CD274 and neoplasm: Similarly, a second class of approved antibodies target PD-1 (pembrolizumab, nivolumab, cemiplimab), a second checkpoint receptor or its ligand PD-L1 (atezolizumab, avelumab, durvalumab), which are thought to augment anti-tumor immunity by reinvigorating PD-1-expressing, exhausted tumor-specific CD8+ T cells [17,46,47].