Extension Study of Infigratinib in Children With Achondroplasia (ACH)

This is a Phase 2, multicenter, open-label, extension (OLE) study to evaluate the long-term safety, tolerability, and efficacy of infigratinib, an FGFR 1-3-selective tyrosine kinase inhibitor, in participants with ACH who previously completed a QED-sponsored interventional study, and in additional participants who are naïve to infigratinib treatment. Quality of Life assessments for this participant population will also be evaluated. Treatment-naïve participants must have at least a 6-month period of growth assessment in study QBGJ398-001 (PROPEL) and will be enrolled in this OLE study if the sponsor deems additional long-term safety and/or efficacy data are necessary, and participants are not otherwise eligible to enroll in another QED-sponsored Phase 2 or Phase 3 ACH study.

Key Rollover Participants Inclusion Criteria: 1. Pediatric participants ≥3 years old with ACH who have completed a previous QED-sponsored interventional study with infigratinib. 2. Participants and parent(s), legal guardian(s), or caregiver(s) are willing and able to comply with study visits and study procedures. 3. Participants are able to swallow oral medication. 4. Negative pregnancy test in girls ≥10 years of age or girls of any age who have experienced menarche. 5. If sexually active, participant must be willing to use a highly effective method of contraception while taking study drug and for 1 month after the last dose of study drug. 6. The PI, or a person designated by the PI, will obtain written informed consent from each participant's parent(s), legal guardian(s), or caregiver(s) and the participant's assent, when applicable, before any study-specific activity is performed. Key Rollover Participants Exclusion Criteria: 1. Participant has concurrent circumstance, disease, or condition that, in the view of the PI and/or sponsor, would interfere with study participation or safety evaluations. 2. Participants who developed a medical condition that will require the initiation of treatment with a prohibited medication. 3. Participants prematurely discontinued a prior QED-sponsored interventional study with infigratinib 4. Current participation in an ongoing clinical study with a sponsor other than QED 5. Participants that have reached final height or near final height. Key Inclusion Criteria for Treatment Naïve Participants: 1. Participants must be 3 to \