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）将阻碍这种新一代神经疗法的发展和临床实现。这是因为除非药物很小（<500 Da）且亲脂，否则它不能有效地从血液中转运，穿过血脑屏障进入大脑。由于这些对脑药物属性的限制，大多数小分子治疗药物的吸收非常有限，而蛋白质和基因药物不具有血脑屏障渗透性。一种很有前景的无创给药方法是利用内源性血脑屏障运输机制将药物从血液运送到大脑。这种受体介导的运输系统可以利用抗体的精细特异性来靶向，而抗体又与药物有效载荷相关联，包括小分子、蛋白质或DNA疗法。在与血液一侧的受体结合后，抗体-药物偶联物作为转运蛋白的人工底物，并将通过血脑屏障转糖进入大脑。目前的方法已经产生了有限的脑摄取，因为靶向转运蛋白无处不在地表达，抗体靶向试剂的血脑屏障通透性低于预期。因此，本研究的重点是发现和表征具有提高脑特异性和运输效率的新型抗体递送载体。大型人单链抗体（scFv）文库将被寻找新的抗体结合和内吞到脑内皮细胞通过同源细胞表面运输系统。这些抗体将在体外血脑屏障模型中进行转糖能力测试，并根据其血脑屏障通透性对运输效率进行定量排名。最后，将脑靶向和转细胞scFv移植到人IgG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IgG的器官摄取。这些抗体表现出显著和特异性的脑摄取，将有极好的潜力作为无创脑药物传递载体。确定新的无创大脑药物输送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，从而治疗数百万患有衰弱性神经系统疾病的患者。特别是，将抗体与血脑屏障特异性运输系统耦合的递送方法不会比静脉注射更具侵入性，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.