A New PD-L1 Nanobody Enhances Cell Death in Lung Cancer In Vitro and In Vivo.

Background/aim: The development of immune checkpoint blockade (ICB) agents targeting programmed death protein 1(PD-1), PD-1 ligand (PD-L1), cytotoxic T-lymphocyte- associated protein 4 (CTLA-4), and CD40 has gained increasing interest in clinical cancer treatment. Among these targets, blocking of PD-1 binding to its ligand PD-L1 managed to induce immune responses and inhibit tumor growth. In this work, we aimed to screen a specific PD-L1 nanobody against human PD-L1, derived through phage display assay, and further study its biological characteristics and antitumor ability.

Materials and methods: Specific PD-L1 nanobody was screened through phage display and its biological characteristics were explored by surface plasmon resonance (SPR) analysis. In addition, its cytotoxicity and antitumor ability was confirmed in vitro and in vivo.

Results: After all, an anti-PD-L1 nanobody with high specificity and affinity was generated. This PD-L1 nanobody was highly specific for human PD-L1 and had strong penetration ability due to its size. PD-L1 nanobody enhanced immune cell-killing ability by inhibiting the immune checkpoint and further activating innate response. Furthermore, this new PD-L1 nanobody also had high binding affinity, as shown by its use in western blotting, flow cytometry staining and immunofluorescence staining methods.

Conclusion: The new PD-L1 nanobody substantially improved upon the FDA-approved PD-L1 monoclonal antibody by surpassing the disadvantage of having large molecular weight (MW) and low tissue penetration. The cytotoxicity and antitumor ability of PD-L1 nanobody, in vitro and in vivo, also support its potential as a therapeutic agent for lung cancer immunotherapy.