Oral Infigratinib Demonstrates Phase 3 Efficacy Breakthrough in Achondroplasia, With Expanded Plans for Hypochondroplasia

BridgeBio Pharma has announced encouraging Phase 3 results from its PROPEL 3 trial of oral infigratinib in children with achondroplasia, marking a significant milestone in the development of targeted therapies for this genetic skeletal disorder. The data reveal that infigratinib not only improves linear growth but also addresses body proportionality—an outcome that has eluded previous therapeutic approaches in achondroplasia.

Achondroplasia affects approximately 55,000 people across the United States and European Union, including up to 10,000 children and adolescents with open growth plates. As the most common cause of disproportionate short stature, the condition stems from an activating variant in the FGFR3 gene and carries broader health implications beyond height limitations, including obstructive sleep apnea, middle ear dysfunction, and spinal stenosis. Prior to infigratinib, treatment options for children have been limited, creating substantial unmet clinical needs.

First Oral Therapy to Significantly Improve Body Proportionality in Achondroplasia

The PROPEL 3 trial, a global randomized placebo-controlled study conducted over 52 weeks in children aged 3 to <18 years, achieved its primary efficacy target with robust statistical significance. The primary endpoint—change from baseline in annualized height velocity (AHV)—showed a mean treatment difference of +2.10 cm/year with an LS mean of +1.74 cm/year compared to placebo (p<0.0001).

More notably, infigratinib achieved what no other therapy has accomplished: statistically significant improvement in body proportionality. In a pre-specified exploratory analysis of children younger than 8 years (representing >50% of trial participants), oral infigratinib demonstrated an LS mean decrease of -0.05 in upper-to-lower body proportionality ratio against placebo (p<0.05). This represents the first therapeutic option in a randomized trial to show statistical significance for this important clinical parameter, addressing a concern that has been identified as meaningful by patients and families living with the condition.

Annualized Height Velocity Gains Outperform Previous Therapeutic Approaches

Beyond the primary endpoint, secondary efficacy measures reinforced infigratinib’s clinical profile. The absolute AHV achieved on the treatment arm reached 5.96 cm/year—the highest reported in any randomized achondroplasia trial to date, compared to 4.22 cm/year on placebo. The improvement in height Z-score (using achondroplasia-specific reference standards) achieved an LS mean treatment difference of +0.32 SD against placebo, described as the largest differential observed in randomized trial data for this condition. On the treatment arm alone, the LS mean improvement of +0.41 SD represents the largest individual arm response documented in achondroplasia trials.

These numerical gains translate to meaningful clinical consequences. Children receiving oral infigratinib experienced growth improvements that exceed historical therapeutic benchmarks, positioning infigratinib as a transformative option for the achondroplasia population.

Favorable Safety Profile With Manageable Adverse Events

A critical advantage of oral infigratinib is its safety and tolerability profile. Throughout the 52-week trial period, there were no discontinuations related to study drug and no serious adverse events attributable to the medication. Hyperphosphatemia—an expected pharmacological effect of FGFR3 inhibition—occurred in only 3 cases (4% of participants), all classified as mild and transient, asymptomatic, and requiring neither dose reduction nor discontinuation.

Notably, infigratinib demonstrated no adverse events associated with inhibition of off-target FGFR1 or FGFR2, indicating a favorable selectivity profile. The trial also documented no adverse events associated with secondary mechanisms (such as those seen with CNP analogue approaches), including symptomatic hypotension, injection site reactions, or hypertrichosis. This safety pattern distinguishes oral infigratinib from alternative treatment modalities, particularly non-injectable approaches that address the preferences of families seeking practical, daily-use options.

Regulatory Pathway and Breakthrough Designation Status

BridgeBio intends to initiate regulatory discussions with health authorities regarding submission timelines, with New Drug Application (NDA) and Marketing Authorization Application (MAA) filings anticipated in the second half of 2026. Infigratinib carries FDA Breakthrough Therapy Designation for achondroplasia—a status shared by no other therapeutic candidate currently in development for this indication. The drug has also received Orphan Drug Designation from both the FDA and European Medicines Agency (EMA), Fast Track Designation, and Rare Pediatric Disease Designation, collectively expediting its development pathway.

The company plans to host an investor webcast on February 12, 2026 at 8:00 AM ET to elaborate on these findings and discuss commercial strategy. Additional information regarding ongoing trials, including PROPEL Infant & Toddler (studying infants and toddlers aged <3 years), will be available through the company’s official communications.

Expanding Development to Hypochondroplasia and Other Age Groups

Beyond achondroplasia, BridgeBio has announced plans to accelerate development of oral infigratinib in hypochondroplasia, a related but distinct skeletal dysplasia. The company is currently enrolling participants in the observational run-in phase for the Phase 3 ACCEL trial in hypochondroplasia, signaling confidence in extending the drug candidate’s potential application across the skeletal dysplasia spectrum.

Additionally, an ongoing Phase 3 trial is evaluating infigratinib in the younger pediatric population (newborn to <3 years old) with achondroplasia, as part of the PROPEL Infant & Toddler initiative. These parallel programs suggest that BridgeBio is positioning oral infigratinib as a foundational therapy applicable across multiple indications and age ranges within the genetic skeletal dysplasia space, with potential implications for the hypochondroplasia patient population currently lacking effective treatment options.

Clinical Significance and Patient Community Perspective

The achievement of body proportionality improvements holds particular significance beyond the numerical endpoints. Ravi Savarirayan, M.D., Ph.D., global lead investigator for PROPEL 3 from Murdoch Children’s Research Institute, characterized the findings as representing “best-in-class results” that highlight infigratinib’s potential to address aspects of achondroplasia extending beyond linear height considerations. The oral formulation—a departure from injectable or other non-oral alternatives—offers practical advantages for family adherence and daily-life integration.

Michael Hughes, representing the advocacy community through Little People of America’s Biotech Industry Liaison Committee, highlighted that the observed body proportionality improvement aligns with priorities identified by individuals and families affected by dwarfism conditions, potentially influencing physical function and long-term quality of life outcomes. This alignment between clinical trial endpoints and real-world patient priorities strengthens the clinical relevance of the PROPEL 3 results.

The Phase 3 data establish infigratinib as a significant advancement in achondroplasia therapeutics, with the regulatory pathway and expanded hypochondroplasia development plans positioning oral infigratinib as a potential standard therapeutic approach for multiple skeletal dysplasia conditions.