Identification of Diketopiperazine-Containing 2-Anilinobenzamides as Potent Sirtuin 2 (SIRT2)-Selective Inhibitors Targeting the Selectivity Pocket, Substrate-Binding Site, and NAD+-Binding Site

The NAD(+)-dependent deacetylase SIRT2 represents an attractive target for drug development. Here, we designed and synthesized drug-like SIRT2-selective inhibitors based on an analysis of the putative binding modes of recently reported SIRT2-selective inhibitors and evaluated their SIRT2-inhibitory activity. This led us to develop a more drug-like diketopiperazine structure as a hydrogen bond (H-bond) hunter to target the substrate-binding site of SIRT2. Thioamide 53, a conjugate of diketopiperazine and 2-anilinobenzamide which is expected to occupy the selectivity pocket of SIRT2, exhibited potent SIRT2-selective inhibition. Inhibition of SIRT2 by 53 was mediated by the formation of a 53-ADP-ribose conjugate, suggesting that 53 is a mechanism-based inhibitor targeting the selectivity pocket, substrate-binding site, and NAD(+)-binding site. Furthermore, 53 showed potent antiproliferative activity toward breast cancer cells and promoted neurite outgrowth of Neuro-2a cells. These findings should pave the way for the discovery of novel therapeutic agents for cancer and neurological disorders.