Co M S, Baker J, Bednarik K, Janzek E, Neruda W, Mayer P, Plot R, Stumper B, Vasquez M, Queen C, Loibner H
Protein Design Labs, Mountain View, California 94043, USA.
Cancer Res. 1996 Mar 1;56(5):1118-25.
ABL 364 is a murine monoclonal IgG3 antibody directed against the Lewis Y carbohydrate antigen (Le(y)) expressed on the surface of many epithelial cell tumors. The antibody mediates cytotoxicity via activation of human complement or human effector cells, and has been evaluated in several clinical trials including two Phase I/II trials in relapsed small cell lung cancer and metastatic breast cancer. To improve the effector functions of the antibody, increase its half-life in circulation, and avoid the human antimouse antibody response, two chimeric and several humanized antibodies were constructed for evaluation. The chimeric IgG1 is more potent than the murine IgG3 in tumor cell lysis via activation of human peripheral mononuclear cells (10-fold), but somewhat less effective in complement-dependent lysis (2-3 fold). The chimeric IgG3 is slightly less potent than the IgG1. A humanized IgG1 was constructed by combining the complementarity-determining regions of the ABL 364 antibody with human framework and constant regions. Several additional variants were subsequently constructed to improve the binding affinity and increase expression of the antibody. Two of the variants, designated I and K, differ by a single amino acid at position 75 of the heavy chain. Both variants have affinity within 2-fold of the chimeric IgG1 antibody and retain the cytolytic activities toward tumor cell lines. However, it was possible to express variant K at a significantly higher level (5- 10-fold) than variant I. Pharmacokinetics of the humanized ABL 364 antibody variant K was compared with that of the parent murine antibody in rhesus monkeys. It was shown that the terminal half-life of the humanized antibody in rhesus monkeys is 14-20 days, with a mean of 16.3 days, while that of the parent murine antibody is only 1.9 days.
ABL 364是一种鼠单克隆IgG3抗体，可靶向许多上皮细胞瘤表面表达的Lewis Y碳水化合物抗原（Le(y)）。该抗体通过激活人补体或人效应细胞介导细胞毒性，并已在多项临床试验中进行评估，包括两项针对复发性小细胞肺癌和转移性乳腺癌的I/II期试验。为了提高抗体的效应功能、延长其在循环中的半衰期并避免人抗鼠抗体反应，构建了两种嵌合抗体和几种人源化抗体进行评估。嵌合IgG1在激活人外周单核细胞方面比鼠IgG3在肿瘤细胞裂解中更有效（10倍），但在补体依赖性裂解方面效果稍差（2 - 3倍）。嵌合IgG3的效力略低于IgG1。通过将ABL 364抗体的互补决定区与人框架区和恒定区相结合构建了一种人源化IgG1。随后构建了几种其他变体以提高抗体的结合亲和力并增加其表达。其中两种变体，命名为I和K，重链第75位氨基酸仅相差一个。两种变体的亲和力均在嵌合IgG1抗体的2倍以内，并保留了对肿瘤细胞系的细胞溶解活性。然而，变体K的表达水平比变体I显著更高（5 - 10倍）。在恒河猴中比较了人源化ABL 364抗体变体K与亲本鼠抗体的药代动力学。结果表明，人源化抗体在恒河猴中的终末半衰期为14 - 20天，平均为16.3天，而亲本鼠抗体的终末半衰期仅为1.9天。
