Systemic Delivery of CpG Oligonucleotides

说明（申请人提供）：细菌提取物通常具有抗肿瘤作用。直到最近才发现，在不明确的癌症治疗中，有效成分是细菌DNA，而不是蛋白质、碳水化合物或脂质。与人类基因组DNA相反，细菌DNA显示未甲基化的胞嘌呤-胍二核苷酸序列，通常称为CpG。我们身体的宿主防御系统已经进化出这样一种方式，即只要在体内发现CpG，它就会作为“危险”信号。由此产生的先天免疫可以用来对抗肿瘤的生长。最吸引人的是，一旦肿瘤相关抗原从肿瘤中脱落，被CpG激活的树突状细胞可以处理它们并呈递给T淋巴细胞，T淋巴细胞可以杀死肿瘤细胞。总之，基于cpg的免疫治疗不仅可以利用其先天免疫反应，还可以利用随后的适应性免疫反应。因此，CpG已成为近年来最令人兴奋的免疫疗法之一。然而，在动物模型中，该方法仅适用于肿瘤内或肿瘤周围的给药途径。在II期人体研究中，静脉给药无效，而皮下给药仅产生轻微影响。综上所述，这些相当令人失望的结果可归因于体内CpG的递送不良。最近，我们能够演示一种方法来规避交付中的这个关键问题。我们的方法是基于这样一个事实，即免疫复合物可以在血液中循环很长一段时间，只要它们不引发抗原交联。在荷瘤小鼠中，我们的制剂在血液中的半衰期为几天，在肿瘤组织中积累的剂量高达20%。根据这种有利的药代动力学，静脉注射CpG成功地延缓了实体瘤的生长。最近我们还发现皮下注射同样有效。我们对这些令人兴奋的结果有自己的解释，而这项提议旨在测试这些假设。这部分是提案的一个方面。提案的另一部分涉及两种新系统的开发，这两种系统将不需要在动物研究中可以接受但在人类研究中可能不可行的步骤。这些研究的成功结果无疑将加速基于cpg的免疫癌症治疗，并将与其他现有治疗方法一起为治疗癌症提供另一种可行的选择。

DESCRIPTION (provided by applicant): Bacterial extracts often show anti-tumor effect. It was only recently discovered that the active component in the ill-defined cancer treatment is bacterial DNA, not protein, carbohydrate, or lipid. In contrast to human genomic DNA, bacterial DNA shows unmethylated cytidine-guanidine dinucleotide sequences, commonly referred to as CpG. Our own body's host defense system has evolved such a way that whenever CpG is found in the body, it serves as a "danger" signal. Resulting innate immunity can be harnessed to fight against tumor growth. Most attractively, once tumor-associated antigens are shed from the tumor, dendritic cells activated by CpG can process them and present to T lymphocytes that can kill the tumor cells. In short, CpG-based immunotherapy can exploit not only its innate immune response but also subsequent adaptive immune response. Thus CpG has become one of the most exciting immunotherapies in recent years. However, the approach works only with intra-tumoral or peri-tumoral route of administration in animal models. In Phase II human studies, intravenous route was ineffective while subcutaneous administration produced only minor effects. Taken together these rather disappointing outcomes can be attributed to poor delivery of the CpG in vivo. Recently we were able to demonstrate a way to circumvent this critical problem in delivery. Our approach was based on the fact that immune complexes can circulate in the blood for a long time so long as they do not trigger antigen crosslinking. In tumor-bearing mice our formulation showed a half-life of several days in the blood and as much as 20% of the dose accumulated in tumor tissue. In accordance with this favorable pharmacokinetic, intravenously administered CpG successfully retarded solid tumor growth. More recently we also discovered that a subcutaneous route was as effective. We have our own explanations of these exciting results and this proposal is designed to test these hypotheses. This portion constitutes one aspect of the proposal. The other portion of the proposal is concerned with development of two new systems that will not require a step that may be acceptable in animal studies but may not be in humans. Successful outcome of the proposed studies will undoubtedly accelerate CpG-based immunocancer therapy and will provide another viable option in treating cancer along with other existing treatments. Public Health Relevance: It has been known for many years that bacterial DNA fragments exert anti-tumor effect. To be effective, they must be introduced where tumor is growing. This proposal deals with strategies for developing a convenient intravenous or subcutaneous route of administration that will deliver the agents to the tumor tissue.