SUN-333 Burosumab Improves Bone Density in Patients with X-Linked Hypophosphatemia

• Published in: Journal of the Endocrine Society 2020-05, Vol.4 (Supplement_1)
• Main Authors: Murari, Keerti, Insogna, Karl Leonard
• Format: Article
• Language: English
• Subjects: Bone and Mineral Metabolism
• ISSN: 2472-1972; 2472-1972
• DOI: 10.1210/jendso/bvaa046.1470

Background: X-linked hypophosphatemia (XLH) causes rickets in children and osteomalacia in adults due to lifelong renal phosphate wasting that is mediated by high circulating levels of FGF-23. Burosumab, is a recently approved fully human monoclonal antibody that blocks FGF23, thereby correcting the renal phosphate leak, improving mineral metabolism and reducing osteomalacia by 50-75% in adults [1]. Whether this results in measurable changes in skeletal mass and microarchitecture is unclear. Objective: We examined the impact of burosumab on regional bone mineral density (BMD) and trabecular bone scores (TBS) in study subjects involved in two phase III clinical trials of burosumab. Methods: In these trails subjects received burosumab 1 mg/kg every 4 weeks. Some patients received placebo for the first 6 months of one trial so we considered their month 6 data as their baseline. Most of the patients had been treated at some point in the past with calcitriol and phosphorus. DXA and TBS were obtained at baseline and then after 6, 12 and 18-24 months of drug treatment. Paired t-tests and ANOVA were performed to assess changes in L-spine BMD, Total Hip BMD and TBS. Results: 25 subjects with XLH (mean age 38.9 years, 56% female) were enrolled in these studies. Paired data were available in 23 subjects at 6 months, 15 subjects at 12 months and 18 subjects at 18-24 months. Compared to baseline, there were significant increases in L-spine BMD at all time points by paired analysis: 6 months (+6.0%, p=