Oncolytic viruses can selectively kill cancer cells and cancer-promoting cells, either directly by binding and infecting them, or indirectly by eliciting a targeted immune response against them. UPCI investigators have been examining the anti-cancer efficacy of an immune-stimulating vaccinia virus, vvDD, and found it to be safe in humans in a phase I clinical trial. However, the overall anti-cancer effects of this treatment were limited, especially in certain tumor types that are not commonly infiltrated by immune cells, such as colorectal cancer.
In recent pre-clinical studies, a research team demonstrated that vvDD treatment caused tumor and immune cells to increase production of the protein PD-L1, which is involved in immune suppression. When the investigators then combined vvDD therapy with a targeted checkpoint inhibitor that blocks PD-L1, they observed a synergistic effect in which over 40% of aggressive colon and ovarian cancers were cured in mice.