Discovery, design and synthesis of a selective S1P3 receptor allosteric agonist

Potent and selective S1P(3) receptor (S1P(3)-R) agonists may represent important proof-of-principle tools used to clarify the receptor biological function and assess the therapeutic potential of the S1P(3)-R in cardiovascular, inflammatory and pulmonary diseases. N, N-Dicyclohexyl-5-propylisoxazole-3-carboxamide was identified by a high-throughput screening of MLSMR library as a promising S1P(3)-R agonist. Rational chemical modifications of the hit allowed the identification of N, N-dicyclohexyl-5-cyclopropylisoxazole-3-carboxamide, a S1P(3)-R agonist endowed with submicromolar activity and exquisite selectivity over the remaining S1P(1,2,4,5)-R family members. A combination of ligand competition, site-directed mutagenesis and molecular modeling studies showed that the N, N-dicyclohexyl-5-cyclopropylisoxazole-3-carboxamide is an allosteric agonist and binds to the S1P(3)-R in a manner that does not disrupt the S1P(3)-R-S1P binding. The lead molecule herein disclosed constitutes a valuable pharmacological tool to explore the molecular basis of the receptor function, and provides the bases for further rational design of more potent and drug-like S1P(3)-R allosteric agonists. (C) 2013 Elsevier Ltd. All rights reserved.