PF-06873600

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 for the first 2 cycles and every cycle thereafter.