MCL1 and cancer: In our hands, S63845 bound MCL-1 more extensively than A-1210477 and resulted in marked apoptosis in MCL-1-dependent cell lines (Fig. 1), and synergized with ABT-199 and A-1331852 to induce apoptosis in various cancer cell lines (Figs. 2 and 3), supporting the concept that a potent MCL-1 inhibitor, such as S63845, could be a valuable addition to the BH3 mimetic armamentarium.