Design, synthesis and evaluation of C-terminal heat shock protein 90 (Hsp90) modulators as anticancer agents

This thesis describes C-terminal heat shock protein 90 (Hsp90) modulators as potential anticancer agents. The McAlpine lab developed two molecules SM145 and SM122, which both bind between the N and middle domain of Hsp90 and allosterically modulate the C-terminus. SM145 and SM122 disrupt Hsp90's protein folding function as well as the interactions between co-chaperones and the C-terminus of Hsp90. Unlike current Hsp90 inhibitors, these molecules also inhibit Hsp90 without inducing the problematic cell rescue response. Chapter 2 describes the synthesis and structure-activity relationship (SAR) studies of SM145. Two new Hsp90 inhibitors were identified during these studies: 12 and 23, where both of these compounds contained a single thiazolyl side chain. The author designed and synthesized these molecules, and they were made using a method that allowed them to be produced in significantly improved yields over SM145. They also had much greater solubility, and approximately 2-fold greater potency than SM145. Mechanistic studies of these derivatives have validated Hsp90 as a potential target. Both 12 and 23 effectively suppressed Hsp90's function by disrupting the C-terminus chaperone function without inducing the cell rescue response. Chapter 3 describes the synthesis of five derivatives where an N-methylation scan was performed at a different position around the 23 backbone. Backbone N-methylation was also undertaken on seven other derivatives that also incorporated two thiazolyl moieties, versus 23, which only has one thiazolyl moiety. N-methylation introduced a conformational impact on cyclic peptides, and impacted cytotoxicity. Chapter 4 describes the tumor selectivity between two classes of Hsp90 inhibitors, N-terminal inhibitor (AUY922) and C-terminal modulators (12 and 23) in cancer versus normal cells. Comparison of both inhibitor classes revealed that 12 and 23 bound preferentially to Hsp90 from tumor cells, selectively induce apoptosis and client protein degradation that are associated with Hsp90 ...