A Phase I Study of GDC-0077 with Palbociclib and/or Letrozole in Patients with Breast Cancer


Full Title

GO39374: A Phase I, Open-Label, Dose-Escalation Study Evaluating the Safety, Tolerability, and Pharmacokinetics of GDC-0077 as a Single Agent in Patients with Locally Advanced or Metastatic PIK3CA-Mutant Solid Tumors and in Combination with Endocrine and Targeted Therapies in Patients with Locally Advanced or Metastatic PIK3CA-Mutant Hormone-Receptor Positive Breast Cancer


The purpose of this study is to assess the safety and effectiveness of the investigational drug GDC-0077 in patients with locally advanced or metastatic breast cancer that contains a mutation in a gene called PIK3CA. GDC-0077 blocks an enzyme involved in cancer growth called PI3K. In this study, it will be given alone or with the anticancer drugs palbociclib and/or letrozole.

Palbociclib is a drug approved to treat metastatic breast cancer that is fueled by estrogen. It blocks the activity of two enzymes (CDK4 and CDK6) that are involved in the growth of some breast cancers. Letrozole is an “aromatase inhibitor” which blocks estrogen production. It is used to treat metastatic breast cancer in postmenopausal women whose tumors contain hormone receptors.

Patients will receive one of these treatment regimens:

  • GDC-0077 alone
  • GDC-0077 plus palbociclib and letrozole
  • GDC-0077 plus letrozole

All of the medications in this study are taken orally (by mouth).


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

  • Patients receiving GDC-0077 alone may be male or female and must have locally advanced or metastatic PIK3CA-mutated breast cancer.
  • Patients receiving GDC-0077 with palbociclib and letrozole must be postmenopausal females with locally advanced or metastatic PIK3CA-mutated breast cancer that contains hormone receptors and is not positive for the HER2 protein.
  • Patients must recover from the serious side effects of prior therapies.
  • 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 patients age 18 and older.

For more information about this study and to inquire about eligibility, please contact Alexandra Burleigh at 646-422-4394. The Principal Investigator for this study is Dr. Komal Jhaveri.