Cancer Immunotherapy Targeting Co-signal Molecules

Great success of immune checkpoint blockade represented by anti-PD-1 monoclonal antibodies (mAbs) has changed a landscape of cancer immunotherapy. There is no doubt about an importance of co-signal molecules as one of the most promising targets in anti-cancer drugs. However, it should be noted that the proportion of patients who have objective and durable responses to immune checkpoint blockade remains less than 30% in majority of cancers. Thus, in addition to refine the usage of existing drugs for checkpoint blockade, identification and characterization of novel checkpoint molecules other than CTLA-4 and PD-1 is a highly anticipated research subject. In addition, agonists of stimulatory co-signal molecules have a potential to further improve anti-tumor effects, rendering them attractive in research and drug development. In this chapter, functions of co-signal molecules in anti-tumor immunity in terms of pre-clinical animal models as well as clinical trials are described.