Kyowa Kirin Infigratinib development partner BridgeBio Pharma, Inc. has announced the publication of positive results from its global Phase 3 PROPEL 3 clinical study evaluating oral infigratinib in pediatric patients living with achondroplasia. The groundbreaking clinical data was published as an original research article in The New England Journal of Medicine (NEJM) on July 2, 2026. This pivotal, global, placebo-controlled study focused on evaluating the safety and efficacy of the investigational drug in children.
The inclusion of these Phase 3 findings in a premier, peer-reviewed medical publication like NEJM demonstrates that the research underwent rigorous peer review. Significantly, this marks the first and only Phase 3 dataset from an achondroplasia clinical evaluation to be published in NEJM. Given the journal’s profound global influence, such publications are widely recognized as vital contributions to clinical medicine.
Simultaneously, the comprehensive clinical results from PROPEL 3 were presented at the International Congress of Children’s Bone Health (ICCBH) 2026. These joint milestones offer critical insights for evaluating the potential of oral infigratinib as a novel therapeutic option. The drug operates as a selective, oral small-molecule inhibitor targeting FGFR1-3.
Clinical Efficacy Data for Kyowa Kirin Infigratinib
During the evaluation of the primary endpoint, Kyowa Kirin Infigratinib demonstrated a significant change from baseline in annualized height velocity. The trial achieved a least squares (LS) mean treatment difference of +1.74 cm/year against placebo (p<0.0001), with an observed mean difference of +2.10 cm/year (p<0.0001). Both statistics represent the largest differences ever observed in a Phase 3 clinical study for achondroplasia.
The trial also successfully met its key secondary endpoint, revealing an LS mean increase of +0.41 SD (p<0.0001) in height Z-score relative to the achondroplasia reference population at Week 52. In a pre-specified exploratory analysis, the drug achieved the first statistically significant improvement in body proportionality against placebo, showing an LS mean treatment difference of -0.05 (p<0.05) in children under 8 years of age, who represented over 50% of the participants. Furthermore, data presented at ICCBH indicated an improvement in arm span Z-score against placebo by +0.37 SD (p<0.0001), marking the first statistically significant arm span improvement in a placebo-controlled trial at 52 weeks.
Safety evaluations revealed that oral infigratinib was well-tolerated, showing no serious adverse events or discontinuations related to the study drug. Only three cases (4%) of hyperphosphatemia occurred, all of which were mild, transient, and asymptomatic, requiring no dose reductions or treatment withdrawals. Crucially, there were no adverse events associated with the inhibition of FGFR1 or FGFR2, such as corneal or retinal complications.
Regulatory Milestones for Kyowa Kirin Infigratinib
The regional development of Kyowa Kirin Infigratinib is highlighted by the AOBA study (RCT2031240562), a Phase 3 clinical trial initiated in Japan in November 2025. Kyowa Kirin Co., Ltd., which secured an exclusive license for the development and commercialization of infigratinib for skeletal dysplasia in Japan in February 2024, aims to leverage global clinical data to provide a new oral option for Japanese patients. Meanwhile, BridgeBio plans to submit a New Drug Application (NDA) in the United States in Q3 2026, anticipating a launch in early to mid-2027, alongside a Marketing Authorization Application (MAA) in Europe in H2 2026.
Achondroplasia is a genetic condition characterized by short stature and severe health complications like spinal stenosis and sleep apnea, affecting about 1 in 20,000 live births globally. Since over 97% of cases stem from activating mutations in FGFR3, targeted therapies provide crucial interventions. Through strategic advances in life sciences, the firm remains committed to addressing these severe unmet medical needs via its main news releases portal.
PROPEL 3 Phase 3 Clinical Study Endpoints and Statistical Outcomes
| Endpoint Type | Parameter / Measurement | Outcome / Value | Statistical Significance | Clinical Context / Comparative Distinction |
| Primary Endpoint | Change from baseline in annualized height velocity (LS Mean treatment difference vs. Placebo) | +1.74 cm/year | p < 0.0001 | Largest observed in a Phase 3 clinical study in achondroplasia |
| Primary Endpoint | Change from baseline in annualized height velocity (Observed Mean difference vs. Placebo) | +2.10 cm/year | p < 0.0001 | Largest observed in a Phase 3 clinical study in achondroplasia |
| Key Secondary Endpoint | Change from baseline in height Z-score (achondroplasia reference population) at Week 52 | +0.41 SD (LS Mean increase on treatment arm) | p < 0.0001 | Successfully achieved key secondary efficacy criteria |
| Key Secondary Endpoint (ICCBH Data) | Improvement in arm span Z-score vs. Placebo at 52 weeks | +0.37 SD | p < 0.0001 | First statistically significant improvement in arm span from a placebo-controlled trial |
| Pre-specified Exploratory Analysis | Improvement in body proportionality against placebo in children younger than 8 years old | -0.05 (LS Mean treatment difference) | p < 0.05 | First statistically significant body proportionality improvement against placebo (>50% participants) |
Safety, Tolerability, and Adverse Events Profile
| Adverse Event Category | Reported Metric / Incidence Rate | Severity and Duration | Management / Required Actions | FGFR1 / FGFR2 Inhibition Association (e.g., Retinal/Corneal) |
| Discontinuations | 0 cases (0%) | N/A | None required; no discontinuations related to study drug | None |
| Serious Adverse Events (SAEs) | 0 cases (0%) | N/A | None required; no serious adverse events related to study drug | None |
| Hyperphosphatemia | 3 cases (4%) | Mild, transient, and asymptomatic | No dose reductions or discontinuations required | None |
| FGFR1 or FGFR2 Specific Risks | 0 cases (0%) | N/A | No associated adverse events observed | Completely absent |
