Unlike targeted therapies, which target a specific pathway thought to be involved in cancer growth, the goal of cancer immunotherapy is to activate the body's immune system. As they grow, many tumors gain the ability to suppress the immune system by turning off nearby T-cells. A new class of immunotherapies called checkpoint inhibitors help "release the brakes" of the immune system, by allowing T-cells to operate efficiently. A number of checkpoint inhibtors, including those against CTLA4, PD-1, and PD-L1, are now avaialble, and many others are being developed.
Another class of cancer immunotherapies being developed are the oncolytic viruses. These are viruses that have been genetically engineered to target and kill cancer cells. In addition to directly attacking cancer cells, oncolytic therapies activate the immune system by sensitizing and activating T-cells against the tumor. Imlygic, developed by BioVex and Amgen, is the first oncolytic virus to be available, approved by FDA and EMA in Q4-2015. Results have been very promising, particularly in combination with checkpoint inhibitors like CTLA-4 and PD-1.
