This study is testing an experimental drug called GB-4362 with two other drugs, enfortumab vedotin and pembrolizumab, in adults with advanced urothelial cancer. Urothelial cancer affects the urinary system. GB-4362 is a special protein that helps target and neutralize a chemical called monomethyl auristatin E (MMAE), which is used in enfortumab vedotin but can cause side effects. Pembrolizumab is a drug that helps the immune system fight cancer.

The study has two parts: dose escalation, where different amounts of GB-4362 are tested for safety, and dose expansion, where more people receive the chosen dose to see how well it works. The study checks the safety and effects of these drugs together.

• Participants need to be 18 or older and have a life expectancy of at least 3 months.
• You must not have taken enfortumab vedotin or similar drugs before.
• The study involves multiple visits for assessments and monitoring.