Single-center phase 1b trial of entinostat, nivolumab and ipilimumab for women with advanced HER2-negative breast cancer

In murine models of breast cancer, the HDAC inhibitor entinostat improved the efficacy of immune checkpoint inhibitors. A phase 1b trial at Johns Hopkins School of Medicine (Baltimore, MD) evaluated the combination of entinostat with nivolumab (anti-PD-1) and ipilimumab (anti-CTLA-4) in women with advanced HER2-negative breast cancer. There were no dose-limiting toxicities. The overall response rate to the combination was 25%, with 40% in triple-negative breast cancer and 10% in hormone receptor-positive breast cancer. The clinical benefit rate was 40%, and the progression-free survival rate at 6 months was 50%. The authors conclude that further investigation of the combination in a phase 2 trial is warranted.