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[Display omitted] • New A56 -based PROTACs target-degrading PD-L1 have been designed and synthesized. • Compounds 9i and 9j induce the internalization and degradation of PD-L1 in HCC-827 cells. • Compounds 9i and 9j degrade of PD-L1 through dual means of lysosome and proteasome. • The compounds have good anti-tumor activity by activating immunity in vivo. Currently, antibody drugs targeting programmed cell death ligand 1 (PD-L1) have achieved promising results in cancer treatment, while the development of small-molecule drugs lags behind. In this study, we designed and synthesized a series of PD-L1-degrading agents based on the PROTAC design principle, utilizing the PD-L1 inhibitor A56. Through systematic screening of ligands and linkers and investigating the structure–activity relationship of the degraders, we identified two highly active compounds, 9i and 9j. These compounds enhance levels of CD4+, CD8+, granzyme B, and perforin, demonstrating significant in vivo antitumor effects with a tumor growth inhibition (TGI) of up to 57.35 %. Both compounds facilitate the internalization of PD-L1 from the cell surface and promote its degradation through proteasomal and lysosomal pathways, while also maintaining inhibition of the PD-1/PD-L1 interaction. In summary, our findings provide a novel strategy and mechanism for developing biphenyl-based PROTAC antitumor drugs targeting and degrading PD-L1. [ABSTRACT FROM AUTHOR]