Simultaneous Inhibition of SIRT2 Deacetylase and Defatty-Acylase Activities via a PROTAC Strategy.

As a member of the sirtuin family of enzymes, SIRT2 promotes tumor growth and regulates various biological pathways through lysine deacetylation and defatty-acylation. In the past few years, many SIRT2-selective small molecule inhibitors have been developed, but none have demonstrated simultaneous inhibition of both SIRT2 activities in cells. To further scrutinize the physiological importance and significance of SIRT2 deacetylase and defatty-acylase activities, small molecules that can selectively inhibit both activities of SIRT2 in living cells are needed. Here, we have applied the Proteolysis Targeting Chimera (PROTAC) strategy and synthesized a new SIRT2 inhibitor (TM-P4-Thal) to degrade SIRT2 selectively, which led to simultaneous inhibition of its deacetylase and defatty-acylase activities in living cells. Additionally, this compound exemplifies the advantage of the PROTAC strategy that allows complete eradication of an enzyme and its activity in biological settings.

A Glycoconjugated SIRT2 Inhibitor with Aqueous Solubility Allows Structure-Based Design of SIRT2 Inhibitors.

Small molecule inhibitors for SIRT2, a member of the sirtuin family of nicotinamide adenine dinucleotide-dependent protein lysine deacylases, have shown promise in treating cancer and neurodegenerative diseases. Developing SIRT2-selective inhibitors with better pharmacological properties is key to further realize the therapeutic potential of targeting SIRT2. One of the best SIRT2-selective inhibitors reported is a thiomyristoyl lysine compound called TM, which showed promising anticancer activity in mouse models without much toxicity to normal cells. The main limitations of TM, however, are the low aqueous solubility and lack of X-ray crystal structures to aid future drug design. Here, we designed and synthesized a glucose-conjugated TM (glucose-TM) analog with superior aqueous solubility. Although glucose-TM is not cell permeable, the excellent aqueous solubility allowed us to obtain a crystal structure of SIRT2 in complex with it. The structure enabled us to design several new TM analogs, one of which, NH4-6, showed superior water solubility and better anticancer activity in cell culture. The results of these studies provided important insights that will further fuel the future development of improved SIRT2 inhibitors as promising therapeutics for treating cancer and neurodegeneration.

Novel Lysine-Based Thioureas as Mechanism-Based Inhibitors of Sirtuin 2 (SIRT2) with Anticancer Activity in a Colorectal Cancer Murine Model.

Sirtuin 2 (SIRT2) is a protein lysine deacylase that has been indicated as a therapeutic target for cancer. To further establish the role of SIRT2 in cancers, it is necessary to develop selective and potent inhibitors. Here, we report the facile synthesis of novel lysine-derived thioureas as mechanism-based SIRT2 inhibitors with anticancer activity. Compounds AF8, AF10, and AF12 selectively inhibited SIRT2 with IC50 values of 0.06, 0.15, and 0.08 µM, respectively. Compounds AF8 and AF10 demonstrated broad cytotoxicity amongst cancer cell lines, but minimal toxicity in noncancerous cells. AF8 and AF10 inhibited the anchorage-independent growth of human colorectal cancer cell line HCT116 with GI50 values of ∼7 µM. Furthermore, AF8 potently inhibited tumor growth in a HCT116 xenograft murine model, supporting that SIRT2 is a viable therapeutic target for colorectal cancer.