PDCD1 and cancer: To date, seven ICIs have been approved by the FDA for various cancer types: anti-CTLA-4 mAb (ipilimumab), anti-PD-1 mAbs (pembrolizumab, nivolumab, cemiplimab) and anti-programmed cell death 1 ligand (PD-L1) mAbs (atezolizumab, durvalumab, avelumab) (Vaddepally et al. 2020).