Phase III study of Crysvita demonstrates superiority in X-linked hypophosphatemia.- Ultragenyx Pharma + Kyowa Hakko Kirin

Ultragenyx Pharmaceutical, Kyowa Hakko Kirin, and Kyowa Kirin International announced positive results of a 64-week efficacy and safety analysis of the randomized active-controlled Phase III study of Crysvita (burosumab) in children with X-linked hypophosphatemia compared with oral phosphate and active vitamin D (current conventional therapy). The new results showed that Crysvita was superior to conventional therapy for all key efficacy endpoints, showing a meaningful improvement in rickets severity, lower limb deformity, growth, and physical functioning as demonstrated by increases in distance walked.

Rickets scores were superior with Crysvita compared to conventional therapy, as assessed by three independent blinded pediatric radiologists using the Rickets Global Impression of Change (RGI-C) Global Score (LS mean treatment difference of +1.02). RGI-C scores showing substantial healing of rickets was observed in 86.2% of patients receiving Crysvita compared to 18.8% of patients receiving conventional therapy (p=0.0002). Rickets Severity Scores (RSS) improved more with Crysvita compared to conventional therapy (LS mean treatment difference of -1.21). Mean serum alkaline phosphatase levels as a biochemical measure of rickets were decreased by Crysvita into the normal range and were superior to conventional therapy at 64 weeks. Lower limb deformity (RGI-C score for bowing/limb deformity) was reduced more with Crysvita compared with conventional therapy (LS mean treatment difference +0.971).

The 64-week safety profile was similar to that observed at 40 weeks and in other Crysvita pediatric XLH studies. At 64 weeks, there were no treatment discontinuations and no deaths reported in the study. There were three serious adverse events in the Crysvita arm and three serious adverse events in the conventional therapy arm, none of which were considered treatment-related.