FDA Expands Indication of Voxzogo for Young Children with Dwarfism

The FDA granted accelerated approval to BioMarin Pharmaceutical’s supplemental new drug application (sNDA) for Voxzogo (vosoritide) to treat children younger than five years of age with achondroplasia with open epiphyses, which is growth plates that haven’t fully formed.

Achondroplasia is the most common form of dwarfism. This condition is caused by a change in the FGFR3 gene. 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 acts as a positive regulator of the signaling pathway downstream of FGFR3 to promote endochondral bone growth. Previously, it had received accelerated approved by the FDA to increase growth in pediatric patients with achondroplasia who are 5 years of age and older with open epiphyses. As of December 2021, Voxzogo’s list price was $8,990 for 10 single-dose vials. BioMarin offers a copay assistance program that covers up to $17,000 a year.

William Wilcox, M.D.

“Voxzogo is the only approved treatment for children with achondroplasia. Until now, it has only been approved in the U.S. for children aged 5 and older with open growth plates," William Wilcox, M.D., professor of human genetics at Emory University, said in a press release. "I am delighted that Voxzogo is now approved for younger children where we hope to have potentially greater impact by starting treatment earlier and, as a result, a much longer treatment window."

The approval was based on a phase 2 clinical trial in children aged 5 and under. The trial demonstrated that children over the age of 2 years who received Voxzogo saw a mean height gain of 6.3 to 7.8 centimeters (cm) when compared with untreated children. Children under the age of 2 years had a height gain between 3.5 and 3.9 cm.

The safety profile was consistent with that seen in older patients. The most common adverse events were mild and injection site reactions.

Voxzogo has also recently received orphan drug designation from the FDA to treat patients with hypochondroplasia, a genetic condition caused by a mutation in the fibroblast growth factor receptor 3 (FGFR3) gene that results in impaired bone growth. While similar to achondroplasia, people with hypochondroplasia present with less severe short stature.