OR27-03 Oral Infigratinib Treatment Is Well Tolerated And Significantly Increases Height Velocity In Children With Achondroplasia: Month 6 Results From The PROPEL 2 Dose-finding Study

Abstract Disclosure: R. Savarirayan: Advisory Board Member; Self; Ascendis Pharma, BioMarin, QED Therapeutics, Sanofi. Consulting Fee; Self; BioMarin. Grant Recipient; Self; Ascendis Pharma, BioMarin, QED Therapeutics, Theracon. Research Investigator; Self; Ascendis Pharma, BioMarin, QED Therapeutics, Theracon. J. De Bergua: None. P. Arundel: None. J. Salles: None. V. Saraff: None. B. Delgado: None. A. Leiva-Gea: None. H. McDevitt: None. M.P. Nicolino: None. M. Rossi: Advisory Board Member; Self; BioMarin. M. Salcedo: None. V. Cormier-Daire: Advisory Board Member; Self; BioMarin. M. Skae: None. P. Kannu: Advisory Board Member; Self; Novartis, Ipsen. Grant Recipient; Self; CIHR. M.B. Bober: Advisory Board Member; Self; Biomarin. Consulting Fee; Self; Ascendis Pharma, BioMarin, Pfizer, QED Therapeutics. Grant Recipient; Self; Ascendis Pharma, BioMarin, Pfizer, QED Therapeutics. Research Investigator; Self; Ascendis Pharma, BioMarin, Pfizer, QED Therapeutics. J. Phillips: None. H. Saal: Advisory Board Member; Self; Alexion. Grant Recipient; Self; Alexion, BioMarin, Pfizer, QED Therapeutics. Research Investigator; Self; Alexion, BioMarin, Pfizer, QED Therapeutics. P. Harmatz: Consulting Fee; Self; Audentes, Aeglea, Homology, JCR, Denali, Inventiva, Paradigm, Capsida, Chiesi, Avrobio. Grant Recipient; Self; BioMarin, Inventiva. Research Investigator; Self; BioMarin, Shire/Takeda, QED, RegenXbio, Denali, Ascendis, Amicus, Allievex, JCR, Orphazyme, Idorsia, Sangamo. C.P. Burren: Grant Recipient; Self; Amgen, Pfizer, QED Therapeutics. Research Investigator; Self; Amgen, Pfizer, QED Therapeutics. T. Candler: None. T. Cho: Employee; Self; QED Therapeutics. Stock Owner; Self; QED Therapeutics. E. Muslimova: Employee; Self; QED Therapeutics. Stock Owner; Self; QED Therapeutics. R. Weng: Employee; Self; QED Therapeutics. Stock Owner; Self; QED Therapeutics. S. Raj: None. J. Hoover-Fong: Consulting Fee; Self; Pfizer/Therachon, BioMarin, QED Therapeutics, Sanofi, Ascendis Pharma. Grant Recipient; Self; Pfizer/Therachon, BioMarin, Ascendis Pharma. Research Investigator; Self; Pfizer/Therachon, BioMarin, Ascendis Pharma. M. Irving: Advisory Board Member; Self; Ascendis Pharma, BioMarin, QED Therapeutics, Sanofi, Therachon/Pfizer. Speaker; Self; BioMarin, QED Therapeutics. D. Rogoff: Employee; Self; QED Therapeutics. Stock Owner; Self; QED Therapeutics. Background: Achondroplasia (ACH), the most common short-limbed skeletal dysplasia, is characterized by impaired endochondral ossification resulting from gain-of-function pathogenic variants in the fibroblast growth factor receptor 3 (FGFR3) gene, a negative regulator of endochondral bone growth. People with ACH are at risk for several significant co-morbidities, including compression of the brainstem due to foramen magnum stenosis, sleep-disordered breathing, chronic otitis media with conductive hearing loss, and symptomatic spinal stenosis. Infigratinib is an oral, selective FGFR1-3 tyrosine kinase inhibitor being investigated for the treatment of children with ACH in a phase 2 interventional study (PROPEL 2). Methods: PROPEL 2 (NCT04265651) is a phase 2 dose-finding, open-label study of infigratinib in children 3−11 years of age with ACH who participated for ≥6 months in PROPEL (NCT04035811), a non-interventional clinical assessment study. The PROPEL 2 dose-escalation (DE) phase comprises 5 ascending dose cohorts ranging from 0.016 mg/kg/day to 0.25 mg/kg/day. The primary endpoints are safety; change from baseline (BL) in annualized height velocity (AHV); and infigratinib pharmacokinetics in this population. Secondary endpoints include changes from BL in body proportions, and changes in quality of life. Other parameters of disease burden are evaluated as exploratory endpoints. Summary: Children enrolled in the PROPEL 2 DE phase completed ≥6 months of treatment at the assigned cohort dose. Cohorts 1-3 (n=37; doses 0.016, 0.032, and 0.064 mg/kg/day) did not show a significant increase in AHV and these doses were assessed as non-efficacious. Treatment at the cohort 4 dose (0.128 mg/kg/day) resulted in an increase in AHV from BL of 1.52 cm/year in children ≥5 years old (n=11; p=0.02). Infigratinib at the cohort 5 dose (n=10 with month 6 data, 0.25 mg/kg/day) resulted in a significant mean increase from BL of 3.03 cm/year (p=0.0022). In children considered responders (Δ in AHV ≥25% from BL, n=8/10), the mean change in AHV at the cohort 5 dose was +3.81±1.8 cm/year, with a median of +4.14 cm/year. Infigratinib was well tolerated with no serious AEs or AEs that led to study discontinuation, with most AEs mild or moderate in severity. At the cohort 5 dose level, no grade 3 AEs or treatment-related AEs were reported. Conclusion: Oral infigratinib in children with ACH, up to a dose of 0.25 mg/kg/day, was well tolerated and showed dose-dependent increases in AHV, with a significant mean change from BL of +3.03cm/year at the cohort 5 dose. The safety and efficacy of this oral, once-daily dose of infigratinib at 0.25 mg/kg/day will be further explored in a phase 3 randomized controlled study. If these phase 2 data are confirmed, infigratinib could potentially offer children with ACH the first safe and effective oral therapy to improve growth, enhance functionality and decrease medical complications. Presentation: Saturday, June 17, 2023

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