A Study of PF-06873600 in People With Cancer

The purpose of this clinical trial is to learn about the safety and effects of study medicine (PF-06873600) when taken alone or with hormone therapy by people with cancer.

People may be able to participate in this study if they have the following types of cancer: Hormone Receptor positive (HR+) breast cancer; Human Epidermal Growth Factor Receptor 2 (HER2)-negative breast cancer that is advanced or metastatic (spread to other parts of the body); triple negative breast cancer; epithelial ovarian cancer; fallopian tube cancer; or primary peritoneal cancer.

All participants in this study will receive the study medicine by mouth, 1 to 2 times a day at home. The dose of the study medicine may be changed during the study.

Some participants will also receive hormone therapy. The hormone therapy will be either letrozole by mouth once a day at home, or fulvestrant as a shot into the muscle. Fulvestrant will be given every two weeks at the study clinic for the first month, and then once a month after that.

Participants will take part in this study for at least 7 to 8 months, depending on how they respond to the therapy. During this time participants will visit the study clinic once a week.

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 and Part 1C, 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 1C) and then dose finding with PF-06873600 in combination with endocrine therapy (Part 1B) followed by dose expansion arms of PF-06873600 in combination with endocrine therapy (Part 2).