A Phase I Study of ARN-810 in Postmenopausal Women with Locally Advanced or Metastatic Estrogen Receptor-Positive Breast Cancer

Full Title

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


Women with breast cancers that are fueled by the female hormone estrogen often receive treatment that blocks the effects of these hormones on cancer cells. However, in some cases, the cancer stops responding to hormonal therapy and begins growing again.

The purpose of this study is to find the highest dose of an investigational drug called ARN-810 in postmenopausal women with estrogen receptor-positive breast cancer that has returned or continued growing after hormonal therapy such as tamoxifen or aromatase inhibitors. ARN-810 works by blocking the actions of female sex hormones on cancer growth and has been shown in laboratory studies to shrink breast cancers. It works by lowering the amount of estrogen receptors on breast cancer cells (to which estrogen binds so it can exert its activity) and by causing any remaining estrogen receptors to become inactive.

ARN-810 is a tablet that 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 be postmenopausal women with estrogen receptor-positive breast cancer that continued to grow despite at least 6 months of hormonal therapy.
  • Patients should have HER-negative cancer. (There are other therapies for HER-positive breast cancer.)
  • Women who have received chemotherapy for advanced breast cancer may not have received more than two prior regimens.
  • At least 2 months must have passed since the last use of tamoxifen, 6 months since fulvestrant, 2 weeks since other anticancer hormonal therapy, and 3 weeks since receiving any chemotherapy and entry into the study.
  • Patients must be able to be ambulatory for more than half of their normal waking hours.
  • This study is open to patients age 18 and older.

For more information about this study and to inquire about eligibility, please contact Dr. Maura Dickler at 646-888-5456.