Spark Therapeutics announced preliminary data from part one of the ongoing Phase 1/2 open-label, non-randomized, dose-finding study of the investigational SPK-8016 in hemophilia A. Part one of the Phase 1/2 study is designed to evaluate the safety and efficacy of SPK-8016 in adult males with clinically severe hemophilia A and no measurable inhibitor against FVIII. These data were presented at the European Association for Haemophilia and Allied Disorders (EAHAD) 2021 Virtual Congress by investigator Spencer Sullivan, M.D., Mississippi Center for Advanced Medicine. All four participants who have hemophilia A and no history of FVIII inhibitors received a single intravenous administration of SPK-8016 at a dose of 5X1011 vg/kg. As of the October 26, 2020 data cutoff, participants have stable and durable factor VIII (FVIII) activity at greater than 52 weeks ranging from 5.9-percent to 21.8-percent with no serious adverse events (AEs), and no FVIII inhibitor development. Data show a 98-percent reduction in annualized infusion rate (AIR) and 85-percent reduction in annualized bleed rate (ABR) after a follow up of between 15 and 18 months or 5.5 total patient years. One of four participants did not receive immunomodulatory agents and demonstrated the high level of FVIII activity (21.8-percent at greater than 52 weeks). Three of four participants received oral corticosteroid therapy, which was initiated between three- and six-weeks following vector infusion upon clinical suspicion of a hepatocyte-directed immune response. Daily oral corticosteroid therapy was administered in tapering doses for a range of 43 and 48 weeks. Two participants received azathioprine and/or tacrolimus as steroid-sparing immune-modulating co-therapy to limit total exposure to prednisone. No participant demonstrated persistent liver enzyme (alanine aminotransferase [ALT]/aspartate transaminase [AST]) elevations outside of the normal range, with the exception of transaminitis associated with azathioprine toxicity in one participant that resolved as expected after azathioprine was discontinued. No serious AEs were observed. The three participants who received immunomodulatory agents experienced mild-to-moderate, non-serious steroid-associated AEs. Investigational SPK-8016 is a novel, internally developed gene therapy for hemophilia A to address the unmet medical need within the hemophilia A inhibitor patient community. Inhibitors occur in as many as 30 percent of people with severe or moderately severe hemophilia A. Spark retains global commercialization rights to SPK-8016.