PD-1-Blocking Compounds and CTLA-4-Blocking Compounds
Checkpoint inhibitors can be divided into two different groups: PD1-blocking and PD2-blocking compounds. The first group includes drugs that kill PD-1 or programmed cell death protein 1, which can be found on the outside of cancerous and immune cells, and PD-L1, the ligand of PD-1. By inhibiting the PD-1 checkpoint, they would improve the response of the immune system to cancerous cells. This helps the body identify and kill them more effectively. Six immunotherapy drugs that block PD-1 have been proved, including durvalumab, atezolizumab, nivolumab, pembrolizumab, avelumab, and cemiplimab. [4]
As the name implies, CTLA-4-blocking compounds work by killing CTLA-4 or cytotoxic T-lymphocyte antigen-4, a checkpoint that is responsible for regulating the activity of cytotoxic T lymphocytes. These are specialized cells in the immune system that play a key role in killing and eliminating harmful components from the body, including cancerous cells. Ipilimumab is the only type of CTLA-4-blocking medication that has been currently approved by the FDA for treating small cell lung cancer. [5]
