Whyte MP, et al. - In younger children (aged 1–4 years) with X-linked hypophosphatemia, researchers evaluated the safety and effectiveness of burosumab. Children with X-linked hypophosphatemia received burosumab (0.8 mg/kg) via subcutaneous injection every 2 weeks for 64 weeks in this open-label, phase 2 trial at three hospitals in the US. Thirteen children with X-linked hypophosphatemia were enrolled between May 16, 2016 and June 10, 2016. In children aged 1–4 years with X-linked hypophosphatemia, burosumab had a favorable safety profile, increased serum phosphorus, improved rickets and prevented early declines in growth. These findings could significantly alter young children's treatment with X-linked hypophosphatemia. A severe food allergy that was considered unrelated to treatment was reported; other adverse events were mild to moderate.