Multinational randomised phase 2 trial of enobosarm for AR-positive, ER-positive, HER2-negative advanced breast cancer

The androgen receptor (AR) is a tumor suppressor in ER-positive breast cancer. Enobosarm is an oral selective AR modulator. The phase 2 G200802 trial, at 35 centers in nine countries, randomized postmenopausal patients with previously treated ER-positive, HER2-negative advanced breast cancer to enobosarm 9 mg or 18 mg once daily. The primary endpoint was clinical benefit rate at 24 weeks among patients with (centrally confirmed) AR-positive disease. Among these patients, CBR at 24 weeks was 32% (95% CI 20-47) in the 9 mg group and 29% (17-43) in the 18 mg group, with median progression-free survival 5.6 months (IQR 2.8-NR) and 4.2 months (2,7-11,8), respectively. Grade 3 or 4 treatment-related adverse events were seen in 8% and 16%, respectively. The authors conclude that enobosarm had antitumor activity in patients with AR-positive, ER-positive, HER2-negative advanced breast cancer.