BioMarin Pharmaceutical Inc. has announced positive new data from studies of VOXZOGO (vosoritide) in children with achondroplasia in ongoing clinical trials and real-world studies. The latest findings reinforce the importance of early treatment and the well-known, established efficacy and safety of VOXZOGO. The data will be presented at the 2026 American College of Medical Genetics and Genomics (ACMG) Annual Clinical Genetics Meeting in Baltimore.
Achondroplasia, the most common form of skeletal dysplasia leading to disproportionate short stature in humans, is characterized by slowing of endochondral ossification, which results in disproportionate short stature and disordered architecture in the long bones, spine, face and base of the skull. This condition is caused by a change in the FGFR3 gene, a negative regulator of bone growth.
More than 80% of children with achondroplasia have parents of average stature and have the condition as the result of a spontaneous gene mutation. The worldwide incidence rate of achondroplasia is about one in 25,000 live births. VOXZOGO is being tested in children whose growth plates are still “open,” typically those under 18 years of age. Approximately 25% of people with achondroplasia fall into this category.
New data will be presented from a study of children who started VOXZOGO before age 2, which showed treatment was associated with durable, multi-year growth improvements, including body proportionality and arm span compared to untreated children, as well as improvements in height over time.
For proportionality, measured by change from baseline in upper‑to‑lower body segment ratio (ULBR), the least squares mean difference versus untreated children showed improvement by year one in children initiating VOXZOGO under age 2, and this difference continued to improve each year through year four. Specifically, the least squares mean difference versus untreated children in year one was −0.33 in children initiating VOXZOGO under age 2, and −0.10 in those initiating treatment with VOXZOGO under 6 months; by year four, this trend continued, with a least squares mean difference of −0.53 in children initiating VOXZOGO under age 2 compared to untreated children, and −0.23 in those who initiated treatment with VOXZOGO under 6 months.
Additional analyses further emphasize that these children showed durable improvements in height while maintaining stable arm‑to‑height ratios, consistent with arm span improvements compared to untreated children, which is particularly relevant in early life. Researchers also saw significant improvements in body mass index (BMI) in children who initiated treatment when compared to untreated children.
“It is encouraging to see increasing data on outcomes beyond height, including measures such as body proportionality and arm span,” said Michael Hughes, chair of the Biotech Industry Liaison Committee at Little People of America (LPA).
“BioMarin’s continued efforts on studying these outcomes, along with findings suggesting improvements in these areas with treatments such as VOXZOGO, help expand our understanding of skeletal development in achondroplasia and inform conversations between families and their healthcare providers.”
With regard to growth measures, among more than 20 children who began treatment between 0.5 to <2 years of age, average additional height gain after four years of treatment was 4.7cm, and an average height Z‑score improvement of 0.8 was observed compared to untreated children in the same reference population, supporting sustained improvement in height relative to expected growth rates in children with achondroplasia.
“Today’s results reaffirm what treating physicians have consistently told us and what was published in consensus clinical guidelines: the earlier you treat with VOXZOGO, the greater the likelihood of maximising the benefit seen with this treatment, not just in height but more importantly, other measures of health including proportionality,” said Greg Friberg, executive vice president and chief R&D officer at BioMarin.
“As the only approved medicine for children with achondroplasia starting at birth, VOXZOGO provides physicians a medicine that we know is effective and has a positive safety profile in the youngest children with achondroplasia, where there is the greatest opportunity to make an impact on the overall health of these children.”
To date, more than 5,000 infants and children across more than 50 countries have received VOXZOGO. At ACMG, researchers will present findings on real-world evidence highlighting the impact of VOXZOGO in children who were treated in Japan, Europe and the US.
Children with achondroplasia in Japan under the age of 2 years who received VOXZOGO demonstrated good adherence to treatment and robust height improvements, including a mean change from baseline at 12 months of 9.91cm, and a mean height change from baseline at 24 months of 15.62cm. In a real-world study out of France, children who received VOXZOGO for 36 months demonstrated sustained growth benefits, including a mean height gain of 16.7cm with a 0.75 increase in height Z-score compared to the average population.
These findings were supported by interim results from the Acorn Study, a multicentre, post-authorisation safety study enrolling participants throughout Europe with an observation period of 10 years from enrolment of the first participant. In addition, the real-world benefit of VOXZOGO was also demonstrated in the VIrtual STudy in Achondroplasia (VISTA) in the US, where effectiveness data were consistent with clinical trial data, and trends in improvements in physical functioning underscored the importance of early treatment initiation to maximize clinical benefit.