to treat visual impairment are due by year-end and could have profound implications for the broader gene therapy field, leading to the first approved product in the U.S. A detailed analysis of the design and use of SPK-RPE65 to treat Leber congenital amaurosis type 2 (LCA2), the possibility of expanding its use to other patient populations, and the anticipated impact of a first commercial gene therapy product is explored in Human Gene Therapy Clinical Development.