Inclusion Criteria:  Cohort 1: Patients with histologically confirmed epithelial ovarian cancer, fallopian tube, or primary peritoneal cancer subjects with any high-grade serous component, progressed on or after platinum-containing therapy and not eligible for further platinum containing treatment (platinum-resistant, platinum-refractory disease defined by progression of disease on a platinum-containing regimen or recurrence of disease within 180 days of receiving the last dose of platinum-based treatment).  Cohort 2: Patients with selected tumor types that have relapsed or progressed after 2 lines of therapy or who are ineligible for other standard of care (SOC) therapies:  Histologically or cytologically confirmed metastatic NSCLC Histologically or cytologically confirmed recurrent or metastatic HNSCC (oral cavity, oropharynx, hypopharynx, or larynx) Histologically or cytologically confirmed metastatic or non-resectable advanced metastatic gastric or gastroesophageal adenocarcinoma Histologically or cytologically confirmed unresectable, locally advanced or metastatic TNBC (confirmed HER2-negative, estrogen receptor-negative and progesterone receptor-negative) Histologically confirmed ovarian cancer of all high-grade epithelial types who are IO treatment naïve and have progressed after 3 months on or after platinum-containing therapy PD-L1 expression Tumor Proportion Score (TPS) ≥ 1% for NSCLC and Combined Proportion Score (CPS) ≥ 1% for all other tumor types A 28-day washout period after the completion of programmed death-1 (PD-1)/PD-L1 therapy Patients should have no more than 5 prior lines of therapies Cohort 2 - (Optional for the ovarian cohort) Pre-treatment fresh tumor biopsies and paired treatment fresh tumor biopsies will be collected from at least 5 patients. Biopsy must be excisional, incisional, or core.  Exclusion Criteria:  Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (e.g. cytotoxic T-lymphocyte-associated protein 4 [CTLA-4], OX 40 [Tumor necrosis factor receptor superfamily, member 4 (TNFRSF4)], CD137 [tumor necrosis factor receptor superfamily member 9 (TNFRSF9)]) (only applies to ovarian cancer patients in Cohorts 1 and 2) Disease progression within 6 months of starting anti-PD-1 and anti-PD-L1 inhibitors Known active or chronic Hepatitis B or Hepatitis C, other hepatitides (non-alcohol steatohepatitis, alcohol or drug-related, autoimmune) serology at screening or cirrhosis Active autoimmune disease requiring systemic treatment within the past 12 months Active interstitial lung disease (ILD) or pneumonitis or a history of ILD Brain involvement with cancer, spinal cord compression, carcinomatous meningitis, or new evidence of brain or leptomeningeal disease; unless the lesion(s) have been radiated or resected, are considered fully treated and inactive, are asymptomatic, and no steroids have been administered for CNS disease over the 7 days prior to study treatment Angina, myocardial infarction (MI), symptomatic congestive heart failure, cerebrovascular accident, transient ischemic attack TIA), arterial embolism, pulmonary embolism, percutaneous transluminal coronary angioplasty (PTCA), or coronary artery bypass grafting (CABG) within 6 months prior to study treatment Known human immunodeficiency virus (HIV) unless CD4+ T cell count > 350 cells/μL with an undetectable viral load