PD-1 and PD-L1 inhibitors
A PD-L1 Inhibitor (PDL1I) is a novel type of drug which acts as an inhibitor for the Programmed death-ligand 1 (PD-L1), a protein that in humans has been speculated to play a major role in suppressing the immune system during particular events such as pregnancy, tissue allografts, autoimmune disease and other disease states such as hepatitis and many types of cancer. Many PD-L1 inhibitors are being successfully tested for advanced melanoma, non-small cell lung cancer, renal cell carcinoma, bladder cancer and Hodgkin lymphoma, amongst other tumor types.[1]
They work by targeting the physiologic checkpoints for immunomodulation creted by tumors, as it appears that upregulation of PD-L1 is the main mechanism that allows cancers to evade the host immune system. It is considered the most promising category of drug for many types of cancer.[2] Hence PD-L1 inhibitors are a type of immune checkpoint inhibitor.
Examples
PD-L1 inhibitors such as MPDL3280 and avelumab are currently undergoing clinical trials for treatment of various types of cancer; however, no PD-L1 inhibitors have been approved by the FDA.
PD-L1 inhibitors which bind the ligand on the extracellular surface of cancer cells in the neoplastic setting should not be confused with PD-1 inhibitors such as pembrolizumab (Keytruda) and nivolumab (Opdivo) which bind the receptor on the extracellular surface of T cells of the immune system.