A Phase 1/1b of RNDO-564 Single Agent or in Combination With Pembrolizumab in Bladder Cancer and Other Solid Tumors Associated With Nectin-4

The main goal of this study is to evaluate how safe and tolerable RNDO-564 is and to identify the best dose of RNDO-564 as a single agent and in combination with pembrolizumab. The study is focused on participants with certain solid tumors that are in an advanced stage and have certain tumor makers. This will be done by measuring the side effects that participants experience and how severe they are. Additionally, the study will evaluate how RNDO-564 moves into, through, and out of the body and how the treatment affects the body. The second goal of this study is to evaluate how well RNDO-564 works by itself or in combination with pembrolizumab at treating participants' cancer. This will be done by measuring the number of participants who respond to the treatment. The length of time where the tumor does not grow or spread will also be measured. Participants will take RNDO-564 weekly on Days 1, 8 and 15 of a 21 day cycle. Participants in the combination arms will take RNDO-564 as described with pembrolizumab every 3 weeks.