Sumbria Rachita K, Hui Eric Ka-Wai, Lu Jeff Zhiqiang, Boado Ruben J, Pardridge William M
Department of Medicine, UCLA, Los Angeles, California 90024, United States.
Mol Pharm. 2013 Sep 3;10(9):3507-13. doi: 10.1021/mp400348n. Epub 2013 Aug 20.
Anti-amyloid antibodies (AAA) are under development as new therapeutics that disaggregate the amyloid plaque in brain in Alzheimer's disease (AD). However, the AAAs are large molecule drugs that do not cross the blood-brain barrier (BBB), in the absence of BBB disruption. In the present study, an AAA was re-engineered for receptor-mediated transport across the BBB via the endogenous BBB transferrin receptor (TfR). A single chain Fv (ScFv) antibody form of an AAA was fused to the carboxyl terminus of each heavy chain of a chimeric monoclonal antibody (mAb) against the mouse TfR, and this produced a tetravalent bispecific antibody designated the cTfRMAb-ScFv fusion protein. Unlike a conventional AAA, which has a plasma half-time of weeks, the cTfRMAb-ScFv fusion protein is cleared from plasma in mice with a mean residence time of about 3 h. Therefore, a novel protocol was developed for the treatment of one year old presenilin (PS)-1/amyloid precursor protein (APP) AD double transgenic PSAPP mice, which were administered daily subcutaneous (sc) injections of 5 mg/kg of the cTfRMAb-ScFv fusion protein for 12 consecutive weeks. At the end of the treatment, brain amyloid plaques were quantified with confocal microscopy using both Thioflavin-S staining and immunostaining with the 6E10 antibody against Abeta amyloid fibrils. Fusion protein treatment caused a 57% and 61% reduction in amyloid plaque in the cortex and hippocampus, respectively. No increase in plasma immunoreactive Abeta amyloid peptide, and no cerebral microhemorrhage, was observed. Chronic daily sc treatment of the mice with the fusion protein caused no immune reactions and only a low titer antidrug antibody response. In conclusion, re-engineering AAAs for receptor-mediated BBB transport allows for reduction in brain amyloid plaque without cerebral microhemorrhage following daily sc treatment for 12 weeks.
抗淀粉样蛋白抗体（AAA）作为一种新型疗法正在研发中，用于分解阿尔茨海默病（AD）患者大脑中的淀粉样斑块。然而，在没有破坏血脑屏障（BBB）的情况下，AAA是大分子药物，无法穿过血脑屏障。在本研究中，通过内源性血脑屏障转铁蛋白受体（TfR）对一种AAA进行了重新设计，使其能够通过受体介导转运穿过血脑屏障。将AAA的单链Fv（ScFv）抗体形式与抗小鼠TfR的嵌合单克隆抗体（mAb）的每条重链的羧基末端融合，产生了一种四价双特异性抗体，称为cTfRMAb-ScFv融合蛋白。与血浆半衰期为数周的传统AAA不同，cTfRMAb-ScFv融合蛋白在小鼠血浆中的清除平均停留时间约为3小时。因此，开发了一种新方案，用于治疗1岁的早老素（PS）-1/淀粉样前体蛋白（APP）AD双转基因PSAPP小鼠，连续12周每天皮下（sc）注射5mg/kg的cTfRMAb-ScFv融合蛋白。治疗结束时，使用硫黄素-S染色和针对β淀粉样原纤维的6E10抗体进行免疫染色，通过共聚焦显微镜对脑淀粉样斑块进行定量。融合蛋白治疗使皮质和海马体中的淀粉样斑块分别减少了57%和61%。未观察到血浆免疫反应性β淀粉样肽增加，也未出现脑微出血。用融合蛋白对小鼠进行慢性每日sc治疗未引起免疫反应，仅产生低滴度的抗药物抗体反应。总之，将AAA重新设计用于受体介导的血脑屏障转运，在每日sc治疗12周后，可减少脑淀粉样斑块且不发生脑微出血。
