CYD-2-11 is a selective Bax agonist with a K i value of 34.1 nM. CYD-2-11 induces cell apoptosis and shows antiproliferative activity to breast cancer MDA-MB-231 and MCF-7 cell lines with IC 50 values of 3.22 and 3.81 μM, respectively. CYD-2-11 suppresses tumor growth in MDA-MB-231 tumor models. CYD-2-11 can be used for the research of breast and lung cancer.