Long-Acting G-CSF Analog for Treating ARS

描述（由申请人提供）：开发放射/核医学对策以治疗急性辐射综合征（ARS）是NIAID的一个高度优先研究领域。骨髓是对辐射损伤最敏感的组织之一，造血功能受损是过度辐射暴露的最初临床体征之一，通常导致死亡。粒细胞集落刺激因子（G-CSF）是一种19 kDa的蛋白质，可刺激骨髓细胞分裂和分化为中性粒细胞。重组人G-CSF被广泛用于治疗癌症患者的化疗相关中性粒细胞减少症，最近的研究表明，它提高了ARS动物模型的总生存率，尽管该药物需要每日给药，但在放射性/核灾难后可能无法实现。G-CSF在人体中的半衰期较短，需要每天给药两周或更长时间，并且可能无法优化该蛋白质对患者的治疗益处。不需要频繁给药的长效G-CSF类似物可以在核紧急情况下提供显着的治疗优势，其中医疗保健提供者的时间将非常宝贵，并且患者的每日给药可能是不可能的。我们开发了一个合理设计的，长效的G-CSF类似物，通过与聚乙二醇（PEG）的蛋白质的位点特异性化学修饰。我们的长效PEG-G-CSF类似物具有比未修饰的G-CSF长10倍的半衰期，并且在加速化疗治疗的大鼠中的中性粒细胞恢复方面比G-CSF显著更有效。在I期SBIR资助期间进行的研究证明了这种新型长效G-CSF类似物在良好表征的小鼠ARS模型中用于改善存活率的实用性。与G-CSF相反，我们的长效G-CSF类似物仅需单次给药即可有效。值得注意的是，与媒介物处理的小鼠的50%（10/20只小鼠）的死亡率相比，在照射后24小时用该长效G-CSF类似物的单次施用处理的致死照射小鼠的100%（20/20只小鼠）存活30天。与安慰剂相比，我们的长效G-CSF类似物在多次注射到辐射小鼠中后也改善了存活率。用我们的长效G-CSF类似物治疗的辐射小鼠与溶剂治疗的小鼠相比显示出嗜中性粒细胞、红细胞和血小板的加速恢复，表明该蛋白质积极影响多种血细胞类型的恢复。第二阶段赠款有三个主要目标。首先，我们将在受辐射的小鼠中进行额外的研究，以确定在辐射后多久可以施用药物并仍然改善存活率。其次，我们将确定该蛋白质是否能提高致命辐射的非人灵长类动物的存活率，这是FDA采用的金标准ARS模型。第三，我们将在IND使能、GLP动物药理学和毒理学研究中测量蛋白质的安全性特征和药代动力学特性，以确定用于人体试验的药物安全剂量。我们的新型G-CSF类似物将为医生提供治疗ARS的所有主要造血并发症的有效和方便的疗法，并改善由于放射性/核灾难而暴露于高辐射剂量的受试者的存活率。事实上，这种药物只需要一个 为了有效性而给药代表了ARS治疗的显著进步，并将优化放射/核紧急情况下的医疗保健提供者时间，其中患者数量预计将超过可用的医疗保健资源。该药物应被证明可用于治疗G-CSF用作治疗的其他疾病，例如癌症患者化疗引起的中性粒细胞减少症。

DESCRIPTION (provided by applicant): Development of radiological/nuclear medical countermeasures to treat Acute Radiation Syndrome (ARS) is a high priority research area for NIAID. Bone marrow is one of the most sensitive tissues to radiation damage and impaired hematopoiesis is one of the first clinical signs of excessive radiation exposure, often resulting i death. Granulocyte colony-stimulating factor (G- CSF) is a 19 kDa protein that stimulates bone marrow cells to divide and differentiate into neutrophils. Recombinant human G-CSF is widely used to treat chemotherapy-related neutropenia in cancer patients, and recent studies indicate that it improves overall survival in animal models of ARS, although the drug requires daily administration, which may not be possible following a radiological/nuclear disaster. G-CSF has a short half-life in humans, which necessitates daily dosing for two weeks or more, and may not optimize therapeutic benefits of the protein for patients. Long-acting G-CSF analogs that do not require frequent dosing could provide significant treatment advantages in a nuclear emergency setting, where healthcare provider time will be at a premium and daily dosing of patients may not be possible. We developed a rationally designed, long-acting G-CSF analog through site-specific chemical modification of the protein with polyethylene glycol (PEG). Our long-acting PEG-G-CSF analog has a 10-fold half-life than unmodified G-CSF and is significantly more effective than G-CSF at accelerating neutrophil recovery in chemotherapy-treated rats. Studies performed during the Phase I SBIR grant demonstrated the utility of this novel, long-acting G-CSF analog for improving survival in a well characterized mouse ARS model. In contrast to G-CSF, our long-acting G-CSF analog required only a single administration to be effective. Notably, 100% (20/20 mice) of lethally irradiated mice treated 24h post-irradiation with a single administration of this long-acting G-CSF analog survived 30 days compared to a mortality rate of 50 % (10/20 mice) for vehicle-treated mice. Our long-acting G-CSF analog also improved survival compared to placebo following multiple injections into irradiated mice. Irradiated mice treated with our long-acting G-CSF analog showed accelerated recovery of neutrophils, red blood cells and platelets compared to vehicle-treated mice, indicating that the protein positively affected recovery of multiple blood cell types. The Phase II grant has three major goals. First, we will perform additional studies in irradiated mice to determine how long after irradiation the drug can be administered and still improve survival. Second, we will determine whether the protein improves survival of lethally-irradiated non-human primates, which is the gold standard ARS model adopted by the FDA. Third, we will measure the safety profile and pharmacokinetic properties of the protein in IND-enabling, GLP animal pharmacology and toxicology studies in order to identify safe doses of the drug for testing in humans. Our novel G- CSF analog will provide physicians with an effective and convenient therapy for the treatment of all of the major hematopoietic complications of ARS, and improve survival of subjects exposed to high radiation doses as a result of a radiological/nuclear disaster. The fact that the drug requires only a single administration for effectiveness represents a significance advance in the treatment of ARS and will optimize healthcare provider time in a radiological/nuclear emergency setting, where patient numbers are expected to overwhelm available healthcare resources. The drug should prove useful for treating other diseases for which G-CSF is used as a therapy, such as neutropenia resulting from chemotherapy use in cancer patients.