BridgeBio Pharma has bounced back from the withdrawal of infigratinib in oncology, linking the molecule to a BioMarin-beating height increase in children with a growth disorder in a midphase clinical trial.
The FDA withdrew accelerated approval of infigratinib in May, completing a process that began one year earlier when BridgeBio’s then-partner Helsinn asked the agency to pull the authorization. Helsinn made the request after struggling to enroll subjects for a required confirmatory clinical trial. As the cancer program went off the rails, BridgeBio continued to advance low-dose infigratinib in a form of dwarfism.
BridgeBio reported top-line data from the midphase PROPEL 2 trial in March 2023 and followed up with six-month data around one year ago. Tuesday, the biotech unwrapped 12- and 18-month data that add to evidence that the daily oral FGFR3 inhibitor infigratinib may have an edge over BioMarin’s approved dwarfism therapy Voxzogo.
On infigratinib, children with achondroplasia, the most common type of dwarfism, had mean increases in annualized height velocity (AHV) of 2.51 cm/year after 12 months and 2.50 cm/year after 18 months. The FDA approved (PDF) Voxzogo on the basis of a trial that reported a 1.40 cm/year increase in AHV at 12 months.
BridgeBio also shared data on a secondary endpoint. The ratio of the upper to lower body improved in children on infigratinib, falling from 2.02 at baseline to 1.88 after 18 months. The 0.14 improvement is greater than the change BioMarin reported across two years of follow up.
Ravi Savarirayan, M.D., Ph.D., of Murdoch Children’s Research Institute, said in a statement that changes in body ratio are encouraging and suggest infigratinib “has the potential to enhance functionality for people living with achondroplasia in addition to increasing growth.”
Infigratinib appears capable of beating Voxzogo, with the usual caveats about cross-trial comparisons, but its effect on AHV fell between the six- and 12-month updates. After six months, the mean increase in AHV was 3.38 cm/year from baseline.
Even so, with no patients having treatment-related adverse events, BridgeBio is sufficiently encouraged by the data to expand development. A phase 3 study in achondroplasia is already underway and on track to complete enrollment by the end of the year. BridgeBio is now working to enter phase 3 in hypochondroplasia, a form of short-limbed dwarfism.
After talking to regulators, BridgeBio has begun a small, open-label phase 2 trial in hypochondroplasia. The study will test infigratinib at one dose, the level that has shown most promise in achondroplasia, to support progression into a placebo-controlled registrational phase 3 study in hypochondroplasia. Last month, BioMarin said it aimed to start a phase 3 trial in hypochondroplasia by midyear.
BioMarin reported a 74% increase in Voxzogo revenue in the first quarter, causing sales of the product to reach $153 million, but multiple companies are aiming to challenge the biotech for the achondroplasia market. Ascendis Pharma and Sanofi are among the drug developers with achondroplasia assets in the clinic.