Identification of Potent In Vivo Autotaxin Inhibitors that Bind to Both Hydrophobic Pockets and Channels in the Catalytic Domain

Recent research advances in ATX inhibitors: An overview of primary literature

The autoglobulin gene is the main enzyme for circulating LPA production and has lysophosphatidylcholine D activity, which catalyzes the production of lysophosphatidic acid and choline with lysophosphatidylcholine as substrate. A growing body of experimental evidence suggests that autoglobulin is involved in the pathogenesis of a variety of diseases. This review summarizes the different structural ATX inhibitors classified according to their binding mode to the ATX triple orientation site, and summarizes the conformational relationships and molecular docking of each type with ATX structure, hoping to contribute to the development of novel ATX inhibitors.

Dietary Lactobacillus-Derived Exopolysaccharide Enhances Immune-Checkpoint Blockade Therapy

Microbes and their byproducts have been reported to regulate host health and immune functions. Here we demonstrated that microbial exopolysaccharide produced by Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1 (EPS-R1) induced CCR6+ CD8+ T cells of mice and humans. In mice, ingestion of EPS-R1 augmented antitumor effects of anti-CTLA-4 or anti-PD-1 monoclonal antibody against CCL20-expressing tumors, in which infiltrating CCR6+ CD8+ T cells were increased and produced IFNγ accompanied by a substantial immune response gene expression signature maintaining T-cell functions. Of note, the antitumor adjuvant effect of EPS-R1 was also observed in germ-free mice. Furthermore, the induction of CCR6 expression was mediated through the phosphorylated structure in EPS-R1 and a lysophosphatidic acid receptor on CD8+ T cells. Overall, we find that dietary EPS-R1 consumption induces CCR6+ CD8+ T cells in Peyer's patches, favoring a tumor microenvironment that augments the therapeutic effect of immune-checkpoint blockade depending on CCL20 production by tumors.

SIGNIFICANCE

Gut microbiota- and probiotic-derived metabolites are attractive agents to augment the efficacy of immunotherapies. Here we demonstrated that dietary consumption of Lactobacillus-derived exopolysaccharide induced CCR6+ CD8+ T cells in Peyer's patches and improved the tumor microenvironment to augment the therapeutic effects of immune-checkpoint blockade against CCL20-producing tumors. See related commentary by Di Luccia and Colonna, p. 1189. This article is highlighted in the In This Issue feature, p. 1171.

Aberrant ENPP2 expression promotes tumor progression in multiple myeloma

Ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2) has been recently linked to tumor development. However, its role in modulating multiple myeloma (MM) disease progression remains unclear. Here, we demonstrated that CD138+ cells isolated from MM patients presented with higher expression of ENPP2 compared with CD138- cells. Treatment of MM cells with IL-6 resulted in ENPP2 upregulation. ENPP2 overexpression promoted proliferation, inhibited apoptosis, increased lysophosphatidic acid (LPA) generation, and upregulated osteoclastogenesis mediator expression in MM cells. In contrast, ENPP2 inhibition induced apoptosis, suppressed proliferation and survival, decreased LPA generation and downregulated osteoclastogenesis mediator expression. In an MM xenograft mouse model, ENPP2 knockdown significantly reduced MM tumor burden by inhibiting cell proliferation and inducing apoptosis. Furthermore, ENPP2 knockdown decreased the levels of LPA, osteoclastogenesis mediators in sera of mice with MM. Our findings revealed the tumor-promoting role of ENPP2 in MM, thus providing new molecular evidence for targeting the ENPP2-LPA axis in MM therapy.

Design and Development of Autotaxin Inhibitors

Autotaxin (ATX) is the only enzyme of the ecto-nucleotide pyrophosphatase/phosphodiesterase (ENPP2) family with lysophospholipase D (lysoPLD) activity, which is mainly responsible for the hydrolysis of extracellular lysophosphatidylcholine (LPC) into lysophosphatidic acid (LPA). LPA can induce various responses, such as cell proliferation, migration, and cytokine production, through six G protein-coupled receptors (LPA1-6). This signaling pathway is associated with metabolic and inflammatory disorder, and inhibiting this pathway has a positive effect on the treatment of related diseases, while ATX, as an important role in the production of LPA, has been shown to be associated with the occurrence and metastasis of tumors, fibrosis and cardiovascular diseases. From mimics of ATX natural lipid substrates to the rational design of small molecule inhibitors, ATX inhibitors have made rapid progress in structural diversity and design over the past 20 years, and three drugs, GLPG1690, BBT-877, and BLD-0409, have entered clinical trials. In this paper, we will review the structure of ATX inhibitors from the perspective of the transformation of design ideas, discuss the advantages and disadvantages of each inhibitor type, and put forward prospects for the development of ATX inhibitors in the future.

Structure-Based Discovery of Novel Chemical Classes of Autotaxin Inhibitors

Autotaxin (ATX) is a secreted glycoprotein, widely present in biological fluids, largely responsible for extracellular lysophosphatidic acid (LPA) production. LPA is a bioactive growth-factor-like lysophospholipid that exerts pleiotropic effects in almost all cell types, exerted through at least six G-protein-coupled receptors (LPAR1-6). Increased ATX expression has been detected in different chronic inflammatory diseases, while genetic or pharmacological studies have established ATX as a promising therapeutic target, exemplified by the ongoing phase III clinical trial for idiopathic pulmonary fibrosis. In this report, we employed an in silico drug discovery workflow, aiming at the identification of structurally novel series of ATX inhibitors that would be amenable to further optimization. Towards this end, a virtual screening protocol was applied involving the search into molecular databases for new small molecules potentially binding to ATX. The crystal structure of ATX in complex with a known inhibitor (HA-155) was used as a molecular model docking reference, yielding a priority list of 30 small molecule ATX inhibitors, validated by a well-established enzymatic assay of ATX activity. The two most potent, novel and structurally different compounds were further structurally optimized by deploying further in silico tools, resulting to the overall identification of six new ATX inhibitors that belong to distinct chemical classes than existing inhibitors, expanding the arsenal of chemical scaffolds and allowing further rational design.