Overcoming Membrane Transporters to Improve CNS Drug Therapy

描述（由申请人提供）：有一种紧迫感，以推进药物治疗，改善脑损伤后的结果。值得注意的是，创伤性脑损伤（TBI）仍然是儿童和年轻人死亡和残疾的主要原因。迄今为止，所有探索TBI单一药物或疗法的临床试验都失败了。有效治疗TBI的独特障碍是血脑（BBB）和血脑脊髓液（CSF）屏障上的ATP结合盒转运蛋白和溶质载体，其通过药物的主动和快速再摄取和输出回到血液中而限制药物对正常和受损脑的生物利用度。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，并明显限制了许多在非CNS疾病中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，这些转运蛋白的药理学抑制剂已经存在了几十年，用于提高作为膜转运蛋白底物的药物的生物利用度。原型膜转运蛋白抑制剂是丙磺舒。丙磺舒目前在临床上用于治疗尿酸血症，并在第二次世界大战期间开发，以增加青霉素对受伤士兵的生物利用度。 丙磺舒或任何膜转运蛋白抑制剂与潜在的神经保护底物的组合从未被评估用于TBI的治疗，尽管丙磺舒单独用于（安全地）评估TBI后脑CSF中有机酸的浓度。由于这些抑制剂利用还原型谷胱甘肽（GSH）共同输出物质的细胞，丙磺舒也保持细胞内储存的GSH，一个突出的内源性抗氧化剂。因此，丙磺舒本身可能通过维持内源性抗氧化剂储备（AOR）而具有神经保护作用，补充其通过减少跨膜屏障的外排来改善外源性治疗的脑生物利用度的能力。PI具有挑衅性的初步数据，显示丙磺舒和FDA批准的抗氧化剂N-乙酰半胱氨酸（NAC）的组合，其CNS使用受到脑生物利用度差的限制，协同恢复小鼠TBI后受损脑中的总AOR。这与PI先前的报告显示TBI后患者CSF中的总AOR降低> 50%相结合，提供了支持这种组合策略的令人信服的翻译数据。 PI的假设是，包括克服膜转运障碍的疗法在内的组合策略将协同改善TBI后临床使用的和新型疗法的生物利用度和疗效。具体目的是确定丙磺舒和NAC的组合协同降低氧化应激和改善神经功能的能力在体外拉伸诱导的创伤后的神经元和在体内TBI后的小鼠;并确定丙磺舒和NAC的组合安全和协同降低严重TBI儿童的氧化应激的能力。 公共卫生相关性：创伤性脑损伤是成人发病和死亡的主要原因，也是儿童死亡的主要原因。该提案将评估膜转运抑制剂（丙磺舒）和抗氧化剂（N-乙酰半胱氨酸）的有前途和临床可用的组合，以协同改善TBI后的结果。该提案包括当代脑损伤的体外和体内模型以及I期临床安全性/药代动力学试验。

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.