Bifunctional Nitric Oxide Donor Refractory to Nitrate Tolerance

描述（由申请方提供）：硝酸盐治疗外周高血压（HTN）的疗效有限，因为通过其对线粒体醛脱氢酶的失活快速诱导快速耐受。引入无耐受诱导的硝酸盐疗法将代表一个重要的商业机会，并解决一个主要的未满足的医疗需求。Radikal Therapeutics（RTX）正在开发R-100，这是一种由以下物质共价键合而成的小分子药物：1）释放一氧化氮（NO）的有机硝基血管扩张剂结构域，和2）作为活性氧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、过氧化氢解毒的过氧化氢酶模拟物和过氧亚硝酸盐分解催化剂。R-100已在离体和体内啮齿动物系统中被证明是一种强大的血管扩张剂，不会诱导耐受性。R-100尚未在长期给药的清醒大型动物中评估硝酸盐耐受性的诱导，这是其药物开发的一个重要里程碑。目标一：在HTN的清醒、非卧床、大型动物模型中建立R-100的药效学（PD）特征将在患有继发于血管内形成的单侧肾血管狭窄的HTN的清醒、仪器化、非卧床和遥测小型猪中进行一系列血液动力学研究。在系列A中，我们将关联R-100（3、10、20、30 mg/kg）单次给药的药代动力学（PK）特征和血流动力学效应，在连续剂量水平之间有1周的洗脱期。将对动物进行24小时监测，以收集连续血流动力学数据和R-100及其代谢产物的间歇血浆浓度。在系列B中，我们将通过进行R-100 q6 h给药3天的重复给药研究，评价系列A中最有希望的2种R-100剂量。R-100的血流动力学效应将与每6小时获得的R-100及其代谢产物的血浆峰浓度和谷浓度相关。在系列C中，我们将使用系列B中确定的最佳剂量在2周重复给药研究（q6 h）中评价R-100快速耐受的出现，其中血流动力学将与系列B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）相关剂量范围，2）PK特征，3）PD特征和4）耐受程度。目的#2：确定暴露于人肝和肠微粒体诱导的R-100的体外代谢特征。将合成主要代谢物，并评价其在人微粒体中的次级代谢。这些发现将通过鉴定负责R-100代谢转化的人CYPP 450酶来进一步完善。最后，我们将确定R-100是否抑制主要的人类CYP 450酶。拟议研究的结果预计将作为向FDA提交的1a期IND申请的基础，以检查口服R-100在稳定的原发性HTN受试者中的安全性和有效性。后续1b期重复给药2周研究将进一步确定R-100是否诱导人体耐受性。 公共卫生相关性：难治性周围性高血压是一种常见的危及生命的疾病，可增加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难治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有效。我们现在建议在一个明确的临床相关的高血压大型动物模型中确定我们的技术的价值。

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.