The clinical approval of p110δ PI3K inhibitors raised hopes in treating aggressive tumours expressing high levels of non-mutated p110δ, however, the severe adverse effects that those inhibitors caused became a barrier to their clinical application. IOA-244 is the first-in-class, highly selective and non-ATP competitive p110δ PI3K inhibitor showing high selectivity and low toxicity in several preclinical models. Here we show that IOA-244, as a single agent treatment, blocks the progression of early phase breast tumours by attacking the survival of cancer cells and the polarisation of TAMs to a pro-tumourigenic phenotype leading to suppression of TAMs-expressed ATX. In established tumours, IOA-244 alone was insufficient to control the high levels of both M2-like macrophages and ATX, and while it reduced tumour progression, it did not completely block it. Full tumour control, however, was achieved when IOA-244 used in a combinatorial regimen with the PF-8380 ATX inhibitor. In agreement with the mouse model, the amount of CD163+/CD204+macrophages and ATX were much higher in grade III human breast carcinomas compared to grade I. Our work provides the first in vivo preclinical evidence showing that IOA-244 is a potential highly effective drug for breast cancer treatment and depending on the phase of the tumour can be used either as a single agent or as a combinatorial regimen.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by dense stromal fibrosis that promotes immune exclusion and treatment resistance, yet the upstream drivers of this pro-fibrotic cascade remain poorly defined. Here, we identify phosphoinositide 3-kinase δ (PI3Kδ) as a previously unrecognized driver of fibrosis in PDAC. Pharmacological inhibition of PI3Kδ reduces collagen deposition while enhancing the infiltration of activated CD8+ T cells, thereby reprogramming the tumor microenvironment toward an antitumor state. Mechanistically, we reveal that PI3Kδ regulates the biosynthesis of lysophosphatidic acid (LPA), a key lipid mediator of stromal remodeling, by controlling phosphatidylcholine-derived precursors in both cancer cells and stromal fibroblasts. By regulating both LPA-driven stromal remodeling and immune suppression, PI3Kδ emerges as a central regulator of the PDAC tumor microenvironment. Co-inhibition of autotaxin, an enzyme contributing to LPA production, and PI3Kδ further amplifies stromal disruption and improves chemo-immunotherapy efficacy in preclinical PDAC models. These findings position PI3Kδ as a central therapeutic target in PDAC, offering a dual-action strategy to simultaneously dismantle stromal fibrosis and immune suppression.

Supplementary Figure S5 shows RNA-seq analysis of 0082T CAFs after treatment with ATX inhibitors.

Supplementary Figure S1 shows the validation of ESTIMATE stromal and immune gene signatures and mRNA expression in tumour-rich and TME-rich samples.

Supplementary Figure S4 shows LPAR expression in PDAC cell lines and ATX-mediated pro-tumorigenic stimulation by 0082T conditioned media.

Supplementary Table S1 shows the list of Taqman assays used for qPCR experiments.

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.

Supplementary Figure S2 shows the validation of 0082T CAF phenotype.

Supplementary Figure S3 shows ATX antibody validation and ATX detection in cancer and CAF co-cultures.

Supplementary Figure S6 shows LLPs expression in PDAC cancer and CAFs cells.

Supplementary Table S5 shows the hematological results of cynomolgus monkeys treated with vehicle (Ctr.) or NI-1701 (Treat.) at 30 and 100 mg/kg over 4 weeks.

Tumor experiments showing monotherapy testing of IOA-244

Supplementary Table S2 shows the cell surface density (expressed as number of receptors per cell) for CD19, CD47, CD20 on different human tumor cell lines.

Supplementary Table S4 shows the mean Cmax values from the DRF and the single dose study.

Supplementary Table S3 shows the ratio of AUC0-inf low/high dose for the PK single dose study.

Supplementary Figure S1 shows shows the percentage of in vitro phagocytosis of Raji cells by macrophages with NI-1701 or CD19/CD47hi biAb.

Supplementary Figure S2 shows in vitro hemagglutination in human or cynomolgus monkeys whole blood, or platelet aggregation in human platelet rich-plasma (PRP)in presence of NI-1701

Supplementary material and methods

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.

Video 1 shows the real time phagocytosis of cancer cells in presence of NI-1701