Sustained growth-promoting effects of vosoritide in children with achondroplasia from an ongoing phase 3 extension study.

BACKGROUND

Vosoritide is a C-type natriuretic peptide analog that addresses an underlying pathway causing reduced bone growth in achondroplasia. Understanding the vosoritide treatment effect requires evaluation over an extended duration and comparison with outcomes in untreated children.

METHODS

After completing ≥6 months of a baseline observational growth study and 52 weeks in a double-blind, placebo-controlled study (ClinicalTrials.gov: NCT03197766), participants were eligible to continue treatment in an open-label extension (ClinicalTrials.gov: NCT03424018) wherein all received 15 μg/kg vosoritide daily. Data from the CLARITY achondroplasia study provided an external untreated control population and reference data.

FINDINGS

The population comprised 119 participants. Annualized growth velocity with vosoritide was similar to the average-stature population before puberty. The mean (SD) differences in annualized growth velocity across each integer age (6-16 years) between treated and untreated children were 1.84 (0.38) cm/year in boys and 1.44 (0.63) cm/year in girls. Three-year comparisons of treated versus untreated children demonstrated an additional height gain of 5.75 cm (95% confidence interval [CI]: 4.93, 6.57) with vosoritide. A significant improvement in upper-to-lower body segment ratio at 3 years of treatment was observed for participants with assessments at age <11 (females) and <12 years (males) versus population-level, age-matched, untreated controls (p = 0.0087). The arm span-to-standing height ratio remained consistent with untreated participants. Vosoritide had a favorable safety profile with continuous treatment for up to 6 years (464.05 person years of exposure). No long-term harms or deaths were observed.

CONCLUSIONS

Vosoritide treatment was well tolerated and had sustained growth-promoting effects in children with achondroplasia treated for up to 6 years.

FUNDING

This work was funded by BioMarin Pharmaceutical.