Hyperion Therapeutics has reached agreement with the FDA under the Special Protocol Assessment (SPA) process for the pivotal Phase III trial of investigational product HPN-100 (glycerol phenylbutyrate) in adults with urea cycle disorders (UCD). The SPA is a written agreement between the trial sponsor and the FDA regarding the design, endpoints, and planned statistical analysis of the Phase III trial to be used in support of a New Drug Application (NDA). The 4-week, multi-center, randomized, double-blind, cross-over, Phase III study in adults with urea cycle disorders is designed to evaluate the non-inferiority of HPN-100 (glycerol phenylbutyrate) to BUPHENYL(R) (sodium phenylbutyrate). The primary efficacy measure is blood ammonia, assessed as 24-hour area under the curve on Days 14 and 28 (last day of each treatment period). The study will enroll approximately 44 adults, and all subjects completing the study will be eligible to enter a 12-month, open label safety study. Hyperion will concurrently conduct a 2-3 week open label study of the safety, pharmacokinetics, and pharmacodynamics of glycerol phenylbutyrate compared to sodium phenylbutyrate in approximately 10 children ages 6-17. Bruce Scharschmidt, MD, Chief Medical Officer of Hyperion Therapeutics, commented, “We appreciate the input from FDA on the pivotal Phase III study protocol and look forward to continuing development of HPN-100 for urea cycle disorder patients, a population with limited treatment options.”
