Bifunctional Nitric Oxide Donor Refractory to Nitrate Tolerance

描述(申请人提供)：硝酸盐疗法治疗周围性高血压(HTN)的疗效有限，因为它通过灭活线粒体乙醛脱氢酶而迅速诱导快速反应。引进一种无耐受诱导的硝酸盐疗法将是一个重要的商业机会，并解决了一个重大的未得到满足的医疗需求。Radikal Treeutics(RTX)正在开发R-100，这是一种小分子制剂，由以下两种共价键形成：1)释放一氧化氮(NO)的有机硝基血管扩张剂结构域，2)用作活性氧物种降解催化剂的吡咯烷氮氧化物结构域：超氧化物歧化酶(SOD)模拟物、解毒过氧化氢的过氧化氢酶模拟物和过氧亚硝酸盐分解催化剂。R-100已在体外和体内啮齿动物系统中被证明是一种强大的血管扩张剂，不会诱导耐受。R-100尚未在长期给药的清醒大型动物中被评估为诱导硝酸盐耐受，这是其药物开发的一个关键里程碑。目的#1：在清醒的、可移动的、大动物HTN模型中建立R-100的药效学(PD)谱一系列血流动力学研究将在清醒、可移动、可远程测量的小型猪中进行，这些小型猪继发于血管内所致的单侧肾血管狭窄。在A系列中，我们将对单次注射R-100(3、10、20、30 mg/kg)的药代动力学(PK)曲线和血流动力学效应进行关联，在连续剂量水平之间有一周的洗脱期。将对动物进行24小时的监测，以收集连续的血流动力学数据和R-100及其代谢物的间歇性血浆浓度。在B系列中，我们将对A系列中最有希望的两剂R-100进行评估，方法是对R-100进行为期3天的重复剂量研究。R-100的血流动力学效应与血浆R-100及其代谢物Q6h的峰、谷浓度相关。在C系列中，我们将利用B系列中确定的最佳剂量，在为期两周的重复剂量研究(Q6h)中评估R-100的快速反应的出现，其中血流动力学将与B系列中的血浆PK测定相关。总之，这些研究将在大型动物模型中建立：1)相关的剂量范围，2)PK曲线，3)PD曲线，以及4)耐受程度。目的#2：建立人肝和肠道微粒体作用下R-100的体外代谢谱。主要的代谢物将被合成，并被评估为人类微生物体中的次生代谢。这些发现将通过识别负责R-100代谢转化的人类CYP450酶来进一步完善。最后，我们将确定R-100是否抑制人类主要的细胞色素P450酶。拟议的研究结果有望作为FDA 1a期IND应用的基础，以检查口服R-100在稳定性基本HTN受试者中的安全性和有效性。后续的1b期重复给药两周的研究将进一步确定R-100是否会诱导人体耐受。 公共卫生相关性：顽固性外周高血压是一种常见的危及生命的疾病，它增加了中风和主动脉瘤等心血管事件的风险。我们正在开发一种针对顽固性高血压基本机制的新药，并已在小动物模型的初步研究中证明是有效的。我们现在建议在一个明确的、与临床相关的大动物高血压模型中定义我们的技术的价值。

DESCRIPTION (provided by applicant): Nitrate therapy for peripheral hypertension (HTN) is limited in efficacy due to the rapid induction of tachyphylaxis, via its inactivation of mitochondrial aldehyde dehydrogenase. The introduction of a nitrate therapy free of tolerance induction would represent a significant commercial opportunity and address a major unmet medical need. Radikal Therapeutics (RTX) is developing R-100, a small molecule agent formed from the covalent linkage of: 1) an organic nitrovasodilator domain that releases nitric oxide (NO), and 2) a pyrrolidine nitroxide domain that acts as a catalyst of reactive oxygen species degradation: a superoxide dismutase (SOD) mimetic, a catalase mimic that detoxifies hydrogen peroxide, and a peroxynitrite decomposition catalyst. R-100 has been proven in ex vivo and in vivo rodent systems to act as a powerful vasodilator that does not induce tolerance. R-100 has not yet been evaluated for induction of nitrate tolerance in chronically-dosed conscious large animals, a critical milestone in its pharmaceutical development. Aim #1: Establish the pharmacodynamic (PD) profile of R-100 in a conscious, ambulatory, large-animal model of HTN A series of hemodynamic studies wil be conducted in conscious, instrumented, ambulatory, and telemetered minipigs with HTN secondary to an endovascular-created, unilateral, renovascular stenosis. In Series A, we will correlate the pharmacokinetic (PK) profile and hemodynamic effect of single administration of R-100 (3, 10, 20, 30 mg/kg), with a 1-week washout period between successive dose levels. Animals will be monitored for 24 h to collect continuous hemodynamic data and intermittent plasma concentrations of R-100 and its metabolites. In Series B, we will evaluate the most promising 2 doses of R-100 from Series A, by carrying out a repeat-dose study of R-100 administered q6h for a period of 3 days. The hemodynamic effects of R-100 will be correlated with plasma peak and trough concentrations of R-100 and its metabolites obtained q6h. In Series C, we will evaluate the emergence of tachyphylaxis to R-100 in a 2-week repeat-dose study (q6h) utilizing the optimal dose determined in Series B, wherein hemodynamics will be correlated with plasma PK determinations as in Series B. Taken together, these studies will establish in a large animal model: 1) the relevant dose range, 2) the PK profile, 3) the PD profile, and 4) the extent of tolerance. Aim #2: Establish the in vitro metabolic profile of R-100 induced by exposure to human liver and intestinal microsomes. Prominent metabolites will be synthesized and evaluated for secondary metabolism in human microsomes. These findings will be further refined by identifying human CYPP450 enzymes that are responsible for metabolic transformation of R-100. Lastly, we will determine if R-100 inhibits major human CYP450 enzymes. The results of the proposed studies are expected to serve as the basis for a Phase 1a IND application to the FDA examining the safety and efficacy of oral R-100 in subjects with stable essential HTN. Follow-on Phase 1b repeat-dose 2-week studies will additionally establish whether R-100 induces tolerance in man. PUBLIC HEALTH RELEVANCE: Refractory peripheral hypertension is a frequent and life-threatening condition that increases the risk of cardiovascular events such as stroke and aortic aneurysm. We are developing a novel drug that targets the basic mechanisms of refractory hypertension and has been shown to be effective in pilot studies in a small animal model. We now propose to define the value of our technology in a definitive clinically-relevant large animal model of hypertension.