SNDX-275-0602 is a Phase 1b/2 study evaluating the combination of entinostat plus atezolizumab in patients with aTNBC. The study has 2 phases: an open-label Dose Determination Phase (Phase 1b) followed by an Expansion Phase (Phase 2). The Expansion Phase will evaluate the efficacy and safety of entinostat when administered at the RP2D with atezolizumab in patients with aTNBC in a randomized, double-blind, placebo-controlled setting. Up to 88 evaluable patients are anticipated if the study completes all phases of evaluation (up to 18 patients for Phase 1b, up to 70 patients for Phase 2). Up to 30 study centers in the US and Europe may participate.