靶向PD-1的多肽阻断剂的设计及评价

Currently cancer immunotherapy is one of the most popular cancer treatments. Programmed death receptor 1 /programmed death ligand-1 (PD-1/PD-L1) signaling pathway is an important immune checkpoint. Blocking the PD-1/PD-L1 signaling pathway can reactivate the exhausted T cells and enhance the immune response. Therefore, the PD-1/PD-L1 pathway has become one of the new targets in the development of anticancer drug. The monoclonal antibodies (mAbs) targeting the PD-1/PD-L1 pathway have showed remarkable clinical efficacy in various malignancies. Several mAbs targeting PD-1 (nivolumab and pembrolizumab) and PD-L1 (atezolizumab, avelumab and durvalumab) have been approved by Food and Drug Administration (FDA) for cancer therapy. However, the disadvantages of antibody drugs, such as high production cost, low stability and immunogenicity, limit their clinical applications. Therefore, discovery of low-molecular-weight blockers that disrupting the PD-1/PD-L1 pathway may provide alternatives for addressing these issues. In this study, we used the E.coli expression system to express the extracellular domain of PD-1 and obtained the recombinant PD-1 after the refolding and purification process. We designed one peptide P5-1 by computer-aided drug design, which showed a K_D value of 0.21 μmol/L with PD-1. The Surface Plasmon Resonance (SPR) competitive binding assay indicated that the peptide P5-1 could block the interaction between PD-1 and PD-L1. Subsequently, we assessed the effect of the peptide P5-1 on IL-2 production of Jurkat T cells. The addition of IFN-γ pretreated BxPC-3 cells led to significant decrease in the Jurkat T cells production of IL-2, while the addition of the peptide P5-1 could restore the IL-2 production. These results suggest that the peptide P5-1 can restore the suppressed function of Jurkat T cells by blocking the interaction between PD-1 and PD-L1. Our study provided a basis on developing peptide blockers targeting PD-1 as durg candidates for cancer immunotherapy.