Discovery of GS-2278, a Potent and Selective LPAR1 Antagonist for the Treatment of Idiopathic Pulmonary Fibrosis

We describe the discovery and preclinical characterization of a potent and selective lysophosphatidic acid receptor 1 (LPAR1) antagonist with a direct-acting antifibrotic mechanism. <b>18a</b> was initially identified as a potent non-carboxylic acid LPAR1 antagonist in an LPA-induced myocardin-related transcription factor A (MRTF-A) nuclear translocation assay. Modifications to the aromatic elements in the structure allowed for improvements in metabolic stability and the mitigation of GSH adduct formation, but in vitro to in vivo clearance disconnects were observed with several potent sulfonamides (e.g., <b>27b</b>) across preclinical species. Through modification of the sulfonamide, <b>42</b> (<b>GS-2278</b>) emerged as a potent LPAR1 antagonist with a suitable in vitro profile and desirable pharmacokinetic properties for oral QD dosing. <b>GS-2278</b> dose-dependently blocked LPA-induced histamine release and demonstrated efficacy in an interventional model of bleomycin-induced lung fibrosis. However, CNS-related toxicity was observed in dogs, and based on these findings, the clinical development of <b>GS-2278</b> for IPF was halted.