Bifunctional Redox Agent for the Treatment of PPHN

描述（由申请人提供）：新生儿持续性肺动脉高压（PPHN）是一种危及生命的新生儿疾病，其中出生后肺血管阻力升高使肺血流通过动脉导管和卵圆孔水平的右向左分流转向体循环。目前的治疗包括机械通气、氧气和吸入性一氧化氮（iNO），一种选择性扩张肺血管的气体，但仅对30-50%的患者有效。对iNO治疗无反应者通过体外膜氧合（ECMO）进行支持。虽然PPHN有多种生物学触发因素，但我们目前的理解与新生儿肺血管中过量的超氧化物和NO缺乏所产生的最终常见损伤效应机制的趋同是一致的。这两种自由基的失衡直接损害了出生后肺小动脉适当扩张的能力。为了解决这一未满足的需求，并克服iNO治疗的局限性，Radikal Therapeutics正在开发R-100，这是一种由以下共价键形成的小分子药物：1）释放NO的有机硝基血管扩张剂结构域，和2）作为超氧化物歧化酶模拟物，过氧化氢酶模拟物和过氧亚硝酸盐分解催化剂的吡咯烷氮氧化物结构域。R-100已被证明在选择性缓解野百合碱攻击大鼠的肺动脉高压和新生羔羊模型的严重PPHN难治性iNO的初步研究中显着有效。I期具体目标：在iNO难治性重度PPHN的新生羔羊模型中对比iNO和R-100的疗效和选择性。我们将在麻醉和机械通气的新生羔羊中进行剂量递增研究，其中PPHN已通过子宫内动脉导管结扎诱导。预计R-100在选择性降低平均肺动脉血压方面上级于iNO。进展至II期NIH SBIR的标准：相对于基线血流动力学，R-100治疗必须满足以下所有血流动力学终点：1）平均肺动脉血压（MPAP）相对于基线的升高降低> 50%，3）外周平均动脉血压降低< 10%，4）停止治疗后基线MPAP增加< 10%，和5）在所有上述参数上等同于或优于iNO。II期特定目的：在GLP毒理学和安全药理学研究中确定IV R-100的亚急性安全性和耐受性。遗传毒理学研究将包括艾姆斯试验、染色体畸变试验和大鼠微核试验。安全药理学研究将包括幼龄大鼠神经行为和呼吸研究以及幼龄犬心血管研究。将在新生大鼠和幼犬中进行为期4周的毒理学研究。这些研究将确定每个种属的无明显不良事件水平（NOAEL），并为人类新生儿的安全性、耐受性和药代动力学探索的剂量范围提供监管依据。 公共卫生相关性：新生儿持续性肺动脉高压（PPHN）是一种罕见但危及生命的足月儿疾病，出生后肺部血压未能降至正常水平。现有的治疗方法包括吸入一氧化氮气体，但事实证明，这对三分之一以上的婴儿无效。我们正在开发一种针对PPHN基本机制的新药，并已在大型动物PPHN模型的初步研究中显示出有效性，其中吸入一氧化氮仅表现出微弱的反应。我们现在建议在一个明确的临床相关的PPHN动物模型中定义我们的技术的价值。

DESCRIPTION (provided by applicant): Persistent pulmonary hypertension of the newborn (PPHN) is a life-threatening neonatal condition wherein an elevation in pulmonary vascular resistance after birth diverts pulmonary blood flow via a right-to-left shunt, at the levels of the ductus arteriosus and foramen ovale, into the systemic circulation. Current therapy includes mechanical ventilation, oxygen, and inhalational nitric oxide (iNO), a gas that selectively dilates the pulmonary vasculature but is only effective in 30-50% of patients. Non-responders to iNO therapy are supported via extracorporeal membrane oxygenation (ECMO). Although PPHN has multiple biological triggers, our current understanding is consistent with a convergence to a final common effector mechanism of injury produced by an excess of superoxide and a deficiency of NO in the newborn pulmonary vasculature. The imbalance of these two free radicals directly impairs the ability of the pulmonary arteriole to dilate appropriately after birth. To address this unmet need, and overcome the limitations in response to iNO therapy, Radikal Therapeutics is developing R-100, a small molecule agent formed from the covalent linkage of: 1) an organic nitrovasodilator domain that releases NO, and 2) a pyrrolidine nitroxide domain that acts as a superoxide dismutase mimetic, catalase mimetic, and peroxynitrite decomposition catalyst. R-100 has been shown to be dramatically effective in selectively relieving pulmonary arterial hypertension in monocrotaline-challenged rats and in pilot studies of newborn lamb models of severe PPHN refractory to iNO. Phase I Specific Aim: Contrast the efficacy and selectivity of iNO and R-100 in a newborn lamb model of severe PPHN refractory to iNO. We will carry out a dose-escalation study in anesthetized and mechanically-ventilated newborn lambs in which PPHN has been induced by in utero ligation of the ductus arteriosus. R-100 is expected to be superior to iNO in selectively reducing mean pulmonary arterial blood pressure. Criteria for progression to the Phase 2 NIH SBIR: Treatment with R-100 must satisfy, relative to baseline hemodynamics, all of the following hemodynamic endpoints: 1) > 50% reduction in the elevation relative to baseline in mean pulmonary arterial blood pressure (MPAP), 2) > 50% increase relative to baseline in pulmonary blood flow, 3) < 10% reduction in peripheral mean arterial blood pressure, 4) < 10% increase in baseline MPAP after cessation of treatment, and 5) equivalence or superiority to iNO on all of the above parameters. Phase II Specific Aim: Establish the subacute safety and tolerance of IV R-100 in GLP toxicology and safety pharmacology studies. Genetic toxicology studies will include the Ames, chromosomal aberration assay, and rat micronucleus assay. Safety pharmacology studies will include juvenile rat neurobehavioral and respiratory studies and juvenile canine cardiovascular studies. Toxicology investigations will be carried out over 4 weeks in newborn rats and dog pups. These studies will identify the No Observed Adverse Event Level (NOAEL) in each species, and provide the regulatory basis for a dose range to be explored for safety, tolerance, and pharmacokinetics in human neonates. PUBLIC HEALTH RELEVANCE: Persistent pulmonary hypertension of the newborn (PPHN) is a rare but life-threatening condition of the term infant in which the blood pressure in the lungs fails to decrease to a normal level after birth. Existing therapy for this condition involves the inhalation of nitric oxide gas, but this proves ineffective in more than a third of infants. We are developing a novel drug that targets the basic mechanisms of PPHN and has been shown to be effective in pilot studies in a large animal PPHN model wherein inhaled nitric oxide exhibits only a weak response. We now propose to define the value of our technology in a definitive clinically-relevant animal model of PPHN.