UBE2D2 and urinary bladder cancer: Three factors justify a clinical pilot trial of UBC4: (1) the UBC4 drugs are usually well tolerated and carry a low risk of harm, (2) the commonly fatal outcome of bladder cancer once it has widely metastasized, plus (3) the strong preclinical database showing UBC growth inhibition by each of the individual UBC4 drugs as outlined in this paper.