A Study of PF-06873600 in People With Cancer

Inclusion Criteria: * Have a diagnosis of Hormone Receptor Positive (HR+), Human Epidermal Growth Factor Receptor 2 Negative (HER2-) breast cancer • Prior combined CDK 4/6 inhibitor and endocrine therapy and 1 or 2 prior lines of chemotherapy * Have a diagnosis of metastatic triple negative breast cancer (TNBC) • Up to 1-2 prior lines of chemotherapy * Have a diagnosis of advanced platinum resistant epithelial ovarian cancer (EOC)/fallopian tube cancer/primary peritoneal cancer (PPC) • Up to 2-3 prior lines of therapy * Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) 0 or 1 * Measurable disease or non-measurable disease and refractory to or intolerant of existing therapies (Part 1) * Measurable disease as defined by RECIST 1.1 is required (Part 1B and Part 2 only) Exclusion Criteria: * Known active uncontrolled or symptomatic Central Nervous System (CNS) metastases * Other active malignancy within 3 years prior to randomization, except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ * Major surgery or radiation within 4 weeks prior to study entry * Last anti-cancer treatment within 2 weeks prior to study entry * Participation in other studies involving investigational drug(s) within 4 weeks prior to study entry * Pregnant or breastfeeding female patients * Active inflammatory gastrointestinal (GI) disease, known diverticular disease or previous gastric resection or lap band surgery including impairment of gast…