ZENO/ZN-c5-001: A Study to Assess ZN-c5 Alone or with Palbociclib in HER2-negative Advanced Breast Cancer Patients (H-43419)

The Phase 1 part of the study is being done to test the safety and effectiveness of ZN-c5 (investigational oral medication) at different dose levels. The study will also find out the safety and effectiveness of ZN-c5 in combination with palbociclib (an oral medication approved by the FDA for the treatment of breast cancer).

The Phase 2 part of the study is being done to further find out what effects, good and/or bad, ZN-c5 in combination with palbociclib has on patients and their breast cancer at a dose that is determined from the Phase 1 part of the study.