Effect of Vosoritide on Spine Morphology in Children With Achondroplasia: 1-Year Results From a Randomized Phase 2 Study

Achondroplasia is a skeletal dysplasia condition caused by reduced endochondral ossification resulting in disproportionate short stature and skeletal deformities, including thoracolumbar kyphosis (TLK) and spinal stenosis. Vosoritide, the first and only approved targeted therapy for achondroplasia, increases bone growth, but its impact on spinal morphology has not been assessed. The randomized, double-blind, placebo-controlled phase 2 CANOPY ACH-2I study (111-206; NCT03583697) evaluated safety and efficacy of vosoritide in 75 children aged 0 to <5 years. Interpedicular distances (IPD), sagittal width of the lumbar spinal canal, and TLK angle were measured on spinal radiographs taken at baseline and 1 year after vosoritide or placebo treatment. Differences in least-square squares mean (LSM) change from baseline (95% confidence interval [CI]) between treatment groups were determined with an analysis of covariance model. Measurable improvements in IPD and spinal canal width across L1–L5 were observed with vosoritide compared with placebo after 1 year. L4 was the most impacted by vosoritide for IPD (LSM difference [95% CI], 0.509 [−0.034 to 1.052] mm, P = 0.066) and canal width (1.433 [0.547 to 2.320] mm, P = 0.002). Vosoritide treatment also reduced the natural increase in TLK angle in children 0 to <0.5 years and provided greater improvements in children ≥0.5 to <5 years. After 1 year, fewer children treated with vosoritide (33.3%) vs placebo (59.3%) had pathological (≥20°) TLK angles (P = 0.037). These preliminary results suggest that early vosoritide treatment may improve spinal morphology and reduce the risk of spinal stenosis in children with achondroplasia.