PO-425 The effect of bis structured schiff base material on apoptosis, cytotoxicity and DNA damage of breast cancer cell line

Abstract

IntroductionHarnessing CD8 T cells to respond to tumorigenic antigens remains a supreme therapeutic strategy for sustained clearance of tumours and a resulting cancer-free life for patients. Efficient tumor-initiated T cell priming requires interferon-beta (IFN-b) production by dendritic cells and the expression of IFN-b has been demonstrated to be dependent upon activation of the Stimulator of Interferon Genes (STING) pathway. Indeed, intratumoral delivery of nucleotide-based STING agonists induces a profound regression of established tumours in syngeneic mouse models.Material and methodsHere, we describe a high-throughput screening platform for identifying non-nucleotide small molecule STING agonists. This has been established using a primary assay involving a human THP-1 cell line carrying an IRF-inducible reporter with 5 copies of the IFN signalling response element. Counter screens, involving alternative reporter constructs, rodent cell-based assays, as well as cGAS and STING knockout cell lines, are used to eliminate luciferase artefacts and ensure human-rodent cross species reactivity, as well as pathway selectivity. Biochemical assays, involving cGAS enzymatic activity and STING protein binding assays, are used to identify the specific target of identified hits.Results and discussionsTo date, from an initial screen of ~1 00 000 compounds we have identified at least one novel highly tractable STING agonist scaffold (SRCB-0001, EC50 ~1 µM), which induces expression of a type I interferon-stimulated gene signature in relevant cell types and IFN-b protein production in human peripheral blood mononuclear cells (PBMCs) with efficacy that is comparable to that observed for 2’3’-cGAMP, a natural dinucleotide STING ligand. Unlike nucleotide-based STING agonists, we have found that SRCB-0001 can be dosed orally in mice thereby lifting the restrictions of intratumoral injection as the route of administration.ConclusionThus, we propose SRCB-0074 as a first-in-class small molecule STING agonist for immuno-oncology applications.