Hexa-D-Arg: A Furin Inhibitor for Anthrax Biodefense

描述(由研究人员提供)：炭疽毒素靶向并杀死哺乳动物细胞的能力涉及两个关键步骤。第一步是通过最近克隆的炭疽毒素受体(ATR)与哺乳动物细胞表面结合。第二步是利用广泛表达的哺乳动物细胞蛋白水解酶Furin对炭疽毒素PA(保护性抗原)残基进行蛋白分解，使之能够形成多聚体复合体(孔)，使炭疽毒素的LF(致死因子)和EF(水肿因子)亚单位能够进入细胞。针对这两个步骤开发抗毒素策略的优势是，一次打击将中和LF和EF介导的毒性。这两个步骤作为靶点的有效性来自于最近的研究，即使用可溶的ATR受体(以防止与细胞结合)来保护细胞免受炭疽毒素的影响，以及研究表明，使用六-D-精氨酸(D6R)抑制Furin可以保护小鼠免受假单胞菌外毒素A和炭疽毒素相关的毒性。D6R对毒素致死效应的保护能力在药物预处理时最强。由于不可能预测一个人何时会接触到毒素，D6R在现场的成功使用将需要开发一种缓释制剂，使个人受到1-4周的保护。在具体目标1中，我们将测定D6R在大鼠模型中的药代动力学，以确定皮下(Sc)给药的最佳剂量。具体目标2的实验将侧重于确定单次注射的最大耐受量，以及为期4周的治疗剂量的毒理学评估。AIMS 1和AIMS 2的研究结果将用于特定的AIMS 3和4，以开发一种缓释皮下制剂，使药物在血浆中的保护性浓度保持较长时间(4周)。这些研究将产生一种D6R配方，它将为个人(例如战地士兵)提供长期保护，使其免受炭疽毒素的致命影响。

DESCRIPTION (provided by investigator): There are two key steps involved in the ability of anthrax toxin to target and kill mammalian cells. The first step involves binding to the mammalian cell surface through the recently cloned Anthrax Toxin Receptor (ATR). The second step involves proteolytic cleavage of the anthrax toxin-PA (protective antigen) residue by a ubiquitously expressed mammalian cell protease furin, such that it now is able to form a multimeric complex (pore) that enables entry of the LF (lethal factor) and EF (edema factor) subunits of anthrax toxin into the cell. The advantage of targeting these two steps for the development of anti-toxin strategies is that a single hit would neutralize both the LF and EF mediated toxicities. The validity of these two steps as targets comes from recent work that used a soluble ATR receptor (to prevent binding to cells) to protect cells from anthrax toxin as well as studies that demonstrate that inhibition of furin using hexa-D-arginine (D6R) protects mice from the toxicity associated with Pseudomonas exotoxin A as well as anthrax toxin. The ability of D6R to protect from the lethal effects of toxin was greatest when mice were pretreated with the drug. Since it is impossible to predict when an individual is going to be exposed to toxin, successful use of D6R in the field will require the development of a slow release formulation such that an individual is protected for 1-4 weeks. In specific aim 1, we will determine the pharmacokinetics of D6R in a rat model to determine the optimal dose of the peptide by subcutaneous (sc) route of administration. Experiments in specific aim 2 will focus on the determination of the maximum tolerated dose (MTD) as a single injection as well as toxicological assessment of therapeutic dose for a period of 4 weeks. Results of studies in aims 1 and 2 will be used in specific aims 3 and 4, to develop a slow release subcutaneous formulation such that protective concentrations of the drug within the plasma are maintained for a prolonged period (4 weeks). These studies will result in a formulation of D6R that will provide prolonged protection of an individual (e.g. a soldier in the field) from the lethal effects of anthrax toxin.