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PI3K delta (PI3Kδ) inhibitors are used to treat lymphomas but safety concerns and limited target selectivity curbed their clinical usefulness. PI3Kδ inhibition in solid tumors has recently emerged as a potential novel anticancer therapy through the modulation of T-cell responses and direct antitumor activity. Here we report the exploration of IOA-244/MSC2360844, a first-in-class non–ATP-competitive PI3Kδ inhibitor, for the treatment of solid tumors. We confirm IOA-244’s selectivity as tested against a large set of kinases, enzymes, and receptors. IOA-244 inhibits the in vitro growth of lymphoma cells and its activity correlates with the expression levels of PIK3CD, suggesting cancer cell–intrinsic effects of IOA-244. Importantly, IOA-244 inhibits regulatory T cell proliferation while having limited antiproliferative effects on conventional CD4+ T cells and no effect on CD8+ T cells. Instead, treatment of CD8 T cells with IOA-244 during activation, favors the differentiation of memory-like, long-lived CD8, known to have increased antitumor capacity. These data highlight immune-modulatory properties that can be exploited in solid tumors. In CT26 colorectal and Lewis lung carcinoma lung cancer models, IOA-244 sensitized the tumors to anti-PD-1 (programmed cell death protein 1) treatment, with similar activity in the Pan-02 pancreatic and A20 lymphoma syngeneic mouse models. IOA-244 reshaped the balance of tumor-infiltrating cells, favoring infiltration of CD8 and natural killer cells, while decreasing suppressive immune cells. IOA-244 presented no detectable safety concerns in animal studies and is currently in clinical phase Ib/II investigation in solid and hematologic tumors. Significance: IOA-244 is a first-in-class non–ATP-competitive, PI3Kδ inhibitor with direct antitumor in vitro activity correlated with PI3Kδ expression. The ability to modulate T cells, in vivo antitumor activity in various models with limited toxicity in animal studies provides the rationale for the ongoing trials in patients with solid tumors and hematologic cancers.

Target engagement kinase tree

Table summarizing the IC50 values derived from previous published experiments performed with IOA-244

PI3K delta (PI3Kδ) inhibitors are used to treat lymphomas but safety concerns and limited target selectivity curbed their clinical usefulness. PI3Kδ inhibition in solid tumors has recently emerged as a potential novel anticancer therapy through the modulation of T-cell responses and direct antitumor activity. Here we report the exploration of IOA-244/MSC2360844, a first-in-class non–ATP-competitive PI3Kδ inhibitor, for the treatment of solid tumors. We confirm IOA-244’s selectivity as tested against a large set of kinases, enzymes, and receptors. IOA-244 inhibits the in vitro growth of lymphoma cells and its activity correlates with the expression levels of PIK3CD, suggesting cancer cell–intrinsic effects of IOA-244. Importantly, IOA-244 inhibits regulatory T cell proliferation while having limited antiproliferative effects on conventional CD4+ T cells and no effect on CD8+ T cells. Instead, treatment of CD8 T cells with IOA-244 during activation, favors the differentiation of memory-like, long-lived CD8, known to have increased antitumor capacity. These data highlight immune-modulatory properties that can be exploited in solid tumors. In CT26 colorectal and Lewis lung carcinoma lung cancer models, IOA-244 sensitized the tumors to anti-PD-1 (programmed cell death protein 1) treatment, with similar activity in the Pan-02 pancreatic and A20 lymphoma syngeneic mouse models. IOA-244 reshaped the balance of tumor-infiltrating cells, favoring infiltration of CD8 and natural killer cells, while decreasing suppressive immune cells. IOA-244 presented no detectable safety concerns in animal studies and is currently in clinical phase Ib/II investigation in solid and hematologic tumors.Significance:IOA-244 is a first-in-class non–ATP-competitive, PI3Kδ inhibitor with direct antitumor in vitro activity correlated with PI3Kδ expression. The ability to modulate T cells, in vivo antitumor activity in various models with limited toxicity in animal studies provides the rationale for the ongoing trials in patients with solid tumors and hematologic cancers.

Table showing the raw data of the AUC value of figure 2A

Correlation analysis of PI3Kd levels and the response to IOA-244 and Idelalisib

Phosphoinositide 3-kinase delta (PI3Kd) inhibitors are used to treat lymphomas but safety concerns and limited target selectivity curbed their clinical usefulness. PI3Kd inhibition in solid tumors has recently emerged as a potential novel anti-cancer therapy through the modulation of T cell responses and direct anti-tumor activity. Here we report the exploration of IOA-244/MSC2360844, a first-in-class non-ATP-competitive PI3Kd inhibitor, for the treatment of solid tumors. We confirm IOA-244’s selectivity as tested against a large set of kinases, enzymes, and receptors. IOA-244 inhibits the in vitro growth of lymphoma cells and its activity correlates with the expression levels of PIK3CD, suggesting cancer cell-intrinsic effects of IOA-244. Importantly, IOA-244 inhibits Treg proliferation while having limited anti-proliferative effects on conventional CD4+ T cells and no effect on CD8+ T cells. Instead, treatment of CD8 T cells with IOA-244 during activation, favors the differentiation of memory-like, long-lived CD8, known to have increased antitumor capacity. These data highlight immune-modulatory properties that can be exploited in solid tumors. In CT26 colorectal and LLC lung cancer models, IOA-244 sensitized the tumors to anti-PD-1 (Programmed cell death protein 1) treatment, with similar activity in the Pan-02 pancreatic and A20 lymphoma syngeneic mouse models. IOA-244 reshaped the balance of tumor-infiltrating cells, favoring infiltration of CD8 and NK cells, while decreasing suppressive immune cells. IOA-244 presented no detectable safety concerns in animal studies and is currently in clinical Phase Ib/II investigation in solid and hematological tumors.

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.