Positive Phase III study of burosumab in X-linked hypophosphatemia

US clinical-stage biotech firm Ultragenyx Pharmaceutical (Nasdaq: RARE) and Japan’s Kyowa Hakko Kirin (TYO: 4151) have announced positive 24-week data from the randomized, double-blind, placebo-controlled Phase III study of burosumab (KRN23) in adults with X-linked hypophosphatemia (XLH).

Patients treated with burosumab demonstrated a statisticall- significant improvement in serum phosphorus levels, with 94% of patients achieving normal levels compared to 8% on placebo (p<0.0001). Patients treated with burosumab also achieved a statistically-significant improvement in stiffness and strong trends in improvements in physical function and pain. Adverse events were consistent with what has been previously observed in open label studies in adults and children. Ultragenyx is conducting the study under a collaboration and license agreement with Kyowa Hakko Kirin

“These data demonstrate a clinical improvement in patients treated with burosumab and support the potential for treatment of adults,” said Emil Kakkis, chief executive and president of Ultragenyx. “When combined with a favorable safety profile and a strong serum phosphorus response, we believe these clinical data should support regulatory submissions in adults with XLH, and we look forward to discussing our filing plans with the US FDA.”