Novel water-soluble substituted pyrrolo[3,2-d]pyrimidines: design, synthesis, and biological evaluation as antitubulin antitumor agents.

Objective: 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.

Conclusions: 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.