For example, antibodies against cytotoxic T-lymphocyte antigen 4 (CTLA4), programmed cell death protein 1 (PD-1) and its ligand (PD-L1) target immune checkpoints and activate immune cells to better fight cancers, such as melanoma (Robert et al., 2015; Marzagalli et al., 2019) and non-small-cell lung cancer (NSCLC) (Fehrenbacher et al., 2016; Sun et al., 2020). Here, PDCD1 is linked to melanoma.