scRNAseq of EMT6.5 mammary tumors 24 hours after vehicle or treatment with the TLR2/6 agonist AXA-042

Cancer immunotherapies targeting the adaptive immune system have revolutionized the treatment for many cancer patients. However, a considerable fraction of patients does not benefit from targeting only the adaptive arm of the immune system. Here, we demonstrate that priming the innate immune system via systemic delivery of a novel synthetic TLR2/6 agonist, AXA-042, represents a rational strategy to boost anti-tumor immunity. TLR2 and TLR6 expression in mouse and human was predominantly confined to tumor-infiltrating myeloid immune cells. Activation of TLR2-signalling induced a pro-inflammatory phenotype in myeloid immune cells with increased cytokine production which resulted in strong T cell dependent anti-tumor immune responses. Systemic delivery of AXA-042 was well tolerated in mouse and non-human primates, demonstrated innate response engagement and anti-tumor efficacy as monotherapy and in combination with checkpoint inhibitors across a wide range of preclinical mouse models. Preclinical efficacy and safety studies provide evidence that priming and re-shaping the innate immune system with the systemic administration of a TLR2 agonist may represent a promising approach for cancer patients. AXA-042 has completed GLP toxicology studies and is currently in clinical development (ACTRN12622000993796) in advanced solid tumors. Overall design: Female Balb/c mice bearing orthotopic EMT6.5 mammary tumors received a single intravenous treatment of saline or AXA-042 (10 µg/mouse), 10 days after implantation of 1x105 cells, when tumors were ~300mm3. Mice were culled 24h later and tumors recovered for single cell transcriptomic analysis.