This phase III trial compares the effect of decreased number of radiation (ultra-hypofractionated) treatments to the usual radiation number of treatments (hypofractionation) with standard of care chemotherapy, with cisplatin, gemcitabine or mitomycin and 5-fluorouracil for the treatment of patients with muscle invasive bladder cancer. Hypofractionated radiation therapy delivers higher doses of radiation therapy over a short period of time. Ultra-hypofractionated radiation therapy delivers radiation over an even shorter period of time than hypofractionated radiation therapy. Cisplatin is in a class of medications known as platinum-containing compounds. It works by killing, stopping or slowing the growth of tumor cells. Gemcitabine is a chemotherapy drug that blocks the cells from making DNA and may kill tumor cells. Chemotherapy drugs, such as mitomycin-C and 5-fluorouracil (5-FU), work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving ultra-hypofractionated radiation may be equally effective as hypofractionated therapy for patients with muscle invasive bladder cancer.

The main purpose of this study is to find out whether the study drug, LY4050784, is safe, tolerable and effective in participants alone or in combination with other anticancer agents. In addition, with locally advanced or metastatic solid tumors with a BRG1 (Brahma-related gene 1, also known as SMARCA4) alteration who have previously received, do not qualify for, or are refusing standard of care treatments, or there is no standard therapy available for the disease. The study is conducted in two parts - phase Ia (dose-escalation) and phase Ib (dose-optimization, dose-expansion). The study will last up to approximately 4 years.