A Study of Vepugratinib (LY3866288) in Adults With Non-Muscle Invasive Bladder Cancer and Upper Tract Urothelial Cancer

The main purpose of this study is to see how well vepugratinib works in adults with low grade, intermediate risk, non-muscle invasive bladder cancer (LG IR NMIBC) or low-grade upper tract urothelial carcinoma (LG UTUC). Safety tests will also be conducted. For each participant, the study will last up to 5 years.

Inclusion Criteria: * All Participants: * Have a PS of 0 to 2 on the Eastern Cooperative Oncology Group Performance Status (ECOG PS) scale * Cohort A * Have histologically confirmed LG NMIBC. * Have LG IR NMIBC at time of screening * Have a documented qualifying fibroblast growth factor receptor 3 protein (FGFR3) mutation or fusion * Cohort B * Have histologically confirmed LG UTUC. Exclusion Criteria: * All Participants * Have had a prior positive urine cytology within 6 weeks of first day of treatment. * Have received prior local instillation (for example, intravesical chemotherapy, Bacillus Calmette-Guerin, Jelmyto) therapy within 8 weeks of the first day of treatment. * Cohort A * Have synchronous UTUC disease. * Have presence of, or history of, high-grade urothelial carcinoma within 3 years of the first day of treatment, or presence of, or history of, carcinoma in situ. * Cohort B * Have presence of bladder tumors at the time of enrollment. * Have presence of, or history of, high-grade urothelial carcinoma or carcinoma in situ.