This study will evaluate the safety, pharmacokinetic (PK), pharmacodynamic (PD) activity, and preliminary anti-tumor activity of GDC-9545 as a single agent and in combination with palbociclib and/or luteinizing hormone-releasing hormone (LHRH) agonist in participants with advanced or metastatic estrogen receptor (ER)-positive (human epidermal growth factor receptor 2 \[HER2\]-negative) breast cancer.
Age range
18 Years
Sex
FEMALE
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AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.
Bring these to your next appointment. They're a starting point for a shared conversation — not a sign you qualify or a recommendation to enrol.
Generated to help you prepare — always confirm anything about your own eligibility and care with the study team and your doctor.
The trial coordinator is the person who runs the study day to day. These cover the practical side — logistics, costs, and what taking part would actually mean for your life. The study team confirms whether you meet the criteria; these are questions to ask, not a sign you qualify.
A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.
Number of Participants with Adverse Events by Severity, According to National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0 (NCI-CTCAE v4.0)
Timeframe: From Baseline until 28 days after the last dose of study treatment (up to 84 months)
Dose Escalation: Maximum Tolerated Dose (MTD) or Maximum Administered Dose (MAD) of GDC-9545 When Administered as a Single Agent or in Combination with Palbociclib
Timeframe: Days -7 to 28 of Cycle 1
Dose Escalation: Number of Participants with Dose-Limiting Toxicities When GDC-9545 is Administered as a Single Agent or in Combination with Palbociclib
Timeframe: Days -7 to 28 of Cycle 1
Change from Baseline in Systolic Blood Pressure Over Time
Timeframe: Baseline and at each treatment cycle (1 cycle is 28 days) through to 28 days after the last dose of study treatment
Change from Baseline in Diastolic Blood Pressure Over Time
Timeframe: Baseline and at each treatment cycle (1 cycle is 28 days) through to 28 days after the last dose of study treatment
Change from Baseline in Body Temperature Over Time
Timeframe: Baseline and at each treatment cycle (1 cycle is 28 days) through to 28 days after the last dose of study treatment
Change from Baseline in Pulse Rate Over Time
Timeframe: Baseline and at each treatment cycle (1 cycle is 28 days) through to 28 days after the last dose of study treatment
Change from Baseline in Respiration Rate Over Time
Timeframe: Baseline and at each treatment cycle (1 cycle is 28 days) through to 28 days after the last dose of study treatment
Change from Baseline in Electrocardiogram (ECG) Results Over Time: Heart Rate
Timeframe: Baseline and at predefined intervals from Cycle 1 and at each subsequent cycle (1 cycle is 28 days) through to the last dose of study treatment
Change from Baseline in ECG Results Over Time: PR Duration
Timeframe: Baseline and at predefined intervals from Cycle 1 and at each subsequent cycle (1 cycle is 28 days) through to the last dose of study treatment
Change from Baseline in ECG Results Over Time: QRS Duration
Timeframe: Baseline and at predefined intervals from Cycle 1 and at each subsequent cycle (1 cycle is 28 days) through to the last dose of study treatment
Change from Baseline in ECG Results Over Time: QT Duration
Timeframe: Baseline and at predefined intervals from Cycle 1 and at each subsequent cycle (1 cycle is 28 days) through to the last dose of study treatment
Change from Baseline in ECG Results Over Time: QTcF Duration
Timeframe: Baseline and at predefined intervals from Cycle 1 and at each subsequent cycle (1 cycle is 28 days) through to the last dose of study treatment
Change from Baseline in ECG Results Over Time: RR Duration
Timeframe: Baseline and at predefined intervals from Cycle 1 and at each subsequent cycle (1 cycle is 28 days) through to the last dose of study treatment
Number of Participants with Clinical Laboratory Abnormalities in Hematology Tests by Highest Grade According to NCI-CTCAE v4.0
Timeframe: Baseline, Cycle 1, and at each subsequent cycle (1 cycle is 28 days) or at every other cycle starting from Cycle 3 (Cohort X only), up to 28 days after the last dose of study treatment
Number of Participants with Clinical Laboratory Abnormalities in Blood Chemistry Tests by Highest Grade According to NCI-CTCAE v4.0
Timeframe: Baseline, Cycle 1, and at each subsequent cycle (1 cycle is 28 days) or at every other cycle starting from Cycle 3 (Cohort X only), up to 28 days after the last dose of study treatment
Number of Participants with Clinical Laboratory Abnormalities in Urinalysis Tests by Highest Grade According to NCI-CTCAE v4.0
Timeframe: Baseline, Cycle 3, and at every other cycle (1 cycle is 28 days) up to 28 days after the last dose of study treatment