AZD5991 is a potent and selective Mcl-1 inhibitor aimed at treating hematological cancers. As a well-designed macrocyclic compound, AZD5991 exhibits sub-nanomolar affinity for Mcl-1. It primarily inhibits the myeloid cell leukemia-1 protein (Mcl-1; Bcl2-L-3), showing potential pro-apoptotic and anti-tumor activity. AZD5991 binds to Mcl-1, preventing its interaction with certain pro-apoptotic proteins, leading to apoptosis in cells overexpressing Mcl-1.