A Phase II, Open-Label, Randomized Study of GDC-0810 Versus Fulvestrant in Postmenopausal Women With Advanced or Metastatic ER+ /HER2- Breast Cancer Resistant to Aromatase Inhibitor Therapy

The primary purpose of this study is to evaluate the efficacy, safety, and tolerability of
GDC-0810 compared with fulvestrant in postmenopausal women with advanced or metastatic
estrogen receptor positive (ER+)/ human epidermal growth factor receptor 2 negative (HER2-)
breast cancer resistant to AI therapy. The development of GDC-0810 has been halted by the
Sponsor and the enrollment in this study has been discontinued. Participants currently
enrolled in the study who are experiencing clinical benefit may continue receiving GDC-0810
as a single agent or fulvestrant until disease progression (PD), unmanageable toxicity,
withdrawal of consent, exhaustion of GDC-0810 drug supply, or termination of the study by the
Sponsor.