Ligand discovery for delineating cholesterol homeostasis in the brain

描绘大脑胆固醇稳态的配体发现

• 批准号: 10605057
• 负责人: Steven H Liang
• 金额: $ 77.48万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-01-01 至 2025-12-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10605057
• 关键词: ABCB1 gene; Affinity; Alzheimer' s Disease; Alzheimer' s disease brain; Alzheimer' s disease therapeutic; Amyloid beta-Protein; Autopsy; Autoradiography; Binding; Biochemical Process; Biodistribution; Biological; Biological Assay; Biological Process; Blood specimen; Brain; Carbon Dioxide; Cerebellum; Cessation of life; Characteristics; Chemistry; Cholesterol; Cholesterol Homeostasis; Clinical; Corpus striatum structure; Deposition; Development; Disease; Disease Progression; Docking; Dose; Evaluation; Functional disorder; Goals; Human; Huntington Disease; Hydroxycholesterols; Image; Imaging Device; In Vitro; Kinetics; Label; Lead; Length; Libraries; Ligands; Mediating; Messenger RNA; Modeling; Molecular; Monitor; Neurodegenerative Disorders; Neurofibrillary Tangles; Penetration; Permeability; Pharmaceutical Chemistry; Pharmaceutical Preparations; Positioning Attribute; Positron-Emission Tomography; Protein Isoforms; Radioactivity; Radiolabeled; Research; Rodent; Schizophrenia; Site; Specificity; Standardization; Testing; Therapeutic; Transgenic Organisms; Translations; United States; Validation; Work; antagonist; brain tissue; cholesterol 24-hydroxylase; clinical translation; design; drug discovery; image translation; imaging study; improved; in vitro Assay; in vivo; in vivo evaluation; knockout gene; mouse model; nervous system disorder; next generation; nonhuman primate; novel; pharmacologic; prototype; radioligand; response; sample fixation; uptake

Alzheimer’s disease (AD) is a long-term neurodegenerative disorder that ranks sixth in the leading cause of all deaths in the United States and features amyloid β protein deposition and neurofibrillary tangles. At present, there are no drugs available to halt or reverse disease progression, and all efforts to create such therapies have failed. Recent studies have demonstrated that abnormalities of cholesterol homeostasis in the brain are strongly associated with several neurodegenerative diseases, including AD. The CYP46A1 enzymatic conversion of brain cholesterol into 24S-hydroxycholesterol is the major elimination mechanism to maintain brain cholesterol homeostasis. Disturbances in CYP46A1 is implicated in the AD physiopathology. Therefore, pharmacological modulation of CYP46A1 represents an attractive AD therapeutic approach. Positron emission tomography (PET) is capable of quantifying biochemical processes in vivo, and a suitable CYP46A1 ligand would substantially improve our understanding of CYP46A1-mediated cholesterol homeostasis under AD physiopathological conditions otherwise inaccessible by ex vivo (destructive) analysis. Quantification of CYP46A1 in living AD brain by PET would provide the assessment of distribution, target engagement and dose occupancy of new AD therapeutics. To date, no successful examples have been demonstrated to image CYP46A1 for clinical use, representing a significant deficiency of our ability to study this target in vivo. Therefore, we propose to develop a novel PET ligand that can fill this void, as the first translational imaging tool for AD. Our ligand [11C]CYP-507 demonstrated the first prototype for imaging towards CYP46A1, but was discontinued due to marginal binding specificity and low brain penetration. In our next generation, we successfully identified a lead molecule, CYP-812, which showed high binding affinity and high selectivity. An 11C-isotopologue of CYP-812 was synthesized and preliminary PET studies confirmed that we have overcome the major obstacles for CYP46A1 ligand development by achieving: 1) reasonable and regional-specific brain uptake; 2) moderate target specificity. Though CYP-812 is a promising lead, further optimizations aimed at higher brain permeability, improved potency and binding specificity with proper brain kinetics are sought for translational cross-species (rodents and nonhuman primates) imaging studies to achieve optimal CYP46A1 quantification for AD research. As specific goals, we will design and prepare a focused library of CYP46A1 modulators amenable for labeling with 11C or 18F, and evaluate their ability to quantify CYP46A1 activity and changes during drug challenge in rodents and nonhuman primates, as well as autoradiography and biological validation in postmortem human brain tissues. The impact of this work is not only to develop the first potent and selective CYP46A1 PET ligand for the study of AD-related biological processes, but also ultimately, via PET imaging validation in higher species, to advance this ligand for potential clinical translation and monitor target response of novel AD neurotherapeutics.

阿尔茨海默病 (AD) 是一种长期神经退行性疾病，在美国所有死亡原因中排名第六，其特点是淀粉样蛋白沉积和神经原纤维缠结，目前尚无药物可阻止或逆转疾病进展。最近的研究表明，大脑中胆固醇稳态的异常与包括 AD 在内的多种神经退行性疾病有关。 24S-羟基胆固醇是维持大脑胆固醇稳态的主要消除机制，CYP46A1 的紊乱与 AD 病理生理学有关，因此，CYP46A1 的药理学调节代表了一种有吸引力的 AD 治疗方法，能够量化 AD 的生化过程。体内，合适的 CYP46A1 配体将大大提高我们对 AD 病理生理学下 CYP46A1 介导的胆固醇稳态的理解通过 PET 对活体 AD 大脑中的 CYP46A1 进行定量，可以评估新的 AD 疗法的分布、靶点参与和剂量占用情况，迄今为止，还没有成功的例子可以对 CYP46A1 进行成像。因此，我们建议开发一种新型 PET 配体来填补这一空白，作为 AD 的第一个转化成像工具。 我们的配体 [11C]CYP-507 展示了第一个针对 CYP46A1 成像的原型，但由于边缘结合特异性和低脑渗透性而停止。在我们的下一代中，我们成功鉴定了一个先导分子 CYP-812，它表现出高结合力。合成了 CYP-812 的 11C 同位素体，初步 PET 研究证实，我们通过实现以下目标克服了 CYP46A1 配体开发的主要障碍：1)合理且区域特异性的大脑摄取；2) 虽然 CYP-812 是一种有前途的先导药物，但仍需针对跨物种（啮齿类动物和动物）寻求进一步优化，以提高大脑通透性、提高效力和结合特异性以及适当的大脑动力学。非人类灵长类动物）成像研究，以实现 AD 研究的最佳 CYP46A1 定量 作为具体目标，我们将设计和准备一个适合标记的 CYP46A1 调节剂的重点库。 11C 或 18F，并评估其在啮齿动物和非人类灵长类动物的药物挑战期间量化 CYP46A1 活性和变化的能力，以及在死后人类脑组织中进行放射自显影和生物验证。这项工作的影响不仅是开发第一个有效的和选择性 CYP46A1 PET 配体用于研究 AD 相关的生物过程，但最终，通过高等物种的 PET 成像验证，推进该配体的潜在临床转化并监测新型 AD 的靶标反应神经治疗学。