Pre-Clinical Studies of the NO Scavenger Cobinamide

描述（由申请人提供）：脓毒性休克以及其他形式的休克具有极高的死亡率，这在一定程度上是继发于这些临床状态的特征性严重低血压。一氧化氮（NO）是一种非常有效的血管扩张剂，休克时诱导型NO合酶（NOS）过度产生NO，明显导致休克时血管加压药难治性低血压。三种哺乳动物NOS酶的非选择性抑制剂在脓毒症动物模型中显示出一些成功，但不幸的是，这些药物中的一种在III期临床试验中导致死亡率增加，可能继发于抑制内皮NOS导致的组织和器官灌注减少。NO清除剂在降低休克中的高NO浓度方面具有优于NOS抑制剂的理论优势，因为前者化合物应优先中和过量的循环NO，而不显著影响细胞内和细胞间NO信号传导。事实上，三种不同的NO清除剂，血红蛋白，NOX-100和钴胺素（维生素B12）都在败血症的动物模型中显示出希望，NOX-100在感染性休克的早期人类临床试验中是有益的。我们已经发现，钴胺素生物合成中的倒数第二个前体和大多数维生素B12制剂的污染物钴氨酰胺以比钴胺素高>100倍的亲和力结合NO。在培养的哺乳动物细胞和果蝇马氏管中，可宾酰胺是一种有效的NO清除剂，并且在治疗过量NO状态所需的浓度下没有表现出毒性。使用完善的果蝇细菌脓毒症模型，我们发现可宾酰胺显著增加了果蝇的存活率，其机制似乎是清除过量的NO。我们建议进行临床前动物研究，以确定是否cobinamide是一种潜在的有用的候选药物;这项工作的结果将形成研究者的新药申请的基础，预期进行临床试验。

DESCRIPTION (provided by applicant): Septic shock, as well as other forms of shock, have extremely high mortality rates, and this, in part, is secondary to the severe hypotension that characterize these clinical states. Nitric oxide (NO) is an extremely potent vasodilator, and its overproduction in shock by inducible NO synthase (NOS) clearly contributes to the vasopressor-refractory hypotension of shock. Non- selective inhibitors of the three mammalian NOS enzymes showed some success in animal models of sepsis, but unfortunately one of these agents led to increased mortality in a Phase III Clinical Trial, possibly secondary to decreased tissue and organ perfusion from inhibition of endothelial NOS. NO scavengers have a theoretical advantage over NOS inhibitors in reducing high NO concentrations in shock, since the former compounds should preferentially neutralize excess circulating NO, without significantly affecting intra- and inter-cellular NO signaling. Indeed, three different NO scavengers, hemoglobin, NOX-100, and cobalamin (vitamin B12) have all shown promise in animal models of sepsis, and NOX-100 has been beneficial in early human clinical trials of septic shock. We have found that cobinamide, the penultimate precursor in the biosynthesis of cobalamin and a contaminant of most vitamin B12 preparations, binds NO with >100 times more affinity than cobalamin. In cultured mammalian cells and in Drosophila Malpighian tubules, cobinamide was an effective NO scavenger, and did not exhibit toxicity at concentrations that would be required to treat states of excess NO. Using a well-established Drosophila model of bacterial sepsis, we have found that cobinamide strikingly increased fly survival, and the mechanism appeared to be from scavenging excess NO. In this R21 application, we propose to perform pre-clinical animal studies to determine if cobinamide is a potentially useful drug candidate; the results of this work will form the basis for an Investigator's New Drug application in anticipation of conducting clinical trials.