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.

Hemin blocks TIGIT/PVR interaction and induces ferroptosis to elicit synergistic effects of cancer immunotherapy

The immune checkpoint TIGIT/PVR blockade exhibits significant antitumor effects through activation of NK and CD8^(+)T cell-mediated cytotoxicity.Immune checkpoint blockade(ICB)could induce tumor ferroptosis through IFN-γreleased by immune cells,indicating the synergetic effects of ICB with ferroptosis in inhibiting tumor growth.However,the development of TIGIT/PVR inhibitors with ferroptosis-inducing effects has not been explored yet.In this study,the small molecule Hemin that could bind withTIGIT to block TIGIT/PVR interaction was screened by virtual molecular docking and cell-based blocking assay.Hemin could effectively restore the IL-2 secretion from Jurkat-hTIGIT cells.Hemin reinvigorated the function of CD8^(+)T cells to secrete IFN-γand the elevated IFN-γcould synergize with Hemin to induce ferroptosis in tumor cells.Hemin inhibited tumor growth by boosting CD8^(+)T cell immune response and inducing ferroptosis in CT26 tumor model.More importantly,Hemin in combination with PD-1/PD-L1 blockade exhibited more effective antitumor efficacy in anti-PD-1 resistant B16 tumor model.In summary,our finding indicated that Hemin blocked TIGIT/PVR interaction and induced tumor cell ferroptosis,which provided a new therapeutic strategy to combine immunotherapy and ferroptosis for cancer treatment.

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.

A novel cyclic peptide targeting LAG-3 for cancer immunotherapy by activating antigenspecific CD8^+ T cell responses

PD-1 and CTLA-4 antibodies offer great hope for cancer immunotherapy.However,many patients are incapable of responding to PD-1 and CTLA-4 blockade and show low response rates due to insufficient immune activation.The combination of checkpoint blockers has been proposed to increase the response rates.Besides,antibody drugs have disadvantages such as inclined to cause immune-related adverse events and infiltration problems.In this study,we developed a cyclic peptide C25 by using Ph.D.-C7C phage display technology targeting LAG-3.As a result,C25 showed a relative high affinity with human LAG-3 protein and could effectively interfere the binding between LAG-3 and HLA-DR(MHC-II).Additionally,C25 could significantly stimulate CD8^+T cell activation in human PBMCs.The results also demonstrated that C25 could inhibit tumor growth of CT26,B16 and B 16-OVA bearing mice,and the infiltration of CD8^+T cells was significantly increased while FOXP3^+Tregs significantly decreased in the tumor site.Furthermore,the secretion of IFN-γby CD8^+T cells in spleen,draining lymph nodes and especially in the tumors was promoted.Simultaneously,we exploited T cells depletion models to study the anti-tumor mechanisms for C25 peptide,and the results combined with MTT assay confirmed that C25 exerted anti-tumor effects via CD8+T cells but not direct killing.In conclusion,cyclic peptide C25 provides a rationale for targeting the immune checkpoint,by blockade of LAG-3/HLA-DR interaction in order to enhance anti-tumor immunity,and C25 may provide an alternative for cancer immunotherapy besides antibody drugs.

Tryptophan 2,3-dioxygenase 2 controls M2 macrophages polarization to promote esophageal squamous cell carcinoma progression via AKT/GSK3β/IL-8 signaling pathway

Tryptophan 2,3-dioxygnease 2(TDO2) is specific for metabolizing tryptophan to kynurenine(KYN),which plays a critical role in mediating immune escape of cancer.Although accumulating evidence demonstrates that TDO2 overexpression is implicated in the development and progression of multiple cancers,its tumor-promoting role in esophageal squamous cell carcinoma(ESCC) remains unclear.Here,we observed that TDO2 was overexpressed in ESCC tis sues and correlated significantly with lymph node metastasis,advanced clinical stage,and unfavorable prognosis.Functional experiments showed that TDO2 promoted tumor cell proliferation,migration,and colony formation,which could be prevented by inhibition of TDO2 and aryl hydrocarb on receptor(AHR).Further experimentation demonstrated that TDO2 could promote the tumor growth of KYSE150 tumor-bearing model,tumor burden of C57 BL/6 mice with ESCC induced by 4-NQO,enhance the expression of phosphorylated AKT,with subsequent pho sphorylation of GSK3β,and polarization of M2 macrophages by upregulating interleukin-8(IL-8) to accelerate tumor progression in the tumor microenvironment(TME).Collectively,our results discovered that TDO2 could upregulate IL-8 through AKT/GSK3β to direct the polarization of M2 macrophages in ESCC,and suggested that TDO2 could represent as an attractive therapeutic target and prognostic marker to ESCC.

Blocking of the PD-1/PD-L1 interaction by a novel cyclic peptide inhibitor for cancer immunotherapy

The interaction of PD-1/PD-L1 allows tumor cells to escape from immune surveillance.Clinical success of the antibody drugs has proven that blockade of PD-1/PD-L1 pathway is a promising strategy for cancer immunotherapy.Here,we developed a cyclic peptide C8 by using Ph.D.-C7 C phage display technology.C8 showed high binding affinity with h PD-1 and could effectively interfere the interaction of PD-1/PD-L1.Furthermore,C8 could stimulate CD8^(+)T cell activation in human peripheral blood mononuclear cells(PBMCs).We also observed that C8 could suppress tumor growth in CT26 and B16-OVA,as well as anti-PD-1 antibody resistant B16 mouse model.CD8^(+)T cells infiltration significantly increased in tumor microenvironment,and IFN-γsecretion by CD8^(+)T cells in draining lymph nodes also increased.Simultaneously,we exploited T cells depletion models and confirmed that C8 exerted anti-tumor effects via activating CD8^(+)T cells dependent manner.The interaction model of C8 with h PD-1 was simulated and confirmed by alanine scanning.In conclusion,C8 shows anti-tumor capability by blockade of PD-1/PD-L1 interaction,and C8 may provide an alternative candidate for cancer immunotherapy.

Screening and identification of HLA-A2-restricted neoepitopes for immunotherapy of non-microsatellite instability-high colorectal cancer

Colorectal cancer has one of the highest mortality rates among malignant tumors,and most patients with non-microsatellite instability-high (MSI-H) colorectal cancer do not benefit from targeted therapy or immune checkpoint inhibitors.Identification of immunogenic neoantigens is a promising strategy for inducing specific antitumor T cells for cancer immunotherapy.Here,we screened potential high-frequency neoepitopes from non-MSI-H colorectal cancer and tested their abilities to induce tumorspecific cytotoxic T cell responses.Three HLA-A2-restricted neoepitopes (P31,P50,and P52) were immunogenic and could induce cytotoxic T lymphocytes in peripheral blood mononuclear cells from healthy donors and colorectal cancer patients.Cytotoxic T lymphocytes induced in HLA-A2.1/K^(b) transgenic mice could recognize and lyse mutant neoepitope-transfected HLA-A2^(+) cancer cells.Adoptive transfer of cytotoxic T lymphocytes induced by the peptide pool of these three neoepitopes effectively inhibited tumor growth and increased the therapeutic effects of anti-PD-1 antibody.These results revealed the potential of high-frequency mutation-specific peptide-based immunotherapy as a personalized treatment approach for patients with non-MSI-H colorectal cancer.The combination of adoptive T cell therapy based on these neoepitopes with immune checkpoint inhibitors,such as anti-PD-1,could provide a promising treatment strategy for non-MSI-H colorectal cancer.