Overcoming Membrane Transporters to Improve CNS Drug Therapy

描述（由申请人提供）：迫切需要推进改善脑损伤后预后的药物治疗。值得注意的是，创伤性脑损伤（TBI）仍然是儿童和青年死亡和残疾的主要原因。迄今为止，所有探索单一药物或治疗TBI的临床试验都失败了。TBI有效治疗的唯一障碍是血脑屏障（BBB）和血脑脊液（CSF）上的atp结合盒转运体和溶质载体，它们通过主动和快速的再摄取和出口药物回到血液中，限制了药物对正常和受损大脑的生物利用度。这些障碍通常被认为是CNS损伤临床药物试验失败的主要原因，并且明显限制了许多对非CNS疾病有效的药物的治疗适应症。膜转运蛋白包括多药耐药蛋白、多药耐药相关蛋白和有机阴离子转运蛋白。重要的是，这些转运体的药理学抑制剂已经存在了几十年，用于提高作为膜转运体底物的药物的生物利用度。一种原型膜转运蛋白抑制剂是probenecid。Probenecid目前用于临床治疗尿酸血症，它是在第二次世界大战期间开发的，目的是提高青霉素对受伤士兵的生物利用度。probenecid或任何膜转运蛋白抑制剂与潜在的神经保护底物的联合治疗从未被评估过，尽管probenecid已被（安全地）单独用于评估TBI后脑- csf有机酸浓度。由于这些抑制剂利用还原性谷胱甘肽（GSH）共同输出物质出细胞，probenecid也维持细胞内GSH的储存，GSH是一种重要的内源性抗氧化剂。因此，probenecid本身可能通过维持内源性抗氧化储备（AOR）而具有神经保护作用，并通过减少跨膜屏障的外排来提高外源性治疗的脑生物利用度。PIs的初步数据显示，probenecid和fda批准的抗氧化剂n -乙酰半胱氨酸（NAC）联合使用可协同恢复小鼠脑外伤后脑损伤的总AOR。NAC的中枢神经系统使用受到脑生物利用度差的限制。再加上pi先前的报告显示，TBI后患者脑脊液的总AOR降低了50%，为支持这种联合策略提供了令人信服的转化数据。pi的假设是，包括克服膜运输障碍的治疗在内的组合策略将协同提高TBI后临床使用和新疗法的生物利用度和疗效。具体目的是确定probenecid和NAC联合使用的能力，以协同减少氧化应激和改善神经系统的神经元后拉伸诱导的创伤在体外和TBI后小鼠的神经功能；并确定probenecid和NAC联合使用安全、协同降低严重TBI患儿氧化应激的能力。

DESCRIPTION (provided by applicant): There is a sense of urgency to move forward with pharmacological therapies that improve outcome after brain injury. Notably, traumatic brain injury (TBI) remains the leading cause of death and disability amongst children and young adults. To date, all clinical trials exploring single agents or therapies for TBI have failed. Unique impediments to effective treatment for TBI are ATP-binding cassette transporters and solute carriers on the blood-brain (BBB) and blood-cerebrospinal fluid (CSF) barriers which limit bioavailability of drugs to normal and injured brain by active and rapid re-uptake and export of drug back into blood. These barriers are often cited as a major explanation for the failure of clinical drug trials for CNS injury, and clearly limit the therapeutic indications for many drugs otherwise effective in non-CNS diseases. Membrane transporters include the multidrug resistance proteins, multidrug resistance-associated proteins, and organic anion transporters. Importantly, pharmacological inhibitors of these transporters have existed for decades, used to enhance bioavailability of drugs that are membrane transporter substrates. A prototype membrane transporter inhibitor is probenecid. Probenecid is currently in clinical use to treat uric acidemia, and was developed during World War II to increase the bioavailability of penicillin to wounded soldiers. The combination of probenecid or any membrane transporter inhibitor with a potentially neuroprotective substrate has never been evaluated for the treatment of TBI, although probenecid alone has been used (safely) to evaluate brain-CSF concentrations of organic acids after TBI. Since these inhibitors utilize reduced glutathione (GSH) to co-export substances out of cells, probenecid also maintains intracellular stores of GSH, a prominent endogenous antioxidant. As such, probenecid itself may be neuroprotective by maintaining endogenous antioxidant reserves (AOR), complimenting its capacity to improve brain bioavailability of exogenous treatments by reducing efflux across membrane barriers. The PIs have provocative preliminary data showing that the combination of probenecid and the FDA-approved antioxidant N-acetylcysteine (NAC), whose CNS use is limited by poor brain bioavailability, synergistically restore total AOR in injured brain after TBI in mice. This coupled with the PIs' previous report showing that total AOR in CSF from patients are reduced by > 50% after TBI, provides compelling translational data in support of this combinational strategy. The PIs' hypothesis is that combinational strategies that include therapies that overcome membrane transport barriers will synergistically improve bioavailability and efficacy of both clinically used and novel therapies after TBI. Specific aims are to define the capacity of the combination of probenecid and NAC to synergistically reduce oxidative stress and improve neurological outcome in neurons after stretch-induced trauma in vitro and in mice after TBI in vivo; and to define the capacity of the combination of probenecid and NAC to safely and synergistically reduce oxidative stress in children with severe TBI. PUBLIC HEALTH RELEVANCE: Traumatic brain injury is a major cause of morbidity and mortality in adults, and is the leading cause of death in children. This proposal will evaluate the promising and clinically available combination of a membrane transport inhibitor (probenecid) and an antioxidant (N-acetylcysteine) for the capacity to synergistically improve outcome after TBI. This proposal includes contemporary in vitro and in vivo models of brain injury and a Phase I clinical safety/pharmacokinetics trial.