BioMarin Pharmaceutical (Nasdaq: BMRN) reported that vosoritide (Voxzogo) met its primary endpoint in the Phase III CANOPY-HCH-3 study in children with hypochondroplasia, producing a 2.33 cm/yr improvement in annualized growth velocity versus placebo — the first pivotal trial to demonstrate a statistically significant growth benefit in this condition, which currently has no approved pharmacotherapy.
CANOPY-HCH-3 is a Phase III, randomized, double-blind, placebo-controlled, multicenter study enrolling 80 children aged 3 to 17 with hypochondroplasia in a 1:1 ratio. The primary endpoint was change from baseline in annualized growth velocity at 52 weeks.
The primary endpoint was met with a least-squares mean difference in annualized growth velocity of +2.33 cm/yr compared to placebo at week 52, which BioMarin described as highly statistically significant (p-value not fully disclosed in the press release). Arm span, a prespecified key secondary endpoint and a measure linked to functional independence in daily activities, also improved significantly versus placebo (p=0.004). Statistically significant increases in standing height and height Z-score were additionally reported, though full numerical data for these and other secondary endpoints — including upper-to-lower body segment ratio and health-related quality of life — are pending presentation at a forthcoming medical meeting.
The safety profile was consistent with vosoritide's established record in achondroplasia, with no new safety signals identified. Known effects include injection site reactions, transient reductions in blood pressure, elevated alkaline phosphatase, and gastrointestinal symptoms.
The trial context
Hypochondroplasia is a rare skeletal dysplasia caused by mutations in the fibroblast growth factor receptor 3 (FGFR3) gene, the same receptor implicated in achondroplasia, though the clinical presentation is generally milder and more variable. Unlike achondroplasia, hypochondroplasia has received comparatively limited clinical trial attention, and no drug has been approved by the US FDA or the European Medicines Agency for its treatment.
Vosoritide is a C-type natriuretic peptide (CNP) analog that activates natriuretic peptide receptor-B (NPR-B/NPR2), increasing intracellular cGMP signaling in growth-plate chondrocytes to promote endochondral bone growth. The mechanistic rationale for extending the drug into hypochondroplasia follows directly from the shared FGFR3 biology: both conditions involve dysregulated FGFR3 signaling that suppresses the CNP/NPR-B pathway in the growth plate. The 2.33 cm/yr AGV improvement observed in CANOPY-HCH-3 is notable in this context, as it suggests the CNP-axis intervention translates across FGFR3-related dysplasias beyond achondroplasia.