双特异性抗体及其在肿瘤治疗中的应用

双特异性抗体（BsAb）是改造抗体治疗效果的发展方向之一,现已成为抗体工程研究领域的热点。在过去20年的研究中．研究人员看到了常规BsAb的潜能以及它的不足。随着分子生物学技术的迅速发展,出现了利用基因工程手段构建的BsAb的多种模式,并且有多种BsAb制剂已经用于肿瘤的初期临床诊断和治疗。该文对BsAb最新的研究进展和肿瘤治疗中的应用进行了阐述。     

双特异性抗体的结构及应用研究进展

双特异性抗体(bi-specific antibody,BsAb)是具有双功能的抗体分子,可同时结合两种不同的抗原或表位,将T细胞和自然杀伤细胞重定向到肿瘤细胞,在功能分子(细胞)和靶细胞之间架起桥梁,产生导向性作用。目前,BsAb已广泛应用于癌症、炎症、病毒感染及其他疾病的治疗。现就BsAb的结构、应用等方面的研究进展作一综述。     

双特异性抗体靶向治疗及动物模型的设计

由于双特异性抗体可以同时结合两种不同的抗原,因此和传统的单克隆抗体相比,往往可以更好的发挥靶向治疗的作用.随着各种生物技术的发展,不同靶向的双特异性抗体被构建出来并被用于肿瘤治疗的研究.本文综述了人工产生的双特异性抗体在靶向治疗中的进展,并且探讨了用于肿瘤治疗的动物模型的建立.     

双特异性抗体在肿瘤治疗中的研究

双特异性抗体(bispecific antibody,BsAb)有两个抗原结合位点,其中一个位点可与靶细胞表面抗原结合,另一个位点则可与载荷物(如效应细胞,分子等)结合。将BsAb应用于肿瘤治疗,发挥抗肿瘤效应的思想已有二十多年历史,随着对效应细胞生物学了解的加深和抗体工程的飞速发展,各种形式的BsAb相继出现,多种BsAb药物已进入临床初期试验或治疗使用阶段。本文就BsAb的各种新形式及其在肿瘤治疗中的应用新进展作简要概述。     

基于单克隆抗体的肿瘤免疫疗法研究进展

一百多年前,"魔术子弹"学说首次提出了具有靶向特异性的抗体可以用来治疗疾病。此后,随着单克隆抗体制备技术的成熟,以及癌症血清疗法的发展,靶向肿瘤抗原的治疗性抗体开始进入临床,至今已有20余种抗体药物用于癌症的治疗。近两年,以免疫检查点蛋白拮抗剂、双特异性抗体、抗体药物偶联药物等为代表的新一代抗体药物,不断在治疗恶性肿瘤上取得突破性进展。本文回顾了抗肿瘤抗体的发展历程,总结了新一代抗体药物的作用机制与构建策略,以及主要临床副作用。并对基于抗体的肿瘤免疫疗法未来发展趋势进行了展望。     

抗α2δ1/CD3双特异性抗体的制备和功能的初步研究

目的:构建抗α2δ1和CD3的双特异性抗体,并在体外初步评价其杀伤肝癌细胞的功能。方法:通过基因工程技术,构建BiTE形式的anti-α2δ1/CD3双特异性抗体(BsAb),转染Expi 293F细胞96h后,使用镍离子亲和色谱纯化出双特异性抗体,使用流式细胞术检测anti-α2δ1/CD3BsAb对α2δ1和CD3的结合性质,使用Perkin Elmer Operetta高内涵成像仪测定anti-α2δ1/CD3BsAb介导细胞毒性T淋巴细胞(CTLs)对高表达α2δ1的人肝癌细胞Hep-12的杀伤效应,ELISA法检测杀伤过程中CTLs分泌hIL-2和hIFN-γ的变化。结果:anti-α2δ1/CD3 BsAb可以特异性结合α2δ1和CD3,anti-α2δ1/CD3 BsAb可以有效介导CTLs靶向杀伤高表达α2δ1的人肝癌细胞Hep-12,其介导杀伤Hep-12细胞的EC_(50)为8pmol/L,对于低表达α2δ1的人肝癌细胞Hep-11,anti-α2δ1/CD3 BsAb不能介导CTLs发挥杀伤作用,并且在杀伤过程中Hep-12细胞组CTLs释放的hIL-2和h IFN-γ比Hep11细胞组显著增多(P 0.05)。结论:anti-α2δ1/CD3 BsAb能有效介导CTLs体外杀伤高表达α2δ1的人肝癌细胞Hep-12,为双特异性抗体的肝癌免疫治疗奠定了一定的基础。     

HIV双特异性抗体研究进展

双特异性抗体(bispecific antibody,BsAb)是一种人工制备的非自然抗体。该抗体含两种特异性结合位点,能在抗原抗体反应的同时结合多种功能分子与细胞,从而介入引导免疫反应的方向。上述特性使BsAb在对抗人免疫缺陷病毒(human immunodeficiency virus,HIV)时具有广谱效能。目前,BsAb已成为抗HIV研究领域中的一大热点。现就BsAb在抗HIV病毒中表位的设计选择与优化、作用机制等方面的研究进展作一概述。     

抗体Fc片段特异寡核苷酸配基介导的实时定量免疫PCR

目的:利用小鼠IgG抗体Fc片段高特异、高亲和寡核苷酸配基,构建实时定量免疫PCR检测方法,提高抗体检测的灵敏度。方法:用SELEX技术从随机寡核苷酸文库中筛选抗体Fc片段特异寡核苷酸配基,设计合成信标序列,通过不对称PCR法,制备IgG Fc片段的核酸信标配基分子;32P标记核酸信标配基,采用琼脂糖凝胶阻滞双显色法鉴定核酸信标配基与IgG Fc片段结合的亲和力和特异性;制备IgG Fc特异性寡核苷酸信标配基-抗体复合检测分子,构建小鼠IgG Fc片段特异核酸信标配基介导的实时定量免疫PCR检测方法。结果:制备了IgG Fc片段的核酸信标配基分子;凝胶阻滞放射自显影和考马斯亮蓝二次染色结果显示该核酸信标配基分子与IgG Fc片段具有高度亲和力和活性,而且只与非变性IgG结合,与变性IgG不结合;IgG Fc片段的特异核酸信标配基与IgG结合形成复合检测分子,有效完成了信号传递和实时定量PCR信号放大过程。结论:初步建立了一种全新的核酸信标配基介导的免疫PCR检测方法,可有效提高现有IgG类抗体免疫检测的灵敏度和特异性。     

新型抗体药物在肝细胞癌免疫治疗中的研究进展

肝细胞癌(hepatocellular carcinoma, HCC)免疫疗法中最常用的是Ig G单克隆抗体(monoclonal antibodies,mAbs),其具有血清半衰期长、稳定性高、靶向能力强等优点。单克隆抗体药物在临床取得的重大进展推动了各种新型治疗性抗体的发展,例如抗体-药物偶联物、放射性核素标记抗体、小分子抗体、双特异性细胞激动剂、免疫细胞因子、免疫毒素以及免疫促凋亡分子等。近年来抗体的小型化和多功能化是在复杂肿瘤微环境中治疗HCC的富有临床潜力的策略。该文总结了各种类型的新型抗体的结构、作用机制及其在HCC免疫治疗中的研究进展,并对其应用前景进行展望。     

双特异性抗体药物应用进展

基因工程的飞速发展推动了新型双功能抗体药物的成功研制。目前双功能抗体药物主要应用于肿瘤的免疫治疗、自身免疫疾病和感染类疾病的治疗,在组织再生和临床诊断领域也有应用。就双特异性抗体的发展史进行了简要回顾,对其在免疫治疗、组织再生和临床诊断等领域中的应用进展进行了综述,并展望了未来的发展方向,以期为新型双特异性抗体药物的研制提供参考。     

肿瘤浸润淋巴细胞在实体肿瘤中作用的研究进展

肿瘤是21世纪威胁人类健康的主要疾患之一。临床上,实体瘤治疗仍以手术切除、放化疗和靶向治疗为主,但这些方法往往不能根除肿瘤病灶,易导致肿瘤复发和进展。肿瘤免疫治疗是利用人体的免疫系统,通过增强或恢复抗肿瘤免疫力实现控制和杀伤肿瘤的一种新的治疗模式。肿瘤免疫治疗能够在众多患者中产生持久反应,过继性免疫治疗和免疫检查点阻断剂治疗均可产生显著的抗原特异性免疫反应。肿瘤浸润淋巴细胞(TILs)是一种存在于肿瘤组织内部具有高度异质性的淋巴细胞,在宿主抗原特异性肿瘤免疫应答中发挥关键作用。最新研究表明,在肿瘤发生和治疗过程中,TILs的亚群组成和数量与患者预后密切相关;抗肿瘤的TILs介导的过继性免疫治疗方法已在多种实体瘤中取得了良好的疗效。文中就实体肿瘤中TILs的研究进展作一综述。     

肿瘤免疫治疗研究现状及发展趋势

肿瘤免疫治疗是继传统的手术、化疗、放疗之后的一种新兴的肿瘤治疗手段,因其具有特异性高、疗效显著等优点而备受学者们的关注。随着对肿瘤微环境和肿瘤逃逸机制的深入了解,调动机体免疫系统去抵御肿瘤逐渐成为一种新的研究方向。肿瘤免疫治疗主要包括特异性疗法和非特异性疗法,目前以肿瘤疫苗和单克隆抗体为代表的特异性免疫疗法在临床上得到广泛应用,并显示出良好的发展前景。但肿瘤免疫治疗仍存在认识不足、临床适应证有限等问题,与此同时,我国肿瘤免疫治疗的发展较国外仍相对不足且面临一些特殊的问题。本文将对目前已有的肿瘤免疫治疗方法及评价体系进行综述,并对一些新的技术手段和治疗思路展开讨论,此外还将结合国内外最新研究进展深入探讨这一新兴疗法的缺陷及未来的发展趋势。     

A Novel Bispecific Antibody against Human CD3 and Ephrin Receptor A10 for Breast Cancer Therapy

Ephrin receptor A10 (EphA10), a transmembrane receptor that binds to ephrin, is a newly identified breast cancer marker protein that has also been detected in HER2-negative tissue. In this study, we report creation of a novel bispecific antibody (BsAb) binding both EphA10 and CD3, thereby forming a bridge between antigens expressed on both tumor and immune cells and promoting recognition of tumor cells by immune cells and redirection of cytotoxic T cells (CTL). This BsAb (EphA10/CD3) was expressed in supernatants of BsAb gene-transfected cells as monomeric and dimeric molecules. Redirected T-cell lysis was observed when monomeric and dimeric BsAb were added to EphA10-overexpressing tumor cells in vitro. Furthermore, dimeric BsAb (EphA10/CD3) was more cytotoxic than monomeric BsAb, with efficient tumor cell lysis elicited by lower concentrations (≤10⁻¹ μg/mL) and a lower effector to target (E/T) cell ratio (E/T = 2.5). Dimeric BsAb (EphA10/CD3) also showed significant anti-tumor effects in human xenograft mouse models. Together, these results revealed opportunities to redirect the activity of CTL towards tumor cells that express EphA10 using the BsAb (EphA10/CD3), which could be tested in future clinical trials as a novel and potent therapeutic for breast cancer tumors.     

Single variable domain-IgG fusion. A novel recombinant approach to Fc domain-containing bispecific antibodies

Both laboratory and early clinical studies to date have demonstrated that bispecific antibodies (BsAb) may have potentially significant application in cancer therapy. The clinical development of BsAb as therapeutics has been hampered, however, by the difficulty in preparing the materials in sufficient quantity and quality by traditional methods. In recent years, a variety of recombinant methods has been developed for efficient production of BsAb, both as antibody fragments and as full-length IgG-like molecules. Here we describe a novel recombinant approach for the production of an Fc domain-containing, IgG-like tetravalent BsAb, with two antigen-binding sites to each of its target antigens, by genetically fusing a single variable domain antibody to the N terminus of the light chain of a functional IgG antibody of different specificity. A model BsAb was constructed using a single variable domain antibody to mouse platelet-derived growth factor receptor alpha and a conventional IgG antibody to mouse vascular endothelial growth factor receptor 2. The BsAb was expressed in mammalian cells and purified to homogeneity by one-step protein A affinity chromatography. Furthermore, the BsAb retains the antigen binding specificity and the receptor neutralizing activity of both of its parent antibodies. This design and expression of Fc domain-containing, IgG-like BsAb should be applicable to the construction of similar BsAb from antibodies recognizing any pair of antigens.     

Nanocell targeting using engineered bispecific antibodies

There are many design formats for bispecific antibodies (BsAbs), and the best design choice is highly dependent on the final application. Our aim was to engineer BsAbs to target a novel nanocell (EnGeneIC Delivery Vehicle or EDV^TMnanocell) to the epidermal growth factor receptor (EGFR). EDV^TMnanocells are coated with lipopolysaccharide (LPS), and BsAb designs incorporated single chain Fv (scFv) fragments derived from an anti-LPS antibody (1H10) and an anti-EGFR antibody, ABX-EGF. We engineered various BsAb formats with monovalent or bivalent binding arms and linked scFv fragments via either glycine-serine (G4S) or Fc-linkers. Binding analyses utilizing ELISA, surface plasmon resonance, bio-layer interferometry, flow cytometry and fluorescence microscopy showed that binding to LPS and to either soluble recombinant EGFR or MDA-MB-468 cells expressing EGFR, was conserved for all construct designs. However, the Fc-linked BsAbs led to nanocell clumping upon binding to EDV^TMnanocells. Clumping was eliminated when additional disulfide bonds were incorporated into the scFv components of the BsAbs, but this resulted in lower BsAb expression. The G4S-linked tandem scFv BsAb format was the optimal design with respect to EDV binding and expression yield. Doxorubicin-loaded EDV^TMnanocells actively targeted with tandem scFv BsAb in vivo to MDA-MB-468-derived tumors in mouse xenograft models enhanced tumor regression by 40% compared to passively targeted EDV^TMnanocells. BsAbs therefore provide a functional means to deliver EDV^TMnanocells to target cells.     

A stable IgG-like bispecific antibody targeting the epidermal growth factor receptor and the type I insulin-like growth factor receptor demonstrates superior anti-tumor activity

The epidermal growth factor receptor (EGFR) and the type I insulin-like growth factor receptor (IGF-1R) are two cell surface receptor tyrosine kinases known to cooperate to promote tumor progression and drug resistance. Combined blockade of EGFR and IGF-1R has shown improved anti-tumor activity in preclinical models. Here, we report the characterization of a stable IgG-like bispecific antibody (BsAb) dual-targeting EGFR and IGF-1R that was developed for cancer therapy. The BsAb molecule (EI-04), constructed with a stability-engineered single chain variable fragment (scFv) against IGF-1R attached to the carboxyl-terminus of an IgG against EGFR, displays favorable biophysical properties for biopharmaceutical development. Biochemically, EI-04 bound to human EGFR and IGF-1R with sub nanomolar affinity, co-engaged the two receptors simultaneously, and blocked the binding of their respective ligands with similar potency compared to the parental monoclonal antibodies (mAbs). In tumor cells, EI-04 effectively inhibited EGFR and IGF-1R phosphorylation, and concurrently blocked downstream AKT and ERK activation, resulting in greater inhibition of tumor cell growth and cell cycle progression than the single mAbs. EI-04, likely due to its tetravalent bispecific format, exhibited high avidity binding to BxPC3 tumor cells co-expressing EGFR and IGF-1R, and consequently improved potency at inhibiting IGF-driven cell growth over the mAb combination. Importantly, EI-04 demonstrated enhanced in vivo anti-tumor efficacy over the parental mAbs in two xenograft models, and even over the mAb combination in the BxPC3 model. Our data support the clinical investigation of EI-04 as a superior cancer therapeutic in treating EGFR and IGF-1R pathway responsive tumors.     

Nanocell targeting using engineered bispecific antibodies

There are many design formats for bispecific antibodies (BsAbs), and the best design choice is highly dependent on the final application. Our aim was to engineer BsAbs to target a novel nanocell (EnGeneIC Delivery Vehicle or EDV^TMnanocell) to the epidermal growth factor receptor (EGFR). EDV^TMnanocells are coated with lipopolysaccharide (LPS), and BsAb designs incorporated single chain Fv (scFv) fragments derived from an anti-LPS antibody (1H10) and an anti-EGFR antibody, ABX-EGF. We engineered various BsAb formats with monovalent or bivalent binding arms and linked scFv fragments via either glycine-serine (G4S) or Fc-linkers. Binding analyses utilizing ELISA, surface plasmon resonance, bio-layer interferometry, flow cytometry and fluorescence microscopy showed that binding to LPS and to either soluble recombinant EGFR or MDA-MB-468 cells expressing EGFR, was conserved for all construct designs. However, the Fc-linked BsAbs led to nanocell clumping upon binding to EDV^TMnanocells. Clumping was eliminated when additional disulfide bonds were incorporated into the scFv components of the BsAbs, but this resulted in lower BsAb expression. The G4S-linked tandem scFv BsAb format was the optimal design with respect to EDV binding and expression yield. Doxorubicin-loaded EDV^TMnanocells actively targeted with tandem scFv BsAb in vivo to MDA-MB-468-derived tumors in mouse xenograft models enhanced tumor regression by 40% compared to passively targeted EDV^TMnanocells. BsAbs therefore provide a functional means to deliver EDV^TMnanocells to target cells.     

Simultaneous blockade of both the epidermal growth factor receptor and the insulin-like growth factor receptor signaling pathways in cancer cells with a fully human recombinant bispecific antibody

Both the epidermal growth factor receptor (EGFR) and the insulin-like growth factor receptor (IGFR) have been implicated in the tumorigenesis of a variety of human cancers. Effective tumor inhibition has been achieved both experimentally and clinically with a number of strategies that antagonize either receptor activity. Here we constructed and produced two fully human recombinant bispecific antibodies (BsAb) that target both EGFR and IGFR, using two neutralizing human antibodies originally isolated from a phage display library. The BsAb not only retained the antigen binding capacity of each of the parent antibodies, but also were capable of binding to both targets simultaneously as demonstrated by a cross-linking enzyme-linked immunosorbent assay. Furthermore, the BsAb effectively blocked both ligands, EGF and IGF, from binding to their respective receptors, and inhibited tumor cell proliferation as potently as a combination of both the parent antibodies. More importantly, the BsAb were able to completely block activation of several major signal transduction molecules, including Akt and p44/p42 MAP kinases, by both EGF and IGF, whereas each individual parent antibody was only effective in inhibiting those signal molecules activated by the relevant single growth factor. The BsAb molecules retained good antigen binding activity after incubation with mouse serum at 37 degrees C for up to 6 days. Taken together, our results underscore the benefits of simultaneous targeting multiple growth factor receptor pathways for more efficacious cancer treatment. This report describes the first time use of a recombinant BsAb for targeting two tumor-associated molecules on either a single or adjacent tumor cells for enhanced antitumor activity.     

A bispecific antibody targeting CD47 and CD20 selectively binds and eliminates dual antigen expressing lymphoma cells

Agents that block the anti-phagocytic signal CD47 can synergize with pro-phagocytic anti-tumor antigen antibodies to potently eliminate tumors. While CD47 is overexpressed on cancer cells, its expression in many normal tissues may create an ‘antigen sink’ that could minimize the therapeutic efficacy of CD47 blocking agents. Here, we report development of bispecific antibodies (BsAbs) that co-target CD47 and CD20, a therapeutic target for non-Hodgkin lymphoma (NHL), that have reduced affinity for CD47 relative to the parental antibody, but retain strong binding to CD20. These characteristics facilitate selective binding of BsAbs to tumor cells, leading to phagocytosis. Treatment of human NHL-engrafted mice with BsAbs reduced lymphoma burden and extended survival while recapitulating the synergistic efficacy of anti-CD47 and anti-CD20 combination therapy. These findings serve as proof of principle for BsAb targeting of CD47 with tumor-associated antigens as a viable strategy to induce selective phagocytosis of tumor cells and recapitulate the synergy of combination antibody therapy. This approach may be broadly applied to cancer to add a CD47 blocking component to existing antibody therapies.     

A trivalent anti-erbB2/anti-CD16 bispecific antibody retargeting NK cells against human breast cancer cells

Bispecific antibody (BsAb) can physically cross-link immune cells to tumor cells, circumventing the proper structures for tumor cell-immune cell interactions and activating the cellular cytotoxic mechanisms. The optimal BsAb should target tumor cells with high affinity, but activate trigger molecules on cytotoxic cells by monovalent binding of Fab fragments. In the present study, a trivalent anti-erbB2/anti-CD16 BsAb was produced. This BsAb possesses bivalent arms specifically binding to the extracellular domain of erbB2 and monovalent Fab fragment redirecting NK cells. The recombinant protein could be expressed and purified from Escherichia coli as native proteins without refolding. It was fully functional in bispecific binding to SKBR3 and NK cells. The molecular size of this trivalent BsAb protein is larger than diabody and smaller than whole antibody and expected to have advantages for both high penetration of small antibody fragments and the slow circulation clearance of whole antibody. This novel protein may be an attractive target for further improvement and evaluation.