With phase 3 results that have “exceeded” BioMarin’s expectations, according to R&D chief Greg Friberg, M.D., the California biotech appears set up to gain a label expansion for its top-selling product, dwarfism drug Voxzogo.
The Canopy-HCH-3 study in children with hypochondroplasia (HCH) has met its primary endpoint, with Voxzogo providing “highly statistically significant” improvements in annualized growth velocity (AGV), the company said. In a trial of 80 patients, ranging from ages 3 to 17, those on Voxzogo had an AGV of 2.33 centimeters more than those on placebo at week 52.
In addition, Voxzogo provided a statistically significant increase in two other height measurements—standing height and height Z-score—and in arm span, which is key in providing patients with a longer reach and allowing them to gain independence, the company said.
The results are “tremendously encouraging,” according to Andrew Dauber, the lead investigator of the study and the chief of endocrinology at Children's National Hospital in Washington, D.C.
“Seeing these improvements in growth is a milestone we have hoped for after so many years without treatment options,” Dauber added in a release. “These data suggest we may be approaching a new era in how we care for children with hypochondroplasia.”
HCH is a rare genetic condition that limits bone growth, resulting in short-limbed dwarfism. It is caused by a mutation in the FGFR3 gene, which slows the conversion of cartilage into bone. Those with HCH typically have an average-sized torso but disproportionately short arms, legs, hands, and feet. The condition can lead to otolaryngologic (ear, nose and throat) issues and neurological complications.
HCH is a milder form of achondroplasia (ACH). In 2021, the FDA approved CNP analog Voxzogo as a treatment for ACH and two years later expanded the nod to children aged 5 and younger.
With the results—which the company will present in full at a medical conference later this year—BioMarin said it expects to file for approval of Voxzogo in HCH in the third quarter of this year, followed by submissions to the European Medicines Agency and other regulators.
“While this is an important win for the Voxzogo franchise and provides incremental expansion beyond achondroplasia (ACH), we remain cautious that success in HCH alone is unlikely to fully offset growing competitive pressures emerging in ACH,” analysts from Leerink Partners wrote in a note to clients.
Two months ago, Ascendis gained FDA approval for its ACH treatment, Yuviwel. The approval covers children aged 2 and older who have open growth plates, which are areas where cartilage develops at the end of bones, allowing them to lengthen. The advantage Yuviwel offers is that it is dosed weekly as opposed to daily for Voxzogo.
In February, BridgeBio revealed the success of a phase 3 trial of its FGFR1-3 selective tyrosine kinase inhibitor infigratinib in children with ACH. BridgeBio and its partner Kyowa Kirin plan to apply for approval of infigratinib in the second half of this year.
“We think it will be important to understand how BioMarin plans to help drive disease awareness and enhance the diagnosis journey as HCH is not diagnosed at the same rate as ACH,” Leerink added. “Based on (KOL) discussions, we think there is a fairly wide spectrum of severity in HCH where some patients might already be on Voxzogo, while other patients may be milder.”
With sales of $927 million, which were up 26%, Voxzogo accounted for 29% of the company’s revenue in 2025. The Leerink team said it projects “significantly lower peak sales in HCH vs. ACH.”
In March, BioMarin announced that it had discontinued phase 2 trials for Voxzogo across three potential indications: Turner syndrome, SHOX-deficiency and aggrecan (ACAN)-deficiency. Still underway are phase 2 trials of Voxzogo for kids with Noonan syndrome and idiopathic short stature (ISS) without ACAN-deficiency.