Study of GB-4362 With Enfortumab Vedotin and Pembrolizumab for Advanced Urothelial Cancer

Inclusion Criteria * Planned to receive standard-of-care treatment with enfortumab vedotin (EV) (starting dose 1.25 mg/kg) in combination with pembrolizumab for locally advanced or metastatic urothelial cancer. * Age ≥18 years. * ECOG Performance Status score of 0 or 1 (ECOG 2 excluded in Dose Escalation but allowed in Dose Expansion). * Weight ≥50 kg at screening. * Life expectancy ≥3 months, as determined by the investigator. * Participants must provide written informed consent before any study-related activities are carried out and must be able to understand the nature and purpose of the study, including potential risks and adverse effects. * Willing and able to comply with all study assessments and adhere to the protocol schedule and restrictions. Exclusion Criteria * Previously received enfortumab vedotin (EV) or other MMAE-based antibody-drug conjugates (ADCs). * Received anti-cancer treatment with chemotherapy, biologics, or investigational agents within 4 weeks before the first dose of EV/pembrolizumab. * Uncontrolled diabetes. * Active CNS metastases. Participants with treated CNS metastases are permitted if all of the following criteria are met: * CNS metastases have been clinically stable for at least 4 weeks prior to screening and baseline scans show no evidence of new or enlarged metastasis. * The participant is on a stable dose of ≤10 mg/day of prednisone or equivalent for at least 2 weeks (if requiring steroid treatment). * The participant does not have leptomeningeal disease. * Ongoing clinically significant toxicity associated with prior treatment (including radiotherapy or surgery) that has not resolved to Grade ≤1 or returned to baseline. * History of a severe (Grade ≥3) allergic or infusion-related reaction to any monoclonal antibody. * Another underlying medical condition that, in the opinion of the investigator, would impair the ability of the participant to receive or tolerate the planned treatment and follow-up. * Known psychiatric or substance abuse disorders that would interfere with cooperating with study requirements