Main Inclusion Criteria:

          -  Patient has histologically proven advanced (unresectable) or metastatic cancer as
             outlined below according to study phase and disease type:

               1. Phase 1 patients (breast or ovarian cancer)

                    -  Patients with advanced or metastatic breast cancer must have disease that is
                       HER2-negative, estrogen receptor-negative, and progesterone
                       receptor-negative (ie, TNBC). Patients with advanced or metastatic disease
                       may have up to 4 lines of cytotoxic therapy. Neoadjuvant and adjuvant
                       therapies are not counted towards lines of therapy.

                    -  Patients must have any epithelial (ie, serous, endometroid, mucinous, clear
                       cell) ovarian, fallopian tube, or primary peritoneal cancer. Patients must
                       have experienced a response lasting at least 6 months to first-line
                       platinum-based therapy but currently considered to have platinum-resistant
                       disease per investigator's assessment (e.g, patient is not eligible for
                       further platinum containing treatment). Patients may have received up to 5
                       lines of cytotoxic therapy for advanced or metastatic cancer. Neoadjuvant
                       and adjuvant therapies are not counted towards lines of therapy.

               2. Phase 2 patients (breast or ovarian cancer)

                    -  Patients with advanced or metastatic breast cancer must have TNBC. Patients
                       with advanced or metastatic disease may have received up to 2 lines of
                       cytotoxic therapy. Adjuvant and/or neoadjuvant therapies are not counted in
                       the number of lines of therapy. TNBC patients who have previously received
                       platinum chemotherapy in the metastatic setting are allowed to enroll in the
                       study as long as they did not progress while on or within 8 weeks from the
                       day of the last platinum administration.

                    -  Patients must have with high-grade serous or endometroid ovarian, fallopian
                       tube, or primary peritoneal cancer. Patients must have experienced a
                       response lasting at least 6 months to first-line platinum-based therapy but
                       currently considered to have platinum-resistant disease per investigator's
                       assessment (e.g, patient is not eligible for further platinum containing
                       treatment). Patients may have had up to 4 lines of cytotoxic therapy for
                       advanced or metastatic cancer. Neoadjuvant, adjuvant, and the combination of
                       both will be considered as one line of therapy.

          -  Archival tumor tissue available or a fresh biopsy must be obtained prior to study
             treatment initiation

          -  Measurable lesions by RECIST v1.1

          -  Eastern Cooperative Oncology Group (ECOG) 0 or 1

          -  Adequate organ function

          -  Able to take oral medications

          -  Female patient, if of childbearing potential, has a negative serum pregnancy test
             within 72 hours of taking study medication and agrees to abstain from activities that
             could result in pregnancy from enrollment through 120 days after the last dose of
             study treatment

          -  Male patient agrees to use an adequate method of contraception

        Main Exclusion Criteria:

          -  Patients with primary platinum refractory ovarian cancer (ie, progressive disease on
             or within 6 months of first-line platinum therapy)

          -  Known active central nervous system (CNS) metastases and/or carcinomatous meningitis
             Note: Patients previously treated for brain metastases may be able to participate
             provided they are stable

          -  Patient has a known additional malignancy that progressed or required active treatment
             within the last 2 years. Exceptions include basal cell carcinoma of the skin, squamous
             cell carcinoma of the skin that has undergone potentially curative therapy, or in situ
             cervical cancer

          -  Poor medical risk

          -  Condition (such as transfusion dependent anemia or thrombocytopenia), therapy, or
             laboratory abnormality that might confound the study results, or interfere with the
             patient's participation for the full duration of the study treatment.

          -  Pregnant or breastfeeding, or expecting to conceive children within the projected
             duration of the study

          -  Immunodeficiency or is receiving systemic steroid therapy or any other form of
             immunosuppressive therapy within 7 days prior to the first dose of study treatment

          -  Known history of human immunodeficiency virus (HIV) (HIV 1/2 antibodies)

          -  Known active hepatitis B or hepatitis C

          -  Active autoimmune disease that has required systemic treatment in the past 2 years
             (ie, with use of disease-modifying agents, corticosteroids, or immunosuppressive
             drugs). Replacement therapy (eg, thyroxine, insulin, or physiologic corticosteroid
             replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a
             form of systemic treatment

          -  Prior treatment with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent

          -  Prior treatment with a known poly(ADP-ribose) polymerase (PARP) inhibitor

          -  Heart-rate corrected QT interval (QTc) prolongation > 470 msec at screening

          -  Known history or current diagnosis of myelodysplastic syndrome (MDS) or acute myeloid
             leukemia (AML)