DESIGN AND EVALUATION OF MECHANISM-BASED SIRT2 INHIBITORS WITH ENHANCED ANTICANCER POTENCY

Abstract

SIRT2 regulates various biological pathways through lysine deacetylation and de-fatty acylation, thereby promoting tumor growth. Subsequently, many SIRT2 selective inhibitors have been developed to target cancers. Among them, a mechanism-based SIRT2 inhibitor named TM is a lead compound with a potent antiproliferative effect. TM-induced SIRT2 inhibition had degraded oncoprotein c-Myc and effectively reduced breast cancer tumor growth. Nevertheless, TM possesses several limitations. Due to its long thiomyristoyl hydrophobic chain, TM has poor aqueous solubility, which makes the collection of the X-ray crystal structure of TM and SIRT2 challenging. Also, TM with poor aqueous solubility portrays limited bioavailability in cellular and animal studies. Another limitation of TM is that it can only inhibit SIRT2 deacetylase, not de-fatty acylase. Such simultaneous inhibition of both SIRT2 enzymatic activities could potentially increase the antiproliferative effect. In this thesis, several new SIRT2 selective inhibitors that have overcame these issues will be discussed. To improve the aqueous solubility, we have synthesized a glycoconjugated TM, named glucose-TM (Chapter Two). Even though glucose-TM had poor permeability, it had enabled us to collect X-ray co-crystal structure with SIRT2 and design additional inhibitors. To design a new SIRT2 modulator that inhibits both deacetylase and defatty-acylase, we have developed SIRT2 selective Proteolysis Targeting Chimera (PROTAC) inhibitor named TM-P4-Thal to degrade SIRT2 in cells (Chapter Three). For the accurate comparison of a pan SIRT1-3 inhibitor and a SIRT2 selective inhibitor, we synthesized NH4-6 and NH4-13 that have only one atom difference, but completely different sirtuin inhibition profile (Chapter Four). From the previous chapters, we have learned that both solubility and permeability are important for drug designs. To gain both characteristics, we have designed a simpler SIRT2 inhibitor with a benzodiazapienedione core, named NH-C1-10 (Chapter Five). NH-C1-10 inhibited SIRT2 slightly weaker than TM. However, in cellular studies, NH-C1-10 with improved bioavailability had shown stronger cytotoxicity and SIRT2 inhibition than TM.