Caron P C, Co M S, Bull M K, Avdalovic N M, Queen C, Scheinberg D A
Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Cancer Res. 1992 Dec 15;52(24):6761-7.
Human-mouse chimeric immunoglobulins G1 and G3 (IgG1 and IgG3) (ChG1, ChG3) and "complementarity-determining region"-grafted, humanized IgG1 and IgG3 (HuG1, HuG3) constructs of the mouse monoclonal antibody (mAb) M195 were characterized. M195 is a murine immunoglobulin G2a (IgG2a), anti-CD33 mAb, specifically reactive with acute myelogenous leukemia cells, that is active as an antileukemia agent in humans. The new mAb constructs maintained specificity and biological function, including rapid internalization after binding to the cell surface, which has been important for delivery of therapeutic isotopes in patients. Although previously reported complementarity-determining region-grafted mAbs had reduced avidities, the HuG1 and HuG3 M195 showed up to an 8.6- and 4-fold higher binding avidity, respectively, than the original murine mAb. All constructs were effective at mediating rabbit complement-mediated cytotoxicity against HL60 targets. Fibroblasts transfected with CD33 genes and expressing high levels of CD33 antigen were also lysed in the presence of human complement, but HL60 cells or fibroblasts with lower CD33 levels were not killed. Thus, the inability of M195 and constructs to kill HL60 targets with human complement is due to the much lower antigen density on HL60 cells compared to CD33+ fibroblasts. Unlike the murine M195, the chimeric and humanized M195 demonstrated antibody-dependent cell-mediated cytotoxicity using human peripheral blood mononuclear cells as effectors. Because the chimeric and humanized M195 have improved avidities as compared to the original M195 and have, in addition, the potential to avoid human anti-mouse antibody responses and to recruit human effector functions, these new constructs may be useful therapeutically, either alone or conjugated to toxins or isotopes, in the treatment of acute myelogenous leukemia.
对人-鼠嵌合免疫球蛋白G1和G3（IgG1和IgG3）（ChG1、ChG3）以及小鼠单克隆抗体（mAb）M195的“互补决定区”移植人源化IgG1和IgG3（HuG1、HuG3）构建体进行了表征。M195是一种鼠源免疫球蛋白G2a（IgG2a）抗CD33单克隆抗体，与急性髓性白血病细胞具有特异性反应，在人类中作为抗白血病药物具有活性。新的单克隆抗体构建体保持了特异性和生物学功能，包括与细胞表面结合后快速内化，这对于在患者中递送治疗性同位素很重要。尽管先前报道的互补决定区移植单克隆抗体亲和力降低，但HuG1和HuG3 M195的结合亲和力分别比原始鼠源单克隆抗体高8.6倍和4倍。所有构建体在介导兔补体介导的针对HL60靶标的细胞毒性方面均有效。用CD33基因转染并表达高水平CD33抗原的成纤维细胞在人补体存在下也会被裂解，但CD33水平较低的HL60细胞或成纤维细胞不会被杀死。因此，M195及其构建体无法用人补体杀死HL60靶标是由于HL60细胞上的抗原密度比CD33+成纤维细胞低得多。与鼠源M195不同，嵌合和人源化M195使用人外周血单核细胞作为效应细胞表现出抗体依赖性细胞介导的细胞毒性。由于与原始M195相比，嵌合和人源化M195具有更高的亲和力，此外还具有避免人抗鼠抗体反应和募集人效应功能的潜力，这些新构建体可能在治疗急性髓性白血病方面单独或与毒素或同位素偶联使用具有治疗用途。
