Inclusion Criteria:

          -  Hormone-sensitive, histologically proven adenocarcinoma of the prostate with BRCAness
             (defined as an alteration in one or more of the following genes: ATM, ATR, BARD1,
             BRCA1, BRCA2, BRIP1, CDK12, CHEK1, CHEK2, ERCC3, FAM175A, FANCA, FANCL, GEN1, HDAC2,
             MLH1, MRE11, NBN, PALB2, PPP2R2A, RAD51, RAD54L) from soft-tissue based genomic
             testing or liquid biopsy based genomic or genetic testing.

          -  ECOG/Zubrod score of 0-2.

          -  At a minimum, subjects must have received definitive local therapy with curative
             intent (i.e., prostatectomy, and/or radiation therapy) with or without systemic
             therapy.

          -  Testosterone level is > 50 ng/dL.

          -  Be at least 18 years old at the time the informed consent form is signed.

          -  Demonstrate adequate organ function as defined in the table in the protocol, all
             screening labs should be performed within 28 days of treatment initiation.

          -  Highly effective barrier methods must be used with all sexual activity and
             contraception methods must be practiced for all subjects throughout the study and for
             at least 6 months after last rucaparib treatment administration if the risk of
             conception exists (section 7.2).

          -  Recovery to baseline or Grade ≤ 1 CTCAE v5.0 from toxicities related to any prior
             treatments within the context of their definitive local therapy for their prostate
             cancer, unless AE(s) are clinically nonsignificant and/or stable on supportive
             therapy.

          -  Subject is able to provide informed consent and willing to sign an approved consent
             form that conforms to federal and institutional guidelines.

          -  Subject must have confirmed PSA progression based on at least two time points taken at
             least one week apart to confirm rising trend.

        Exclusion Criteria:

          -  Subjects with metastases defined by conventional scans (CT, MRI, NM Bone Scan).
             Disease identified on molecular imaging (e.g. fluciclovine-PET) is not exclusionary.

          -  Arterial or venous thrombi (including cerebrovascular accident), myocardial
             infarction, admission for unstable angina, cardiac angioplasty, or stenting within the
             last 90 days prior to screening.

          -  Pre-existing duodenal stent, recent (within < 3 months) or existing bowel obstruction,
             and/or any gastrointestinal disorder or defect that would, in the opinion of the
             Investigator, interfere with absorption of rucaparib.

          -  Inability to swallow tablets.

          -  Evidence or history of clinically significant bleeding disorder per the determination
             of the treating investigator.

          -  Prior systemic therapy within the past 30 days prior to Day 1 (or 5 half-lives of the
             drug, whichever is shorter).

          -  Diagnosis of another malignancy within 2 years before first dose of study treatment
             only if the cancer will either interfere with patient safety or interfere with the
             primary endpoint, per the judgement of the Principal Investigator. Patients, who have
             been diagnosed with, superficial skin cancers, or localized, low grade tumors deemed
             cured or with a prolonged natural history (e.g estimated overall survival > 5 years)
             may be included.

          -  Prior treatment with any PARP inhibitor, mitoxantrone, cyclophosphamide, or any
             platinum based chemotherapy.

          -  Clinically significant (i.e., active) cardiovascular disease at the time of
             enrollment: congestive heart failure (> New York Heart Association Classification
             Class II), or serious cardiac arrhythmia requiring medication.

          -  Other severe acute or chronic medical conditions including cardiovascular, endocrine,
             neurologic, pulmonary or psychiatric conditions including recent (within the past
             year) or active suicidal ideation or behavior; or laboratory abnormalities that may
             increase the risk associated with study participation or study treatment
             administration or may interfere with the interpretation of study results and, in the
             judgment of the investigator, would make the patient inappropriate for entry into this
             study.

          -  Major surgery (eg, GI surgery, removal or biopsy of brain metastasis) within 8 weeks
             before first dose of study treatment. Complete wound healing from major surgery must
             have occurred 1 month before first dose and from minor surgery (eg, simple excision,
             tooth extraction) at least 28 days before first dose. Subjects with clinically
             relevant ongoing complications from prior surgery are not eligible.