Effect of vosoritide on genu varum in children with achondroplasia after 1 year in randomized placebo-controlled trials

Abstract Achondroplasia is a skeletal dysplasia associated with multisystem complications including genu varum, which causes pain and limits mobility. Vosoritide, a targeted treatment for achondroplasia, improves growth in children and has an established safety profile, but its effect on genu varum is unclear. Data were collected from 183 participants from randomized, double-blind, placebo-controlled phase 2 (CANOPY ACH-2I [111-206; NCT03583697]) and phase 3 (CANOPY ACH-3 [111-301; NCT03197766]) studies evaluating vosoritide (weight-based dose of 15 or 30 µg/kg/day) in children aged 0-5 and >5 years, respectively. Anterior/posterior lower limb radiographs were taken at baseline and 1 year to measure parameters associated with genu varum. Differences in least-squares mean (LSM) change from baseline were calculated for vosoritide vs placebo using an analysis of covariance model. In both studies, age at treatment initiation and sex distribution were generally balanced between vosoritide and placebo (except 58% males received vosoritide in CANOPY ACH-2I). After 1 year of vosoritide treatment vs placebo, tibial bowing decreased in children who initiated treatment aged