Recently, the high-affinitymutant of the N-terminal domain ofPD-1, termed high-affinity consensus PD-1 (HAC-PD-1, hereafter), hasbeen developed and successfully investigated for immunotherapy andPET imaging of cancers overexpressing PD-L1.16 A limitation of this effective mutant is, however, its limited versatilityin terms of bioconjugation. This evidence concerns the gene PDCD1 and cancer.