CD274 and cancer: Yang et al. developed a new PROTAC compound, 21a, which significantly reduced PD-L1 protein levels in MC-38 cancer cells, thereby enhancing the infiltration of CD8 + T cells and inhibiting the in vivo growth of MC-38.508 Moreover, in 2020, Bertozzi’s group synthesized LYTAC Ab-3, incorporating polyclonal anti-mouse IgG and azide-terminated M6Pn glycopolypeptides via copper-free strain-promoted azide–alkyne cycloaddition.