Phase III study of KRN 23 (burosumab) in X-linked hypophosphatemia meets primary endpoint- Ultragenyx Pharmaceutical/ Kyowa Hakko Kirin

Ultragenyx Pharmaceutical, Kyowa Hakko Kirin Co and Kyowa Kirin International announced positive 24-week data from the randomised, double-blind, placebo-controlled Phase III study of KRN 23 (burosumab) in adults with X-linked hypophosphatemia (XLH). The study enrolled 134 patients, randomised 1:1 to burosumab at a dose of 1 mg/kg or placebo every four weeks for 24 weeks. The study met the primary endpoint of increasing serum phosphorus levels as 94% of patients treated with burosumab (n=68) achieved serum phosphorus levels above the lower limit of normal and maintained levels in the low normal range through 24 weeks, compared to 8% in the placebo arm (n=66; p<0.0001).>

Patients treated with burosumab demonstrated a statistically 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.>