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

描述（由研究者提供）：炭疽毒素靶向和杀死哺乳动物细胞的能力涉及两个关键步骤。第一步涉及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。第二步涉及通过普遍表达的哺乳动物细胞蛋白酶弗林蛋白酶对炭疽毒素-PA（保护性抗原）残基的蛋白水解切割，使得其现在能够形成多聚体复合物（孔），其使得炭疽毒素的LF（致死因子）和EF（水肿因子）亚基能够进入细胞。靶向这两个步骤用于开发抗毒素策略的优点在于，单次命中将中和LF和EF介导的毒性。这两个步骤作为靶标的有效性来自于最近的工作，该工作使用可溶性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，以及证明使用六-D-精氨酸（D 6 R）抑制弗林蛋白酶保护小鼠免受与假单胞菌外毒素A以及炭疽毒素相关的毒性的研究。当小鼠用药物预处理时，D 6 R保护免受毒素致死作用的能力最大。由于不可能预测个体何时将暴露于毒素，因此D 6 R在该领域的成功使用将需要开发缓释制剂，使得个体被保护1-4周。在具体目标1中，我们将确定D 6 R在大鼠模型中的药代动力学，以确定通过皮下（sc）施用途径的肽的最佳剂量。具体目标2中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中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，使血浆中的药物保护浓度保持较长时间（4周）。这些研究将产生一种D 6 R制剂，该制剂将为个体（例如野外士兵）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.