Safety, Efficacy of Burosumab vs Placebo for X-Linked Hypophosphatemia Examined

This article is part of Endocrinology Advisor’s coverage of the 2017 American Society for Bone and Mineral Research (ASBMR) Annual Meeting taking place in Denver, CO. Check back regularly for more news on the latest clinical research in bone health from ASBMR 2017.

Treatment with burosumab — an investigational, fully human monoclonal antibodiy — was well-tolerated in patients with X-linked hypophosphatemia (XLH), according to research presented at the 2017 American Society for Bone and Mineral Research (ASBMR) Annual Meeting, held September 8-11 in Denver, Colorado

Karl L. Insogna, MD, of Yale University School of Medicine in New Haven, Connecticut, and colleagues presented data from the ongoing phase 3 trial of anti-FGF23 antibody burosusmab (KRN23) therapy in adults with x-linked hypophosphatemia (Study of KRN23 in Adults With X-linked Hypophosphatemia [XLH]; ClinicalTrials.gov Identifier NCT02526160). Data was collected during the first 24 weeks of the double-blind multicenter study.

Study participants (n=134) were randomly assigned 1:1 to receive either subcutaneous burosumab (1 mg/kg) or placebo every 4 weeks. At 24 weeks, 94.1% of patients in the burosumab group reached the study’s primary end point (mean serum phosphorous levels above the lower limit of normal) vs 7.6% of patients in the placebo group. Significantly more patients in the burosumab group also reached secondary end points, including Western Ontario and McMaster University Osteoarthritis Index (WOMAC)-measured stiffness and physical function and Brief Pain Inventory (BPI) pain severity. Patients in the burosumab group also experienced a greater percentage of fully healed fractures and pseudofractures vs patients in the placebo group (36.9% vs 9.9%, respectively).

Two patients in each group reported non-drug related serious adverse events. Injection site reaction was experienced by 12% of patients in both the burosumab and placebo groups.

“[B]urosumab was well tolerated, restored serum [phosphorous] homeostasis, reduced stiffness, improved physical functioning, and increased markers of bone remodeling with consequent improved healing of [fractures/pseudofractures] in adults with XLH,” Dr Insogna and colleagues concluded.

Reference

Insogna K, Briot K, Imel E, et al. A phase 3 randomized, 24 week, double-blind, placebo-controlled study evaluating the efficacy of burosumab, an anti-FGF23 antibody, in adults with x-linked hypophosphatemia (XLH). Presented at: 2017 American Society for Bone and Mineral Research annual meeting; September 8-11, 2017; Denver, CO. Abstract LB-1159