A Phase I Study of GDC-9545 Alone or with Palbociclib and/or Hormonal Therapy to Treat Advanced or Metastatic ER-Positive, HER2-Negative Breast Cancer


Full Title

A Phase Ia/Ib Multicenter, Open-Label, Dose Escalation, Dose Expansion Study Evaluating the Safety, Pharmacokinetics, and Activity of GDC-9545 Alone or In Combination with Palbociclib and/or LHRH Agonist in Patients with Locally Advanced or Metastatic Estrogen Receptor-Positive Breast Cancer


The purpose of this study is to assess the investigational drug GDC-9545 when given alone or with palbociclib or hormonal therapy (drugs such as goserelin and leuprolide) in women with advanced estrogen receptor (ER)-positive, HER2-negative breast cancer that has continued to grow despite prior treatment. Researchers want to find the highest dose of GDC-9545 that can be given safely alone and in combination with the other medications.

GDC-9545 is designed to block the female sex hormones that make some breast cancers grow. It is taken orally (by mouth).


To be eligible for this study, patients must meet several criteria, including but not limited to the following:

  • Patients must have ER-positive, HER2-negative metastatic breast cancer that has continued to grow despite prior treatment.
  • Patients may have received up to two previous regimens of treatment for advanced breast cancer. At least 2 weeks must pass between the completion of prior therapies and entry into the study.
  • Patients must be physically well enough that they are fully ambulatory, capable of all self care, and are capable of all but physically strenuous activities. As an example, patients must be well enough that they would be able to carry out office work or light housework.
  • This study is for women age 18 and older.

For more information about this study and to inquire about eligibility, please contact Dr. Maura Dickler at 646-888-4560.





Disease Status

Relapsed or Refractory