BridgeBio's Oral Infigratinib Adds 2.1 cm/Year of Growth in Achondroplasia Phase 3, Published in NEJM
PROPEL 3 met its primary endpoint, positioning infigratinib as a potential first oral rival to BioMarin's injectable Voxzogo. NDA filing is planned for Q3 2026.
Overview
BridgeBio Pharma has published positive Phase 3 results for oral infigratinib in children with achondroplasia, reporting an observed mean improvement in annualized height velocity of +2.10 cm per year over placebo, according to Quiver Quantitative, which reproduced the company’s announcement. The data from the trial, known as PROPEL 3, were published in The New England Journal of Medicine and presented at the International Congress of Children’s Bone Health (ICCBH) 2026, Quiver Quantitative reported.
If approved, infigratinib would offer a once-daily pill as an alternative to the only existing approved therapy, BioMarin’s injectable Voxzogo (vosoritide).
What We Know
PROPEL 3 is registered as “A Phase 3, Multicenter, Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of Infigratinib in Children 3 to <18 Years of Age With Achondroplasia,” with an enrollment of 114 participants, according to the ClinicalTrials.gov registry record. The registry lists the intervention as daily doses of oral infigratinib delivered in sprinkle capsules, and the primary outcome as change from baseline in annualized height velocity, ClinicalTrials.gov shows. The trial’s lead sponsor is listed as QED Therapeutics, a BridgeBio company.
On the primary endpoint, infigratinib produced a least squares (LS) mean treatment difference of +1.74 cm per year against placebo (p<0.0001), alongside an observed mean difference of +2.10 cm per year (p<0.0001), as reported by Biotech Reality. Clinical Trial Vanguard characterized the result as the largest mean height velocity increase versus placebo recorded in any Phase 3 achondroplasia study to date.
The trial also reported improvements on measures beyond height velocity. Infigratinib improved arm span versus placebo by +0.37 SD (p<0.0001), and showed an LS mean increase in height Z-score of +0.41 SD at Week 52 (p<0.0001), according to StockTitan, which reproduced the company release. On body proportionality, the drug produced an LS mean treatment difference of -0.05 (p<0.05) against placebo in children younger than 8 years old, StockTitan reported; Clinical Trial Vanguard noted this reflected a statistically significant improvement in the sitting height-to-standing height ratio versus placebo.
On safety, there were no discontinuations and no serious adverse events related to the study drug, according to StockTitan. The most notable finding was 3 cases (4%) of hyperphosphatemia, all mild, transient, and asymptomatic, StockTitan reported. Biotech Reality added that there were no adverse events associated with the inhibition of FGFR1 or FGFR2.
Infigratinib is described as a selective, oral small-molecule inhibitor targeting FGFR1-3, according to Biotech Reality. BridgeBio describes it as an investigational small molecule designed to inhibit FGFR3 signaling and target skeletal dysplasias, including achondroplasia and hypochondroplasia, at their source, per StockTitan. “The publication of our pivotal trial data (PROPEL 3) in the New England Journal of Medicine is a defining milestone for the field of skeletal dysplasia,” said Dr. Ravi Savarirayan, quoted by StockTitan.
Why It Matters
Achondroplasia is caused by variants in the FGFR3 gene that make the FGFR3 protein overly active, interfering with skeletal development, according to the NIH’s MedlinePlus. It is the most common form of short-limbed dwarfism and occurs in 1 in 15,000 to 40,000 newborns, MedlinePlus states. The average height of an adult male with achondroplasia is 131 centimeters (4 feet, 4 inches), and for adult females 124 centimeters (4 feet, 1 inch), per MedlinePlus. Beyond stature, the condition is associated with complications including spinal stenosis, compression at the foramen magnum at the base of the skull, sleep apnea, and hydrocephalus, MedlinePlus notes.
Infigratinib’s oral, FGFR3-targeting approach positions it against BioMarin’s Voxzogo (vosoritide), whose FDA approval was initially granted in November 2021 and which is an analog of the C-type natriuretic peptide, according to BioSpace. By comparison with infigratinib’s results, Clinical Trial Vanguard reported that vosoritide showed 1.57 cm per year over placebo at 52 weeks.
Infigratinib is being developed in partnership with Kyowa Kirin, which secured an exclusive license for development and commercialization in Japan in February 2024, according to Biotech Reality.
What We Don’t Know
The two therapies were not compared head-to-head; the cross-trial figures cited above come from separate studies and are not a direct comparison. Long-term effects on final adult height and on the medical complications of achondroplasia were not established by the 52-week primary analysis.
BridgeBio plans to submit a New Drug Application to the FDA in the third quarter of 2026 and a Marketing Authorization Application to the EMA in the second half of 2026, with a U.S. launch anticipated in early to mid 2027 if approved, according to Clinical Trial Vanguard and Biotech Reality. Those timelines remain subject to regulatory review.