Pembrolizumab Plus CA-4948 for the Treatment of Patients With Progressive Metastatic Urothelial Cancer Despite Prior Immunotherapy

Inclusion Criteria: * Patients must have histologically confirmed urothelial cancer that is metastatic or unresectable and must have had the prior treatments outlined * Age ≥ 18 years * Because no dosing or adverse event data are currently available on the use of CA-4948 in combination with pembrolizumab in patients \< 18 years of age, children are excluded from this study, but will be eligible for future pediatric trials * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 (Karnofsky ≥ 60%) within 28 days prior to registration * Leukocytes ≥ 3,000/mcL * Absolute neutrophil count (ANC) ≥ 1,500/mcL * Platelets ≥ 100,000/mcL * Hemoglobin ≥ 9 g/dL or ≥ 5.6 mmol/L * Criteria must be met without packed red blood cell (pRBC) transfusion within the prior 2 weeks. Participants can be on stable dose of erythropoietin (≥ approximately 3 months) * Creatine phosphokinase (CPK) \< grade (Gr) 2 ( \</= 2.5 upper limit of normal \[ULN\]) * Creatinine \< 1.5 × institutional ULN or creatinine clearance of ≥ 30 mL/min for patient with creatine levels ≥ 1.5 x institutional ULN * Creatinine clearance (CrCl) should be calculated per institutional standard * Total bilirubin ≤ 1.5 x institutional upper limit of normal (IULN) * Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase \[SGOT\]) ≤ 3 x ULN * Alanine aminotransferase (ALT) (serum glutamic pyruvic transaminase \[SGPT\]) ≤ 3 x ULN * International normalized ratio (INR) or prothrombin time (PT) ≤ 1.5…