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

1. Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) 0 or 1
2. Measurable disease or non-measurable disease and refractory to or intolerant of existing therapies (Part 1)
3. Measurable disease as defined by RECIST 1.1 is required (Part 1B and Part 2 only)

Exclusion Criteria:

1. Known active uncontrolled or symptomatic Central Nervous System (CNS) metastases
2. Other active malignancy within 3 years prior to randomization, except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ
3. Major surgery or radiation within 4 weeks prior to study entry
4. Last anti-cancer treatment within 2 weeks prior to study entry
5. Participation in other studies involving investigational drug(s) within 4 weeks prior to study entry
6. Pregnant or breastfeeding female patients
7. Active inflammatory gastrointestinal (GI) disease, known diverticular disease or previous gastric resection or lap band surgery including impairment of gastro intestinal function or GI disease