A Phase 1, Open-Label Study to Evaluate the Safety, Pharmacokinetics, and Pharmacodynamics of GB-4362 Administered with Enfortumab Vedotin and Pembrolizumab in Participants with 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