Design And Development Of Experimental Therapeutics

实验疗法的设计和开发

• 批准号: 6530309
• 负责人: Nigel H. Greig
• 金额: --
• 依托单位: NATIONAL INSTITUTE ON AGING
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6530309
• 关键词: Alzheimer's disease; Parkinson's disease; aging; brain disorder chemotherapy; cardiovascular agents; cardiovascular disorder chemotherapy; cardiovascular pharmacology; drug design /synthesis /production; drug screening /evaluation; endocrine pharmacology; human subject; human therapy evaluation; hypoglycemic agents; neuropharmacologic agent; neuropharmacology; noninsulin dependent diabetes mellitus; patient oriented research; stroke

Design and Development of Drugs and Pharmacologic Probes The goal of the Drug Design & Development Section is to develop novel agents against rate-limiting steps involved in the pathophysiology of diseases associated with aging, with particular interest in neurological diseases, such as Alzheimer's disease (AD) and stroke, as well as in systemic diseases, such as diabetes. Alzheimer's Disease: Although the neuropathological quantification of beta-amyloid (Ab) plaques and neurofibrillary tangles in the AD brain is the basis for confirming disease diagnosis after death, it is the neocortical synapses rather than the plaques and tangles that correlates best to psychometric indices of cognitive performance in AD. The loss of cholinergic synaptic markers in selected brain regions remains one of the earliest events leading to AD, with the cholinergic system being the most affected of the neurotransmitters and intimately involved in memory processing. Anticholinesterases: Our efforts have focused on augmenting the cholinergic system, but maintaining the normal temporal pattern of neurotransmitter release by selectively inhibiting the enzyme acetylcholinesterase (AChE), acetylcholine?s (ACh) degrading enzyme. Extensive studies involving chemistry, X-ray crystallography, biochemistry and pharmacology resulted in the ability to differentiate between the cholinesterase subtypes. This has provided us the ability to develop novel agents to selectively and reversibly inhibit either AChE or butyrylcholinesterase (BChE) in either the brain or periphery for an optimal duration for the potential treatment of a variety of diseases, such as AD, Myasthenia Gravis, and as chemical warfare prophylactics. Acetylcholinesterase: Two of numerous novel synthesized AChE inhibitors are in development for the treatment of AD; specifically, the pure non-competitive inhibitors, phenserine and tolserine. Both are phenylcarbamates of physostigmine that are 70- and 190-fold selective for AChE vs. BChE. Compared to current agents for AD treatment, they have a favorable toxicologic profile and robustly enhances cognition in animal models. Studies were undertaken to determine their time-dependent effects on cholinergic function, AChE activity, brain and plasma drug levels and brain extracellular ACh concentrations in rodents to support clinical studies. They possess along duration of action, coupled with a short pharmacokinetic half-life, reduces dosing frequency, decreases body drug exposure and minimizes the dependence of drug action on the individual variations of drug metabolism commonly found in the elderly In a collaboration with Axonyx Corp. (New York), clinical studies were undertaken to evaluate the safety, maximum tolerated dose (MTD), pharmacokinetics (PK), and pharmacodynamics (PD) of phenserine tartrate, in healthy elderly subjects to support efficacy trials. Specifically, a Phase I, blinded, placebo controlled, dose escalation study, was undertaken in healthy elderly volunteers (n=32) that received single oral doses (5 to 20 mg). In conclusion, phenserine tartrate was safe and well tolerated as a single oral dose of either 5 or 10 mg. Further studies demonstrated safety following twice daily dosing for 5 consecutive days, and the agent is currently in phase II clinical efficacy trials in volunteers with mild to moderate AD. Butyrylcholinesterase: In the normal brain, approximately 80% of brain cholinesterase activity is AChE, 20% is BChE. AChE activity is concentrated mainly in neurons, while BChE is primarily associated with glial cells. Kinetic evidence indicates a role for BChE, in hydrolysing excess ACh. In advanced AD, however, AChE activity decreases to 15% of normal levels in specific brain regions, whereas BChE activity increases. The ratio of BChE to AChE is set in normal brain to achieve optimal brain activity and changes dramatically in cortical regions as AD progresses, thereby changing BChE?s role. Highly potent BChE inhibitors have been synthesized and are in preclinical assessment to evaluate their potential AD drug candidates. Molecular events associated with AD: The reduction in levels of the potentially toxic amyloid-b peptide (Ab) has emerged as an important therapeutic goal in AD. Key targets for this goal are factors that affect the expression and processing of the Ab precursor protein (bAPP). Our earlier research showed that our AChE inhibitor, phenserine, reduces bAPP levels in vivo. We therefore studied the mechanism of phenserine's actions to define the regulatory elements in bAPP processing. Phenserine treatment resulted in decreased secretion of soluble bAPP and Ab in cultured human neuroblastoma cells without toxicity. This activity was unrelated to its action as an anticholinesterase, but was post-transcriptional as it suppressed bAPP protein expression without altering bAPP mRNA levels. This was mediated via 5' untranslated region (5 UTR) of bAPP mRNA. We have synthesized novel agents to both characterize the target as well as to selectively and optimally regulate bAPP mRNA translation to reduce Ab synthesis. Stroke and Parkinson's disease: Drugs currently used in patients with stroke and Parkinson's disease (PD) provide temporary relief of symptoms, but do not prevent the cell death. Cell death in both results from a process called apoptosis, which may be triggered by mitochondrial impairment and oxidative stress. As up-regulation of p53 has been described as a common feature of several neurodegenerative disorders, and is a critical and rate-limiting step in the cascade of biochemical events that leads to apoptosis, it represents a potential target for interventive drug development. As a consequence, we recently designed and synthesized a novel series of tetrahydrobenzothiazole analogues that are based on the structure of the antihelminthic compound, pifithrin-a . Compounds are currently being assessed for neuroprotective action in tissue culture and in animal models to select agents of potential for evaluation as drug candidates. Diabetes: Type 2 diabetes is a prevalent disease in the elderly. It is caused by a relative deficiency of insulin and a decrease in insulin action at insulin-sensitive tissues. Present treatments are less than satisfactory. In collaborative studies with Josephine Egan, M.D. (Diabetes Section, LCS, NIA), we have extensive experience with GLP-1, a peptide that is actively secreted from the gut in response to food and is a potent secretagogue (i.e., insulinotropic), as a potential treatment for diabetes. When given continuously to diabetic subjects, pharmacological concentrations of GLP-1 can maintain blood glucose levels within their normal range. However, a major shortcoming of GLP-1 given exogenously as a potential therapeutic is its brief biological half-life, it is cleared within minutes in both rodents and humans. As a consequence, GLP-1 was used as a starting point to develop longer acting peptides Studies with exendin-4, an endogenous peptide from the Gila monster lizard that shares 53% homology with GLP-1, have shown that it, is (i) more potent and (ii) maintains higher plasma levels of insulin over, (iii), a longer time duration than does GLP-1, and (iv) have supported the development of exedin-4 into phase II efficacy studies for the treatment of type 2 diabetes. Novel, chimeric peptides that combine the best features of GLP-1 and exendin-4 have been design, synthesized and are under assessment in a variety of cell culture and animal models to assess their potential for clinical development.

药物设计与开发部门的目标是开发针对与衰老相关的疾病病理生理学中涉及的限速步骤的新型药物，特别关注神经系统疾病，如阿尔茨海默病（AD）和中风，以及全身疾病，如糖尿病。阿尔茨海默病：虽然阿尔茨海默病大脑中β -淀粉样蛋白（Ab）斑块和神经原纤维缠结的神经病理学定量是确认死亡后疾病诊断的基础，但与阿尔茨海默病认知表现的心理测量指标相关性最好的是新皮质突触，而不是斑块和缠结。脑区胆碱能突触标记物的缺失是导致阿尔茨海默病的最早事件之一，胆碱能系统是受神经递质影响最大的系统，与记忆加工密切相关。抗胆碱酯酶：我们的研究重点是增强胆碱能系统，但通过选择性抑制乙酰胆碱酯酶（AChE）来维持神经递质释放的正常时间模式。s （ACh）降解酶。广泛的研究涉及化学，x射线晶体学，生物化学和药理学导致区分胆碱酯酶亚型的能力。这为我们提供了开发新型药物的能力，以选择性和可逆地抑制脑或外周的乙酰胆碱酯酶或丁酰胆碱酯酶（BChE），以达到治疗多种疾病的最佳持续时间，如AD，重症肌无力，以及作为化学战预防。乙酰胆碱酯酶：两种新型合成乙酰胆碱酯酶抑制剂正在开发中，用于治疗阿尔茨海默病；特别是纯非竞争性抑制剂，phenserine和tolserine。这两种物质都是苯基氨基甲酸盐，对乙酰胆碱的选择性分别为70倍和190倍。与目前治疗阿尔茨海默病的药物相比，它们具有良好的毒理学特征，并在动物模型中有力地增强了认知能力。研究确定了它们对啮齿动物胆碱能功能、乙酰胆碱酯酶活性、脑和血浆药物水平以及脑细胞外乙酰胆碱酯酶浓度的时间依赖性影响，以支持临床研究。它们具有较长的作用时间，加上较短的药代动力学半衰期，减少给药频率，减少体内药物暴露，并最大限度地减少药物作用对老年人中常见的药物代谢个体差异的依赖。与Axonyx公司（纽约）合作，进行了临床研究，以评估酒石酸苯丝氨酸的安全性，最大耐受剂量（MTD），药代动力学（PK）和药效学（PD）。在健康老年人受试者中支持疗效试验。具体而言，在健康老年志愿者（n=32）中进行了一项I期，盲法，安慰剂对照，剂量递增研究，接受单次口服剂量（5至20mg）。综上所述，酒石酸非丝氨酸单次口服5或10毫克是安全且耐受性良好的。进一步的研究表明，连续5天每天两次给药是安全的，该药物目前正在轻度至中度阿尔茨海默病志愿者中进行II期临床疗效试验。丁胆碱酯酶：在正常的大脑中，大约80%的脑胆碱酯酶活性是乙酰胆碱酯酶，20%是BChE。AChE活性主要集中在神经元中，而BChE主要与神经胶质细胞相关。动力学证据表明BChE在水解过量乙酰胆碱中起作用。然而，在晚期AD中，特定脑区乙酰胆碱酯酶活性下降到正常水平的15%，而脑乙酰胆碱酯酶活性则增加。BChE与AChE的比值是在正常大脑中设定的，以达到最佳的大脑活动，随着AD的进展，皮质区域的BChE与AChE的比值发生了显著变化，从而改变了BChE？年代的角色。高效的BChE抑制剂已被合成，并处于临床前评估，以评估其潜在的AD候选药物。与AD相关的分子事件：降低潜在毒性淀粉样蛋白b肽（Ab）的水平已成为AD的重要治疗目标。这一目标的关键靶点是影响Ab前体蛋白（bAPP）表达和加工的因素。我们早期的研究表明，我们的AChE抑制剂phenserine可以降低体内bAPP水平。因此，我们研究了phenserine的作用机制，以确定bAPP加工中的调控元件。Phenserine使培养的人神经母细胞瘤细胞可溶性bAPP和Ab分泌减少，但无毒性。这种活性与其作为抗胆碱酯酶的作用无关，但它是转录后的，因为它抑制了bAPP蛋白的表达，而不改变bAPP mRNA的水平。这是通过bAPP mRNA的5'非翻译区（5utr）介导的。我们已经合成了新的药物来表征靶标，并有选择地和最佳地调节bAPP mRNA的翻译，以减少Ab合成。中风和帕金森氏病：目前用于中风和帕金森氏病（PD）患者的药物可以暂时缓解症状，但不能防止细胞死亡。两者的细胞死亡都是由一种叫做细胞凋亡的过程引起的，这种过程可能是由线粒体损伤和氧化应激引起的。由于p53的上调已被描述为几种神经退行性疾病的共同特征，并且是导致细胞凋亡的生化事件级联中的关键和限速步骤，因此它代表了干预性药物开发的潜在靶点。因此，我们最近设计并合成了一系列新的四氢苯并噻唑类似物，这些类似物是基于杀虫化合物氟虫菊酯-a的结构。目前正在组织培养和动物模型中评估化合物的神经保护作用，以选择潜在的候选药物进行评估。糖尿病：2型糖尿病是老年人的常见病。它是由胰岛素相对缺乏和胰岛素敏感组织中胰岛素作用减少引起的。目前的治疗并不令人满意。在与Josephine Egan， M.D.（糖尿病科，LCS， NIA）的合作研究中，我们在GLP-1方面有丰富的经验，GLP-1是一种肠道对食物反应时积极分泌的肽，是一种有效的促分泌剂（即胰岛素促分泌剂），作为糖尿病的潜在治疗方法。连续给予糖尿病患者GLP-1药理学浓度可使血糖水平维持在正常范围内。然而，外源性GLP-1作为潜在治疗药物的一个主要缺点是其生物半衰期短，在啮齿动物和人类中均在几分钟内被清除。因此，GLP-1被用作开发长效肽的起始点，exendin-4是一种来自Gila怪物蜥蜴的内源性肽，与GLP-1有53%的同源性，研究表明，exendin-4 (i)更有效，（ii）维持更高的血浆胰岛素水平，（iii）比GLP-1持续时间更长，（iv）支持exendin-4进入治疗2型糖尿病的ii期疗效研究。结合GLP-1和exendin-4最佳特征的新型嵌合肽已被设计、合成，并正在各种细胞培养和动物模型中进行评估，以评估其临床开发潜力。