Novel Antibody-Transporter Conjugates for Brain Drug Delivery

描述（由申请人提供）：美国有数百万人患有神经系统疾病，如阿尔茨海默病、中风和脑癌。蛋白质/基因谱分析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治疗药物的开发和临床实现。这是因为除非药物是小的（<500 Da）和亲脂性的，否则它不能有效地从血流中运输，穿过BBB，进入大脑。由于对脑药物属性的这些限制，大多数小分子治疗剂的摄取极其有限，而蛋白质和基因药物不是BBB可渗透的。具有相当大前景的非侵入性递送方法涉及采用内源性BBB转运机制作为将药物货物从血液穿梭至脑的手段。这种受体介导的转运系统可以使用抗体的精确特异性来靶向，所述抗体又与药物有效载荷连接，所述药物有效载荷可以包括小分子、蛋白质或DNA治疗剂。在与血液侧的受体结合后，抗体-药物缀合物充当转运蛋白的人工底物，并将胞质转运穿过BBB进入脑。目前的方法已经产生了有限的脑摄取，因为靶向转运蛋白是普遍表达的，并且抗体靶向试剂具有低于预期的BBB渗透性。因此，该提议集中于具有改善的脑特异性和转运效率的新型抗体递送载体的发现和表征。将在大型人单链抗体（scFv）文库中搜索通过同源细胞表面转运系统结合并内吞入脑内皮细胞的新型抗体。将测试这些抗体在体外BBB模型中转胞吞的能力，并将基于其BBB渗透性对转运效率进行定量排名。最后，将脑靶向和转胞吞scFv移植到人IgG支架上用于体内测试。将进行药代动力学分析，以确定大鼠脑靶向IgG的器官摄取。这些抗体表现出显着的和特定的脑摄取将有很好的潜力作为非侵入性脑药物输送载体。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上可行的药物的能力产生重大影响，用于治疗数百万患有衰弱性神经系统疾病的患者。特别地，将抗体与BBB特异性转运系统偶联的递送方法不会比静脉内注射更具侵入性，并且允许递送各种药物货物，包括小分子、基因和蛋白质。

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.