FORAGER-1: A Study of LOXO-435 (LY3866288) in Participants With Cancer With a Change in a Gene Called FGFR3

Inclusion Criteria: * Have solid tumor cancer with an FGFR3 pathway alteration on molecular testing in tumor or blood sample that is deemed as actionable * Cohort A1: Presence of an alteration in FGFR3 or its ligands * Cohort A2, B2, B3, and B5: Histological diagnosis of urothelial cancer (UC) that is locally advanced or metastatic with a qualifying FGFR3 genetic alteration * Cohorts B1 and B4: Histological diagnosis of urothelial cancer that is locally advanced or metastatic * Cohort C1: Must have histological diagnosis of a non-urothelial solid tumor malignancy that is locally advanced or metastatic with a qualifying FGFR3 genetic alteration * Measurability of disease: * Cohort A1 and B3: Measurable or non-measurable disease as defined by Response Evaluation Criteria in Solid Tumors v 1.1 (RECIST v1.1) * Cohorts A2, B1, B2, B4, B5, and C1: Measurable disease required as defined by RECIST v1.1 * Have adequate tumor tissue sample available. Participants with inadequate tissue sample availability may still be considered for enrollment upon review * Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 for Cohorts A1, A2, B3, and B5 * Less than or equal to 2 for Cohorts B1, B2, B4, and C1 * Prior Systemic Therapy Criteria: * Cohort A1/C1: Participant has received all standard therapies for which the participant was deemed to be an appropriate candidate by the treating Investigator; OR the participant is refusing the remaining most a…