Burosumab for adults with tumor-induced osteomalacia in China

A better understanding of the benefit of burosumab for treating tumor-induced osteomalacia (TIO) in Chinese patients is needed. The objective of this open-label, multicenter, single-cohort, post-marketing Phase 4 study was to assess the efficacy, pharmacokinetics, pharmacodynamics, and safety of burosumab after repeated administration in Chinese adults with TIO. Burosumab was administered subcutaneously every 4 weeks for up to 48 weeks at an initial 0.3 mg/kg dose. We investigated the change from baseline in mean serum phosphorus level over time, and changes in serum and urinary phosphorus levels, bone turnover biomarkers, patient-reported outcomes, and other parameters after repeated burosumab administration. Nine patients were treated. Serum phosphorus levels increased and remained above baseline and lower limit of normal at the end of the dosing cycles (averaged over Weeks 20 to 48) (mean [standard deviation] change, 1.5 [0.86] mg/dL). Tubular reabsorption of phosphate and the renal tubular maximum reabsorption rate of phosphate to glomerular filtration rate level ratio increased and remained above baseline values. Alkaline phosphatase (ALP), bone-specific ALP, carboxy-terminal cross-linked telopeptide of type I collagen, and procollagen type 1 N propeptide levels increased, reaching maximums at Weeks 16 or 24. The distance walked in 6 minutes nearly doubled from baseline by Week 48. Patients reported improvements in pain and quality of life over time. There were no serious adverse events and only five treatment-related adverse events (all mild in severity) in three patients. In Chinese patients with TIO, continued treatment with burosumab can provide sustained clinical benefit and a favorable safety profile.