Defining the Role of Affinity in Antibody-Based Tumor Targeting and Penetration

由于最近证实了它们对许多恶性肿瘤的疗效，所以单克隆抗体(Mab)是 在癌症治疗中变得越来越重要。开发基于抗体的新分子的最大努力 专注于识别那些对肿瘤抗原具有最高亲和力的人。使用小的，单一的- 链Fv(ScFv)分子对同一HER2表位的亲和力在1x10-7M到1x10-11M之间。 我们发现，高亲和力可能会削弱抗体穿透实体肿瘤的能力，导致 血管周围定位和潜在的次优治疗效果。这项工作验证了一个“结合位点” 温斯坦提出的“屏障”假说，认为亲和力很高的抗体将被限制在 它们穿透实体肿瘤的能力。我们早期工作的一个局限性是scFv被迅速消除 从循环中分离出来，从而限制了研究肿瘤随时间渗透的能力。我们最近产生了 上面描述的ScFv分子的全长Ig G版本，并能够阐明 在肿瘤靶向和渗透中的亲和力，并确定这一过程背后的机制。 初步数据表明，高亲和力也削弱了Ig对肿瘤的靶向性和穿透性。这个 支持这一提议的假设是：1)对肿瘤抗原有很高亲和力的免疫球蛋白G分子 表现出穿透实体肿瘤的能力降低，2)受限背后的主要机制 高亲和力抗体对实体瘤的穿透是肿瘤细胞的内化和降解 3)低亲和力免疫球蛋白分子在介导抗肿瘤方面可能优于高亲和力抗体 效果。我们将评估结合亲和力、抗原脱落、抗原/单抗内化和 抗HER2单抗对肿瘤靶向性和肿瘤穿透性的影响我们会 还确定亲和力的变化以及随之而来的对肿瘤靶向和渗透的影响 非偶联抗肿瘤单抗的抗肿瘤效果，从而提供有助于指导 未来合理开发抗肿瘤单抗。这项研究与公共健康直接相关，它将 引导开发治疗癌症的新抗体。学习如何结合强度 抗体对肿瘤细胞表面靶标的(亲和力)影响抗体进入 肿瘤和杀死肿瘤细胞将使我们能够创造更有效的基于抗体的癌症治疗方法。

Due to their recent demonstration of efficacy in a number of malignancies, monoclonal antibodies (MAb) are becoming increasingly important in cancer therapy. Most efforts to develop new antibody-based molecules are focused on identifying those with the highest possible affinity for the tumor antigen. Using small, single- chain Fv (scFv) molecules that ranged in affinity for the same epitope of HER2 from 1x10-7 M to 1x10-11 M. We showed that high affinity may impair the ability of an antibody to penetrate into a solid tumor, leading to perivascular localization and potential suboptimal therapeutic efficacy. This work validated a "Binding Site Barrier" hypothesis posed by Weinstein that stated that antibodies of very high affinity would be limited in their ability to penetrate solid tumors. A limitation of our earlier work was that scFv are rapidly eliminated from the circulation, thus limiting the ability to study tumor penetration over time. We have recently generated full-length IgG versions of the scFv molecules described above and are in the position to elucidate the role of affinity in tumor targeting and penetration and determine the mechanisms underlying this process. Preliminary data indicate that high affinity also detracts from tumor targeting and penetration of Ig. The hypotheses underlying this proposal are that 1) IgG molecules with very high affinity for tumor antigen will demonstrate a reduced ability to penetrate into solid tumors, 2) a major mechanism behind the restricted penetration of high affinity antibodies into solid tumors is the internalization and degradation by tumor cells and 3) lower affinity IgG molecules may be superior to higher affinity antibodies in mediating anti-tumor effects. We will evaluate the roles of binding affinity, antigen shedding, antigen/MAb internalization and normal tissue antigen expression on the tumor targeting and tumor penetration of anti-HER2 MAbs. We will also determine if changes in affinity, and the attendant impacts on tumor targeting and penetration, influence the anti-tumor efficacy of unconjugated anti-tumor MAbs, thereby providing information that can help guide future rational development of anti-tumor MAbs. This research is directly relevant to public health, as it will guide the development of new antibodies for the treatment of cancer. Learning how the binding strength (affinity) of an antibody for its target on the tumor cell surface affects the ability of the antibody to move into the tumor and kill tumor cells will allow us to create more effective antibody-based treatments for cancer.