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The immune system normally responds to foreign proteins, including tumor cells; however, in patients with cancer, this mechanism is not functional, explains Brian I. Rini, MD. In the past, immunotherapy primarily worked by activating the immune system using cytokines, such as interluekin-2. These therapies were nonspecific, worked in a handful of patients, and were accompanied by side effects, Rini notes.
The new wave of immunotherapy is more specific than traditional cytokine therapies through the selective inhibition of immune checkpoints, notes Rini. The most promising of these novel targeted immunotherapies are those that block PD-1 and PD-L1. By inhibiting these checkpoints, these treatments remove the brakes from the immune system, stimulating an antitumor immune response, Rini states.