Development of a high-affinity inhibitor of the prostaglandin transporter

Prostaglandin E 2 (PGE 2) triggers a vast array of biological signals and physiological events. The prostaglandin transporter (PGT) controls PGE2 influx and is rate-limiting for PGE 2 metabolism and signaling termination. PGT global knockout mice die on postnatal day 1 from patent ductus arteriosus. A high-affinity PGT inhibitor would thus be a powerful tool for studying PGT function in adult animals. Moreover, such an inhibitor could be potentially developed into a therapeutic drug targeting PGT. Based on structure-activity relationship studies that built on recently identified inhibitors of PGT, we obtained N-(2- (2-(2-azidoethoxy)ethoxy)ethyl)-4-((4-((2- (2-(2-benzamidoethoxy) ethoxy)ethyl)amino)-6-((4-hydroxyphenyl)amino)-1,3,5- triazin-2- yl)amino)benzamide (T26A), a competitive inhibitor of PGT, with a K i of 378 nM. T26A seems to be highly selective for PGT, because it neither interacts with a PGT homolog in the organic anion transporter family nor affectsPGE 2 synthesis. In Madin-Darby canine kidney cells stably transfected with PGT, T26A blocked PGE 2 metabolism, resulting in retention of PGE 2 in the extracellular compartment and the negligible appearance of PGE 2 metabolites in the intracellular compartment. Compared with vehicle, T26A injected intravenously into rats effectively doubled the amount of endogenous PGE 2 in the circulation and reduced the level of circulating endogenous PGE 2 metabolites to 50%. Intravenous T26A was also able to slow the metabolism of exogenously injected PGE 2. These results confirm that PGT directly regulates PGE 2 metabolism and demonstrate that a high-affinity inhibitor of PGT can effectively prevent PGE 2 metabolism and prolong the half-life of circulating PGE 2. Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics.