Preparation of Low Valent Tc(1) Imaging Agents

描述(由申请人提供)：本提案中概述的研究项目具有开发一种或多种放射性标记的、部位特定的胃泌素释放肽(GRP)、诊断/治疗放射性药物的潜力。简而言之，本提案描述了新形式[DPR-(Y)-BBN(7-14)NH2]的设计和开发，其中DPR=二氨基丙酸，BBN=蛙黄素，Y=一系列亲水性氨基酸系链，包括残基谷氨酸、天冬氨酸、谷氨酰胺和天冬氨酸。当这些偶联物与新的低价Tc-99m合成子[99mTc(H2O)3(CO)3]放射性标记时，有可能产生针对过度表达GRP受体(GRPR)的人类癌症的高比活性产物。这一建议的具体目标是：1)通过固相多肽合成技术合成有限数量的[DPR-(Y)-BBN(7-14)NH2]形式的GRPR阳性配体；2)将新构建的配体与低价TC(I)(CO)3和Re(I)(CO)3核进行金属化；3)使用GRPR阳性的人前列腺癌细胞系(PC-3)，在体外评价金属[DPR-(Y)-BBN(7-14)NH2]结合物的结合亲和力；4)评价那些显示高受体结合亲和力(即Kd=5 nm)的99mTc(I)标记类似物在正常(CF-1)小鼠模型中的体内药代动力学；5)通过新开发的放射性合成子[188Re(H2O)3(CO)3]优化和验证最有希望的[DPR-(Y)-BBN(7-14)NH2]-衍生物的“配对”188Re-偶联物。所有的金属结合物都将被合成、提纯，并在示踪剂(99mTc和188Re)和宏观(99Tc和186Re)水平上进行表征。在体外和体内筛选每一种新的金属结合物将用于评估受体介导的内化和癌细胞摄取的性质。通过FDA批准的人类患者临床试验，即使只识别一个诊断类似物，也为未来对这一新类别的放射性药物进行评估提供了动力。

DESCRIPTION (provided by applicant): The research project outlined in this proposal holds the potential for development of one or more radiolabeled, site-specific, Gastrin Releasing Peptide (GRP), diagnostic/therapeutic radiopharmaceuticals. Briefly, the proposal describes the design and development of new conjugates of the form [Dpr-(Y)-BBN(7-14)NH2], where Dpr = diaminopropionic acid, BBN = Bombesin, and Y = a series of hydrophilic amino acid tethers including the residues glutamic acid, aspartic acid, glutamine, and asparagine. These conjugates, when radiolabeled with the new low valent Tc-99m synthon [99mTc(H2O)3(CO)3]+, hold potential to produce high specific activity products that specifically target human cancers overexpressing the GRP receptor (GRPr). The specific objectives of this proposal are: 1) Synthesize a limited number of GRPr-positive ligands of the form [Dpr-(Y)-BBN(7-14)NH2] via solid phase peptide synthetic techniques; 2) Metallate the newly constructed ligands with Iow-valent Tc(I)(CO)3 and Re(I)(CO)3 cores; 3) Evaluate the binding affinity of the metallated [Dpr-(Y)-BBN(7-14)NH2]-conjugates in vitro, using GRPr-positive, human prostate, cancer cell lines (PC-3); 4) Evaluate the in vivo pharmacokinetics of those 99mTc(I)-labeled analogs demonstrating high receptor binding affinities (i.e., Kd=5nM) in normal (CF-1) mouse models; 5) Optimize and validate the "matched pair" 188Re-conjugate of the most promising [Dpr-(Y)-BBN(7-14)NH2]-derivative via the newly developed radiosynthon [l88Re(H2O)3(CO)3]+. All of the metallated conjugates, will be synthesized, purified, and characterized at both tracer (99mTc and 188Re) and macroscopic (99Tc and 186Re) levels. In vitro and in vivo screening of each of the new metallated conjugates will serve to evaluate the properties of receptormediated internalization and cancer cell uptake. Identification of even a single diagnostic analog provides impetus for future evaluation of this new class of radiopharmaceuticals, via FDA approved clinical trials, in human patients.