Naptumomab Estafenatox in Combination With Pembrolizumab Preceded by Obinutuzumab in Patients With Urothelial Cancers

The main purpose of this study is to test the safety and tolerability of naptumomab estafenatox (NAP), the planned experimental (investigational) drug, in combination with pembrolizumab following a single pretreatment with Obinutuzumab (Obi), and determine its side effects and effects on urothelial cancer. It is hypothesized that adding NAP will make pembrolizumab more effective. Participants will receive 2 infusions of Obi prior to the treatment of NAP in combination with pembrolizumab. This treatment is given in 21-day cycles for 6 cycles with NAP administered daily for 4 consecutive days, Days 1-4, + pembrolizumab given on day 2 of each cycle. After these six cycles of therapy, participants will continue to receive pembrolizumab every 3 weeks, without NAP, for a total number of up to 34 pembrolizumab administrations since cycle 1. After the treatment of Obi is completed, participants will start NAP in combination with pembrolizumab and continue that treatment in a 28 day cycle period. NAP will be given for a total of 6 cycles and pembrolizumab will be given every 21 days for a total of up to 2 years. After stopping treatment, participants have follow-up visits or phone calls about every 12 weeks until the study is closed.