BridgeBio’s Oral Infigratinib Shows Strong Phase 3 Growth Data in Children With Achondroplasia
BridgeBio Pharma Inc. (NASDAQ: BBIO) announced Phase 3 data for its oral achondroplasia therapy infigratinib from the PROPEL 3 trial at ICCBH 2026, putting a potential first‑in‑class pill for children with achondroplasia in the spotlight. The company has already reported that PROPEL 3 met its primary endpoint with one of the strongest growth signals seen in a randomized achondroplasia study, and it aims to begin regulatory discussions in the second half of 2026.
What PROPEL 3 has shown so far
PROPEL 3 is a one‑year, global Phase 3 trial that randomized children with achondroplasia to oral infigratinib or placebo. The study enrolled children between 3 and under 18 years old who still have open growth plates. It evaluated once‑daily, oral infigratinib, an FGFR1–3 inhibitor also known as KK8398 in partnership with Kyowa Kirin.
The trial met its primary endpoint with a statistically significant improvement in annualized height velocity at Week 52 versus placebo. Children who received infigratinib grew an average of 5.96 cm per year compared with 4.22 cm per year on placebo, for a mean treatment difference of 2.10 cm per year. BridgeBio has described this as the highest mean annualized height velocity reported so far in a randomized achondroplasia study.
PROPEL 3 also hit a key secondary endpoint, height Z‑score change versus an achondroplasia reference population. Children on infigratinib achieved a least‑squares mean increase of 0.41 standard deviations, with a 0.32 standard deviation treatment difference over placebo at Week 52. That result supports the idea that infigratinib may move growth closer to a healthier reference curve for this population.
Body proportionality and safety profile
Beyond growth rate, BridgeBio highlighted body proportionality, a core clinical concern in achondroplasia. In a prespecified exploratory analysis of a key secondary endpoint, infigratinib showed the first statistically significant improvement in body proportionality versus placebo reported in an achondroplasia trial. These data came from detailed anthropometric measurements in younger children. They suggest that infigratinib might not only help children grow taller, but also improve how their bodies grow in relation to head and limb size.
Safety results from PROPEL 3 look supportive so far. Investigators reported no study drug‑related serious adverse events and no discontinuations due to infigratinib over the 52‑week period. Hyperphosphatemia occurred in three children (about 4%), which aligns with the expected on‑target effects of FGFR inhibition, but it did not cause treatment discontinuation in the study.
Next steps and regulatory path
BridgeBio and Kyowa Kirin plan to share the full PROPEL 3 primary results at ICCBH 2026, a major international congress focused on bone health in children. After that presentation, the partners intend to meet with regulators in the United States and European Union in the second half of 2026 to discuss potential marketing applications for infigratinib in achondroplasia.
If regulators ultimately approve infigratinib, the drug could become a new oral option for children living with achondroplasia and their families. It would offer an alternative to injectable growth‑modifying therapies and directly target overactive FGFR3 signaling, the genetic driver of the condition. For investors tracking BridgeBio and Kyowa Kirin, the key upcoming catalysts include the detailed ICCBH 2026 data, regulatory feedback on the Phase 3 package, and future guidance on how the companies plan to position infigratinib in a competitive achondroplasia market.
