BREAST CANCER IMAGING ANTIBODY DERIVED SMALL MOLECULES

近三分之一的人类乳腺癌，包括大多数 高度侵袭性粉刺和炎症型乳腺癌， 在血浆中表达neu/c-erb B-2癌基因产物p185 膜。拟议工作的目标是开发放射性配体。 靶向p185受体。假设是闪光照相 成像技术能准确、无创地检测肿瘤相关基因p185 从而提高乳腺癌分期的准确性和 监测肿瘤超过p185表达的患者亚群。 尽管与人p185反应的单抗(MAb) 受体是可用的，用放射性标记单抗进行肿瘤成像已经 很大程度上令人失望；肿瘤定位很差，背景 活跃度高。完整的单抗未能成为定点生物探针 因为：1)大尺寸(150 KDa)；2)非特异性结合；3)速度慢 血浆清除率；4)免疫原性。为了绕过这些 限制，研究人员建议靶向p185受体使用 新开发的抗体衍生小分子(小于2kda) 模拟抗体互补决定区(CDR)。马克博士 格林和他的同事开发了一种构象受限的， 基于重链CDR3的芳香族修饰多肽类似物 4D5，一种与人p185反应的鼠单抗。这种CDR类似物被称为 4D5.AME，其中AME代表芳香族改性外环。初步 研究表明，4D5.AME具有良好的结合亲和力和 对过度表达的人类乳腺癌具有特殊的生物活性 第185页。因此，4D5.AME是一种潜在的极好的定点定向生物 用于将伽马发射的放射性核素输送到肿瘤相关的探测器 第185页。相应地，具体目标是：1)放射标记4D5AME 碘-123、氚-99m和铟-111；2)测定稳定性， 4D5AME放射性配体的亲和力和特异性 乳腺癌细胞株；3)测定再分布和血浆 4D5.AME放射性配体在异种移植瘤体内的清除率 裸鼠模型；4)执行、优化和评估平面 荷瘤小鼠体内4D5AME放射性配基的闪烁成像。 建议的成像剂结合了显著的设计改进。 与现有的代理商相比。然而，不可能预测到 放射性标记是否会干扰4D5AME的关键残基 受体结合部位。任何有希望的4D5.AME放射性配体被开发出来 在此R21授权期内将用作以下项目的初步数据 支持未来的R01提案。

Nearly one-third of all human breast cancers, including most of the highly aggressive comedo- and inflammatory-type breast cancers, over express the neu/c-erbB-2 oncogene product p185 on their plasma membranes. The goal of the proposed work is to develop radioligands targeted to the p185 receptor. The hypothesis is that scintigraphic imaging can detect tumor-associated p185 accurately and noninvasively and, thereby, improve the accuracy of breast cancer staging and surveillance in the subset of patients whose tumors over express p185. Although monoclonal antibodies (mAb) reactive with the human p185 receptor are available, tumor imaging with radiolabeled Mab has been largely disappointing; tumor localization is poor and background activity is high. Intact Mab fail as site-directed biological probes because of: 1) large size (150 kDa); 2) non-specific binding; 3) slow plasma clearance rate; and 4) immunogenicity. To circumvent these limitations, the investigators propose to target the p185 receptor using newly-developed antibody-derived small molecules (less than 2 Kda) that mimic the antibody complementarily determining region (CDR). Dr. Mark Greene and his co-workers developed a conformationally constrained, aromatically-modified peptide analogue based on the heavy chain CDR3 of 4D5, a murine mAb reactive with human p185. This CDR analogue is called 4D5.AME, where AME stands for Aromatic Modified Exocyclic. Preliminary studies with 4D5.AME demonstrate excellent binding affinity and exceptional bioactivity against human breast cancers that over express p185. Thus, 4D5.AME is a potentially superb site-directed biological probe for delivery of gamma-emitting radionuclides to tumor-associated p185. Accordingly, the specific aims are to: 1) radiolabel 4D5.AME with iodine-123, technetium-99m and indium-111; 2) determine the stability, affinity, and specificity of 4D5.AME radioligands in vitro using human breast cancer cell lines; 3) determine the redistribution and plasma clearance rates of 4D5.AME radioligands in vivo using a xenograft tumor model in nude mice; and 4) perform, optimize, and evaluate planar scintigraphic imaging of 4D5.AME radioligands in tumor-bearing mice. The proposed imaging agents incorporate significant design improvements compared with existing agents. However, it is impossible to predict whether radiolabeling will disturb critical residues in the 4D5.AME receptor binding site. Any promising 4D5.AME radioligands developed during this R21 granting period will be used as preliminary data in support of a future R01 proposal.