A Study of Erdafitinib in Participants With Advanced Solid Tumors and Fibroblast Growth Factor Receptor (FGFR) Gene Alterations

The purpose of this study is to evaluate the efficacy of erdafitinib in terms of overall response rate (ORR) in adult and pediatric participants with advanced solid tumors with fibroblast growth factor receptor (FGFR) alterations (mutations or gene fusions). It will also evaluate ORR in pediatric participants with advanced solid tumors and FGFR alterations.

Erdafitinib is a selective and potent pan FGFR 1-4 inhibitor with demonstrated clinical activity in participants with metastatic urothelial cancer and cholangiocarcinoma identified to have alterations in the FGFR pathway. This study targets the underlying altered biology of FGFR-driven tumors irrespective of solid tumor histology subtype. The study consists of screening phase, treatment phase and the post treatment follow-up phase (from the end of treatment visit until the participant has died, withdraws consent, is lost to follow-up, or the end of study, whichever comes first). End of study is considered as the time when the last participant receives the last dose of study drug on the study and either all pediatric participants are off study or until the most recently enrolled pediatric participant still participating in the study has 6 months of follow-up, whichever occurs first. Currently this study is recruiting pediatric participants only.

Inclusion Criteria: * Histologic demonstration of an unresectable, locally advanced, or metastatic solid tumor malignancy with an fibroblast growth factor receptor (FGFR) mutation or FGFR gene fusion * Measurable disease * Participant must have received at least one prior line of systemic therapy in the advanced, unresectable, or metastatic setting; or is a child or adolescent participant with a newly-diagnosed solid tumor and no acceptable standard therapies * Documented progression of disease, defined as any progression that requires a change in treatment, prior to full study screening Exclusion Criteria: * Has had prior chemotherapy, targeted therapy, or treatment with an investigational anticancer agent within 15 days or less than or equal to (\<=) 5 half-lives of the agent (whichever is longer) and up to a maximum of 30 days before the first dose of erdafitinib * The presence of FGFR gatekeeper and resistance mutations * Histologic demonstration of urothelial carcinoma * Hematologic malignancy (i.e., myeloid and lymphoid neoplasms * For non-small cell lung cancer participants only: pathogenic somatic mutations or gene fusions in the following genes: EGFR, ALK, ROS1, NTRK, BRAF V600E and KRAS * Active malignancies other than for disease requiring therapy