What is Vosoritide?
Vosoritide (brand name VOXZOGO, development code BMN 111) is a modified analogue of the natural human C-type natriuretic peptide (CNP) engineered for resistance to enzymatic degradation. Developed by BioMarin Pharmaceutical, it is administered as a once-daily subcutaneous injection and is the first and only therapy ever approved for achondroplasia, the most common genetic cause of disproportionate short stature.
Achondroplasia is caused by an activating gain-of-function mutation in the fibroblast growth factor receptor 3 (FGFR3) gene — almost always the same Gly380Arg substitution. Constitutively active FGFR3 inhibits chondrocyte proliferation and differentiation in the growth plates of long bones, producing the characteristic skeletal disproportion. Vosoritide pharmacologically counteracts this overactive FGFR3 signaling.
Mechanism of Action
- NPR-B receptor agonist — vosoritide binds and activates natriuretic peptide receptor B (NPR-B, also called NPR2) on chondrocytes
- cGMP elevation — NPR-B activation generates cyclic GMP, which inhibits the MAPK arm of FGFR3 signaling downstream
- Restored chondrocyte differentiation — by suppressing the FGFR3-MAPK axis, vosoritide allows growth-plate chondrocytes to proliferate, hypertrophy, and contribute to endochondral ossification
- Improved bone elongation — annualized growth velocity in treated children is meaningfully restored toward normal
The natural endogenous CNP has a very short half-life (~2 minutes) due to rapid cleavage by neutral endopeptidase (NEP). Vosoritide carries an N-terminal extension that confers protease resistance while preserving NPR-B affinity, extending pharmacokinetic exposure to clinically useful levels.
Clinical Evidence
Phase 3 trial (Lancet 2020, NCT03197766):
- 121 children ages 5–18 with achondroplasia, randomized to once-daily vosoritide or placebo for 52 weeks
- Annualized growth velocity: 5.61 cm/year (vosoritide) vs 4.06 cm/year (placebo) — a 1.57 cm/year gain
- Effect maintained over multi-year extension studies
Long-term extension (NEJM 2022):
- Continued growth-velocity benefit over 2+ years
- Linear improvement in body proportionality (upper-to-lower segment ratio)
- No tachyphylaxis through the treatment period
Approval History
- November 19, 2021 — FDA accelerated approval for children ≥5 years with open epiphyses
- August 2021 — EMA approval (predates FDA)
- October 2023 — FDA expanded approval to all ages with open epiphyses (down to as young as 4 months)
Place in Therapy
Vosoritide does not cure achondroplasia or address its non-stature complications (foramen magnum stenosis, spinal stenosis, otitis media), but it produces sustained, meaningful gains in adult height when started in growing children. It must be discontinued when epiphyses close.
Safety Profile
The most common adverse events are injection-site reactions and transient blood-pressure decrease (CNP/NPR-B activation is naturally vasodilatory). Children require pre-dose food and water intake to maintain blood pressure during dosing. Long-term safety has been favorable through 5+ years of follow-up in clinical trials.