Development of RLIP767 as a Radiation Countermeasure

描述（由申请人提供）：辐射诱导病理的主要诱因是暴露后最初时刻形成的活性氧引起的细胞损伤。大多数治疗剂是自由基清除剂，在暴露时必须以高浓度存在，这使得它们作为治疗方法存在问题。此外，正常细胞已经有清道夫分子存在，如谷胱甘肽。谷胱甘肽接受来自反应性亲电试剂的电子作为正常细胞防御的一部分，但由此产生的亲电性谷胱甘肽偶联物仍然对细胞完整性构成威胁。最终消除风险需要运输和消除这些活性谷胱甘肽s偶联物，这是RLIP76（一种膜相关运输蛋白）的关键功能。Terapio一直在测试RLIP76作为高剂量辐射中毒的全身疗法。对小鼠的初步研究表明，通过全身给药增加RLIP76的细胞含量，即使是在辐射暴露后给药，也能显著提高存活率。除了最高暴露水平外，RLIP76的给药量与存活率之间存在明确的剂量-反应关系。此外，RLIP76可以口服给药，增加了治疗的便利性。为了推进临床开发，关于蛋白质储存、稳定性、最佳剂量和给药计划的额外工作是必要的。此外，尽管人们对这种蛋白质在细胞水平上的作用机制了解甚多，但对器官的特异性作用尚未确定。因此，本提案将侧重于三个主要领域。特异性目标1将研究蛋白质在各种储存条件下的稳定性，以确定活性丧失及其如何影响现场推荐剂量。对蛋白质在体内稳定性的扩展研究将通过随时间跟踪给药蛋白质的组织水平进行。特异性目标2将扩大对小鼠模型中剂量水平、给药时间和计划以及治疗时间之间关系的理解。Specific Aim 3将研究RLIP76如何影响辐射对特定器官的毒性，并在小鼠模型中检查潜在的长期影响。所获得的信息对于规划RLIP76在不同辐射释放情景下的最佳治疗方案是必要的。

DESCRIPTION (provided by applicant): A major instigator of radiation-induced pathology is cellular damage caused by reactive oxygen species formed in the first moments after exposure. Most therapeutic agents are free radical scavengers which must be present in high concentrations as exposure occurs, making their use as treatments problematic. In addition, the normal cell already has scavenger molecules present, such as glutathione. Glutathione accepts electrons from reactive electrophiles as part of the normal cellular defenses, but the resultant electrophilic glutathione conjugates still pose a threat to cellular integrity. Final elimination of risk then requires the transport and elimination of these reactive glutathione S-conjugates - a key function of RLIP76, a membrane-associated transport protein. Terapio has been testing RLIP76 as a systemic therapy for high-dose radiation poisoning. Preliminary studies in mice show that increasing cellular content of RLIP76 by systemic administration significantly increases survival even if the protein is administered AFTER radiation exposure, with a clear dose-response relationship between amount of RLIP76 administered and survival that extends to all but the highest exposure levels. Further, RLIP76 can be orally administered, increasing its ease of treatment. In order to move forward with clinical development, additional work regarding protein storage, stability, optimal dosing and schedule of administration is necessary. Further, although much is known about the protein's mechanism of action on a cellular level, organ-specific effects have yet to be determined. Therefore, this proposal will focus on three main areas. Specific Aim 1 will look at the stability of the protein under a variety of storage conditions to determine loss of activity and how that may affect recommended dosing in the field. Expanded studies of in vivo stability of the protein will be performed by following tissue levels of administered protein over time. Specific Aim 2 will enlarge understanding of the relationship between dose level, timing and schedule of administration and length of treatment in a mouse model. Specific Aim 3 will look at how RLIP76 affects specific organ toxicity from radiation and examine potential long term effects, again in a mouse model. The information obtained is necessary to plan an optimal treatment regimen for RLIP76 under different radiation release scenarios. PUBLIC HEALTH RELEVANCE: RLIP76 is a naturally-occurring protein that can be given orally and counteract the effects of radiation poisoning even if given AFTER exposure occurs. This project will investigate the most effective dosing of the protein and how to optimize packaging for long term storage.