Novel Antibody-Transporter Conjugates for Brain Drug Delivery

描述(申请人提供)：在美国，数以百万计的人患有阿尔茨海默病、中风和脑癌等神经系统疾病。蛋白质/基因图谱技术和高通量药物筛选技术的进步催生了许多新的候选药物。然而，血脑屏障(BBB)将阻碍这一新一代神经疗法的发展和临床实现。这是因为，除非一种药物是小的(500 Da)和亲脂性的，否则它不能有效地从血液中转运，穿过血脑屏障，进入大脑。由于脑部药物属性的这些限制，大多数小分子疗法的吸收极其有限，而蛋白质和基因药物不具有血脑屏障渗透性。一种有相当前景的非侵入性给药方法涉及利用内源性血脑屏障转运机制作为一种将药物从血液运送到大脑的手段。这种受体介导的转运系统可以利用抗体的精致特异性进行靶向，抗体反过来又与药物有效载荷联系在一起，药物有效载荷可以包括小分子、蛋白质或DNA疗法。在与血侧的受体结合后，抗体-药物结合物充当转运体的人工底物，并将通过血脑屏障将细胞糖转运到大脑。目前的方法已经产生了有限的大脑摄取，因为靶向转运蛋白被无处不在地表达，并且抗体靶向试剂具有比预期更低的BBB通透性。因此，这项建议的重点是发现和鉴定具有更高的脑特异性和转运效率的新型抗体递送载体。大型人类单链抗体(ScFv)文库将被寻找通过同源细胞表面运输系统与脑内皮细胞结合和内吞的新抗体。这些抗体将通过体外血脑屏障模型测试其跨细胞糖的能力，并将根据其血脑屏障通透性对运输效率进行定量排名。最后，脑靶向和跨细胞转移的ScFv将被移植到人类免疫球蛋白支架上进行体内测试。将进行药代动力学分析，以确定大鼠脑靶向免疫球蛋白的器官摄取。那些表现出显著和特异性脑摄取的抗体将具有作为非侵入性脑内药物输送载体的极佳潜力。健康相关性识别新的非侵入性药物输送到大脑的途径将对我们将新疗法转化为临床可行药物的能力产生重大影响，以治疗数百万患有衰弱神经疾病的患者。特别是，将抗体与BBB特异性运输系统相结合的递送方法不会比静脉注射更具侵入性，并允许递送包括小分子、基因和蛋白质在内的各种药物。

DESCRIPTION (provided by applicant): Millions of people in the United States suffer from neurological diseases such as Alzheimer's disease, stroke, and brain cancer. Advances in protein/gene profiling techniques and high throughput drug screening technologies have spawned many new drug candidates. However, the blood-brain barrier (BBB) will hamper the development and clinical realization of this new generation of neurotherapeutics. This is because unless a drug is small (<500 Da) and lipophilic, it does not effectively transport from the bloodstream, across the BBB, and into the brain. As a consequence of these restrictions on brain drug attributes, the uptake of most small molecule therapeutics is extremely limited, while protein and gene medicines are not BBB permeable. A noninvasive delivery method with considerable promise involves the employ of endogenous BBB transport mechanisms as a means to shuttle drug cargo from the blood to the brain. Such receptor-mediated transport systems can be targeted using the exquisite specificity of antibodies that are in turn linked to a drug payload that can include small molecules, proteins, or DNA therapeutics. After binding to the receptor on the blood side, the antibody-drug conjugate acts as an artificial substrate for the transporter and will transcytose across the BBB into the brain. Current approaches have yielded limited brain uptake because the targeted transporters are ubiquitously expressed, and the antibody targeting reagents have a lower than expected BBB permeability. Therefore, this proposal is focused on the discovery and characterization of novel antibody delivery vectors having improved brain specificity and transport efficiency. Large human single- chain antibody (scFv) libraries will be searched for novel antibodies that bind to and endocytose into brain endothelial cells via cognate cell surface transport systems. These antibodies will be tested for their ability to transcytose across an in vitro BBB model, and will be quantitatively ranked for transport efficiency based their BBB permeability. Finally, the brain targeting and transcytosing scFv will be grafted onto a human IgG scaffold for in vivo testing. Pharmacokinetic profiling will be performed to determine organ uptake of brain targeting IgG in the rat. Those antibodies exhibiting significant and specific brain uptake will have excellent potential as noninvasive brain drug delivery vectors. HEALTH RELEVANCE Identification of novel noninvasive routes for drug delivery to the brain would have a significant impact on our ability to translate new therapeutics into clinically viable drugs for the treatment of millions of patients who suffer from debilitating neurological diseases. In particular, delivery approaches coupling antibodies with BBB-specific transport systems would be no more invasive than an intravenous injection and allow delivery of a variety of drug cargoes including small molecules, genes, and proteins.