Fuji-Gotemba Research Laboratories, Chugai Pharmaceutical Co. Ltd, Shizuoka 412-8513, Japan.
Protein Eng Des Sel. 2010 May;23(5):385-92. doi: 10.1093/protein/gzq009. Epub 2010 Feb 15.
Fc engineering to increase the binding affinity of IgG antibodies to FcRn has been reported to reduce the elimination of IgG antibodies. Herein, we present a novel non-FcRn-dependent approach to reduce the elimination of IgG antibodies. Pharmacokinetic studies conducted in normal mice of various humanized IgG4 antibodies, which had identical constant regions but different variable region sequences, revealed that an antibody with a lower isoelectric point (pI) has a longer half-life. These antibodies exhibited comparable binding affinity to FcRn, and with the antibodies with lower pIs, a longer half-life was also observed in beta2-microglobulin knockout mice, suggesting that differences in the pharmacokinetics were due to a non-FcRn-dependent mechanism. On the basis of our findings, we attempted to engineer the pharmacokinetic properties of a humanized anti-IL6 receptor IgG1 antibody. Selected substitutions in the variable region, without substitution in the Fc region, lowered the pI but did not reduce the biological activity and showed a significant reduction in the clearance of the antibody in cynomolgus monkey. These results suggest that lowering the pI by engineering the variable region could reduce the elimination of IgG antibodies and could provide an alternative to Fc engineering of IgG antibodies.
Fc 工程改造已被报道可增加 IgG 抗体与 FcRn 的结合亲和力，从而降低 IgG 抗体的清除率。在此，我们提出了一种新的非 FcRn 依赖的方法来降低 IgG 抗体的清除率。在正常小鼠中进行的各种人源化 IgG4 抗体的药代动力学研究表明，等电点（pI）较低的抗体具有更长的半衰期。这些抗体与 FcRn 具有相似的结合亲和力，而对于 pI 较低的抗体，在β2-微球蛋白敲除小鼠中也观察到更长的半衰期，表明药代动力学的差异是由于非 FcRn 依赖的机制所致。基于我们的发现，我们试图改造一种人源化抗 IL6 受体 IgG1 抗体的药代动力学特性。在可变区进行选择替换，而不替换 Fc 区，可降低 pI，但不会降低生物活性，并可显著降低抗体在食蟹猴中的清除率。这些结果表明，通过工程改造可变区降低 pI 可以降低 IgG 抗体的清除率，并可为 IgG 抗体的 Fc 工程改造提供替代方法。
