Infigratinib

Achondroplasia is caused by a change in the FGFR3 gene that leaves the FGFR3 receptor switched on too strongly. FGFR3 normally acts as a brake on bone growth by limiting how much cartilage turns into bone, and the overactive receptor presses that brake too hard in the growth plates, the strips of cartilage near the ends of long bones where children grow^[12].

Infigratinib is a small molecule that blocks the signaling end of FGFR receptors from inside the cell, which turns down the overactive FGFR3 signal^[3]. Voxzogo and Yuviwel work differently: they are versions of a natural hormone called CNP, given by injection, that push back against FGFR3 signaling further down the same pathway. Infigratinib can add height only while the growth plates are still open, which is why the trials enrolled children with growth left^[5].

PROPEL 3 (NCT06164951) was a Phase 3, double-blind trial in children aged 3 to 17 with open growth plates, who were randomized 2 to 1 to infigratinib or placebo for 52 weeks; 114 were randomized^[5][3]. The main measure, how fast children grew over a year (annualized height velocity), was 1.74cm a year higher on infigratinib than on placebo (95% confidence interval 1.31 to 2.17, P<0.001), and height z-score rose 0.32 more than on placebo.

Body proportions, measured by the ratio of the upper to the lower body, did not differ significantly overall^[3]. BridgeBio reported an adjusted average (least-squares mean) growth rate of 5.96cm a year on infigratinib against 4.22cm on placebo, and a prespecified exploratory improvement in body proportions in children under 8^[2]. The results were published in the New England Journal of Medicine in 2026^[3].

The earlier Phase 2 PROPEL 2 study (NCT04265651) in children aged 3 to 11 found growth rose by an average of 2.50cm a year at the 0.25mg/kg dose over 18 months^[4]. Children continue in the PROPEL OLE extension (NCT05145010)^[6], a study in children under 3 (NCT07169279) is recruiting^[7], and BridgeBio is also testing infigratinib in hypochondroplasia in ACCEL 2/3 (NCT06873035)^[8]. No trial has compared infigratinib with Voxzogo or Yuviwel^[3].

Infigratinib has no US label for achondroplasia, so its side effects come from trials. In PROPEL 3, adverse events of any kind occurred in 71 of 74 children on infigratinib (96%) and 37 of 39 on placebo (95%). Serious adverse events occurred in 4 children on infigratinib (5%) and 1 on placebo (3%), and investigators judged none of them, and no stop of the drug, to be related to infigratinib^[3].

BridgeBio reported high blood phosphate (hyperphosphatemia) in 3 children (4%), all mild, short-lived and without symptoms, with no dose cut or stop needed, and it reported no retinal or corneal eye problems^[2]. The Truseltiq cancer label covered adults at a much higher dose, so its warnings do not describe the achondroplasia dose.

Infigratinib was first developed by Novartis under the code BGJ398. The FDA granted it accelerated approval as Truseltiq on May 28, 2021 for adults with previously treated FGFR2 fusion cholangiocarcinoma, a bile duct cancer, and announced on May 16, 2024 that the approval was withdrawn at the sponsor's request^[9][10]. The ASCO Post reported on May 22, 2024 that the sponsor cited trouble enrolling the confirmatory trial and that continued sales were not commercially reasonable^[11].

PROPEL 2 was published in February 2025^[4], BridgeBio reported positive PROPEL 3 results on February 12, 2026^[2], and the full results appeared online on June 28, 2026^[3]. On October 6, 2026 BridgeBio announced that the FDA had accepted its application under priority review with a February 4, 2027 decision date^[1]. The FDA had not announced a decision as of November 7, 2026.