Drug delivery across the blood‐brain barrier (BBB) remains a significant obstacle for the development of neurological disease therapies. The low penetration of blood‐borne therapeutics into the brain can oftentimes be attributed to the restrictive nature of the brain microvascular endothelial cells (BMECs) that comprise the BBB. One strategy beginning to be successfully leveraged is the use of endogenous receptor‐mediated transcytosis (RMT) systems as a means to shuttle a targeted therapeutic into the brain. Limitations of known RMT targets and their cognate targeting reagents include brain specificity, brain uptake levels, and off‐target effects, driving the search for new and potentially improved brain targeting reagent‐RMT pairs. To this end, we deployed human‐induced pluripotent stem cell (iPSC)‐derived BMEC‐like cells as a model BBB substrate on which to mine for new RMT‐targeting antibody pairs. A nonimmune, human single‐chain variable fragment (scFv) phage display library was screened for binding, internalization, and transcytosis across iPSC‐derived BMECs. Lead candidates exhibited binding and internalization into BMECs as well as binding to both human and mouse BBB in brain tissue sections. Antibodies targeted the murine BBB after intravenous administration with one particular clone, 46.1‐scFv, exhibiting a 26‐fold increase in brain accumulation (8.1 nM). Moreover, clone 46.1‐scFv was found to associate with postvascular, parenchymal cells, indicating its successful receptor‐mediated transport across the BBB. Such a new BBB targeting ligand could enhance the transport of therapeutic molecules into the brain.

中文翻译：

---

使用基于人类 iPSC 的血脑屏障模型进行抗体筛选可识别在 CNS 中积累的抗体

跨越血脑屏障 (BBB) 的药物输送仍然是神经疾病疗法发展的重大障碍。血源性治疗剂对大脑的低渗透率通常可归因于构成 BBB 的脑微血管内皮细胞 (BMEC) 的限制性质。一种开始被成功利用的策略是使用内源性受体介导的转胞吞 (RMT) 系统作为将靶向治疗剂运送到大脑中的一种手段。已知 RMT 靶标及其同源靶向试剂的局限性包括脑特异性、脑摄取水平和脱靶效应，从而推动了对新的和可能改进的脑靶向试剂-RMT 对的研究。为此，我们部署了人类诱导多能干细胞 (iPSC) 衍生的 BMEC 样细胞作为模型 BBB 底物，在其上挖掘新的 RMT 靶向抗体对。筛选了一个非免疫的人类单链可变片段 (scFv) 噬菌体展示文库，用于跨 iPSC 衍生的 BMEC 的结合、内化和转胞吞作用。主要候选者表现出与 BMEC 的结合和内化，以及与脑组织切片中人和小鼠 BBB 的结合。在用一种特定的克隆 46.1-scFv 静脉内给药后，抗体靶向鼠 BBB，大脑蓄积增加了 26 倍 (8.1 nM)。此外，发现克隆 46.1-scFv 与血管后实质细胞相关，表明其成功地通过受体介导的跨 BBB 转运。