What Is Vosoritide (Voxzogo)? The CNP Peptide for Achondroplasia and What Its Growth Trials Found

Vosoritide (sold as Voxzogo) is a once daily injectable analog of C-type natriuretic peptide (CNP), and it was the first drug approved to increase linear growth in children with achondroplasia, the most common form of disproportionate short stature. Rather than replacing a missing hormone, vosoritide pushes back against an overactive growth brake in the cartilage of the growth plates.

Most of the peptides you read about here involve metabolism, recovery or aging in adults, so vosoritide is a useful contrast: it is a pediatric peptide drug built around one genetic mechanism, tested in a long chain of randomized trials, and still carrying an open question about final adult height. This article walks you through how vosoritide works, what each trial actually measured, the side effects listed on its label, and what researchers still do not know. It is educational content about published research and is not medical advice.

Achondroplasia is a genetic skeletal condition caused by a gain of function change in the FGFR3 gene, which overactivates a receptor that normally acts as a brake on bone growth. Long bones lengthen through endochondral ossification, a process in which cartilage cells in the growth plate multiply, enlarge and are then replaced by bone, and FGFR3 signaling restrains that process.

When FGFR3 is stuck in the on position, the growth plate makes less new cartilage, so the arms and legs end up shorter relative to the trunk. Achondroplasia also brings medical complications beyond height, which the 2019 New England Journal of Medicine paper describes as clinically significant, and vosoritide was developed to target the growth plate pathway itself rather than to treat those complications one by one.

Vosoritide works by activating the NPR-B receptor on growth plate cartilage cells, which dampens the downstream signals that overactive FGFR3 sends. CNP is the body's own ligand for NPR-B and a potent stimulator of endochondral ossification, so you can picture FGFR3 pressing the brake while the CNP pathway presses the accelerator. Vosoritide boosts the accelerator so that the two forces end up closer to balance.

Natural CNP is broken down very quickly, and even the modified analog does not linger, because the FDA label reports a mean half life for vosoritide of 21.0 to 27.9 minutes. That short exposure is why the drug is injected under the skin once every day rather than once a week. Longer acting CNP drugs are in development, although that research sits outside the scope of this article.

The first pediatric trial showed that vosoritide raised growth velocity in a dose dependent way up to 15.0 μg/kg, and that the effect held over time. In this phase 2 dose finding study (Savarirayan and colleagues, New England Journal of Medicine, 2019), 35 children aged 5 to 14 with achondroplasia were enrolled in sequential cohorts at once daily doses ranging from 2.5 μg/kg up to 30.0 μg/kg.

During the first 6 months, annualized growth velocity rose as the dose rose up to 15.0 μg/kg, and the paper reports the dose response only up to that level. Growth velocity stayed raised at 15.0 and 30.0 μg/kg for up to 42 months. Every child in the study (35 of 35, 100%) had at least one adverse event and 4 of 35 (11%) had a serious adverse event, yet the authors described the side effect profile as generally mild, and the 15.0 μg/kg dose went forward into phase 3.

The phase 3 trial found that vosoritide increased annualised growth velocity by 1.57 cm/year more than placebo over 52 weeks, with a 95% confidence interval of 1.22 to 1.93. This randomised, double blind trial (Savarirayan and colleagues, The Lancet, 2020) enrolled 121 children aged 5 to under 18 at 24 hospital sites. Of those children, 60 received vosoritide 15.0 μg/kg daily and 61 received placebo, with injections given at home by trained caregivers, and 119 children completed the full 52 weeks.

Adverse events were almost universal in both arms, with 59 children (98%) on vosoritide and 60 (98%) on placebo reporting at least one, which reflects how closely a year of childhood illness and injections is tracked inside a trial. None of the serious adverse events were judged to be treatment related, and no deaths occurred.

The authors were careful about the limit of their own result, because growth velocity is a rate measured over a single year. In their interpretation they wrote that it is not known whether final adult height will be increased, or what the harms of long term therapy might be.

In the extension data so far, the growth effect of vosoritide has persisted for years rather than fading after the first one. In the ongoing open label extension (Savarirayan and colleagues, Med, 2025), 119 participants from the phase 3 program continued on 15 μg/kg daily, some of them for up to 6 years, adding up to 464.05 person years of total exposure.

Because there was no long term placebo group, the investigators compared treated children with untreated children from the CLARITY natural history study. Across each year of age from 6 to 16, the gap in annualized growth velocity averaged 1.84 cm/year in boys and 1.44 cm/year in girls, and over 3 years of treatment that added up to an additional height gain of 5.75 cm (95% CI 4.93 to 6.57) compared with untreated children. Before puberty, growth velocity on vosoritide was similar to that of children of average stature.

Body proportions moved in the right direction as well, since the upper to lower body segment ratio improved at 3 years in younger children, and no long term harms or deaths were reported. You should keep the usual caveat in mind, though: an external control group drawn from a different study is weaker evidence than a randomized comparison, and the trial was funded by the manufacturer, BioMarin.

Vosoritide has been tested in children younger than 5, and the current US label no longer sets a minimum age. In a randomised phase 2 trial (Savarirayan and colleagues, Lancet Child and Adolescent Health, 2024), 75 children under 60 months were enrolled, with infants up to 23 months receiving 30.0 μg/kg, children aged 24 to 59 months receiving 15.0 μg/kg, and a matched group receiving placebo for 52 weeks.

The height Z score result in these young children was smaller and less certain than in older children: the difference versus placebo was 0.25, with a 95% confidence interval from -0.02 to 0.53 that crosses zero. Injection site reactions were the main side effect, and serious adverse events occurred in 3 children (7%) on vosoritide and 6 (19%) on placebo. One child in the vosoritide group left the study because of death, and the serious events listed for the vosoritide group were decreased oxygen saturation, respiratory syncytial virus bronchiolitis with sudden infant death syndrome, and pneumonia.

A 2026 meta analysis in the European Journal of Pediatrics pooled 13 studies of children on the approved 15 μg/kg/day dose and found a growth velocity of 5.72 cm/year at 12 months on treatment, along with a pooled height Z score improvement of 0.28 that the authors called modest. The 5.72 cm/year figure is the total growth rate on treatment rather than the extra growth over placebo, so the randomized trial difference of 1.57 cm/year remains the better estimate of what the drug itself adds.

The same meta analysis reported injection site reactions in 51% and gastrointestinal symptoms in 50% of pooled participants, mostly mild to moderate. Because the included studies mixed randomized trials with cohort studies and case reports, the authors called for larger studies with longer follow up.

The most common side effects of vosoritide are injection site reactions, vomiting, joint pain and transient drops in blood pressure. The FDA label lists injection site erythema, injection site swelling, rash, vomiting, injection site urticaria, arthralgia, decreased blood pressure and gastroenteritis as reactions seen in more than 10% of patients, and its adverse reaction table for the 52 week phase 3 trial shows how much of each effect sits above the placebo baseline.

CNP belongs to the natriuretic peptide family, which also acts on blood vessels, so a temporary dip in blood pressure after a dose is an expected effect of this drug class. The label warns that transient decreases in blood pressure were observed in clinical studies, and it tells caregivers to make sure the child is well hydrated and has eaten before each injection, with roughly 240 to 300 mL of fluid in the hour beforehand.

A 2026 case series raised a signal for slipped capital femoral epiphysis (SCFE), a problem at the growth plate of the hip, in some genetic short stature conditions other than achondroplasia. Across two small investigator led trials, SCFE appeared only after more than 12 months on vosoritide, and the authors concluded that vosoritide may be associated with a higher risk of SCFE in some of these groups while calling for further study.

These were off label research populations rather than the achondroplasia population the drug is approved for, which matters when you read the numbers in the table below.

The most advanced new use is hypochondroplasia, a milder condition that also involves FGFR3. In a phase 3 trial published in NEJM Evidence in 2026 (Dauber and colleagues), 81 children aged 3 to under 18 were randomized to vosoritide or placebo for 52 weeks. Growth velocity rose by 1.95 cm/year on vosoritide and fell by 0.39 cm/year on placebo, a difference of 2.33 cm/year (95% CI 1.85 to 2.82), and adverse events occurred in 87.8% on vosoritide and 72.5% on placebo, with no grade 3 or higher events, no discontinuations for side effects and no deaths.

Phase 2 basket trials are also exploring vosoritide in RASopathies, ACAN mutations, NPR2 deficiency and Turner syndrome, which is where the hip signal described above came from. None of these uses is approved, and early growth data from small open label trials do not establish benefit.

The FDA label approves vosoritide to increase linear growth in pediatric patients with achondroplasia with open epiphyses, and the initial US approval came in 2021. The indication is an accelerated approval based on improvement in annualized growth velocity, and the label states that continued approval may be contingent on verification and description of clinical benefit in confirmatory trials. In practice, that means the long term question of whether faster growth translates into meaningful adult outcomes is still being answered.

Vosoritide is given by subcutaneous injection once daily and dosed by body weight, and the label says to permanently stop treatment once the growth plates close and no further growth potential remains. It is a prescription drug managed by pediatric endocrinology and skeletal dysplasia specialists, it is not a research peptide for adults, and it does nothing for height once growth has finished.

Vosoritide is one of the clearest examples of a peptide drug designed around a single genetic mechanism and then tested the slow, careful way. In randomized trials it added about 1.57 cm/year of growth in children with achondroplasia, the extension data suggest that the gain holds over several years, and the side effects on the label are mostly injection site reactions and brief dips in blood pressure that families can plan around.

What you should not take from the evidence is a promise about adult height, because the approval rests on growth velocity and the final height data are still coming. If your family is weighing vosoritide, the right conversation is with a skeletal dysplasia team that can talk through daily injections, monitoring and the remaining unknowns with you.

Savarirayan R and colleagues, C-Type Natriuretic Peptide Analogue Therapy in Children with Achondroplasia, New England Journal of Medicine, 2019, doi.org/10.1056/NEJMoa1813446. Savarirayan R and colleagues, Once daily, subcutaneous vosoritide therapy in children with achondroplasia: a randomised, double blind, phase 3, placebo controlled, multicentre trial, The Lancet, 2020, doi.org/10.1016/S0140-6736(20)31541-5. Savarirayan R and colleagues, Sustained growth promoting effects of vosoritide in children with achondroplasia from an ongoing phase 3 extension study, Med, 2025, doi.org/10.1016/j.medj.2024.11.019. Savarirayan R and colleagues, Vosoritide therapy in children with achondroplasia aged 3 to 59 months: a multinational, randomised, double blind, placebo controlled, phase 2 trial, Lancet Child and Adolescent Health, 2024, doi.org/10.1016/S2352-4642(23)00265-1. Dauber A and colleagues, A Phase 3 Trial of Vosoritide in Children with Hypochondroplasia, NEJM Evidence, 2026, doi.org/10.1056/EVIDoa2600257. Alfaraj GA and colleagues, Efficacy and safety of vosoritide in children with achondroplasia: a systematic review and meta analysis, European Journal of Pediatrics, 2026, doi.org/10.1007/s00431-026-06970-y. Kanakatti Shankar R and colleagues, Slipped Capital Femoral Epiphysis during Vosoritide Therapy for Short Stature: A Case Series, Hormone Research in Paediatrics, 2026, doi.org/10.1159/hrp/adaag011. VOXZOGO (vosoritide) US prescribing information, DailyMed, dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=228e8560-04a4-4bb1-a81f-29531a9e4d27.