Schwartzberg on Bringing Seminal Observations on AR From Bench to Bedside in ER+ Breast Cancer

Welcome to OncLive On Air^®! I’m your host today, Jessica Hergert.

OncLive On Air^® is a podcast from OncLive^®, which provides oncology professionals with the resources and information they need to provide the best patient care. In both digital and print formats, OncLive^® covers every angle of oncology practice, from new technology to treatment advances to important regulatory decisions.

In today’s episode, sponsored by VBL Therapeutics, we had the pleasure of speaking with Lee S. Schwartzberg, MD, FACP, chief medical officer of OneOncology, professor of medicine in the Division of Hematology/Oncology at the University of Tennessee Health Science Center, and the medical director of West Clinic, to discuss research with the novel oral selective androgen receptor (AR)–activating agent, enobosarm in AR-positive, estrogen receptor (ER)–positive metastatic breast cancer.

Enobosarm is a first-in-class, nonsteroidal AR agonist designed to treat patients with AR-positive, ER-positive advanced breast cancer. It is given daily in 3-mg capsules. In cell- and patient-derived xenograft models, enobosarm was found to inhibit AR-positive, ER-positive breast cancers.

Moreover, in prior findings from the phase 2 G200802 trial (NCT02463032), which were presented during the 2021 ASCO Annual Meeting, 9 mg of enobosarm elicited a clinical benefit rate (CBR) of 32% (95% CI, 19.5%-46.7%). In a cohort of patients who received 18 mg of the agent, the agent induced a CBR of 29% (95% CI, 17.1%-43.1%).

Additionally, patients who had greater than 40% AR staining experienced an overall response rate (ORR) of 50% and a CBR of 79%. Patients with an AR staining of less than 40% experienced an ORR of 0% and a CBR of 18%, indicating that AR expression may be a useful biomarker of response for treatment selection.

The ongoing registrational phase 3 ARTEST trial (NCT04869943) is under way and is evaluating 9 mg of enobosarm vs exemestane monotherapy, exemestane plus everolimus, or a selective estrogen receptor modulator in patients with AR-positive, ER-positive metastatic breast cancer who have progressed on a nonsteroidal aromatase inhibitor, fulvestrant (Faslodex), and a CDK4/6 inhibitor.

In our exclusive interview, Schwartzberg discussed the rationale to evaluate enobosarm in AR-positive, ER-positive advanced breast cancer, phase 2 data with the agent, and expectations for the ongoing phase 3 ARTEST trial in this population.

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