Abstract 4272: Potent in situ cancer immunotherapy with synthetic human STING-activating cyclic dinucleotides

Spontaneous tumor-initiated T cell priming is dependent on IFN-β production by tumor-resident dendritic cells. Based on recent observations indicating that IFN-β expression was dependent upon activation of the host STING (Stimulator of Interferon Genes) pathway, we hypothesized that direct engagement of STING through intratumoral administration of specific agonists would result in effective anti-tumor therapy. To this end, we generated novel synthetic cyclic dinucleotide (CDN) derivatives with superior STING-activating and anti-tumor properties. The most potent molecule contains a 2′-5′ and 3′-5′ phosphate bridge that increases its affinity for STING at least 10-fold. Additionally, sulfur atoms at the non-bridging oxygens of the internucleotide phosphate bridge enable both superior STING binding affinity, as well as resistance to host cell phosphodiesterases. Importantly, the lead molecule activates PBMCs from a panel of human donors representing all known STING alleles, including homozygotes for the most refractory allele. Intratumoral injection of the lead CDN molecule induced profound regression of established B16 melanoma tumors, generated substantial systemic immune responses capable of rejecting distant metastases and provided long-lived immunologic memory. Cures in entire cohorts of mice bearing well-established 4T1 mammary and CT26 colon carcinoma models correlated with induction of cytokine-mediated innate and adaptive antigen-specific T cell immunity, both...
Source: Cancer Research - Category: Cancer & Oncology Authors: Tags: Clinical Research (Excluding Clinical Trials) Source Type: research