Developing an inactivated whole cell H. pylori vaccine

描述(由申请人提供)： 目前还没有预防幽门螺杆菌感染的疫苗，这种感染的药物治疗复杂，患者依从性差，治疗费用高，对耐药菌株无效。显然，需要一项新的医学进步来降低消化性溃疡和胃癌的发病率，这两种疾病是由幽门螺杆菌感染引起的。临床前研究表明，接种疫苗不仅可以预防感染，还可以用来解决活动性感染。一种有效的疫苗还可能防止再次感染，并阻碍高危人群的传播。Antex Biologics是幽门螺杆菌疫苗开发的行业领先者，致力于将幽门螺杆菌疫苗推向市场。该公司已经对福尔马林灭活的幽门螺杆菌全细胞(HWC)疫苗进行了两项第一阶段临床试验，该疫苗与佐剂MLT(R192G)联合口服，MLT(R192G)是大肠杆菌不耐热毒素的突变体。临床前结果表明，疫苗效力需要使用具有HWC的佐剂。为了将最安全、稳定和有效的疫苗推向市场，我们建议在这一应用中对疫苗配方的两个新方面进行临床评估，即1)冷冻干燥而不是液体活性成分(HWC)，以及2)新型双突变形式LT(DmLT)，与单一突变MLT(R192G)相比，它降低了肠毒素活性，但仍保持完全佐剂活性。HWC的冷冻干燥工艺将根据产品的特性(如水分含量和重建行为)的体外测试以及基于动物免疫和挑战实验的体内测试来选择。最终选定的配方将用于通过使用CD4、抗体和干扰素-伽马基因敲除小鼠研究以及流式细胞术研究在接种和挑战小鼠中检查胃T细胞渗透的性质来促进对疫苗作用机制的了解。CGMP将生产大量冻干HWC和dmLT，并将在未感染和感染的无症状受试者中进行一期剂量递增安全性试验。由于dmLT尚未进行临床评估，将首先确定两个人群单独使用dmLT的最大耐受量。在dmLT剂量选择之后，将再次在两个人群中确定在固定剂量dmLT的情况下冻干和重组HWC的最大耐受量。腹泻是最有可能定义耐受限度的不良事件。将对接受HWC+dmLT全系列疫苗接种的受试者进行一组免疫学测试，包括针对HWC和dmLT的血清和粘膜抗体，以及对幽门螺杆菌裂解物重新刺激的PBMC增殖和细胞因子产生的反应。还将在接种疫苗后对受感染的受试者进行诊断测试，以评估其定居状态的变化。这项试验将使疫苗进入更强大的第一阶段或早期第二阶段试验，从而使幽门螺杆菌疫苗接种更接近现实。

DESCRIPTION (provided by applicant): Currently there exists no vaccine for the prevention of infection with the ubiquitous gastric pathogen Helicobacter pylori, and drug therapy for the infection is complicated by poor patient compliance, the high cost of treatment, and ineffectiveness against drug resistant strains. Clearly a new medical advancement is required to reduce the incidence of peptic ulcer disease and stomach cancer, two conditions caused by infection with H. pylori. Pre-clinical studies have suggested that vaccination could not only prevent infection, but could also be used to resolve active infections. An effective vaccine may also protect against re-infection as well as be an impediment to transmission in at-risk populations. Antex Biologics is an industry leader in H. pylori vaccine development, and is committed to bringing an H. pylori vaccine to the market. The company has performed two Phase 1 clinical trials with a formalin-inactivated Helicobacter pylori Whole Cell (HWC) vaccine, which was given orally in combination with the adjuvant mLT(R192G), a mutant of E. coli heat-labile toxin. Pre-clinical results suggest that the use of an adjuvant with HWC is required for vaccine efficacy. In an effort to bring to market an optimally safe, stable, and potent vaccine, we propose in this application to evaluate clinically two new aspects of the vaccine formulation, namely 1) a lyophilized rather than liquid active ingredient (HWC), and 2) a novel double mutant form of LT (dmLT) that has reduced enterotoxic activity compared to the single mutant mLT(R192G), yet retains full adjuvant activity. The lyophilization process for HWC will be selected based upon in vitro testing of the product for characteristics such as moisture content and reconstitution behavior, and in vivo based upon animal immunization and challenge experiments. The final formulation selected will be used to advance understanding of the vaccine mechanism of action through the use of CD4, antibody, and IFN-gamma knockout mouse studies, and flow cytometric studies examining the nature of the gastric T cell infiltrate in vaccinated and challenged mice. cGMP lots of lyophilized HWC and dmLT will be produced and a Phase 1 dose escalation safety trial in uninfected and infected, asymptomatic subjects will be performed. Because dmLT has yet to be evaluated clinically, the maximum tolerable dose of dmLT alone will be determined first in both populations. Following dmLT dose selection, the maximum tolerable dose of lyophilized and reconstituted HWC in the context of a fixed dose of dmLT will then be determined, again in both populations. Diarrhea is the most likely adverse event that will define tolerance limits. A panel of immunological tests will be performed on subjects receiving the full vaccination series with HWC + dmLT, including serum and mucosal antibodies to HWC and dmLT, and PBMC proliferation and cytokine production in response to restimulation with H. pylori lysate. Diagnostic testing will also be performed on infected subjects post-vaccination to assess changes in their colonization state. This trial will position the vaccine for more highly powered Phase 1 or early Phase 2 trials, and thus will move H. pylori vaccination one step closer to being a reality.