A Safety, Pharmacokinetic, Pharmacodynamic and Anti-Tumor Study of PF-06873600 as a Single Agent and in Combination With Endocrine Therapy

This is a Phase 1/2a, open-label, multi-center, non-randomized, multiple dose, safety,
tolerability, pharmacokinetic, and pharmacodynamic study of PF-06873600 administered as a
single agent in sequential dose levels and then in combination with endocrine therapy. In
Part 1A, successive cohorts of patients will receive escalating doses of PF-06873600 and then
in dose finding (Part 1B) with PF-06873600 in combination with endocrine therapy (ET). This
study contains 2 parts, dose escalation with single agent (Part 1A) and then dose finding
with PF-06873600 in combination with endocrine therapy (Part 1B) followed by dose expansion
arms as a single agent and PF-06873600 in combination with endocrine therapy (Part 2).

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 2)

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 gastro
intestinal function or GI disease