NOVEL PET TRACERS FOR IMAGING OF ALZHEIMER'S DISEASE

用于阿尔茨海默病成像的新型宠物示踪剂

• 批准号: 9223626
• 负责人: Vijay Sharma
• 金额: $ 31.26万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2020-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9223626
• 关键词: Affinity; Age; Alzheimer' s Disease; Amyloid beta-Protein; Amyloid deposition; Autopsy; Binding; Binding Sites; Biochemical; Biodistribution; Biological; Biological Assay; Biological Markers; Blood; Blood - brain barrier anatomy; Blood Vessels; Brain; Brain Diseases; Brain region; Cerebral Amyloid Angiopathy; Cerebrospinal Fluid; Cerebrum; Characteristics; Clinical; Cognitive; Coupled; Critiques; Data; Dementia; Deposition; Detection; Development; Diagnosis; Diagnostic; Diffuse; Discipline of Nuclear Medicine; Disease; Disease Management; Drug Kinetics; Early Diagnosis; Elderly; Evaluation; Event; FDA approved; FVB Mouse; Functional disorder; Generations; Goals; Hippocampus (Brain); Human; Image; Image Analysis; Imaging Techniques; Impaired cognition; In Vitro; Injection of therapeutic agent; Investigation; Label; Lead; Lesion; Magnetic Resonance Imaging; Metabolism; Microscopy; Modeling; Molecular; Molecular Target; Monitor; Mus; Nerve Degeneration; Neurodegenerative Disorders; Neurofibrillary Tangles; Neurons; Parkinson Disease; Pathogenicity; Patients; Penetration; Permeability; Pharmaceutical Preparations; Phase; Positron-Emission Tomography; Prions; Process; Radiopharmaceuticals; Reporting; Resources; Senile Plaques; Serum; Signal Transduction; Site; Specificity; Specimen; Stratification; Symptoms; Synapses; Tail; Text; Therapeutic Effect; Therapeutic Intervention; Time; Tissues; Toxicology; Tracer; Transgenic Mice; Treatment Efficacy; Validation; Variant; Veins; X-Ray Computed Tomography; amyloid formation; analog; brain parenchyma; brain tissue; cerebrovascular amyloid; clinical imaging; clinically relevant; cross reactivity; density; design; dosimetry; frontal lobe; human tissue; imaging agent; in vivo; microPET; microPET/CT; molecular imaging; multiphoton imaging; neuron loss; non-demented; non-invasive imaging; nonhuman primate; noninvasive diagnosis; normal aging; novel; protein biomarkers; public health relevance; radiotracer; response; single photon emission computed tomography; targeted agent; tau Proteins; two-photon; uptake; white matter

 DESCRIPTION (provided by applicant): Several lines of investigations indicate that amyloid formation precedes decades prior to beginning of neurodegeneration phase, and the presence of senile plaques (SPs) and neurofibrillary tangles (NFTs) in nondemented older adults could represent an earlier manifestation of AD prior to its clinical expression. To further embellish diagnostic nuclear medicine imaging resources, 18F-Avid-45,18F-Flutemetamol, and 18F-Florbetaben have recently gained FDA approval for Aβ imaging. Among these agents, 11C-PIB continues to be the most thoroughly investigated PET radiopharmaceutical for Aβ imaging. Recent reports indicate that 11C-PIB could not detect cerebral Aβ in a patient confirmed via clinical, cognitive, and cerebrospinal fluid biomarkers of AD, thus raising further concerns for sensitivity of PIB and other agents to detect AD variants characterized predominantly by diffuse Aβ plaques. Additionally, recent clinicopathological studies of PD patients have also indicated limitations of PIB imaging to differentiate PD patients with or without dementia, despite the presence of abundant Aβ in brains of those patients. To further supplement armamentarium of promising PET Aβ imaging agents, an easily accessible, efficient, highly specific 18F-PET agent and potentially capable of binding to both fibrillar and diffuse plaques, including the more dense sites on Aβ to enable high sensitivity for detection (at prodromal stages of the disease) would be highly desirable, and continues to be an unmet goal. To accomplish this objective, we have rationally designed a novel heterocyclic fluorescent molecule (18F-AI-187) from an entirely a new class of molecules that shows concentration dependent and saturable binding, with Kd values of 1.4±0.35nM and 2.9 ±1.35nM, to AD homogenates and preformed Aβ1-42 fibrils, respectively, the unlabeled fluorescent counterpart detects both fibrillar plaques and displays cerebral amyloid angiopathy (CAA) ex vivo in the hippocampus regions of brain sections in APPsw+/-/PS1 mice and also detects diffuse plaques, compact plaques, and vascular deposits (CAA) in human tissues. Further, the PET tracer 18F-AI-187 demonstrates an extremely high first pass extraction in brains (8.86 ± 0.32 %ID/g %ID/g; 2 min post tail-vein injection) of FVB mice, and followed by a washout (25% faster than 18F-Avid 45) in absence of targeted plaques. Compared with11C-PIB, 18F-Flutemetamol (metabolizes faster than 11C-PIB), and 18F-Avid45 that undergo facile metabolism in vivo, 18F-AI-187 remains non-metabolized in human serum. Therefore, the high first pass extraction into brains coupled with faster clearance from the blood pool and lack of metabolites offer critical characteristics that could enhance overall signal to background ratios and target specificity to assist image analysis. Preliminary multiphoton microscopy in live APPsw+/-/PS1 (15 months old) mice demonstrates that F-AI- 187 traverses blood brain barrier to instantaneously labels plaques in brain parenchyma and blood vessels (CAA), and plaques remain labeled for investigated time points. Preliminary, microPET/CT imaging shows higher brain uptake of the radiotracer (30 min post-tail-vein injection), and its retention in the cortex of transgenic mice compared with their age-matched Bl6 counterparts, consistent with the binding of the tracer to Aβ plaques. Finally and importantly, the agent is als highly specific for AD (displays no cross-reactivity with biomarkers of other neurodegenerative diseases); while also detecting diffuse and compact plaques in a PIB- Aβ+ AD case. Armed with this highly provocative data on our lead agent, now we propose to: 1) Perform complete pharmacokinetic analysis of 18F-AI-187 or the second generation of lead agents to determine their translational potential to serve as noninvasive Aβ-targeted probes in age-matched APPsw+/- transgenic mice (target specificity), WT counterparts (controls), and nonhuman primates (baseline SNR analysis) via evaluation of time-activity curves (TACs), using either microPET/CT or microPET/MR or PET/MR imaging, perform arterial metabolite analysis and dosimetry studies to identify highly specific imaging agents to advance translational leads into non-GMP-toxicology studies for eIND filing; 2) Perform focused SAR studies to develop second generation of novel heterocyclic molecules capable of detecting Aβ plaques in early stages of AD prior to its clinical expression. 3) Perform complete biochemical characterization of second generation Aβ-targeted agents via multiple binding and competitive displacement assays for evaluation of targeted sites on Aβ, assess BBB permeability and ability to label plaques in parenchyma via biodistribution studies and 2-photon imaging, phosphorimaging studies in vitro, perform ex vivo binding studies of AD brain homogenates and human AD brain tissue sections, including specificity for Aβ compared with other biomarker proteins (tau, prion, TDP43,and α-synclein) prevalent in other neurodegenerative diseases for determining target selectivity of second generation agents. Upon further biochemical validation, these novel molecular imaging agents could enable noninvasive PET interrogation of Aβ in patients at prodromal stages of AD, better guide stratification of AD patients from those of other neurodegenerative diseases, and assist analysis of the efficacy for new molecular-targeted disease-modifying therapies, thus overall assisting management of AD.

 描述（由申请人提供）：多项研究表明，淀粉样蛋白的形成早于神经变性阶段开始的数十年，并且非痴呆老年人中老年斑（SP）和神经原纤维缠结（NFT）的存在可能代表 AD 临床表现之前的早期表现。为了进一步完善诊断核医学成像资源，18F-Avid-45、18F-Frudemetamol 和 18F-Florbetaben 最近已获得 FDA 批准用于 Aβ 成像。在这些药物中，11C-PIB 仍然是研究最彻底的用于 Aβ 成像的 PET 放射性药物。最近的报告表明，11C-PIB 无法检测到通过临床、认知和脑脊液生物标志物确诊为 AD 的患者中的大脑 Aβ，从而进一步引起人们对 PIB 和其他药物检测主要以弥漫性 Aβ 斑块为特征的 AD 变异的敏感性的担忧。此外，最近对 PD 患者的临床病理学研究也表明，PIB 成像在区分患有或不患有痴呆的 PD 患者方面存在局限性，尽管这些患者的大脑中存在丰富的 Aβ。为了进一步补充有前景的 PET Aβ 显像剂，我们将开发一种易于获取、高效、高度特异性的 18F-PET 试剂，并且有可能与纤维状和弥漫性斑块结合，包括 Aβ 上更密集的位点，以实现高灵敏度检测（在疾病的前驱阶段）。 非常令人向往，并且仍然是一个未实现的目标。为了实现这一目标，我们合理地设计了一种新型杂环荧光分子（18F-AI-187），该分子是一类全新的分子，其与AD匀浆和预形成的Aβ1-42原纤维（未标记的荧光对应物）具有浓度依赖性和可饱和结合，Kd值为1.4±0.35nM和2.9±1.35nM。 检测纤维状斑块并在 APPsw+/-/PS1 小鼠脑切片海马区离体显示脑淀粉样血管病 (CAA)，还可以检测人体组织中的弥漫性斑块、致密斑块和血管沉积物 (CAA)。此外，PET 示踪剂 18F-AI-187 在 FVB 小鼠大脑中表现出极高的首过提取率（8.86 ± 0.32 %ID/g %ID/g；尾静脉注射后 2 分钟），随后在没有目标斑块的情况下进行洗脱（比 18F-Avid 45 快 25%）。与体内代谢容易的 11C-PIB、 18F-Frudemetamol（比 11C-PIB 代谢更快）和 18F-Avid45 相比， 18F-AI-187 在人血清中保持非代谢。因此，大脑中的高首过提取率加上从血池中更快的清除和缺乏代谢物提供了关键特征，可以增强整体信号与背景的比率和目标特异性，以协助图像分析。对活体 APPsw+/-/PS1（15 个月大）小鼠进行的初步多光子显微镜检查表明，F-AI-187 穿过血脑屏障，立即标记脑实质和血管 (CAA) 中的斑块，并且斑块在研究的时间点仍保持标记状态。初步的 microPET/CT 成像显示，与年龄匹配的 Bl6 小鼠相比，放射性示踪剂的大脑摄取量更高（尾静脉注射后 30 分钟），并且其在转基因小鼠皮层中的保留量与示踪剂与 Aβ 斑块的结合一致。最后也是重要的是，该药物对 AD 也具有高度特异性（与其他神经退行性疾病的生物标志物没有交叉反应）；同时还检测 PIB-Aβ+ AD 病例中的弥漫性斑块和致密斑块。有了关于我们的首席代理人的高度挑衅性的数据，现在我们建议： 1) 使用 microPET/CT 评估时间-活性曲线 (TAC)，对 18F-AI-187 或第二代先导药物进行完整的药代动力学分析，以确定其在年龄匹配的 APPsw+/- 转基因小鼠（目标特异性）、WT 对应物（对照）和非人灵长类动物（基线 SNR 分析）中作为非侵入性 Aβ 靶向探针的转化潜力 或 microPET/MR 或 PET/MR 成像，进行动脉代谢物分析和剂量测定研究，以确定高度特异性的显像剂，从而将转化线索推进到非 GMP 毒理学研究中，以进行 eIND 备案； 2) 开展重点 SAR 研究，开发第二代新型杂环分子，能够在 AD 临床表达之前的早期阶段检测 Aβ 斑块。 3) 通过多重结合和竞争性置换测定对第二代 Aβ 靶向药物进行完整的生化表征，以评估 Aβ 上的靶位点，通过生物分布研究和双光子成像、体外磷光成像研究评估 BBB 通透性和标记实质斑块的能力，执行 AD 脑匀浆和人 AD 脑组织切片的离体结合研究，包括与其他神经退行性疾病中普遍存在的其他生物标志物蛋白（tau、朊病毒、TDP43 和 α-synclein）相比 Aβ 的特异性，以确定第二代药物的靶点选择性。经过进一步的生化验证，这些新型分子显像剂可以对AD前驱期患者的Aβ进行无创PET检查，更好地指导AD患者与其他神经退行性疾病患者的分层，并协助分析新的分子靶向疾病缓解疗法的疗效，从而全面协助AD的管理。