Enzalutamide With Venetoclax in Treating Patients With Metastatic Castration Resistant Prostate Cancer

Inclusion Criteria: * Histological or cytological documentation of diagnosis of prostate cancer. * Documented progressive metastatic castrate resistant prostate cancer (mCRPC) based on at least one of the following criteria: * Prostate specific antigen (PSA) progression defined as 25% increase over baseline value with an increase in the absolute value of at least 2 ng/mL that is confirmed by another PSA level with a minimum of a 1 week interval and a minimum PSA of 2 ng/mL. * Soft-tissue progression defined as an increase \>= 20% in the sum of the longest diameter (LD) of all target lesions based on the smallest sum LD since treatment started or the appearance of one or more new lesions. * Progression of bone disease (evaluable disease) or, new bone lesion(s), by bone scan. * If on an anti-androgen, must have documented progression 6 weeks after stopping anti-androgen therapy. * Willing to undergo a biopsy, if readily available biopsy site present (i.e., nodal or visceral metastasis). * Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 - 1. * Have testosterone level of \< 50 ng/dL. Note: Patients must continue primary androgen deprivation with a luteinizing hormone-releasing hormone (LHRH) analogue (agonist or antagonist) if they have not undergone orchiectomy. * White blood cells \>= 1.5 x 10\^9/L (obtained within 14 days prior to treatment start) * Platelets (UNVPLT) \>= 100 x 10\^9/L (obtained within 14 days prior to treatment start) * Hem…