Tumors deploy multiple parallel mechanisms that synergize – meaning that they work together to get more bang for their buck. In this way, tumors are able to subvert the immune response and protect themselves from being eradicated by the immune system. Thus, we need to similarly deploy multiple parallel synergistic mechanisms to re-program the immune response – to re-hijack it from tumors.
It is very rare that you find a patient with a tumor that has a dominant immune checkpoint – where you can simply reverse that one mechanism and see an effect. To put it frankly, we need to move towards combination approaches in immunotherapy.