Mechanisms of Action of a TCR-like mAb Directed Against WT1

针对 WT1 的 TCR 样单克隆抗体的作用机制

• 批准号: 9043708
• 负责人: Emily Casey
• 金额: $ 2.76万
• 依托单位: SLOAN-KETTERING INST CAN RESEARCH
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2017-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9043708
• 关键词: Ablation; Adult; Affinity; Antibodies; Antibody Therapy; Antigen Targeting; Binding; Binding Sites; Biology; Cell surface; Cells; Clinic; Clinical; Clinical Trials; Collaborations; Complement; Complex; Cytolysis; Development; Disease; Disease remission; Effector Cell; Engineering; Epitopes; Evaluation; Event; Exhibits; Fc Receptor; Genitourinary system; Haplotypes; Hematopoietic; Human; IgG1; Immune; Immune system; Immunobiology; Immunocompromised Host; Immunologic Receptors; Immunotherapeutic agent; Immunotherapy; In Vitro; Laboratories; Lead; Major Histocompatibility Complex; Malignant Neoplasms; Mediating; Mediator of activation protein; Mentorship; Methods; Modeling; Monoclonal Antibodies; Monoclonal Antibody Therapy; Movement; Mus; NK Cell Activation; Natural Killer Cells; Oncogenes; Oncogenic; Patient Selection; Patients; Peptide Vaccines; Peptides; Pharmaceutical Preparations; Point Mutation; Pre-Clinical Model; Process; Proteins; Recruitment Activity; Resistance; Role; Safety; Site; Solid; Specificity; T-Cell Receptor; T-Lymphocyte; T-Lymphocyte Epitopes; Testing; Therapeutic; Therapeutic Agents; Therapeutic Effect; Therapeutic Monoclonal Antibodies; Time; Tissues; Toxic effect; Transplantation; Treatment Efficacy; Tumor Antigens; Tumor Burden; United States National Institutes of Health; Universities; Vaccines; WT1 gene; Work; Xenograft Model; Xenograft procedure; antibody-dependent cell cytotoxicity; antitumor effect; base; cancer cell; cancer stem cell; cancer type; cell killing; cell type; cytotoxic; cytotoxicity; density; design; effective therapy; experience; human monoclonal antibodies; immune activation; immunodeficient mouse model; immunogenicity; improved; in vitro Assay; in vivo; leukemia; mouse model; novel; public health relevance; receptor; receptor binding; resistance mechanism; response; success; targeted treatment; therapeutic development; tool; transcription factor; tumor

 DESCRIPTION (provided by applicant): The Wilms Tumor 1 (WT1) protein is widely expressed across a variety of cancer types, but is rarely expressed in adult tissues. WT1 is involved in the oncogenic process and in cancer stem cells. However, because WT1 is an intracellular transcription factor, therapies that target the WT1 protein have remained elusive. Our lab has discovered and developed a T-cell receptor (TCR)-like monoclonal antibody (mAb) that specifically binds to a WT1-derived peptide in the context of the major histocompatibility complex (MHC) class I haplotype HLA-A02 expressed on cancer cell surfaces. This mAb, ESK1, is a human IgG1 that has high affinity for this epitope and has demonstrated significant anti-cancer potency in vivo. The efficacy of ESK1 has prompted its movement from the laboratory to development for clinical use. Therefore, it is important for us to understand the mechanism of this antibody in vivo in order to select patients that will benefit most from this therapy, to determine ways to amplify therapeutic efficacy, and to predict mechanisms of resistance and/or toxicities. Studies in vitro and in vivo have demonstrated the dominant role of antibody-dependent cellular cytotoxicity (ADCC) mediated by Fcγ receptors (FcγRs) in ESK1 activity and have ruled out Fc-independent mechanisms. While commercially available mAbs target tens of thousands to hundreds of thousands of epitopes on a cancer cell surface, ESK1 only targets hundreds to a few thousand epitopes. Despite these low numbers, ESK1 exhibits strikingly potent clearance of tumor burden in vivo, which led us to believe that ADCC is more powerful than previously thought. Therefore, in the first aim of this project, we will quantify the minimum number of epitopes required for ESK1 to bind in order to promote the recruitment and activation of effector cells for ADCC. Identifying this binding site number, which we predict to be less than one hundred per cell, will not only inform us on the potential impact of epitope site number in patient selection and in predicting toxicity, but will also support the further development of therapeutic mAbs against other low density cancer specific epitopes. NK cells are the main mediators of ADCC in humans, yet murine NK cells express few low-affinity activating FcγRs, making these cells virtually dispensable for successful antibody therapy in a mouse. As mAb therapies are validated in mouse models before moving to human trials, this may lead to large discrepancies in the observed efficacy, toxicities, and mechanisms of therapy identified. Therefore, this project will also develop a novel mouse model for appropriately evaluating human mAbs for the first time: an immunodeficient, human FcγR-expressing mouse. This mouse model will be used to validate the therapeutic activity of ESK1, as well as to determine which human FcγRs and immune effector cells are involved in its anti-tumor activity. This information will be essential to determine ways to best engineer the Fc region of ESK1 to promote the most effective anti-tumor response, as well as to properly select patients (e.g. based on their immune cell content post therapy or according to disease type) for increasing the chance of success in clinical trials.

 描述（由申请人提供）：Wilms Tumor 1（WT 1）蛋白在多种癌症类型中广泛表达，但很少在成人组织中表达。WT 1参与致癌过程和癌症干细胞。然而，由于WT 1是一种细胞内转录因子，靶向WT 1蛋白的疗法仍然难以捉摸。我们的实验室已经发现并开发了一种T细胞受体（TCR）样单克隆抗体（mAb），其在癌细胞表面表达的主要组织相容性复合体（MHC）I类单倍型HLA-A02的背景下特异性结合WT 1衍生肽。这种mAb ESK 1是一种人IgG 1，对该表位具有高亲和力，并已在体内显示出显著的抗癌效力。ESK 1的功效促使其从实验室发展到临床应用。因此，重要的是我们要了解这种抗体在体内的机制，以选择患者，将受益最多的这种疗法，以确定方法来放大治疗效果，并预测耐药性和/或毒性的机制。体外和体内研究已经证明了Fcγ受体（Fcγ R）介导的抗体依赖性细胞毒性（ADCC）在ESK 1活性中的主导作用，并排除了Fc非依赖性机制。虽然市售的mAb靶向癌细胞表面上的数万至数十万个表位，但ESK 1仅靶向数百至数千个表位。尽管这些数字很低，但ESK 1在体内表现出惊人的肿瘤负荷清除能力，这使我们相信ADCC比以前认为的更强大。因此，在本项目的第一个目标中，我们将量化 ESK 1结合所需的最小数量的表位，以促进ADCC效应细胞的募集和活化。确定这个结合位点的编号，我们预测 每个细胞少于100个，不仅将告知我们表位位点数目在患者选择和预测毒性中的潜在影响，而且还将支持针对其它低密度癌症特异性表位的治疗性mAb的进一步开发。NK细胞是人类ADCC的主要介质，但鼠NK细胞表达很少的低亲和力活化Fcγ R，使得这些细胞实际上不适合在小鼠中成功进行抗体治疗。由于mAb疗法在进入人体试验之前在小鼠模型中进行了验证，这可能导致观察到的疗效、毒性和所确定的治疗机制存在较大差异。因此，本项目还将首次开发一种用于适当评价人mAb的新型小鼠模型：免疫缺陷型人Fcγ R表达小鼠。该小鼠模型将用于验证ESK 1的治疗活性，以及确定哪些人Fcγ R和免疫效应细胞参与其抗肿瘤活性。这些信息对于确定如何最好地改造ESK 1的Fc区以促进最有效的抗肿瘤反应，以及正确选择患者（例如，基于治疗后的免疫细胞含量或根据疾病类型）以增加临床试验成功的机会至关重要。