Inclusion Criteria:

          -  Ability to understand and voluntarily agree to participate by providing written
             informed consent for the trial.

          -  Histologically confirmed prostate adenocarcinoma cancer, either pure or mixed. Small
             cell/neuroendocrine differentiation is not allowed.

          -  Castrate levels of serum testosterone (≤ 50 ng/dL). Patients must continue androgen
             deprivation therapy with an LHRH analogue or antagonist if they have not undergone
             bilateral orchiectomy.

          -  Patients must have metastatic disease; either non-measurable disease OR measurable
             disease per RECIST 1.1.

          -  Progressive disease despite ongoing treatment with Androgen Deprivation Therapy (ADT).

          -  Patients treated with first generation anti-androgen as most recent systemic therapy
             (e.g. bicalutamide, nilutamide) must have at least 4 weeks elapsed from treatment
             discontinuation to start of protocol therapy with evidence of disease progression (per
             protocol) following discontinuation of prior anti-androgen.

          -  Minimum PSA at entry of 1 ng/mL is required.

          -  ECOG Performance Status 0, 1 or 2.

          -  Be ≥18 years of age on the day of signing informed consent.

          -  Demonstrate adequate organ function.

          -  Subjects must agree to use an adequate method of contraception as outlined in the
             protocol starting with the time of informed consent through 120 days after the last
             dose trial therapy.

        Exclusion Criteria:

          -  Prior chemotherapy and/or enzalutamide for metastatic castration-resistant prostate
             cancer. Chemotherapy administered in the castration-sensitive setting is allowed
             provided last dose of chemotherapy was greater than 6 months prior to study entry.

          -  Is currently participating and receiving study therapy or has participated in a study
             of an investigational agent and received study therapy or used an investigation device
             within 4 weeks prior to enrollment.

          -  Has not recovered (i.e., AE ≤Grade 1 or at baseline) from AEs due to a previously
             administered agent. Subjects with ≤Grade 2 neuropathy or ≤Grade 2 alopecia are an
             exception to this criterion and are allowed if relevant toxicity is stabilized.

          -  If subjects received major surgery they must have recovered adequately from the
             toxicity and/or complications from the intervention prior to starting trial therapy.

          -  Has a known additional malignancy that is progressing or requires active treatment.
             Exceptions include basal cell carcinoma of the skin or squamous cell carcinoma of the
             skin.

          -  Has known psychiatric or substance abuse disorders that would interfere with
             cooperation with the requirements of the trial. At the time of signing informed
             consent is a known regular user (including "recreational use") of any illicit drug(s)
             or had a recent history (within the last year) of drug or alcohol abuse.

          -  Has a known history of human immunodeficiency virus (HIV) (HIV 1/2 antibodies).

          -  Has known active hepatitis B (e.g., HBsAg reactive) or hepatitis C (e.g., HCV RNA
             [qualitative] is detected).

          -  Has received a live virus vaccine within 30 days of planned start of trial therapy.

          -  Has known active CNS metastases and/or carcinomatous meningitis. Subjects with
             previously treated brain metastases may participate provided they have stable brain
             metastases (stability is normally defined as a period of 1 to 3 months in which there
             is no evidence of new or enlarging CNS metastases).

          -  Has symptomatic ascites or pleural effusion; a subject who is clinically stable
             following treatment for these conditions is eligible.

          -  Has had a prior allogeneic stem cell or bone marrow transplant.

          -  Has known contraindication to aspirin (81 mg).