Ultragenyx Reports Positive Interim Data From Phase 2 Study In Pediatric XLH

(RTTNews) - Ultragenyx Pharmaceutical Inc. (RARE) announced positive 16-week data from the ongoing pediatric Phase 2 study and provided a regulatory update for its recombinant human monoclonal antibody KRN23 against fibroblast growth factor 23 for the treatment of X-linked hypophosphatemia, or XLH. After 16 weeks of dose-titration, all 36 patients had increases in serum phosphorus levels from baseline. No serious adverse events have been reported and there have been no discontinuations.

Ultragenyx said, in recent discussions with the European Medicines Agency, or EMA, the company received feedback that a Marketing Authorization Application filing for conditional approval may be possible for KRN23 in XLH. Based on the positive 16-week results and the EMA feedback, Ultragenyx is expanding the pediatric Phase 2 study by up to 16 patients to generate additional safety and efficacy data.

Based on discussions with the EMA and U.S. FDA, the company plans to initiate a Phase 3 randomized, double-blind, placebo-controlled study in approximately 120 adult patients with XLH. The planned primary endpoint will be serum phosphorus levels at 24 weeks. Ultragenyx also plans to initiate a 48-week open-label bone quality study in approximately ten adult XLH patients evaluating the impact of KRN23 on underlying osteomalacia via bone biopsy.