The present invention relates to the combination therapy of NDV and anti-PD-1 antibodies for the treatment of cancer. Further described herein are chimeric Newcastle disease viruses engineered to express an agonist of a co-stimulatory signal of an immune cell and compositions comprising such viruses. Also described herein are chimeric Newcastle disease viruses engineered to express an antagonist of an inhibitory signal of an immune cell and compositions comprising such viruses. The chimeric Newcastle disease viruses and compositions are useful in the treatment of cancer. In addition, described herein are methods for treating cancer comprising administering Newcastle disease viruses in combination with an agonist of a co-stimulatory signal of an immune and/or an antagonist of an inhibitory signal of an immune cell.
