ABSTRACT
A class of imidazoisoindole (III) heme-binding indoleamine-2,3-dioxygenase (IDO1) inhibitors were optimized via structure-based drug design into a series of tryptophan-2,3-dioxygenase (TDO)-selective inhibitors. Kynurenine pathway modulation was demonstrated in vivo, which enabled evaluation of TDO as a potential cancer immunotherapy target. As means of mitigating the risk of drug-drug interactions arising from cytochrome P450 inhibition, a novel property-based drug design parameter, herein referred to as the CYP Index, was implemented for the design of inhibitors with appreciable selectivity for TDO over CYP3A4. We anticipate the CYP Index will be a valuable design parameter for optimizing CYP inhibition of any small molecule inhibitor containing a Lewis basic motif capable of binding heme.
ABSTRACT
PURPOSE: To study the effects of a regioisomeric change on the biological activities of previously reported water soluble, colchicine site binding, microtubule depolymerizing agents. METHODS: Nine pyrrolo[3,2-d]pyrimidines were designed and synthesized. The importance of various substituents was evaluated. Their abilities to cause cellular microtubule depolymerization, inhibit proliferation of MDA-MB-435 tumor cells and inhibit colchicine binding to tubulin were studied. One of the compounds was also evaluated in the National Cancer Institute preclinical 60 cell line panel. RESULTS: Pyrrolo[3,2-d]pyrimidine analogs were more potent than their pyrrolo[2,3-d]pyrimidine regioisomers. We identified compounds with submicromolar potency against cellular proliferation. The structure-activity relationship study gave insight into substituents that were crucial for activity and those that improved activity. The compound tested in the NCI 60 cell line is a 2-digit nanomolar (GI(50)) inhibitor of 8 tumor cell lines. CONCLUSION: We have identified substituted pyrrolo[3,2-d]pyrimidines that are water-soluble colchicine site microtubule depolymerizing agents. These compounds serve as leads for further optimization.
