Breast Cancer Coverage from Every Angle

Androgen Receptor–Targeting Agent Under Study in Metastatic Disease

By: Lauren Harrison, MS
Posted: Wednesday, June 9, 2021

Enobosarm, a selective androgen receptor–activating agent that does not cause virilization, has demonstrated clinical activity in patients with androgen receptor/estrogen receptor (AR/ER)-positive metastatic breast cancer when used after palbociclib. Results from this study were reported by Carlo Palmieri, MBBS, PhD, of the University of Liverpool, Great Britain, on behalf of his colleagues at the European Society for Medical Oncology (ESMO) Breast Cancer Virtual Congress 2021 (Abstract 100P).

“Targeting the androgen receptor, a tumor suppressor in breast cancer, provides us with a potential novel endocrine therapy with an excellent safety profile,” said Dr. Palmieri in a press release.

This study enrolled 136 patients who had been heavily pretreated for their AR/ER-positive metastatic breast cancer. Patients were randomly assigned to receive daily dosing of either 9 mg (n = 72) or 18 mg (n = 64) of enobosarm. This particular analysis focused on 10 patients previously treated with palbociclib and had experienced disease progression.

Enobosarm resulted in a clinical benefit rate of 60% at the 9-mg and 18-mg doses. The best objective tumor response to treatment was 33%, consisting of two complete responses and one partial response. The mean radiographic progression-free survival was 10.6 months, and the median progression-free survival was 5.2 months in the 9-mg cohort. Enobosarm was reported to be well tolerated by participants.

Researchers will begin recruiting for a phase III study using the 9-mg dose of enobosarm sometime in 2021. Patients with AR/ER-positive, HER2-negative metastatic breast cancer that progressed on a nonsteroidal aromatase inhibitor (fulvestrant) and CDK4/6 inhibitors will be eligible for enrollment.

Disclosure: For a full list of author disclosures, visit

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