Dataset from An Open-Label, Phase Ia/Ib/IIa Study of GDC-0810 Single Agent or in Combination With Palbociclib and/or an LHRH Agonist in Women With Locally Advanced or Metastatic Estrogen Receptor Positive Breast Cancer

This study is a multi-institution, Phase Ia/Ib/IIa open-label, dose-finding, safety,
pharmacokinetics (PK), and proof-of-concept study of GDC-0810 as a single agent and in
combination with palbociclib and/or LHRH agonist. The study is divided into 3 phases: Phase
Ia, Phase Ib, and Phase IIa. During Phase Ia (dose escalation phase), GDC-0810 single agent
will be administered orally on a continuous daily dosing regimen with a Day -7 lead-in period
for single dose PK evaluation prior to the start of daily treatment. The incidence of
dose-limiting toxicities (DLTs) will be evaluated from Day -7 through the first cycle (28
days) of treatment (35 days total). Depending on safety and tolerability, participants will
be assigned sequentially to escalating doses of GDC-0810 using standard 3 + 3 design. During
Phase Ib (dose escalation and expansion phase), participants will receive GDC-0810 with
palbociclib and/or LHRH agonist to determine the recommended Phase II dose (RP2D) and assess
the safety and tolerability of concomitant administration. During Phase IIa (dose expansion
phase), participants previously treated with an aromatase inhibitor (AI) will be treated at
the RP2D to further characterize the safety, PK, pharmacodynamics, and anti-tumor activity of
GDC-0810.