Preclinical DMPK Department, Merck Research Laboratories, Merck Sharp and Dohme Corp., West Point, PA 19486, United States.
Mol Immunol. 2011 Mar;48(6-7):860-6. doi: 10.1016/j.molimm.2010.12.009. Epub 2011 Jan 21.
IgG monoclonal antibodies (mAbs) consist of two Fab fragments and one Fc fragment. The Fab fragments contain the variable regions and are responsible for drug specificity (via antigen binding); the Fc fragment contains constant regions and is responsible for effector functions (via interactions with Fcγ receptors) and extended serum half-life (via interaction with the neonatal Fc receptor, FcRn). There are two conserved methionine (Met) residues located in the FcRn binding site of the Fc fragment. It has been shown previously that oxidation of these two Met residues decreases the binding affinity to FcRn. We have further evaluated the impact of Met oxidation on serum half-lives of two humanized IgG1 mAbs in transgenic mice with human FcRn. Variable oxidation levels were obtained by several procedures: exposure to an oxidizing agent, accumulation during extended refrigerated storage, or chromatographic separation. Our results show that Met oxidation can result in a significant reduction of the serum circulation half-life and the magnitude of the change correlates well with the extent of Met oxidation and changes in FcRn binding affinities. The relatively low levels of Met oxidation accumulated during 3 years of refrigerated storage had minimal impact on FcRn binding and no detectable impact on the serum half-life.
IgG 单克隆抗体（mAbs）由两个 Fab 片段和一个 Fc 片段组成。Fab 片段包含可变区，负责药物特异性（通过抗原结合）；Fc 片段包含恒定区，负责效应功能（通过与 Fcγ 受体相互作用）和延长血清半衰期（通过与新生儿 Fc 受体 FcRn 相互作用）。Fc 片段的 FcRn 结合位点有两个保守的蛋氨酸（Met）残基。先前已经表明，这两个 Met 残基的氧化会降低与 FcRn 的结合亲和力。我们进一步评估了 Met 氧化对两种人源化 IgG1 mAb 在具有人 FcRn 的转基因小鼠中的血清半衰期的影响。通过几种方法获得了可变的氧化水平：暴露于氧化剂、在延长冷藏储存期间积累或色谱分离。我们的结果表明，Met 氧化可导致血清循环半衰期显著降低，并且变化幅度与 Met 氧化程度和 FcRn 结合亲和力的变化密切相关。在冷藏储存 3 年内积累的相对较低水平的 Met 氧化对 FcRn 结合几乎没有影响，对血清半衰期也没有可检测到的影响。
