Immune Checkpoint Inhibitor Therapy in Cancer: Success versus Limitations

Abstract

The immune system possesses the capability to identify tumor cells and eradicate early malignant tumor cells. Thus, activating the immune system of cancer patients provides great therapeutic benefits. Inhibitory T-cell immune checkpoints play a vital role in tumor immune escape. Thus, immune checkpoint inhibitors (ICIs) have attracted attention in cancer immunotherapy. In ICI therapy, the therapeutic targets are the expressed immune checkpoints of T cells. Immune checkpoints induce T-cell dysfunction in cancer. However, ICIs or immunomodulators restore the antitumor actions of cytotoxic T cells by blocking immune checkpoints. ICIs have become desirable treatment options because of their broad range of activities and response rates ranging from 15% to 90% in several cancer types. Generally, ICIs also have favorable toxicity profiles. This paper will first delve deeper into the best-known immune checkpoints and then review ICIs that are attractive treatment options in immunotherapy.