Real-World Effectiveness of Burosumab in Adults with X-Linked Hypophosphataemia (XLH) in the UK.

X-linked hypophosphataemia (XLH) is a genetic phosphate-wasting disorder caused by excess fibroblast growth factor 23 (FGF23), which leads to skeletal morbidities, pain, stiffness, and impairments in physical function and health-related quality of life. Burosumab inhibits excess circulating FGF23, restoring bone biochemistry. Here we report real-world data from adults with debilitating XLH symptoms who started treatment with burosumab through a UK early access programme. Change from baseline was assessed for bone biochemistry and patient-reported outcomes (PROs) collected from patients' medical records from September 2019 to December 2022. The proportion of patients (n = 136; 66% female, median age 44.0 years [range 18-83]) with normal serum phosphate increased from 5% (6/126) at baseline to 63% (52/82) after 6 months' burosumab treatment; mean serum phosphate increased significantly from baseline. Significant improvements from baseline were observed in Brief Pain Inventory short-form Worst Pain, Pain Severity and Pain Interference scores (mean [SD] improvement at 6 months: 1.8 [2.3], 1.6 [2.1] and 1.9 [2.2] points, respectively). Western Ontario and McMaster Universities Arthritis Index Stiffness, Pain, Physical Function and total scores improved significantly at 6 months (15.9 [29.7], 11.4 [24.3], 15.7 [19.7] and 15.4 [18.3], respectively), as did EuroQol five-dimension five-level (EQ-5D-5L) utility and visual analogue scale (VAS) scores (0.16 [0.22] and 17.0 [21.6]). Most improvements were clinically meaningful (where benchmarks exist). This study demonstrates the effectiveness of burosumab in real-world practice, supporting findings from clinical trials, and provides new evidence that burosumab treatment substantially improves EQ-5D-5L utility and VAS scores in adults with XLH.