Testing the Effectiveness of Two Immunotherapy Drugs (Nivolumab and Ipilimumab) With One Anti-cancer Targeted Drug (Cabozantinib) for Rare Genitourinary Tumors

PRIMARY OBJECTIVE: I. To evaluate the efficacy of cabozantinib s-malate (cabozantinib) combined with nivolumab and ipilimumab in the first or second-line (and beyond) setting for patients within each of the rare genitourinary (GU) variant histology group of interest, as measured by objective response rate (ORR). SECONDARY OBJECTIVES: I. To estimate the progression-free survival (PFS) for patients treated with cabozantinib combined with nivolumab and ipilimumab within each rare variant histology. II. To estimate the overall survival (OS) for patients treated with cabozantinib combined with nivolumab and ipilimumab within each rare variant histology. III. To estimate the clinical benefit rate (defined as complete response \[CR\] or partial response \[PR\] or stable disease \[SD\]) for patients treated with cabozantinib combined with nivolumab and ipilimumab within each rare variant histology. IV. To assess the safety of treating patients with rare variant histologies with cabozantinib combined with nivolumab and ipilimumab. V. To support tissue banking and collection of clinical follow-up data for GU tract rare histological variants. EXPLORATORY OBJECTIVE: I. To assess effects of treatment in patients with bone-only disease by bone scan. OUTLINE: Patients receive cabozantinib orally (PO) once daily (QD) on days 1-21 of cycles 1-4 and on days 1-28 of subsequent cycles. Patients also receive nivolumab intravenously (IV) over 30 minutes on day 1 and ipilimumab IV over 90 minutes on day 1 of cycles 1-4. Patients then receive nivolumab IV over 30 minutes on day 1 of subsequent cycles. Treatment repeats every 21 days for cycles 1-4 and every 28 days for subsequent cycles for 2 years in the absence of disease progression or unacceptable toxicity. Patients may undergo echocardiography during screening and undergo computed tomography (CT) or magnetic resonance imaging (MRI), bone scan and blood and urine sample collection throughout the trial and may undergo positron emission tomography (PET)/CT throughout the trial. After completion of study treatment, patients are followed up every 2 months for up to 5 years.