Photo-induced crosslinked and anti-PD-L1 peptide incorporated liposomes to promote PD-L1 multivalent binding for effective immune checkpoint blockade therapy

Immune checkpoint blockade (ICB) therapy targeting PD-L1 via monoclonal antibody (mAb) has shown extensive clinical benefits in the diverse types of advanced malignancies. However, most patients are completely refractory to ICB therapy owing to the PD-L1 recycling mechanism. Herein, we propose photo-induced crosslinked and anti-PD-L1 peptide incorporated liposomes (immune checkpoint blockade liposomes; ICB-LPs) to promote PD-L 1 multivalent binding for inducing lysosomal degradation of PD-L1 in tumor cells. The ICB-LPs are prepared by formulation of DC8,9PC with photo-polymerized diacetylenic moiety, 1,2-dipalmitoylphosphatidylcholine (DPPC) and anti-PD-L1 peptide (D-form NYSKPTDRQYHF)-conjugated DSPE-PEG2k (anti-PD-L1-DSPE-PEG2k) in a molar ratio of 45:45:10, followed by cross-linking of liposomal bilayer upon UV irradiation. The 10 mol% antiPD-L1-DSPE-PEG2k incorporated ICB-LPs have a nano-sized lipid bilayer structure with an average diameter of 137.7 +/- 1.04 nm, showing a high stability in serum condition. Importantly, the ICB-LPs efficiently promote the multivalent binding with PD -L1 on the tumor cell membrane, which are endocytosed with aim to deliver PD -L1 to the lysosomes, wherein the durable PD -L1 degradation is observed for 72 h, in contrast to anti PD -L1 mAbs showing the rapid PD -L1 recycling within 9 h. The in vitro coculture experiments with CD8 thorn T cells show that ICB-LPs effectively enhance the T cell -mediated antitumor immune responses against tumor cells by blocking the PD-L1/PD-1 axis. When ICB-LPs are intravenously injected into colon tumor -bearing mice, they efficiently accumulate within the targeted tumor tissues via both passive and active tumor targeting, inducing a potent T cell -mediated antitumor immune response by effective and durable PD -L1 degradation. Collectively, this study demonstrates the superior antitumor efficacy of crosslinked and anti -PD -L1 peptide incorporated liposome formulation that promotes PD -L1 multivalent binding for trafficking of PD -L1 toward the lysosomes instead of the recycling endosomes. 2024 The Authors. Published by Elsevier B.V. on behalf of Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. This is an open access article under the CC BY -NCND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).