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

描述（由研究者提供）：炭疽毒素瞄准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。第二步是通过普遍表达的哺乳动物细胞蛋白酶furin对炭疽毒素- pa（保护性抗原）残基进行蛋白水解裂解，使其能够形成多聚体复合物（孔），使炭疽毒素的LF（致死因子）和EF（水肿因子）亚基进入细胞。针对这两个步骤开发抗毒素策略的优势在于，一次打击可以中和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，该研究使用可溶性ATR受体（防止与细胞结合）来保护细胞免受炭疽毒素的侵害，以及研究表明，使用六- d -精氨酸（D6R）抑制furin可以保护小鼠免受与假单胞菌外毒素a和炭疽毒素相关的毒性。D6R保护小鼠免受毒素致命影响的能力在小鼠预先接受药物治疗时是最大的。由于无法预测个人何时会接触到毒素，因此在野外成功使用D6R将需要开发一种缓释配方，使个人受到1-4周的保护。在具体目标1中，我们将在大鼠模型中测定D6R的药代动力学，以确定通过皮下给药途径给药的肽的最佳剂量。特定目标2的实验将侧重于确定单次注射的最大耐受剂量（MTD）以及为期4周的治疗剂量的毒理学评估。目标1和2的研究结果将用于特定目标3和4，以开发一种缓释皮下制剂，使血浆中药物的保护浓度维持较长时间（4周）。这些研究将产生一种D6R配方，该配方将长期保护个人（例如战场上的士兵）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.