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Autotaxin (ATX) is a secreted enzyme that hydrolyzes lysophosphatidylcholine to lysophosphatidic acid (LPA). LPA is a bioactive phospholipid that regulates diverse biological processes, including cell proliferation, migration, and survival/apoptosis, through the activation of a family of G protein-coupled receptors. The ATX-LPA pathway has been implicated in many pathologic conditions, including cancer, fibrosis, inflammation, cholestatic pruritus, and pain. Therefore, ATX inhibitors represent an attractive strategy for the development of therapeutics to treat a variety of diseases. Mouse and rat ATX have been crystallized previously with LPA or small-molecule inhibitors bound. Here, we present the crystal structures of human ATX in complex with four previously unpublished, structurally distinct ATX inhibitors. We demonstrate that the mechanism of inhibition of each compound reflects its unique interactions with human ATX. Our studies may provide a basis for the rational design of novel ATX inhibitors.

Lysophosphatidic acid (LPA) is a bioactive phospholipid that signals through a family of at least six G protein-coupled receptors designated LPA [1][2][3][4][5][6] . LPA type 1 receptor (LPA 1 ) exhibits widespread tissue distribution and regulates a variety of physiological and pathological cellular functions. Here, we evaluated the in vitro pharmacology, pharmacokinetic, and pharmacodynamic properties of the LPA 1 -selective antagonist AM095 (sodium, {4Ј-[3-methyl-4-((R)-1-phenyl-ethoxycarbonylamino)-isoxazol-5-yl]-biphenyl-4-yl}-acetate) and assessed the effects of AM095 in rodent models of lung and kidney fibrosis and dermal wound healing. In vitro, AM095 was a potent LPA 1 receptor antagonist because it inhibited GTP␥S binding to Chinese hamster ovary (CHO) cell membranes overexpressing recombinant human or mouse LPA 1 with IC 50 values of 0.98 and 0.73 M, respectively, and exhibited no LPA 1 agonism. In functional assays, AM095 inhibited LPAdriven chemotaxis of CHO cells overexpressing mouse LPA 1 (IC 50 ϭ 778 nM) and human A2058 melanoma cells (IC 50 ϭ 233 nM). In vivo, we demonstrated that AM095: 1) had high oral bioavailability and a moderate half-life and was well tolerated at the doses tested in rats and dogs after oral and intravenous dosing, 2) dose-dependently reduced LPA-stimulated histamine release, 3) attenuated bleomycin-induced increases in collagen, protein, and inflammatory cell infiltration in bronchalveolar lavage fluid, and 4) decreased kidney fibrosis in a mouse unilateral ureteral obstruction model. Despite its antifibrotic activity, AM095 had no effect on normal wound healing after incisional and excisional wounding in rats. These data demonstrate that AM095 is an LPA 1 receptor antagonist with good oral exposure and antifibrotic activity in rodent models.

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