Currently immunotherapy is becoming a fairly effective approach in the fight against various forms of malignant neoplasms. This is due to the discovery and use in clinical practice immune checkpoint inhibitors, which antitumoral effect is associated with blockage the signaling pathways CTLA-4 (cytotoxic T-lymphocyte associated protein 4), PD-1 (programmed cell death protein 1), PD-L1 (programmed cell death ligand 1). The physiological role of immune points is to prevent autoimmune tissue damage by suppressing effectors. How- ever, cancer cells have adapted for using this mechanism to avoid elimination by escape mechanisms from immuno- logical surveillance. This gave impetus to the development of drugs that can inhibit checkpoints, enabling the immune system to destroy tumor cells. Actually, 7 drugs have been registered, which can be divided into three groups according to the mechanism of action: CTLA-4 (pilimumab), PD-1 (nivolumab, pembrolizumab, prolgolimab) and PD-L1 (atezoli- zumab, avelumab, durvalumab) inhibitors. The medicine of the first group inhibits the cellular response at the stage of its activation. The mechanism of action of the second and third groups medicines is aimed at blocking the binding of the PD-1 receptor of lymphocytes and monocytes with PD-L1 ligands and vice versa. The use of immune checkpoint inhibitors can lead to the occurrence of immune-mediated adverse reactions, the nature and frequency of which differ depending on the class of inhibitors. In this regard, timely diagnosis and treatment of complications is the key to the success of anticancer therapy.