Cisplatin and Gemcitabine Hydrochloride With or Without Berzosertib in Treating Patients With Metastatic Urothelial Cancer

PRIMARY OBJECTIVE: I. To determine if the addition of berzosertib (M6620 \[VX-970\]) to cisplatin/gemcitabine hydrochloride (gemcitabine) improves progression-free survival (PFS) relative to cisplatin/gemcitabine alone. SECONDARY OBJECTIVES: I. To compare overall survival (OS) with the addition of M6620 (VX-970) to cisplatin/gemcitabine relative to cisplatin/gemcitabine alone. II. To compare tumor response rate with the addition of M6620 (VX-970) to cisplatin/gemcitabine relative to cisplatin/gemcitabine alone. III. To compare safety with the addition of M6620 (VX-970) to cisplatin/gemcitabine relative to cisplatin/gemcitabine alone. IV. To assess the role of p53 status in predicting response to M6620 (VX-970)-based therapy. OUTLINE: Patients are randomized to 1 of 2 arms. ARM A: Patients receive gemcitabine hydrochloride intravenously (IV) over 30 minutes on days 1 and 8, and cisplatin IV over 60 minutes on day 1. Patients also receive berzosertib IV over 60 minutes on days 2 and 9. Treatment repeats every 21 days for 6 cycles in the absence of disease progression or unacceptable toxicity. ARM B: Patients receive gemcitabine hydrochloride and cisplatin as in Arm A. After completion of study treatment, patients are followed up to 36 months.