Inclusion Criteria:

          1. Histologic diagnosis of adenocarcinoma of the prostate

          2. Prior local therapy with prostatectomy required, with available tissue from
             prostatectomy specimen to send for genomic and transcriptomic testing.

          3. Prior salvage or adjuvant radiation therapy is allowed but not mandated. Radiation
             therapy must have been completed for at least 6 months.

          4. Absolute PSA ≥1 ng/ml. Prior undetectable PSA post-prostatectomy is not required.

          5. PSADT ≤6 months, based upon ≥3 consecutive measurements collected in the past 12
             months, at least 4 weeks apart

          6. No radiographic evidence of metastatic disease by CT scan and bone scan, performed
             within the prior 4 weeks.

          7. Serum testosterone ≥ 150 ng/dl

          8. Participants must have normal organ and bone marrow function measured within 28 days
             prior to administration of study treatment as defined below:

               -  Hemoglobin ≥ 10.0 g/dL with no blood transfusion in the past 28 days

               -  Absolute neutrophil count (ANC) ≥ 1.5 x 109/L

               -  Platelet count ≥ 75 x 109/L

               -  Total bilirubin ≤ 1.5 x institutional upper limit of normal (ULN)

               -  Aspartate aminotransferase (AST) (Serum Glutamic Oxaloacetic Transaminase (SGOT))
                  / Alanine aminotransferase (ALT) (Serum Glutamic Pyruvate Transaminase (SGPT))
                  <2.5 x institutional upper limit of normal. Note: Patients with elevations in
                  bilirubin, AST, or ALT should be thoroughly evaluated for the etiology of this
                  abnormality prior to entry and patients with evidence of viral infection should
                  be excluded.

               -  Patients must have creatinine clearance estimated using the Cockcroft

                    -  Gault equation of ≥51 mL/min:

             Estimated creatinine clearance = (140-age [years]) x weight (kg) serum creatinine
             (mg/dL) x 72

          9. Eastern Cooperative Oncology Group (ECOG) performance status 0-1

         10. Male participants and their partners, who are sexually active and of childbearing
             potential, must agree to the use of two highly effective forms of contraception in
             combination [see appendix F for acceptable methods], throughout the period of taking
             study treatment and for 3 months after last dose of study drug to prevent pregnancy in
             a partner.

         11. For enrichment stage of trial only (if necessary): Confirmation of a suspected/known
             deleterious mutation in a gene of interest (ATM, BARD1, BRCA1, BRCA2, BRIP1, CDK12,
             CHEK1, CHEK2, FANCL, PALB2, PPP2R2A, RAD51B, RAD51C, RAD51D, or other DNA repair
             genes) via CLIA certified testing.

        Exclusion Criteria:

          1. Prior ADT in the past 6 months. Prior ADT in context of neoadjuvant/adjuvant primary;
             prior ADT for biochemical recurrence is allowed, as long as no ADT has been
             administered in past 6 months and testosterone has recovered (>150 ng/dl). The total
             duration of prior ADT should not exceed 24 months.

          2. Prior oral anti-androgen (e.g. bicalutamide, nilutamide, enzalutamide, apalutamide),
             or androgen synthesis inhibitor (e.g. abiraterone, orteronel) in the past 6 months.
             5-alpha reductase inhibitor therapy (e.g. finasteride, dutasteride) is allowed, as
             long as subject has been stable on medication for past 6 months.

          3. Prior treatment with intravenous chemotherapy.

          4. Involvement in the planning and/or conduct of the study

          5. Participation in another clinical study with an investigational product during the
             last 1 month.

          6. Any previous treatment with PARP inhibitor, including olaparib

          7. Resting ECG with QTc > 470 msec on 2 or more time points within a 24 hour period or
             family history of long QT syndrome

          8. Concomitant use of known strong CYP3A inhibitors (eg. itraconazole, telithromycin,
             clarithromycin, protease inhibitors boosted with ritonavir or cobicistat, indinavir,
             saquinavir, nelfinavir, boceprevir, telaprevir) or moderate CYP3A inhibitors (eg.
             ciprofloxacin, erythromycin, diltiazem, fluconazole, verapamil). The required washout
             period prior to starting olaparib is 2 weeks.

          9. Concomitant use of known strong CYP3A inducers (eg. phenobarbital, enzalutamide,
             phenytoin, rifampicin, rifabutin, rifapentine, carbamazepine, nevirapine and St John's
             Wort ) or moderate CYP3A inducers (eg. bosentan, efavirenz, modafinil). The required
             washout period prior to starting olaparib is 5 weeks for phenobarbital and 3 weeks for
             other agents.

         10. Myelodysplastic syndrome/acute myeloid leukaemia or with features suggestive of
             MDS/AML.

         11. Major surgery within 2 weeks of starting study treatment and patients must have
             recovered from any effects of any major surgery.

         12. Poor medical risk due to a serious, uncontrolled medical disorder, non- malignant
             systemic disease or active, uncontrolled infection. Examples include, but are not
             limited to, uncontrolled ventricular arrhythmia, recent (within 3 months) myocardial
             infarction, uncontrolled major seizure disorder, extensive interstitial bilateral lung
             disease on High Resolution Computed Tomography (HRCT) scan or any psychiatric disorder
             that prohibits obtaining informed consent.

         13. Unable to swallow orally administered medication and patients with gastrointestinal
             disorders likely to interfere with absorption of the study medication.

         14. Immunocompromised patients, e.g., patients who are known to be serologically positive
             for human immunodeficiency virus (HIV).

         15. Known hypersensitivity to olaparib or any of the excipients of the product.

         16. Known active hepatitis (i.e. Hepatitis B or C) due to risk of transmitting the
             infection through blood or other body fluids

         17. Whole blood transfusions in the last 120 days prior to entry to the study (packed red
             blood cells and platelet transfusions are acceptable, for timing refer to inclusion
             criteria no.10)