Multiplexed repression of immunosuppressive genes as combinatorial cancer immunotherapy

Abstract

Checkpoint blockade immunotherapy is a potent class of cancer treatment, however, the complex immunosuppressive tumor microenvironment (TME) often requires multi-agent combinations to be effective. Current cancer immunotherapy combination approaches are cumbersome, usually involving one-drug-at-a-time scheme. Here, we devise Multiplex Universal Combinatorial Immunotherapy via Gene-silencing (MUCIG), as a versatile approach for combinatorial cancer immunotherapy. We harness CRISPR-Cas13d to efficiently target multiple endogenous immunosuppressive genes on demand, allowing us to silence various combinations of multiple immunosuppressive factors in the TME. Intratumoral AAV-mediated administration of MUCIG (AAV-MUCIG) elicits significant anti-tumor activity with several Cas13d gRNA compositions. TME target expression analysis driven optimization led to a simplified off-the-shelf MUCIG targeting a four gene combination (PGGC: Pdl1, Galectin9, Galectin3 and Cd47). AAV-PGGC shows significant in vivo efficacy in syngeneic tumor models. Single cell and flow profiling revealed that AAV-PGGC remodeled the TME by increasing CD8+ T cell infiltration and reducing myeloid-derived immunosuppressive cells (MDSCs). MUCIG thus serves as a universal method to silence multiple immune genes in vivo, and can be delivered via AAV as a therapeutic approach.