Differential killing of CD56-expressing cells by drug-conjugated human antibodies targeting membrane-distal and membrane-proximal non-overlapping epitopes
Differential killing of CD56-expressing cells by drug-conjugated human antibodies targeting membrane-distal and membrane-proximal non-overlapping epitopes
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DOI：
10.1080/19420862.2016.1155014
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发表时间：
2016-01-01
期刊：
影响因子：
5.3
通讯作者：
Dimitrov, Dimiter S.
中科院分区：
文献类型：
--
作者：
Feng, Yang;Wang, Yanping;Dimitrov, Dimiter S.
CD 56（NCAM，神经细胞粘附分子）在许多肿瘤类型中过表达，包括神经母细胞瘤、多发性骨髓瘤、小细胞肺癌、卵巢癌、急性髓性白血病、NK-T淋巴瘤、神经内分泌癌和胰腺癌。使用噬菌体展示，我们鉴定了2种高亲和力抗CD 56人单克隆抗体（mAb），m900和m906，它们以相似的亲和力（平衡解离常数分别为2.9和4.5nM）结合空间上分离的非重叠表位。m900结合到膜近端纤连蛋白III型样结构域，而m906结合到N-末端IgG样结构域。m906诱导的4个神经母细胞瘤细胞系中的CD 56显著下调，而m900诱导的CD 56下调要低得多。通过与高度有效的吡咯并苯并二氮杂卓二聚体（PBD）缀合制备的抗体-药物缀合物（ADC）表现出与CD 56下调相关的杀伤活性，并且在一定程度上与抗体的体内结合能力相关。m906 PBD ADC比m900 PBD有效得多，可能是由于更高的CD 56介导的下调和更强的细胞结合。用m906 PBD ADC处理导致非常有效的细胞毒性（IC 50：0.05-1.7 pM）。这些结果提示了一种靶向表达CD 56的神经母细胞瘤细胞的新方法。需要在动物模型和人类中进行进一步研究，以发现这些抗体及其药物缀合物是否是有希望的候选治疗剂。
CD56 (NCAM, neural cell adhesion molecule) is over-expressed in many tumor types, including neuroblastoma, multiple myeloma, small cell lung cancer, ovarian cancer, acute myeloid leukemia, NK-T lymphoma, neuroendocrine cancer and pancreatic cancer. Using phage display, we identified 2 high-affinity anti-CD56 human monoclonal antibodies (mAbs), m900 and m906, which bound to spatially separated non-overlapping epitopes with similar affinity (equilibrium dissociation constant 2.9 and 4.5nM, respectively). m900 bound to the membrane proximal fibronectin type III-like domains, whereas m906 bound to the N-terminal IgG-like domains. m906 induced significant down-regulation of CD56 in 4 neuroblastoma cell lines tested, while m900-induced downregulation of CD56 was much lower. Antibody-drug conjugates (ADCs) made by conjugation with a highly potent pyrrolobenzodiazepine dimer (PBD) exhibited killing activity that correlated with CD56 down-regulation, and to some extent with in vivo binding ability of the antibodies. The m906PBD ADC was much more potent than m900PBD, likely due to higher CD56-mediated downregulation and stronger binding to cells. Treatment with m906PBD ADC resulted in very potent cytotoxicity (IC50: 0.05-1.7 pM). These results suggest a novel approach for targeting CD56-expressing neuroblastoma cells. Further studies in animal models and in humans are needed to find whether these antibodies and their drug conjugates are promising candidate therapeutics.