Developing a pretargeting strategy to detect Fe(II) for nuclear medicine applications

开发用于核医学应用检测 Fe(II) 的预靶向策略

• 批准号: 10441572
• 负责人: Michael John Evans
• 金额: $ 64.34万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2025-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10441572
• 关键词: Abdomen; Acute; Animal Model; Animals; Antimalarials; Artemisinins; Benchmarking; Biodistribution; Biological; Cardiovascular Diseases; Cell Line; Cells; Chemicals; Child; Chloroquine; Clinical; Clinical Trials; Coupling; Data; Desmoplastic; Development; Discipline of Nuclear Medicine; Disease; Dose; Dose-Limiting; Drug Kinetics; Exhibits; Generations; Genetic; Glioma; Goals; Half-Life; Hepatobiliary; Human; Image; ImmunoPET; In Vitro; Inductively Coupled Plasma Mass Spectrometry; Injections; Iron; KRASG12D; Knowledge; Libraries; Liver; Lysosomes; Malignant Neoplasms; Measurement; Measures; Modeling; Multifocal Lesion; Mus; Neurodegenerative Disorders; Normal Cell; Normal tissue morphology; Nutrient; PET/CT scan; Pancreas; Pancreatic Ductal Adenocarcinoma; Pathology; Pharmaceutical Preparations; Pharmacology; Physiology; Positron-Emission Tomography; Prodrugs; Radioisotopes; Reagent; Refractory; Regulation; Role; Series; Serum; Signal Transduction; Starvation; Techniques; Testing; Therapeutic; Tissues; Toxic effect; Tracer; U251; analog; antimicrobial; base; cancer type; catalyst; clinically relevant; cohort; design; imaging modality; imaging study; improved; in vivo; inhibitor; innovation; insight; iron metabolism; liver cancer model; mouse model; optical imaging; pancreatic cancer model; protein crosslink; prototype; radioligand; radiotracer; response; sensor; small molecule; subcutaneous; success; targeted treatment; tumor; uptake; virtual

Project Abstract While it has been recognized for decades that diseased cells arising from numerous disorders exhibit altered iron metabolism compared to normal cells, only recently has it become apparent that increased concentration of cytosolic free ferrous iron (Fe2+) - the labile iron pool (LIP) – is most associated with these pathologies. Meanwhile, the overwhelming clinical success of the antimalarial artemisinin has established that LIP can be safely exploited to treat diseases in humans (including children), a milestone that has inspired us and others to develop 1,2,4-trioxolane (TRX)-based prodrugs that are activated by LIP and release drug payloads within diseased cells. Although our knowledge of the role of LIP in normal physiology and disease has increased substantially over the past 10 years, virtually all of our insights about LIP are founded on observations from cell lines. Studying LIP in vivo is a major knowledge gap that is currently impeding efforts to apply experimental LIP targeted therapies clinically. We hypothesized based on the well-studied mechanisms of TRX reactivity with LIP that a PET strategy could enable LIP measurements in vivo by sequestering a radioisotope within cells via Fe(II)-dependent protein crosslinking. We designed a prototype, 18F-TRX, and showed that its biodistribution in vivo is Fe2+-dependent, it detects diverse cancer types with an expanded LIP, and tumor uptake of 18F-TRX is directly proportional to tumor response to LIP targeting therapies. However, the tracer's rapid serum clearance (t1/2 ~28 sec) and slow hepatobiliary clearance combine to limit the overall image quality. Thus, the goal of this project is to test if a pre-targeting strategy involving macrodosing of a cold TRX reagent, followed later by a microdose of a cognate 18F-click coupling partner may improve measurements of LIP by eliminating the background signal from unreacted TRX and/or achieving better TRX exposure in tissues with LIP expansion. During Aim 1, we will synthesize and study the in vivo pharmacology of TRX- transcyclooctene (TCO) conjugates and fluoro-tetrazines to identify optimal biorthogonal click partners. During Aim 2, the optimal pre-targeting conditions will be established in tumor bearing mice using immunoPET. Imaging findings (e.g. tumor uptake, tumor to normal ratios) will be benchmarked against 18F-TRX and the 18F- tetrazine alone. During Aim 3, we will perform cohort expansion studies to acquire additional biological replicates while also studying spontaneous and orthotopic tumor models arising in abdominal tissues (e.g. liver, pancreas) that we expect to be occult on 18F-TRX imaging. If successful, defining which disease types harbor high LIP with PET provides a natural segue to clinical trials implementing the myriad experimental LIP targeted therapies currently waiting in the queue. Solving this challenge with pre-targeting would also add a new application for a venerable dosing strategy that could be broadly applied to improve the image quality of other rapidly clearing small molecule radiotracers, or perhaps even the antitumor efficacy of radioligand therapies.

项目摘要 尽管几十年来人们已经认识到，由多种疾病引起的患病细胞表现出改变 与正常细胞相比，铁代谢，直到最近才变得明显，浓度增加 胞质游离二价铁 (Fe2+) - 不稳定铁库 (LIP) - 与这些病理最相关。 与此同时，抗疟疾青蒿素在临床上取得的压倒性成功已经证明 LIP 可以用于治疗疟疾。 安全地用于治疗人类（包括儿童）的疾病，这是一个里程碑，激励我们和其他人 开发基于 1,2,4-三氧戊环 (TRX) 的前药，这些前药可被 LIP 激活并在其中释放药物有效负载 患病细胞。尽管我们对 LIP 在正常生理和疾病中的作用的了解有所增加 在过去的 10 年里，几乎我们所有关于 LIP 的见解都建立在细胞观察的基础上 线。体内研究 LIP 是一个主要的知识差距，目前阻碍了实验应用的努力 LIP靶向治疗临床。我们根据充分研究的 TRX 反应机制进行假设 LIP 表明 PET 策略可以通过将放射性同位素隔离在体内来实现 LIP 测量 细胞通过 Fe(II) 依赖性蛋白质交联。我们设计了一个原型 18F-TRX，并表明其 体内生物分布依赖于 Fe2+，它可以通过扩展的 LIP 检测多种癌症类型，并检测肿瘤 18F-TRX 的摄取与肿瘤对 LIP 靶向治疗的反应成正比。然而，追踪者的 快速血清清除率（t1/2 ~28 秒）和缓慢肝胆清除率相结合限制了整体图像 质量。因此，该项目的目标是测试涉及冷 TRX 大量剂量的预靶向策略是否有效 试剂，随后加入微剂量的同源 18F-点击偶联伴侣可能会改善 LIP 通过消除未反应的 TRX 的背景信号和/或在组织中实现更好的 TRX 暴露 与 LIP 扩展。在目标1期间，我们将合成并研究TRX-的体内药理学 反式环辛烯 (TCO) 缀合物和氟四嗪以确定最佳双正交点击伙伴。期间 目标 2，将使用免疫 PET 在荷瘤小鼠中建立最佳预靶向条件。 影像学结果（例如肿瘤摄取、肿瘤与正常比率）将以 18F-TRX 和 18F- 单独四嗪。在目标 3 期间，我们将进行队列扩展研究，以获得更多的生物 复制的同时还研究腹部组织中出现的自发和原位肿瘤模型（例如， 肝脏、胰腺），我们预计在 18F-TRX 成像中是隐匿的。如果成功，定义哪些疾病类型 港口高 LIP 与 PET 为实施无数实验性 LIP 的临床试验提供了自然的衔接 靶向治疗目前正在排队等待。通过预先定位来解决这一挑战还将增加 古老的剂量策略的新应用，可广泛应用于提高图像质量 其他快速清除的小分子放射性示踪剂，甚至放射性配体的抗肿瘤功效 疗法。