Intramuscular Administration of AAV Vectors Encoding soluble PD-L1 for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a systemic autoimmune disease that predominantly affects the joints. Current therapies aim to reduce synovial inflammation and pain, and prevent joint destruction by targeting pro- inflammatory cytokines or immune cells such as B- and T-cells. The introduction of tumor necrosis factor (TNF) antagonists and other biologics has dramatically improved RA treatment. However, some patients do not respond to these drugs or exhibit an incomplete response, requiring additional interventions applied to active joints. Moreover, these biologics are needed for repeated administration and are very expensive. Recently, gene therapy has been extensively studied through intra-articular administration for arthritis treatment in RA, especially with adeno-associated virus (AAV) vectors. Currently, several clinical trials involving AAV vectors have been initiated. It is well known that T cells play a crucial role in the pathophysiology of RA. Instead of targeting individual cytokines as in other studies, we have used AAV vectors to deliver wild-type (wt) PD-L1, an immune checkpoint to block immune cell function, into the joints of a RA mouse model induced by collagen vaccination (CIA mice) and demonstrated remarkable improvement in pathological score with decreased immune cell infiltration and inflammatory cytokines in treated joints. However, the complete disappearance of pathological changes was not achieved. To overcome the limitation of expression of wtPD-L1 with a transmembrane domain on the AAV transduced cells, we intra-articularly administered AAV vectors encoding a soluble PD-L1 (shPD-L1) that allowed PD-L1 to be evenly distributed in joint fluid, and found a better improvement of arthritis when compared to wtPD-L1 with the same doses. Despite the improvement, a complete disappearance of pathological changes was not observed. The possible reason for the incomplete response with intra-articular AAV/shPD-L1 gene therapy could be given to the autoantibodies and inflammatory cytokines generated in the blood that are still able to migrate into the joint and then induce joint damage. Therefore, simply blocking the infiltration of immune cells in the joint may not be sufficient to inhibit joint damage mediated by autoantibodies or proinflammatory cytokines from the circulation. We hypothesize that systemic modulation of immune response with AAV/shPD-L1 administration would more efficiently block RA development or inhibit RA progress. It is well known from clinical trials that the liver-targeted delivery of AAV vectors induces liver toxicity in 30-50% of patients. In this study, we will explore the effect of AAV/shPD- L1 via muscular delivery on the progression or treatment of RA. The results from this proposal will provide valuable information about the therapeutic efficacy and safety of intra-muscular administration of AAV/shPD-L1 vectors in future clinical trials in patients with RA or other autoimmune disorders.