Daily injection speeds growth in children with hypochondroplasia

Children with hypochondroplasia, a genetic condition that limits bone growth, grew more than 2 cm a year faster on daily vosoritide injections than on placebo in the phase 3 CANOPY-HCH-3 trial. The full results were published in NEJM Evidence on 9 September 2026 and presented the same day as a late-breaking talk at the European Society for Paediatric Endocrinology (ESPE) annual meeting.

BioMarin, which makes vosoritide as Voxzogo, has asked the US Food and Drug Administration (FDA) to approve it for this condition. If that happens, it would be the first medicine approved for hypochondroplasia.

What hypochondroplasia is

Hypochondroplasia is a rare skeletal dysplasia, meaning a condition that affects how bones form and grow. It leads to short stature in which the arms and legs are short compared with the trunk. It can also affect the spine and other parts of the skeleton.

It varies widely, BioMarin says. Some children also have ear, nose and throat problems or neurological complications. It is often diagnosed in toddlerhood or the early school years, based on how a child is growing and on X-rays.

Hypochondroplasia is closely related to achondroplasia, the most common form of dwarfism. Both are usually caused by changes in the same gene, FGFR3. In achondroplasia, the FGFR3 change makes a growth-braking signal overactive in the growth plates, the areas of cartilage near the ends of long bones where growth happens. Hypochondroplasia generally has a milder effect on height.

According to BioMarin, there are no medicines approved by either the FDA or the European Medicines Agency (EMA) for hypochondroplasia. The company estimates that about 14,000 children with the condition in the countries where it operates might be eligible for treatment.

How vosoritide works

Vosoritide is a lab-made version of C-type natriuretic peptide (CNP), a natural signal in the body. CNP acts on the growth plate pathway downstream of FGFR3, counteracting the overactive brake and promoting bone growth.

Vosoritide was first approved in 2021 for achondroplasia. BioMarin says more than 5,000 infants and children in over 50 countries have received it. It is given as a daily injection under the skin, usually by a parent or carer, with the dose based on body weight.

Because hypochondroplasia shares the same gene and pathway, testing vosoritide in it was a logical next step.

The CANOPY-HCH-3 trial

CANOPY-HCH-3 was a placebo-controlled phase 3 study in children with hypochondroplasia. Children received either vosoritide or placebo injections for 52 weeks. The main measure was annualised growth velocity, which is how many centimetres a child grows over a year.

The results

After 52 weeks, BioMarin reports these differences between the vosoritide and placebo groups:

The figures are least squares mean differences, a statistical way of comparing groups after adjusting for differences at the start.

A height Z-score shows how far a child's height sits from the average for children of the same age and sex. An improvement of 0.39 means children on vosoritide moved closer to the typical range over the year.

The arm span result matters because short arms can make daily tasks such as reaching, dressing and personal hygiene harder. Andrew Dauber, lead investigator and Chief of Endocrinology at Children's National in Washington, said: "The changes we observed in annualized growth velocity and arm span provide encouraging evidence of how children with hypochondroplasia responded to treatment throughout the study."

BioMarin also reports numerical improvements in quality of life. Numerical means the scores moved in the right direction, but the release does not say these changes were statistically significant.

Side effects

BioMarin says the safety profile matched what has been seen in achondroplasia. Most side effects were mild, and no serious adverse events were judged to be related to treatment.

In achondroplasia, the most common side effects of vosoritide are injection site reactions, such as redness, swelling and itching, as well as vomiting and a temporary drop in blood pressure. To reduce the risk of low blood pressure, families are advised to make sure the child eats and drinks within an hour before each injection.

What happens next

BioMarin has submitted a supplemental New Drug Application to the FDA for hypochondroplasia. The company says it is on track with submissions to the EMA and other regulators, and it points to a potential launch in 2027. Vosoritide has not yet been approved for hypochondroplasia anywhere.

Points to keep in mind

• One year of data. CANOPY-HCH-3 measured growth over 52 weeks. Whether faster growth adds up to a meaningfully taller adult height will take years to show. BioMarin says follow-up continues.
• Daily injections. Treatment means an injection every day for as long as a child is still growing, which is a real commitment for families.
• Company summary. The detailed numbers here come from BioMarin's release. The full paper in NEJM Evidence gives the complete methods and results.
• Height is not the only goal. Families and patient groups hold differing views about growth treatments. Outcomes such as arm span, spine health and quality of life may matter as much as height to many families.

This article explains research findings and is not medical advice. Families should talk to their child's specialist team about treatment options.