Autotaxin (ATX), encoded by ENPP2, is a clinical target in pancreatic ductal adenocarcinoma (PDAC). ATX catalyzes the production of lysophosphatidic acid (LPA), an important regulator within the tumor microenvironment (TME), yet the protumorigenic action of the ATX/LPA axis in PDAC remains unclear. In this study, by interrogating patient samples and cell line datasets, we show that the PDAC TME, rather than cancer cells, is responsible for the majority of ENPP2 expression and highlight a key role for cancer-associated fibroblast (CAF)-derived ATX in autocrine and paracrine protumorigenic signaling. Using the clinical-stage ATX inhibitor, IOA-289, we identified connective tissue growth factor (CTGF), also known as CCN2, as a downstream mediator of ATX signaling in the PDAC CAF-derived cell line, 0082T. Genetic ablation or pharmacologic inhibition of ATX in 0082T CAFs reduced CTGF secretion via modulation of LPA/LPA receptor signaling. Despite the loss of ATX function, extracellular levels of LPA were paradoxically increased, indicating a role for ATX beyond its enzymatic activity and suggesting a role for its LPA chaperone function in the LPA/LPA receptor signaling in CAFs. As CAFs are the main source for CTGF in the PDAC TME, these findings suggest a role for ATX in promoting a protumorigenic microenvironment via modulation of CAF secretion not only via its LPA-producing activity but also via its LPA chaperone function, providing a potential mechanism for the antitumor effects of ATX inhibition.

Recent findings indicate that in cancer, host immune suppression and resistance to therapy is orchestrated by the presence and activity of stromal cells in the tumor microenvironment. Therefore novel approaches to overcome stromal mediated resistance to therapy represent a potential strategy to improve the outcome to chemotherapy and immune checkpoint blockade, particularly in tumors that have a fibrotic microenviroment. Autotaxin is an enzyme that converts Lysophosphatidylcholine (LPC) to Lysophosphatidic Acid (LPA), a key pathway that is aberrantly activated in fibrosis. LPA has also been described to act directly on tumor cells, promoting their growth and proliferation via G protein-coupled LPA Receptors (LPARs). IOA-289 is a novel, potent, selective and orally bioavailable inhibitor of Autotaxin, a target with known clinical application in fibrotic diseases and with a strong rationale for exploration in cancer. In preclinical models, IOA-289 modulated levels of circulating LPA in a dose dependent manner. At doses achieving at least 50% reduction of circulating LPA, IOA-289 showed monotherapeutic efficacy in in vivo mouse models of cancer. Notably the effects were most prominent in orthotopic models that recapitulate the stromal components of the microenvironment. In vitro studies investigated the mechanism of action of IOA-289, and it was shown to be driven by: (i)Direct anti-tumor activity on cancer cell lines in vitro (ii)Modulation of the secretory profile of fibroblasts(iii)Increased T cell infiltration in vitro and in vivo In a healthy volunteer study following a single oral ascending dose, IOA-289 showed a dose dependent increase in plasma and a corresponding decrease in circulating LPA. We also demonstrated that ATX was elevated in plasma from pancreatic cancer patients compared to samples from healthy volunteers and are correlated with soluble CA19-9. Based on our preclinical data we postulate that inhibition of the ATX/LPA pathway with IOA-289 may be a beneficial therapeutic strategy for cancer patients with fibrotic tumor microenvironments. The predicted biologically effective dose of IOA-289 has been calculated using PK/PD modelling combining data from preclinical studies and from the phase Ia healthy volunteer study. IOA-289 is scheduled to enter a phase Ib clinical trial in pancreatic cancer. Citation Format: Zoe Johnson, Marcel Deken, Ragini Medhi, Lauren Maggs, Alan Carruthers, Anne Cheasty, Alessia Tagliavini, Andrea Nizzardo, Marco Pergher, Karolina Niewola, Amy Fraser, Lars van der Veen, Pritom Shah, Luigi ZIviani, Stefano Milleri, Michael Lahn. Targeting Autotaxin to suppress stromal signaling in the tumor microenvironment to improve outcome to therapy in fibrotic tumor types [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2636.

BackgroundAutotaxin (ATX) is a secreted glycoprotein that hydrolyzes lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA). The expression of both ATX and LPA is elevated in most solid tumors and plasma. LPA signaling directly modulates tumor cell function and contributes to the development of the fibrotic tumor microenvironment, a mechanism by which tumors evade host immunity and impairs response to therapy. IOA-289 is a potent, orally available autotaxin inhibitor which is being developed as a novel treatment of solid tumours burdened with a high degree of fibrosis.MethodsInhibition of ATX activity in human plasma was determined by measuring reduction in LPA species as quantified by LC-MS/MS. In vitro activity on biomarkers of fibrosis was assessed using the BioMAP screen and fibroblast cell cultures. T cell migration was measured using 48-well chemotaxis chambers. PK/PD studies were performed following a single oral dose of IOA-289 in mice, and plasma LPA was used as a PD biomarker. In vivo efficacy was studied in two models of breast cancer, 4T1 and E0771. Bioinformatics used TCGA and GTEX publicly available datasets.ResultsIOA-289 inhibits plasma LPA18:2 with an IC50 of 36nM, with similar results for other LPA species. IOA-289 inhibited fibrosis relevant factors in the BioMAP phenotypic screen, including sIL-6, MCP-1, αSMA, collagen-III, and sVEGF. In further studies, IOA-289 inhibited the secretion of PAI-1 and IL-6 by stimulated fibroblasts. LPA and cancer cell conditioned media inhibited T cell chemotaxis in vitro and the effect was overcome in the presence of IOA-289. The efficacious human dose of IOA-289 was determined following PK/PD studies using plasma LPA as a biomarker of response to ATX inhibition. In vivo studies showed that IOA-289 inhibited metastasis of 4T1 cells, enhanced the infiltration of T cells into 4T1 s.c. implanted tumors and prevented the growth of primary, orthotopically implanted E0771 tumors. Bioinformatics analysis demonstrated elevated ATX expression in pancreatic cancer (PDAC), and PDAC patient plasma showed a correlation of ATX levels with CA-19-9.ConclusionsThe ATX/LPA pathway represents a novel target for anti-cancer therapy with actions on the tumor, immune cell and stromal environment. IOA-289 is a highly potent and selective inhibitor of ATX with demonstrated monotherapy activity in cancer models. Based on the mechanism of action we are investigating combinations of IOA-289 with chemotherapy, immunotherapy and novel agents in ongoing preclinical studies. An acceptable safety and PK profile support the clinical development of IOA-289 which is currently in a phase I clinical trial.Ethics ApprovalThe 4T1 study was approved by The University Claude Bernard Lyon 1 Ethics Board; approval number DR2014-38 (vM). The E0771 study was reviewed and approved by the Institutional Animal Care and Use Committee of the contract research organization (Covance, Ann Arbor, MI, USA), an AAALAC International accredited program.