Peptide drugs: a new direction in cancer immunotherapy

Cancer immunotherapy has emerged as a promising approach in cancer treatment and is considered a major advancement after surgical interventions, radiotherapy, chemotherapy, and targeted therapy. The clinical use of immunotherapeutic drugs, particularly antibody-based drugs that target immune checkpoints, has notably increased~1.

多肽药物在肿瘤免疫治疗中的研究进展

免疫治疗是当前最受关注的肿瘤治疗方式之一,免疫检查点抑制剂、细胞治疗和肿瘤疫苗等免疫治疗手段,在临床上取得了重要进展。近年来,除了以单抗药物为代表的免疫检查点抑制剂以外,多肽药物也逐渐受到关注。本文着重总结多肽药物在免疫检查点抑制剂方面的研究进展及应用,包括单靶点多肽阻断剂、双功能多肽阻断剂、自组装多肽,以及免疫检查点多肽在肿瘤诊断中的应用等,并对多肽药物目前面临的瓶颈问题提出思考,为多肽药物在肿瘤免疫治疗中的应用提供新的思路。

Development of LAG-3/FGL1 blocking peptide and combination with radiotherapy for cancer immunotherapy

Aside from antibodies,peptides show great potential as immune checkpoint inhibitors(ICIs)due to several advantages,such as better tumor penetration and lower cost.Lymphocyte-activation gene 3(LAG-3)is an immune checkpoint which can induce T cell dysfunction through interaction with its soluble ligand fibrinogen like protein-1(FGL1).Here,we found that LAG-3 expression was higher than programmed cell death protein 1(PD-1)in multiple human cancers by TCGA databases,and successfully identified a LAG-3 binding peptide LFP-6 by phage display bio-panning,which specifically blocks the interaction of LAG-3/FGL1 but not LAG-3/MHC-II.Subsequently,D-amino acids were introduced to substitute the N-and C-terminus of LFP-6 to obtain the proteolysis-resistant peptide LFP-D1,which restores T cell function in vitro and inhibits tumor growth in vivo.Further,a bispecific peptide LFOP targeting both PD-1/PD-L1 and LAG-3/FGL1 was designed by conjugating LFP-D1 with PD-1/PD-L1blocking peptide OPBP-1(8-12),which activates T cell with enhanced proliferation and IFN-γ production.More importantly,LFOP combined with radiotherapy significantly improve the T cell infiltration in tumor and elevate systemic antitumor immune response.In conclusion,we developed a novel peptide blocking LAG-3/FGL1 which can restore T cell function,and the bispecific peptide synergizes with radiotherapy to further enhance the antitumor immune response.

Design of a novel chimeric peptide via dual blockade of CD47/SIRPαand PD-1/PD-L1 for cancer immunotherapy

Although immune checkpoint inhibition has been shown to effectively activate antitumor immunity in various tumor types,only a small subset of patients can benefit from PD-1/PD-L1 blockade.CD47 expressed on tumor cells protects them from phagocytosis through interaction with SIRPαon macrophages,while PD-L1 dampens T cell-mediated tumor killing.Therefore,dual targeting PD-L1 and CD47 may improve the efficacy of cancer immunotherapy.A chimeric peptide Pal-DMPOP was designed by conjugating the double mutation of CD47/SIRPαblocking peptide(DMP)with the truncation of PD-1/PD-L1 blocking peptide OPBP-1(8-12)and was modified by a palmitic acid tail.Pal-DMPOP can significantly enhance macrophage-mediated phagocytosis of tumor cells and activate primary T cells to secret IFN-γin vitro.Due to its superior hydrolysis-resistant activity as well as tumor tissue and lymph node targeting properties,Pal-DMPOP elicited stronger anti-tumor potency than Pal-DMP or OPBP-1(8-12)in immune-competent MC38 tumor-bearing mice.The in vivo anti-tumor activity was further validated in the colorectal CT26 tumor model.Furthermore,Pal-DMPOP mobilized macrophage and T-cell anti-tumor responses with minimal toxicity.Overall,the first bispecific CD47/SIRPαand PD-1/PD-L1 dual-blockade chimeric peptide was designed and exhibited synergistic anti-tumor efficacy via CD8^(+)T cell activation and macrophage-mediated immune response.The strategy could pave the way for designing effective therapeutic agents for cancer immunotherapy.

Identification and optimization of peptide inhibitors to block VISTA/PSGL-1 interaction for cancer immunotherapy

Developing new therapeutic agents for cancer immunotherapy is highly demanding due to the low response ratio of PD-1/PD-L1 blockade in cancer patients.Here,we discovered that the novel immune checkpoint VISTA is highly expressed on a variety of tumor-infiltrating immune cells,especially myeloid derived suppressor cells(MDSCs)and CD8^(+)T cells.Then,peptide C1 with binding affinity to VISTA was developed by phage displayed bio-panning technique,and its mutant peptide VS3 was obtained by molecular docking based mutation.Peptide VS3 could bind VISTA with high affinity and block its interaction with ligand PSGL-1 under acidic condition,and elicit anti-tumor activity in vivo.The peptide DVS3-Pal was further designed by D-amino acid substitution and fatty acid modification,which exhibited strong proteolytic stability and significant anti-tumor activity through enhancing CD8^(+)T cell function and decreasing MDSCs infiltration.This is the first study to develop peptides to block VISTA/PSGL-1 interaction,which could act as promising candidates for cancer immunotherapy.