STAT3Antisense Oligonucleotide Remodels the Suppressive Tumor Microenvironment to Enhance Immune Activation in Combination with Anti–PD-L1

Abstract

Purpose: Danvatirsen is a therapeutic antisense oligonucleotide (ASO) that selectively targets STAT3 and has shown clinical activity in two phase I clinical studies. We interrogated the clinical mechanism of action using danvatirsen-treated patient samples and conducted back-translational studies to further elucidate its immunomodulatory mechanism of action. Experimental Design: Paired biopsies and blood samples from danvatirsen-treated patients were evaluated using immunohistochemistry and gene-expression analysis. To gain mechanistic insight, we used mass cytometry, flow cytometry, and immunofluorescence analysis of CT26 tumors treated with a mouse surrogate STAT3 ASO, and human immune cells were treated in vitro with danvatirsen. Results: Within the tumors of treated patients, danvatirsen uptake was observed mainly in cells of the tumor microenvironment (TME). Gene expression analysis comparing baseline and on-treatment tumor samples showed increased expression of proinflammatory genes. In mouse models, STAT3 ASO demonstrated partial tumor growth inhibition and enhanced the antitumor activity when combined with anti–PD-L1. Immune profiling revealed reduced STAT3 protein in immune and stromal cells, and decreased suppressive cytokines correlating with increased proinflammatory macrophages and cytokine production. These changes led to enhanced T-cell abundance and function in combination with anti–PD-L1. Conclusions: STAT3 ASO treatment reverses a suppressive TME and promotes proinflammatory gene expression changes in patients' tumors and mouse models. Preclinical data provide evidence that ASO-mediated inhibition of STAT3 in the immune compartment is sufficient to remodel the TME and enhance the activity of checkpoint blockade without direct STAT3 inhibition in tumor cells. Collectively, these data provide a rationale for testing this combination in the clinic.

Resistance to Durvalumab and Durvalumab plus Tremelimumab Is Associated with Functional STK11 Mutations in Patients with Non–Small Cell Lung Cancer and Is Reversed by STAT3 Knockdown

“…A murine-reactive STAT3 antisense oligonucleotide (ASO) was used as a strategy to inhibit multiple, STAT3-mediated immunosuppressive signaling pathways simultaneously. The physicochemical properties of this drug have been described previously (27), and enable efficient STAT3 ASO transduction and STAT3 RNA knockdown in stromal cells within the TME, particularly macrophages and DCs, CD4+ Tregs, fibroblasts and endothelial cells, with relative sparing of tumor cells and other lymphocytes. The pharmacodynamic effects of the STAT3 ASO within the STK11wt CT26 TME in these previous studies included reductions in immunosuppressive CD206+ myeloid cells and increases in immunoreactive MHCII+ TAMs.…”

Frontiers in cancer immunotherapy—a symposium report

“…In preclinical models, STAT3 ASO treatment remodeled the immunosuppressive tumor microenvironment by decreasing suppressive macrophages and increasing proinflammatory macrophages, resulting in increased infiltration and function of cytotoxic CD8 + T cells. STAT3 ASO also enhanced the antitumor activity of anti‐PD‐L1 treatment, suggesting that the STAT3‐related changes may sensitize tumors to checkpoint blockade 97 …”

Natural Killer Cell Interactions With Myeloid Derived Suppressor Cells in the Tumor Microenvironment and Implications for Cancer Immunotherapy

“…The molecular mechanisms regulating PMN-MDSC and M-MDSC populations differ from the afore-described pathways and are currently under investigation. Danvatirsen, a STAT3 antisense oligonucleotide, reversed the immunosuppressive TME and enhanced immune activity, as well as checkpoint blockades, in patient tumor samples from two phase I clinical trials and murine models ( 237 ).…”