Novel Nanocomposite Formulation for Highly Effective Oral Insulin Delivery

描述（由申请人提供）：大约2080万美国人被诊断患有糖尿病。此外，美国有近5400万人被诊断为糖尿病前期，这意味着血糖水平升高。据估计，到2030年，全球糖尿病患者人数将增加3.5亿以上。目前，糖尿病的治疗是通过肌内或皮下注射胰岛素。由于患者依从性差，人们一直致力于开发口服胰岛素制剂，其也具有模拟非糖尿病个体中所见的生理胰岛素分泌的潜力。然而，口服胰岛素给药遇到两个主要障碍：[1]导致胰岛素快速降解的酶屏障，和[2]限制胰岛素生物利用度的粘膜屏障。目前，通过同时给予蛋白酶抑制剂或将胰岛素包封到保护性载体中，酶屏障已在一定程度上被规避，但粘膜屏障仍然是开发有效口服胰岛素递送系统的挑战。最近发现的一类细胞穿透肽，广泛称为蛋白转导结构域（PTD）肽，提供了一个工具，最终克服细胞膜屏障。细胞培养和动物研究都表明，通过将PTD共价连接到几乎任何类型的货物，包括大蛋白质（MW >150 kDa），PTD能够将附着的货物运送到所有类型的器官组织中。在这项SBIR资助申请中，我们提出了一种创新的口服胰岛素给药方法，该方法可能同时战胜酶和粘膜屏障。该系统的一个主要组成部分将是二氧化硅-藻酸盐纳米复合材料，用于保护胰岛素免受降解，靶向胰岛素释放到胃肠道，并控制药物释放速率。胰岛素将首先通过化学方法与LMWP（一种经证实的PTD肽）缀合，然后将缀合物包封到二氧化硅-藻酸盐纳米复合物网络中。口服给药后，复合物的网络结构将保护包埋的胰岛素免受GI道中蛋白酶的降解，而表面上藻酸盐的粘膜粘附功能将提供载体到肠粘膜上的吸附。一旦在粘膜部位累积，LMWP的有效细胞穿透活性将允许释放的LMWP-胰岛素缀合物快速穿过上皮细胞层，将生物活性胰岛素直接转运到门静脉循环中。有前途的初步体外研究结果令人信服地表明所提出的系统的可行性。在第一阶段研究中，我们计划进行决定性的概念验证动物研究，以充分证明该系统的可行性。基于糖尿病无与伦比的经济和社会影响，所提出的口服胰岛素递送技术的价值是深远的。公共卫生相关性：美国糖尿病协会2002年的一项评估表明，当年因糖尿病造成的费用约为1 320亿美元，其中包括920亿美元的直接医疗支出和400亿美元的生产力损失造成的间接支出。由于几乎所有I型糖尿病患者都需要胰岛素治疗，并且现在越来越多地用于治疗II型糖尿病患者（目前高达35%的II型糖尿病患者需要胰岛素治疗），因此有效的胰岛素输送已成为糖尿病临床管理的最终目标。因此，开发这种高效的胰岛素输送技术不仅会对医疗保健和社会生活产生巨大影响，而且会为该国的整体经济带来重大利益。

DESCRIPTION (provided by applicant): Approximately 20.8 million Americans are diagnosed with diabetes. Additionally, nearly 54 million people in the U.S. are diagnosed as being pre-diabetic, meaning to suffer from elevated blood glucose levels. Worldwide, the number of people with diabetes has been estimated to increase over 350 million by 2030. Presently, diabetes is treated with insulin injected either intramuscularly or subcutaneously. Because of poor patient compliance, a strong effort has been aimed at developing oral insulin formulations, which also has the potential to mimic physiological insulin secretion seen in non-diabetic individuals. Nevertheless, oral insulin delivery encounters two major barriers: [1] the enzyme barrier that leads to rapid insulin degradation, and [2] the mucosal barrier that limits insulin's bioavailability. Presently, the enzyme barrier has been circumvented to a certain degree by concurrent administration of protease inhibitors or encapsulation of insulin into protective carriers, yet the mucosal barrier remains as a challenge in developing an effective oral insulin delivery system. The recent discovery of a class of cell-penetrating peptides, widely termed as protein transduction domain (PTD) peptides, has provided a tool for finally overcoming the cell membrane barrier. Both cell culture and animal studies demonstrate that by covalently linking PTD to almost any type of cargo, including large proteins (MW >150 kDa), PTD was able to ferry the attached cargo into all types of organ tissues. In this SBIR grant application, we propose an innovative oral insulin delivery approach that could potentially prevail over both the enzyme and mucosal barriers concomitantly. A major component of this system will be a silica-alginate nanocomposite that serves to protect insulin from degradation, target insulin release to the GI tract, and also control drug release rate. Insulin will first be conjugated to LMWP (a proven PTD peptide) by chemical method, and the conjugates will then be encapsulated into a silica-alginate nanocomposite network. Following oral administration, the network structure of the composite would protect entrapped insulin from degradation by proteases in the GI track, whereas the mucoadhesive function of alginate on the surface would provide adsorption of the carriers onto intestinal mucosa. Once accumulated at the mucosal site, the potent cell-penetrating activity of LMWP would allow the released LMWP-insulin conjugates to rapidly cross over the epithelial cell layer, transporting biologically active insulin directly into portal circulation. Promising initial in vitro findings convincingly suggest the plausibility of the proposed system. In this Phase I research, we plan to carry out decisive proof-of-concept animal studies to fully demonstrate the feasibility of this system. Based on the unmatched economical and social impacts of diabetes, the value of the proposed oral insulin delivery technology is far-reaching. PUBLIC HEALTH RELEVANCE: An assessment made by the American Diabetes Association in 2002 indicated that costs attributable to diabetes in that year were approximately $132 billion; including $92 billion in direct medical expenditures and $40 billion in indirect expenditures resulting from lost productivity. Because insulin therapy is required by virtually all patients with type I diabetes, and is also now increasingly used in treating patients with type II diabetes (right now up to 35% of patients with type II diabetes require insulin treatment), effective insulin delivery has become the ultimate goal in clinical management of diabetes. Therefore, the development of this highly effective insulin delivery technology would not only impart tremendous impact on healthcare and social lives but also offer significant benefit to the overall economy of this country.