The pro-inflammatory cytokines IL-23 and IL-17A play critical roles in autoimmune uveitis (AU). Current AU treatments include immunosuppressants, including systemic corticosteroids, accompanied by many challenging toxicities. As a novel cytokine gene expression control mechanism, we found that the microRNA (miRNA) miR466l-3p cooperates with the mRNA- stabilizing protein HuR to augment IL-17A mRNA and protein levels. To exploit this unusual miRNA-mediated enhancing mechanism as a potential therapeutic target, TargetSite Therapeutics and Yale University have collaboratively generated a target site blocker (TSB) oligonucleotide that specifically blocks miR466l-3p binding to the IL-17A 3’UTR, leading to transcript decay and decreased IL-17A protein levels both in vitro and in vivo. This includes our preliminary TSB efficacy data in the rat autoimmune uveitis model. The mRNA levels of IL23, a cytokine upstream of IL-17A, are also augmented in miR466l-overexpressing cells. This Phase I SBIR will provide proof-of-concept that miR466l – cytokine mRNA interaction-specific TSB oligos, either singly or in combination, will be a novel effective treatment for AU. We will do so by: (1) designing, validating and evaluating specificity of a miR466l – IL-23 3’UTR TSB; (2) optimizing the IL-17A mRNA-specific TSB for the foundational (rat) model; and (3) assessing the efficacy of the IL-17A and IL-23 TSBs, singly and in combination, in the rat AU model, by clinical scoring, histopathology and aqueous humor levels of the TSBs and relevant cytokines. The achievable milestone for this Phase I SBIR project is >50% reduction in clinical and histopathologic AU parameters, thereby offering therapeutic benefit of this novel approach in autoimmune uveitis.