The present application, among other things, provides compounds that are capable of inhibiting the activity of anti-apoptotic Bcl-2 family proteins, for example, myeloid cell leukemia-1 (Mcl-1) protein. The present invention also provides pharmaceutical compositions as well as methods for using provided compounds for treatment of diseases and conditions (e.g., cancer) characterized by the over-expression or dysregulation of Mcl-1 protein. In some embodiments, a provided compound has the structure of formula I. In some embodiments, a provided compound has the structure of formula II.