What it is
Vosoritide is a 39-amino-acid peptide: the body's own C-type natriuretic peptide with two residues added to the front. The Voxzogo label describes its sequence as the 37 C-terminal amino acids of human CNP-53 plus proline-glycine at the N-terminus. The CNP precursor yields three processed forms — CNP-53, CNP-29 and CNP-22 (UniProt P23582) — all ending in the same 17-residue ring closed by a disulfide bond; vosoritide keeps that ring. The added Pro-Gly is there "to convey resistance to neutral endopeptidase (NEP) degradation" — the enzyme that otherwise breaks CNP down. Formula C176H290N56O51S3, molecular weight 4.1 kDa; it is made in E. coli.
At 39 residues it sits one residue below the 40-residue line that US regulation (21 CFR 600.3) uses to separate a peptide from a protein, and it was approved through a new drug application (NDA 214938).
How it works
Achondroplasia comes from a gain-of-function mutation in FGFR3, a receptor in the growth plate that acts as a brake on bone lengthening. Vosoritide binds a different receptor, natriuretic peptide receptor-B (NPR-B), and the signal it starts cuts across FGFR3's: it inhibits ERK1/2 in the MAPK pathway at the level of RAF-1 (label). With the brake partly released, growth-plate cartilage cells multiply and mature. In mouse models of FGFR3 disorders the label reports "a partial or complete normalization" of the dwarfism; that is animal evidence and is labelled as such in the evidence rows. The effect needs open growth plates, which is why the indication is limited to children who are still growing.
What the label's trial shows
The label rests on one randomised, double-blind, placebo-controlled phase 3 trial (NCT03197766):
| Measure at 52 weeks | Placebo (61) | Vosoritide 15 mcg/kg daily (60) |
|---|---|---|
| Growth velocity at baseline | 4.06 cm/year | 4.26 cm/year |
| Change from baseline | −0.17 cm/year | +1.40 cm/year |
| Difference | — | 1.57 cm/year (95% CI 1.22–1.93) |
| Height score (SDS) change | −0.02 | +0.26 |
| Upper-to-lower body ratio change | −0.02 | −0.03 (difference not significant, p = 0.5) |
The children were 5.1 to 14.9 years old (mean 8.7). In the open-label extension, 58 children who started on vosoritide continued, and among those with two years of follow-up the faster growth "was maintained" (label). What the trial did not measure is adult height or the medical complications of achondroplasia — the outcomes the confirmatory trials under the accelerated approval are meant to address. Body proportions did not change.
Safety
The one warning on the label is low blood pressure: transient falls occurred in 8 of 60 (13%) children on vosoritide vs 3 of 61 (5%) on placebo, starting a median 31 minutes after the injection and resolving within a median 31 minutes; two children on vosoritide had a symptomatic episode with vomiting or dizziness. Children with significant heart or vascular disease, or on blood-pressure medicines, were excluded from the trials. Injection-site reactions were common in both arms (redness 75% vs 69%, swelling 62% vs 36%); vomiting was reported in 27% vs 20%, joint pain in 15% vs 7%, and raised alkaline phosphatase in 17% vs 7% (label). The weight-based dose is set by the treating team.
Where it stands
- Approved in the US on 2021-11-19 under accelerated approval (Voxzogo, NDA 214938, BioMarin), in 0.4, 0.56 and 1.2 mg vials; an efficacy supplement was approved 2023-10-20 (Drugs@FDA, 2026-10-15). The current label (effective 2025-11-25) states the indication as children with achondroplasia "with open epiphyses."
- Research record: PubMed indexes 137 records, 6 tagged as randomised trials; ClinicalTrials.gov lists 17 studies (2026-10-15).
Related reading
Vosoritide belongs to the natriuretic-peptide family; the library's entry on its heart-made relatives is BNP and NT-proBNP. For where 39 residues sit on the peptide–protein line, see peptide vs protein. Another approved peptide that acts on bone, through the parathyroid receptor, is the PTH(1-34) drug teriparatide.