Inclusion Criteria:

• Histologically proven advanced (unresectable) or metastatic cancer as outlined below
  1. Patients with triple-negative breast cancer (TNBC) who have been treated with at least 1 prior regimen for advanced/metastatic disease or who relapsed/progressed while on or within 1 month from completion of adjuvant chemotherapy Phase 1: Up to 3 lines of prior chemotherapy are allowed Phase 2: Up to 2 lines of prior chemotherapy are allowed
  2. Patients with high-grade serous ovarian, fallopian tube, or primary peritoneal cancer who have recurrent disease and have been previously treated with chemotherapy for advanced/metastatic disease and who experienced a response lasting at least 6 months to first-line platinum-based therapy but currently considered platinum-resistant Phase 1: Up to 4 lines of prior chemotherapy are allowed Phase 2: Up to 3 lines of prior chemotherapy are allowed
• 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

Exclusion Criteria:

• Progressed while on platinum treatment or within 1 month from completion of platinum-containing regimen in any line of 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 5 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
• 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
• History of interstitial lung disease
• Known history of platelet transfusion for chemotherapy-induced thrombocytopenia or persistent (> 4 weeks) ≥ Grade 3 hematological toxicity or fatigue from prior cancer therapy
• Prior treatment with an anti-PD-1, anti-PD-L1, or anti-PD-L2
• Prior treatment with a known poly(ADP-ribose) polymerase (PARP) inhibitor
• Heart-rate corrected QT interval (QTc) prolongation > 470 msec at screening
• Known history of myelodysplastic syndrome (MDS) or a pre-treatment cytogenetic testing result at risk for a diagnosis of MDS/acute myeloid leukemia (AML)
• Receiving concomitant medications that prolong QTc and is unable to discontinue use