Ultragenyx Initiates New Development Program Studying KRN23 for the Treatment of Tumor-Induced Osteomalacia

Ultragenyx Pharmaceutical Inc. RARE, a biopharmaceutical company focused on the development of novel products for rare and ultra-rare diseases, announced the initiation of a new development program for the human monoclonal anti-FGF23 antibody KRN23 (UX023) in tumor-induced osteomalacia (TIO). TIO results from typically benign tumors that produce excess levels of fibroblast growth factor 23 (FGF23), which can lead to severe osteomalacia, fractures, bone and muscle pain, and muscle weakness. Ultragenyx intends to initiate a Phase 2 study of KRN23 in six adult TIO patients in the first half of 2015. KRN23 is being developed under a license and collaboration agreement between Ultragenyx and Kyowa Hakko Kirin Co., Ltd. KRN23 is being evaluated in a separate Phase 2 clinical study for pediatric patients with X-linked hypophosphatemia (XLH) and has completed multiple Phase 1/2 studies in adults with XLH. "We are pleased to announce the start of our Phase 2 program in TIO. This decision was based on the clear biological rationale and the particularly high unmet medical need in these patients when tumor resection is not feasible," commented Sunil Agarwal, M.D., Ultragenyx's Chief Medical Officer. "We anticipate interim safety and efficacy data from the Phase 2 study by the end of 2015. With the start of the TIO program, the KRN23 development plan now includes two diseases, TIO and XLH, both sharing the same underlying pathology of excess FGF23 production." The open-label, dose-finding Phase 2 clinical study will evaluate safety and efficacy in approximately six adult patients. The primary objectives of the study are to establish the dose, dosing regimen, and safety profile of treatment with KRN23 in TIO patients. Preliminary clinical effects of KRN23 treatment will be evaluated by radiographic assessments, muscle strength, walking ability, and by patient-reported measures of pain, disability, and quality of life. Markers of bone health and changes in serum phosphorus and other biochemical measures will also be followed. The study will consist of a 16-week individual dose-titration period followed by a 28-week treatment period. The goal of the dose-titration period is to identify the individualized dose of KRN23 required to achieve stable serum phosphorus levels in the target range. Patients will receive subcutaneous injections of KRN23 once every four weeks.