Cabazitaxel, Carboplatin, and Cetrelimab Followed by Niraparib With or Without Cetrelimab for the Treatment of Aggressive Variant Metastatic Prostate Cancer

PRIMARY OBJECTIVES: I. Estimate the progression free survival of men with aggressive variant prostate carcinoma (AVPC) treated with induction cabazitaxel-carboplatin and cetrelimab followed by maintenance niraparib with or without cetrelimab. II. Evaluate changes in the density and localization of immune markers and cell subsets in AVPC tumors treated with or without cetrelimab added to cabazitaxel-carboplatin induction and niraparib maintenance, and screen for their association with outcomes. SECONDARY OBJECTIVES: I. Determine the percentage of patients that are able to complete the 6 cycles of induction chemoimmunotherapy. II. Estimate the Response Evaluation Criteria in Solid Tumors (RECIST), prostate specific antigen (PSA) and circulating tumor cells (CTC) responses in men with AVPC treated with induction cabazitaxel-carboplatin and cetrelimab followed by maintenance niraparib with or without cetrelimab. III. Estimate the overall survival of men with AVPC treated with induction cabazitaxel-carboplatin and cetrelimab followed by maintenance niraparib with or without cetrelimab. IV. Determine the safety and tolerability of each of the regimens. V. Determine the frequency of PD-L1 expression in tumors treated with cabazitaxel-carboplatin induction and niraparib maintenance and its association with outcomes. VI. Collect and archive solid and liquid tumor samples from study patients for later hypothesis generating associations. OUTLINE: Patients are randomized to 1 of 2 groups. GROUP I: INDUCTION: Patients receive cabazitaxel intravenously (IV) over 60 minutes and carboplatin IV over 60 minutes on day 1. Beginning cycle 2, patients also receive cetrelimab IV over 30-60 minutes on day 1. Treatment repeats for up to 6 cycles in the absence of disease progression or unacceptable toxicity. MAINTENANCE: Patients receive niraparib orally (PO) once daily (QD) on days 1-28. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. GROUP II: INDUCTION: Patients receive cabazitaxel IV over 60 minutes and carboplatin IV over 60 minutes on day 1. Beginning cycle 2, patients also receive cetrelimab IV over 30-60 minutes on day 1. Treatment repeats for up to 6 cycles in the absence of disease progression or unacceptable toxicity. MAINTENANCE: Patients receive cetrelimab IV over 30 minutes on day 1 and niraparib PO QD on days 1-28. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment patients are followed up for 30 to 90 days (after last dose cetrelimab), and then every 6 months thereafter.