BioMarin stressed that SCFE events haven’t been noted in its own phase 2 Voxzogo studies in the same indications, and that there haven’t been any cases observed in the more than 5,000 infants and kids who’ve been treated with the drug for achondroplasia, either.
While BioMarin has been focusing heavily on its CNP analogue, Voxzogo, to write the next chapter of the company’s growth story, a change in its clinical development plans introduces further uncertainty into the company’s calculus. BioMarin will discontinue dosing and enrollment of its phase 2 trials for Voxzogo—currently approved for achondroplasia, a form of dwarfism—across three potential indications: Turner syndrome, SHOX-deficiency and aggrecan (ACAN)-deficiency. That move follows reports of “several” slipped capital femoral epiphysis (SCFE) events—in which the head of the thighbone slips out of place—in two investigator-sponsored trials of the drug, BioMarin said in a March 16 securities filing (PDF). BioMarin stressed that SCFE events haven’t been noted in its own phase 2 Voxzogo studies in the same indications, and there haven’t been any cases observed in the more than 5,000 infants and kids who’ve been treated with the drug for achondroplasia, either, according to the company. The medicine is also free of any SCFE reports in its trial in hypochondroplasia, which BioMarin is aiming at for Voxzogo’s next potential label expansion. Not all of BioMarin’s midstage Voxzogo programs have been hit, with the company noting that it will continue phase 2 studies of the medication in kids with Noonan syndrome and those with idiopathic short stature (ISS) without ACAN-deficiency “as planned.” In those ongoing trials, BioMarin said that it will implement new precautionary safety measures, such as additional imaging to mitigate any potential risks to the children taking part. While the dosing and enrollment pause on patients with ACAN-deficiency would likely have a slight impact on that second study, BioMarin pointed out that participants without the deficiency make up some 95% of those enrolled in the ISS trial. Voxzogo, a daily injection, was first approved by the FDA in achondroplasia in Nov. 2021 to increase linear growth in patients aged five years and older with open growth plates. Since then, the drug has received the green light to treat children of all ages with achondroplasia who have open growth plates. As for the indications covered in BioMarin’s clinical pivot, Turner syndrome is a genetic condition affecting girls and women, caused by partial or total loss of the X chromosome, that leads to short stature and premature ovarian failure. SHOX deficiency, or short stature homeobox-containing gene deficiency, is caused by changes to or absence of the SHOX gene and is associated with a “wide spectrum of short-stature phenotypes, including Turner syndrome and Léri–Weill dyschondrosteosis,” according to BioMarin. Aggrecan deficiency stems from mutations in the ACAN gene, causes short stature and, in many cases, can lead to early-onset osteoarthritis and degenerative disc disease. Back in 2024, when BioMarin CEO Alexander Hardy set the goal for the company to reach $4 billion in revenue by 2027, BioMarin noted that Voxzogo nods across Noonan syndrome, Turner syndrome and SHOX deficiency could arrive by 2031. BioMarin has subsequently walked back that $4 billion goal as the threat of Voxzogo competition ramps up, separate from the latest clinical moves. Earlier this month, the FDA gave the all-clear to Ascendis Pharma’s Yuviwel to treat achondroplasia in kids ages 2 and older with open growth plates. Notably, unlike the once-a-day Voxzogo, Yuviwel—also an injection—only needs to be administered once per week. At the time, Ascendis said it planned to get Yuviwel out onto the U.S. market by the second quarter of this year. Voxzogo delivered sales of $927 million for all of 2025, rising 26% over the sum it generated the year prior. For 2026, BioMarin is forecasting sales of the drug between $975 million and a little over $1 billion, according to the company’s latest earnings report. The company’s stock price was trading down around 2% at 11:30 am ET on Monday, March 16.