Burosumab improves alkaline phosphatase and rickets severity in X-linked hypophosphatemia: 3-year SUNFLOWER analysis

SUNFLOWER is a 10-year longitudinal observational cohort study of patients with X-linked hypophosphatemia (XLH) in Japan and South Korea. This report describes the 3-year cut-off of SUNFLOWER, including data from 1 year of burosumab administration (burosumab-treated group) and 1 year after providing informed consent (non-burosumab-treated group). The real-world effectiveness of burosumab and the associations between bone metabolism markers and quality of life (QoL)/patient-reported outcomes (PROs) and rickets severity scores (RSS)/height over 1 year in burosumab-treated patients with XLH were assessed. As burosumab had not been launched in South Korea at the time of cut-off, data from South Korea were not available. The main outcome measures were changes in serum parameters, and correlations between alkaline phosphatase (ALP) levels and RSS and height (children), and between ALP (children) or bone-specific ALP (BALP; adults) levels and QoL/PROs and motor functions. In total, 146 patients were enrolled, including 69 (47.3%) children and 77 (52.7%) adults. After 1 year of treatment, burosumab-treated patients (43 [62.3%] children, 29 [37.7%] adults) had improved serum phosphate levels, 1,25-dihydroxyvitamin D, and ALP/BALP compared with pre-treatment levels. In children, RSS changes significantly correlated with ALP changes (correlation coefficient: 0.806, p < 0.001), but height changes did not show significant correlation. There were no significant correlations between changes in ALP/BALP and QoL/PRO assessments or motor function. In conclusion, decreased ALP correlated with an improvement in rickets severity score in Japanese children with XLH, suggesting that ALP may be a useful marker for monitoring both the severity and improvement of rickets/osteomalacia.

NCT03745521 and UMIN000031605.