Pre-Clinical Studies of the NO Scavenger Cobinamide

描述(由申请人提供)：感染性休克以及其他形式的休克具有极高的死亡率，这在一定程度上是这些临床状态特征的严重低血压的次要原因。一氧化氮(NO)是一种非常有效的血管扩张剂，其在休克时由诱导型一氧化氮合酶(NOS)过度产生，显然与休克的血管加压剂难治性低血压有关。这三种哺乳动物一氧化氮合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，其中一种药物在III期临床试验中导致死亡率增加，可能是由于抑制内皮一氧化氮合酶导致组织和器官灌注量减少所致。与NOS抑制剂相比，NO清除剂在降低休克时的高浓度NO方面具有理论上的优势，因为前者应该优先中和过量的循环NO，而不会显著影响细胞内和细胞间的NO信号转导。事实上，三种不同的NO清除剂，血红蛋白，NOX-100和钴胺(维生素B12)都在败血症的动物模型中显示出希望，并且NOX-100在败血症休克的早期人类临床试验中是有益的。我们发现，钴胺是钴胺生物合成的倒数第二个前体，也是大多数维生素B12制剂的污染物，它与NO的亲和力是钴胺的100倍。在培养的哺乳动物细胞和果蝇的马氏管中，钴胺是一种有效的NO清除剂，并且在处理过量NO所需的浓度下没有毒性。利用已建立的果蝇细菌性败血症模型，我们发现可比酰胺显著提高了果蝇的存活率，其机制似乎是通过清除过量的NO。在R21的应用中，我们建议进行临床前动物研究，以确定可比酰胺是否是一个潜在的有用的候选药物；这项工作的结果将成为研究人员预期进行临床试验的新药申请的基础。

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.