An Interventional Study of Infigratinib in Children With Hypochondroplasia

Key Inclusion Criteria:

• Participants must have completed at least 26 weeks and still be on the observational study (QBGJ398-004).
• Phase 2 portion: Participants 5-11 years of age (inclusive).
• Phase 3 portion: Participants 3 to \<18 years of age at screening with growth potential
• Diagnosis of HCH documented clinically by the presence of disproportionate short stature and confirmed with a molecular test.
• Participants are able to swallow oral medication.
• Participants and parent(s), legal guardian(s), or caregiver(s) are willing and able to comply with study visits and study procedures.
• Participants are ambulatory and able to stand without assistance. Sex and Contraceptive/Barrier Requirements
• Negative pregnancy test in girls ≥10 years of age or girls of any age who have experienced menarche.
• If sexually active, participants whether male or female, must be willing to use a highly effective method of contraception, as relevant, while taking study drug and for 1 month after the last dose of study drug.
• Signed informed consent.

Key Exclusion Criteria:

• Participants who have ACH or a short stature condition other than HCH.
• Significant concurrent disease or condition that, in the view of the investigator and/or sponsor, would confound assessment of efficacy or safety of infigratinib.
• Current evidence of clinically significant corneal or retinal disorder/keratopathy confirmed by ophthalmic examination.
• Concurrent circumstance, disease, or condition that, in the view of the investigator and/or sponsor, would interfere with study participation or safety evaluations.
• History and/or current evidence of extensive ectopic tissue calcification.
• History of malignancy.
• Having received or planning to receive treatment with any other investigational or approved product for the treatment of ACH, HCH, or short stature.
• Regular long-term treatment (≥3 weeks) with supraphysiologic doses of glucocorticoid.
• Previous limb-lengthening surgery at any time or planned/expected to have limb-lengthening or guided growth surgery while participating in the study.
• Participants receiving medications which could increase serum phosphorus and/or calcium concentrations
• Clinically significant abnormality in any laboratory test result at screening.
• Pregnant or breastfeeding at the screening visit or planning to become pregnant (self or partner) at any time during the study.
• Allergy to any components of the study drug.
• Concurrent circumstance, disease, or condition that would interfere with study participation.