PARP inhibitor and Redox Catalyst Conjugate for Traumatic Brain Injury

描述（由申请人提供）：Radikal Therapeutics （RTX）正在开发一种新型双功能药物（R-503），可阻断导致创伤性脑损伤（TBI）的两条主要病理生理途径。R-503是1)核DNA修复酶聚（adp -核糖）聚合（PARP）的有效抑制剂（IC50=20 nM）， 2)基于二氢脂酸酯（DHL）的氧化还原催化剂，是一种模拟超氧化物歧化酶、模拟过氧化氢酶和过氧亚硝酸盐分解催化剂。上述两个功能片段的共价键形成一个单一的治疗剂，有望同时和共定位地中断TBI损伤的氧化和PARP途径。这两种途径与TBI发病机制的相关性已经在TBI的实验模型和临床环境中得到了很好的证实。目前在TBI患者中证实，PARP的过度激活消耗其底物（NAD+），从而消耗ATP储存，引发能量衰竭、细胞稳态丧失、神经元坏死和脑梗死。PARP激活与TBI的相关性不仅体现在脑损伤的开始阶段，还体现在恢复阶段：最近的数据表明，PARP激活通过刺激小胶质细胞和上调NF-:B介导的转录来阻断TBI的恢复性反应（神经发生），而NF-:B介导的转录在炎症因子、趋化因子、粘附分子和炎症介质（包括基质金属蛋白酶）的表达中起着核心作用。尽管PARP活化在TBI的起始和恢复阶段具有明显的中心作用，但在氧化还原介导的损伤中，显然还有其他不依赖PARP的下游效应物。因此，单独的PARP抑制所提供的临床获益水平不太可能足够强大。因此，我们假设更全面的TBI恢复需要：1)上游氧化应激和亚硝化氧化还原应激的消除，以及2)下游PARP活性的抑制。我们将通过比较R-503、DHL（一种氧化还原催化剂）、INO-1001（一种单功能PARP抑制剂）、DHL和INO-1001的联合治疗以及假性损伤组的治疗，寻求在创伤性脑损伤的实验模型中证实这一假设。将采用复苏模式，即在皮质挫伤后2小时引入治疗药物并持续2周。神经行为监测将包括第14天的运动任务评估（平衡木、平衡木行走、莫里斯水迷宫），以及死后脑组织氧化还原和炎症损伤的形态学和生化证据分析，包括组织学评分、脂质过氧化水平、蛋白质亚硝化、PARP激活、细胞凋亡以及TNF-1、MIP- 11、核NF-：的浓度。证实RTX的双功能方法比单功能PARP抑制剂和氧化还原催化剂具有独特的治疗优势，以及它们的组合，将为继续开发R-503作为TBI紧急复苏和恢复的一流药物提供理由。

DESCRIPTION (provided by applicant): Radikal Therapeutics (RTX) is developing a novel bifunctional agent (R-503) that blocks two principal pathophysiolgoical pathways that contribute to traumatic brain injury (TBI). R-503 is both 1) a potent inhibitor of the nuclear DNA repair enzyme poly(ADP-ribose) polymeras ("PARP") (IC50=20 nM), and 2) a dihydrolipoate ("DHL")-based redox catalyst that is a superoxide dismutase mimetic, a catalase mimetic, and a peroxynitrite decomposition catalyst. The covalent linkage of both of the above functional moieties to form a single therapeutic agent is expected to create simultaneous and co-localized interruption of both the oxidant and PARP pathways of injury in TBI. The relevance of both pathways to the pathogenesis of TBI has been well established in experimental models of TBI and in the clinical setting. Overactivation of PARP, now confirmed in patients with TBI, consumes its substrate (NAD+), thereby depleting ATP stores and provoking energetic failure, loss of cellular homeostasis, neuronal necrosis, and brain infarction. The relevance of PARP activation to TBI is not merely in the initiation of brain injury, but also figures prominently in the recovery phase: Recent data indicate that PARP activation blocks the restorative response to TBI (neurogenesis) via its stimulation of microglial cells and its upregulation of NF-:B mediated transcription, which plays a central role in the expression of inflammatory cytokines, chemokines, adhesion molecules and inflammatory mediators, including matrix metalloproteases. Despite the apparent centrality of PARP activation to the initiation and recovery phases of TBI, there are clearly additional PARP-independent downstream effectors of redox-mediated injury. Accordingly, the level of clinical benefit afforded by stand-alone PARP inhibition is not likely to be sufficiently robust. Accordingly, we hypothesize that more comprehensive recovery from TBI wil require both: 1) the elimination of upstream oxidative and nitrosative redox stress, and 2) inhibition of downstream PARP activity. We will seek to confirm this hypothesis in an experimental model of TBI in which rats are subjected to a well- defined cortical contusion trauma, by comparing treatment with R-503, DHL (a redox catalyst), INO-1001 (a monofunctional PARP inhibitor), a combination of DHL and INO-1001, and a sham injury group. A resuscitation paradigm will be employed, whereby therapeutic agents will be introduced 2 h after cortical contusion and continued for 2 weeks. Neurobehavioral monitoring will include assessment of motor tasks (beam balance, beam walking, Morris water maze) on day 14, and post-mortem analysis of brain tissue for morphologic and biochemical evidence of redox and inflammatory injury, as manifested by histology score, levels of lipid peroxidation, protein nitrosation, PARP activation, apoptosis, and concentrations of TNF-1, MIP- 11, nuclear NF-: . Confirmation that RTX's bifunctional approach confers unique therapeutic superiority over a monofunctional PARP inhibitor and redox catalyst, and their combination, would provide justification for the continued development of R-503 as a first-in-class agent for emergent resuscitation and recovery of TBI. PUBLIC HEALTH RELEVANCE: The induction of cellular injury responses contributes importantly to the ultimate neurological outcome after severe head trauma. At present, there are no approved therapeutic measures that arrest inflammation and cell death programs that are triggered after cortical contusion. We are developing a novel drug that targets the basic mechanisms of this condition and will test this agent in a clinically-relevant animal model.