Provided herein are compositions comprising a compound of Formulas I, II, or III, and compositions a compound comprising a moiety of Formula IV, which are useful for sensitizing and/or activating pro-apoptotic activity of BAX. Methods of treating diseases associated with BAX (e.g., cancer) and methods of identifying compounds which sensitize and/or activate the pro-apoptotic activity of a BAX polypeptide are also provided.