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

由于它们最近在许多恶性肿瘤中的功效的证明，单克隆抗体（MAb）被广泛应用于治疗恶性肿瘤。 在癌症治疗中变得越来越重要。开发新的抗体分子的大部分努力 专注于鉴定那些对肿瘤抗原具有最高亲和力的抗原。使用小的，单一的- 链Fv（scFv）分子，其对HER 2的相同表位的亲和力范围为1 × 10 -7 M至1 × 10 -11 M。 我们发现，高亲和力可能会削弱抗体渗透到实体瘤中的能力，从而导致肿瘤细胞增殖。 血管周围定位和潜在的次优治疗效果。这项工作验证了“结合位点 Weinstein提出的“屏障”假说，该假说指出，非常高亲和力的抗体将被限制在 它们穿透实体肿瘤的能力。我们早期工作的一个局限性是， 因此限制了研究肿瘤随时间渗透的能力。我们最近已经产生了 上述scFv分子的全长IgG形式，并且能够阐明 肿瘤靶向和渗透的亲和力，并确定这一过程的机制。 初步数据表明，高亲和力也有损于肿瘤靶向和IG的渗透。的 该建议的基础假设是：1）对肿瘤抗原具有非常高亲和力的IgG分子将 显示出渗透到实体瘤中的能力降低，2）限制性肿瘤的主要机制， 高亲和力抗体渗透到实体瘤中是肿瘤细胞的内化和降解 低亲和力IgG分子在介导抗肿瘤作用方面可能比高亲和力抗体具有上级优势 方面的影响.我们将评估结合亲和力、抗原脱落、抗原/MAb内化和 正常组织抗原表达对抗HER 2单克隆抗体的肿瘤靶向和肿瘤穿透的影响。我们将 还确定亲和力的变化以及随之而来的对肿瘤靶向和穿透的影响， 未缀合的抗肿瘤单克隆抗体的抗肿瘤功效，从而提供可以帮助指导 抗肿瘤单克隆抗体的合理开发。这项研究与公共卫生直接相关，因为它将 指导开发用于治疗癌症的新抗体。了解粘合强度 抗体对其在肿瘤细胞表面上的靶标的亲和力影响抗体移动进入肿瘤细胞表面的能力。 肿瘤和杀死肿瘤细胞将使我们能够创造更有效的抗体为基础的治疗癌症。

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.