MP7 functionally inhibited PD-L1-mediated suppression of IL-2 secretion in primary T lymphocytes, while a PEGylated form of MP7 retained the ability to block the PD-1–PD-L1 interaction, and significantly suppressed the growth of PD-L1+ colon carcinoma cells in vivo with a potency equivalent to an anti-PD-1 antibody. This evidence concerns the gene PDCD1 and colon carcinoma.