Final preclinical development of an immunoadhesin therapy for inhalation anthrax

描述(由申请人提供)：由吸入炭疽芽胞引起的吸入性炭疽病，即使用抗生素治疗也有约50%的死亡率。致病机制由两种有毒的非共价复合体--水肿性毒素和致死性毒素介导。保护性抗原(PA)是这两种复合体的重要组成部分，它与介导体内毒素致死的主要哺乳动物受体--毛细血管形态发生蛋白-2(CMG2)结合。我们利用烟草表达系统制备了人CMG2胞外区和人免疫球蛋白Fc的融合，并证明了其在预防和治疗兔吸入性炭疽病方面的有效性。我们的重组蛋白PBI-220与PA结合，阻止其与细胞表面CMG2结合，从而阻止毒性。值得注意的是，PBI-220在体外试验中中和了抗PA单抗难以中和的工程PA变体，使其潜在地优于其他正在开发的炭疽疗法。我们正在开发PBI-220作为一种被动免疫疗法，以补充吸入性炭疽病治疗过程中抗生素的使用。我们已经完成了PBI-220在老鼠和食蟹猴身上的初步毒理学研究，并正在开发一种cGMP的制造工艺。我们正在与加尔维斯顿国家实验室和杜兰国家灵长类研究中心的研究人员合作，评估PBI-220和抗生素联合治疗在兔疾病晚期阶段的好处，并评估PBI-220作为吸入性炭疽病食蟹猴模型的治疗方法。这笔赠款将通过完成准备研究性新药(IND)申请所需的制造和临床前动物研究来推进我们的PBI-220产品开发计划，从而实现人类安全试验。拨款目标包括：1)开发一种污染植物蛋白的定量分析方法，以确保药品中这些蛋白质的含量达到人体治疗所要求的最低水平；2)对两种动物(大鼠和猴子)进行GLP安全性研究，其药品质量与第一次人类临床试验中使用的药品质量相同；3)为第一阶段临床试验(S)生产cGMP项下的pBI-220；4)建立临床样品分析(定量药物和抗药抗体)所需的免疫分析方法；5)为成功向美国食品和药物管理局提交IND申请提供完整的必要基准。 公共卫生相关性：这项应用侧重于GLP对我们的领先生物防御对策PBI-220的临床前研究，PBI-220是一种免疫粘附素疗法，用于由A类病原体炭疽芽孢杆菌引起的吸入性炭疽症状的患者。我们正在开发PBI-220作为被动免疫疗法，以补充在感染治疗期间使用经批准的抗生素，如环丙沙星。我们将根据《动物规则》(21 CFR 601.90(第H分部))，在GMP下生产PBI-220，用于两个动物物种的GLP毒理学和安全药理研究，从而推动生物许可证申请的批准，这将允许向国家战略储备供应PBI-220，以对抗传统的、增强的和先进的炭疽菌株。

Description (provided by the applicant): Inhalational anthrax, caused by inhaled Bacillus anthracis spores, has a ~50% fatality rate even when treated with antibiotics. Pathogenesis is mediated by two toxic non-covalent complexes - edema toxin and lethal toxin. An essential component of both complexes, protective antigen (PA), binds to the major mammalian receptor which mediates toxin lethality in vivo, capillary morphogenesis protein-2 (CMG2). We have produced a fusion of the extracellular domain of human CMG2 and human IgG Fc, using a tobacco expression system, and demonstrated its effectiveness in treating inhalational anthrax in rabbits, both prophylactically and therapeutically. Our recombinant protein, PBI-220, binds to PA, blocks it from binding to cell-surface CMG2 and thus blocks toxicity. Significantly, PBI-220 neutralizes engineered PA variants that are poorly neutralized by anti-PA monoclonal antibodies in an in vitro assay, making it potentially superior to other anthrax therapeutics under development. We are developing PBI-220 as a passive immunotherapy to complement the use of antibiotics during treatment of inhalational anthrax. We have already completed pilot toxicology studies of PBI-220 in rats and cynomolgus macaques, and are developing a cGMP manufacturing process. We are collaborating with researchers at the Galveston National Laboratory and the Tulane National Primate Research Center to evaluate the benefits of combining PBI-220 and antibiotic treatment in late stages of disease in rabbits and to evaluate PBI-220 as a treatment in a cynomolgus macaque model of inhalational anthrax. This grant will advance our Product Development Plan for PBI-220 by completing the manufacturing and pre-clinical animal studies required for preparing an Investigational New Drug (IND) application, thus enabling human safety trials. Grant objectives include: 1) Develop a quantitative assay for contaminating plant proteins, to assure a minimal level of these proteins in the drug product, as required for human therapeutics; 2) Conduct GLP safety studies in two animal species (rats and monkeys) with drug product of the same quality as will be used in the first human clinical trial; 3 Produce PBI-220 under cGMP for Phase 1 clinical trial(s); 4) Develop immunoassays for clinical sample analyses (quantification of drug and anti-drug antibodies) and 5) Complete required benchmarks for successful submission of an IND application to FDA. PUBLIC HEALTH RELEVANCE: This application focuses on GLP pre-clinical studies of our lead biodefense countermeasure, PBI-220, an immunoadhesin therapy for patients symptomatic for inhalational anthrax caused by Bacillus anthracis, a Category A pathogen. We are developing PBI-220 as a passive immunotherapy to complement the use of approved antibiotics such as Ciprofloxacin during treatment of the infection. We will manufacture PBI-220 under GMP for GLP toxicology and safety pharmacology studies in two animal species, thus advancing towards Biologic License Application (BLA) approval, under the Animal Rule (21 CFR 601.90 (Subpart H), which will allow PBI-220 to be supplied to the Strategic National Stockpile as a countermeasure against traditional, enhanced and advanced anthrax strains.