**11. Importance of immune checkpoint inhibitors as monotherapy**

Immunotherapy stimulates the immune system by active immunization with cancer vaccines or passive immunization with tumor-specific antibodies and immune modulators, such as immune-checkpoint inhibitors. Immune checkpoints are a complex group of adaptive immune system regulatory points that play roles in self-tolerance and antitumor immunity. These checkpoints regulate the immune response in either a negative or positive way, coordinating the magnitude and form of response. Immune checkpoint inhibitors (ICIs) are regarded as the emerging immunotherapy superheroes, allowing a patient's self-immune cells to destroy tumors and remodeling cancer treatment in a board spectrum of cancers. The use of immune checkpoint inhibitors against programmed death receptor-1 (PD-1) or its ligand PD-L1 to treat a wide range of solid and hematologic tumors has dramatically altered the cancer treatment paradigm.

*Integrating Immunotherapy with Chemotherapy: A New Approach to Drug Repurposing DOI: http://dx.doi.org/10.5772/intechopen.100183*
