PRIMARY OBJECTIVES:~I. To evaluate the response rate (RR) in patients with (methylthioadenosine phosphorylase) MTAP-deficient metastatic urothelial cancer treated sequentially with pemetrexed and avelumab.~SECONDARY OBJECTIVES:~I. To estimate the progression-free survival (PFS) and overall survival (OS) in patients with MTAP-deficient metastatic urothelial cancer treated sequentially with pemetrexed and avelumab.~II. To explore the effect of pemetrexed +/- avelumab on the immune system and tumor microenvironment including peripheral T-cells, tumor-infiltrating T-cells, macrophages, and myeloid-derived suppressor cells (MDSCs).~OUTLINE:~Patients receive pemetrexed intravenously (IV) over 10 minutes on day 1. Starting cycle 2, patients also receive avelumab IV over 60 minutes. Cycles repeat every 21 days in the absence of disease progression or unacceptable toxicity.~After completion of study treatment, patients are followed up at 30 and 120 days, and then every 3 months for 2 years.
This phase II trial studies how well pemetrexed and avelumab work in treating patients with MTAP-deficient urothelial cancer that has spread to other places in the body. Pemetrexed may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Immunotherapy with monoclonal antibodies, such as avelumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Giving pemetrexed and avelumab may work better in treating patients with MTAP-deficient urothelial cancer.