Active Not Recruiting
PHASE1
INTERVENTIONAL
NCT03332797
A Study of GDC-9545 Alone or in Combination With Palbociclib and/or Luteinizing Hormone-Releasing Hormone (LHRH) Agonist in Locally Advanced or Metastatic Estrogen Receptor-Positive Breast Cancer
View on ClinicalTrials.gov
Updated Dec 15, 2025
Brief Summary
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.
Interventions
Name:
GDC-9545
Type:
DRUG
Description:
GDC-9545 will be administered orally, once daily, on Days 1-28 of each 28-day cycle, until disease progression, unacceptable toxicity, withdrawal of consent, or study termination.
Name:
Palbociclib
Type:
DRUG
Description:
Palbociclib will be administered orally, once daily, at the label-recommended dose of 125 mg on Days 1-21 of each 28-day cycle, until disease progression, unacceptable toxicity, withdrawal of consent, or study termination.
Name:
LHRH Agonist
Type:
DRUG
Description:
The LHRH agonist (leuprolide acetate, goserelin acetate, or triptorelin pamoate) will be administered by injection once every 4 weeks on Day 1 of each 28-day cycle, according to the label. The investigator will choose the appropriate LHRH agonist approved for use in breast cancer.
Primary Outcomes
Measure:
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)
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Measure:
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
Description:
Laboratory parameters for hematology will be measured and compared with a standard reference range. Values outside of the standard reference range are considered abnormalities. Not every laboratory abnormality qualifies as an adverse event. A laboratory test result will be reported as an adverse event if it meets any of the following criteria: is accompanied by clinical symptoms; results in a change in study treatment, a medical intervention, or a change in concomitant therapy; or is clinically significant in the investigator's judgment.
Measure:
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
Description:
Laboratory parameters for blood chemistry will be measured and compared with a standard reference range. Values outside of the standard reference range are considered abnormalities. Not every laboratory abnormality qualifies as an adverse event. A laboratory test result will be reported as an adverse event if it meets any of the following criteria: is accompanied by clinical symptoms; results in a change in study treatment, a medical intervention, or a change in concomitant therapy; or is clinically significant in the investigator's judgment.
Measure:
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
Description:
Laboratory parameters for urinalysis will be measured and compared with a standard reference range. Values outside of the standard reference range are considered abnormalities. Not every laboratory abnormality qualifies as an adverse event. A laboratory test result will be reported as an adverse event if it meets any of the following criteria: is accompanied by clinical symptoms; results in a change in study treatment, a medical intervention, or a change in concomitant therapy; or is clinically significant in the investigator's judgment.
Trial Information
NCT ID
NCT03332797
Status
Active Not Recruiting
Study Type
INTERVENTIONAL
Phases
PHASE1
Sponsor
Genentech, Inc.
Last Updated
December 15, 2025