Structure Based Design of Non-Natural Peptidic Macrocyclic Mcl-1 Inhibitors.

ABSTRACT: Mcl-1 is a pro-apoptotic BH3 protein family member similar to Bcl-2 and Bcl-xL. Overexpression of Mcl-1 is often seen in various tumors and allows cancer cells to evade apoptosis. Here we report the discovery and optimization of a series of non-natural peptide Mcl-1 inhibitors. Screening of DNA-encoded libraries resulted in hit compound 1, a 1.5 ?M Mcl-1 inhibitor. A subsequent crystal structure demonstrated that compound 1 bound to Mcl-1 in a ?-turn conformation, such that the two ends of the peptide were close together. This proximity allowed for the linking of the two ends of the peptide to form a macrocycle. Macrocyclization resulted in an approximately 10-fold improvement in binding potency. Further exploration of a key hydrophobic interaction with Mcl-1 protein and also with the moiety that engages Arg256 led to additional potency improvements. The use of protein-ligand crystal structures and binding kinetics contributed to the design and understanding of the potency gains. Optimized compound 26 is a <3 nM Mcl-1 inhibitor, while inhibiting Bcl-2 at only 5 ?M and Bcl-xL at >99 ?M, and induces cleaved caspase-3 in MV4-11 cells with an IC50 of 3 ?M after 6 h.

SUBMITTER: Johannes JW 

PROVIDER: S-EPMC5304306 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature