BREAST CANCER IMAGING ANTIBODY DERIVED SMALL MOLECULES

近三分之一的人类乳腺癌，包括大多数 高度侵袭性粉刺型和炎症型乳腺癌， 表达neu/c-erbB-2癌基因产物p185 膜。 这项工作的目标是开发放射性配体 针对P185受体。假设是， 成像可以准确和无创地检测肿瘤相关的p185， 从而提高乳腺癌分期的准确性， 在肿瘤过度表达p185的患者亚组中进行监测。 虽然单克隆抗体（mAb）与人p185反应， 受体可用，放射性标记的单克隆抗体的肿瘤成像已被 很大程度上令人失望;肿瘤定位差，背景 活动很高。 完整Mab不能作为定点生物探针 因为：1）大尺寸（150 kDa）; 2）非特异性结合; 3）慢 血浆清除率;和4）免疫原性。为了规避这些 局限性，研究人员建议靶向p185受体， 新开发的抗体衍生小分子（小于2 Kda）， 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， 基于重链CDR 3的芳香族修饰的肽类似物 4D 5，一种与人p185反应的鼠mAb。 这种CDR类似物被称为 4D5.AME，其中AME代表芳族改性的环外。 初步 使用4D5.AME的研究证明了优异的结合亲和力， 抗人乳腺癌的特殊生物活性， 第185页。 因此，4D5.AME是一种潜在的极好的定点生物学修饰。 用于将发射γ射线的放射性核素输送到肿瘤相关组织的探针 第185页。因此，具体目的是：1）用放射性标记4D5.AME， 碘-123、锝-99m、铟-111; 2）稳定性测定， AME放射性配体的体外亲和力和特异性 乳腺癌细胞系; 3）确定再分布和血浆 使用异种移植肿瘤的体内4D5.AME放射性配体的清除率 裸鼠模型;以及4）执行、优化和评估平面 4D5.AME放射性配体在荷瘤小鼠中的放射性成像。 所提出的显像剂包括显著的设计改进 与现有的代理商相比。 然而，我们无法预测 放射性标记是否会干扰4D5.AME中的关键残留物 受体结合位点 开发的任何有前景的4D5.AME放射性配体 在此R21授权期间，将用作初步数据， 支持未来的R 01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.