Co M S, Scheinberg D A, Avdalovic N M, McGraw K, Vasquez M, Caron P C, Queen C
Protein Design Labs, Mountain View, CA 94043.
Mol Immunol. 1993 Oct;30(15):1361-7. doi: 10.1016/0161-5890(93)90097-u.
M195 is a murine monoclonal antibody that binds to the CD33 antigen and is being tested for the treatment of myeloid leukemia. Surprisingly, a complementarity determining region (CDR)-grafted, humanized M195 antibody displayed a several-fold higher binding affinity for the CD33 antigen than the original murine antibody. Here we show that the increase in binding affinity resulted from eliminating an N-linked glycosylation site at residue 73 in the heavy chain variable region in the course of humanization. Re-introducing the glycosylation site in the humanized antibody reduces its binding affinity to that of the murine antibody, while removing the glycosylation site from the murine M195 variable domain increases its affinity. The removal of variable region carbohydrates may provide a method for increasing the affinity of certain monoclonal antibodies with diagnostic and therapeutic potential.
M195是一种与CD33抗原结合的鼠单克隆抗体，目前正用于髓系白血病治疗的试验。令人惊讶的是，一种互补决定区（CDR）移植的人源化M195抗体对CD33抗原的结合亲和力比原始鼠抗体高几倍。我们在此表明，结合亲和力的增加是由于在人源化过程中消除了重链可变区第73位残基处的一个N-连接糖基化位点。在人源化抗体中重新引入该糖基化位点会使其结合亲和力降低至鼠抗体的水平，而从鼠M195可变结构域中去除该糖基化位点则会增加其亲和力。去除可变区碳水化合物可能为提高某些具有诊断和治疗潜力的单克隆抗体的亲和力提供一种方法。
