Development of an NTSR1-Targeted Radiotherapeutic for Colorectal Cancer

目的：在结直肠癌（CRC）的所有临床阶段都需要更有效的治疗选择， 从消除术后残留疾病，提高手术候选人和开发更有效的 转移性疾病的治疗选择。靶向放射性核素治疗（TRT），靶向肿瘤特异性 生物标志物已经成为寻求有效癌症治疗的一种有吸引力的方法。发展 低分子量的TRT剂由于其快速靶向和非靶向清除而特别有吸引力 特性.然而，对于许多研究的低分子量TRT剂，在肿瘤中的短停留时间 由于药物本身的高清除率及其代谢物抑制了临床转化。目的 该建议的一个目的是设计能够靶向神经降压素受体亚型1的CRC治疗剂 NTSR 1是一种在大部分CRC患者中过度表达的受体。具体地说， 通过将不可逆半胱氨酸蛋白酶捕获剂（CPTA）掺入NTSR 1靶向的 我们试图设计能够在细胞内形成高分子量的TRT， 加合物通过这种保留机制，177 Lu-CPTA-掺入的NTSR 1 TA（177 Lu-CPTA-掺入的NTSR 1 TA）可以被保留。 NTSR 1 TA）将表现出辐射剂量递送的显著增加，导致增强的治疗功效。 此外，作为这项资助的一部分，我们寻求更清楚地了解体内加合物结合伙伴，加合物 半衰期和组织/细胞定位与这种捕获机制。 具体目的：（1）177 Lu-CPTA-NTSR 1靶向药物的合成和初步生物学性能;（2） 检查体内加合物蛋白酶谱、加合物半衰期和组织分布;和（3）治疗 优化的177 Lu-CPTA-NTSR 1靶向剂的评价 研究设计：本提案的第一个目的是研究进一步改进CRC设计的途径 通过1）精制构建体以降低T/K辐射剂量比; 2）探索 具有不同选择性的CPTA的影响;和3）检查不同的半胱氨酸蛋白酶抑制剂类别。 合成后，对177 Lu-CPTA-NTSR 1 TA的体外和体内性能进行初步评估 将被执行。在第二个目标中，将进行更详细的生物学评价，其中加合物- 结合配偶体被鉴定和定量，组织蛋白酶表达水平被确定，加合物半衰期 并测定细胞分布（细胞内、膜或细胞外百分比）。最后，lead TRT候选人将在先进的CRC小鼠模型中进行检查，以确定最佳候选人 进行最大耐受剂量和疗效研究。在这个项目结束时，我们预计 能够确定一个候选人，以推进FDA的研究性新药批准。

Objective: More effective treatment options are needed across all clinical stages of colorectal cancer (CRC), from eliminating residual disease after surgery, improving surgical candidacy and developing more effective treatment options for metastatic disease. Targeted radionuclide therapy (TRT), which targets tumor-specific biomarkers, has been one appealing approach in the pursuit of effective cancer therapeutics. The development of low-molecular-weight TRT agents is particularly attractive due to their rapid targeting and non-target clearance properties. However, for many investigated low-molecular-weight TRT agents, the short residence time in tumors due to inherently high clearance rates of the agents and their metabolites inhibits clinical translation. The purpose of this proposal is to design a CRC therapeutic agent capable of targeting the neurotensin receptor subtype 1 (NTSR1), a receptor found to be overexpressed in large segments of the CRC patient population. Specifically, by incorporating irreversible cysteine protease trapping agents (CPTAs) into the structure of NTSR1-targeted agents (NTSR1TAs), we seek to design TRTs that are capable of forming high molecular weight intracellular adducts. Through this retention mechanism, the 177Lu-labeled, CPTA-incorporated, NTSR1TAs (177Lu-CPTA- NTSR1TAs) will exhibit substantial increases in radiation dose delivery leading to enhanced therapeutic efficacy. Also, as part of this grant, we seek to gain a clearer understanding of the in vivo adduct binding partners, adduct half-lives and tissue/cellular localization associated with this trapping mechanism. Specific Aims: (1) Synthesis and Initial Biological Performance of 177Lu-CPTA-NTSR1-targeted Agents; (2) Examine In Vivo Adduct Protease Profiles, Adduct Half-lives and Tissue Distribution; and (3) Therapeutic Evaluation of Optimized 177Lu-CPTA-NTSR1-targeted Agents Study Design: The first aim of this proposal is to examine pathways to further improve the design of CRC residualizing 177Lu-CPTA-NTSR1TAs by 1) refining the construct to reduce T/K radiation dose ratios; 2) exploring the impact of CPTAs with varying selectivities; and 3) examining different cysteine protease inhibitor classes. After synthesis, initial assessments regarding the in vitro and in vivo performance of the177Lu-CPTA-NTSR1TAs will be performed. In the second aim, a more detailed biological evaluation will be carried out in which adduct- binding partners are identified and quantified, tissue protease expression levels ascertained, adduct half-lives are estimated and cellular distribution (percent intracellular, membrane or extracellular) determined. Lastly, lead TRT candidates will be examined in advanced CRC mouse models to determine the best candidates to move forward to the maximum tolerated dose and therapeutic efficacy studies. At the end of this project, we anticipate being able to identify a candidate to advance towards FDA investigational new drug approval.