Jeffrey D. Marrazzo, Co-Founder and CEO of Spark Therapeutics, discusses the successful Phase III trial of its lead candidate, SPK-RPE65, was able to improve functional vision in patients with a rare form of a genetic disorder known as RPE65-mediated inherited retinal dystrophies. SPK-RPE65 is intended to treat rare blinding conditions caused by mutations in the RPE65 gene, which is linked to subtypes of Leber congenital amaurosis (LCA type 2) and retinitis pigmentosa (RP type 20). Wall St. approved as well--Spark shares rose almost 60% to $70 in trading before the market opened the day of the announcement. The study results represent the first successful randomized, controlled Phase 3 trial ever completed in gene therapy for a genetic disease, Spark executives said.