Stefanich Eric G, Ren Song, Danilenko Dimitry M, Lim Amy, Song An, Iyer Suhasini, Fielder Paul J
Department of Pharmacokinetic and Pharmacodynamic Sciences, Genentech, Inc., South San Francisco, CA 94080, USA.
J Pharmacol Exp Ther. 2008 Nov;327(2):308-15. doi: 10.1124/jpet.108.142232. Epub 2008 Aug 26.
B cell-activating factor receptor 3 (BR3)-Fc is an IgG1-receptor dimeric fusion protein that has multiple O-linked glycosylation sites and sialylation levels that can vary in the manufacturing process. Increased sialic acid levels resulted from increased site occupancy with the O-linked N-acetylgalactosamine (GalNAc-Gal), but because the ratio of sialic acid per mole of oligosaccharide remained approximately 1, this led to increased asialo terminal GalNAc. Previous studies have demonstrated an effect of terminal asialo Gal or GalNAc on the clearance of glycoproteins due to uptake and degradation by lectin receptors in the liver. However, the previous studies examined N-linked oligosaccharides, and there are less data regarding O-linked oligosaccharides. The objective of these studies was to determine the effects on the pharmacokinetics and distribution of the asialo terminal GalNAc and varying amounts of sialic acid residues on BR3-Fc. The results of the data presented here suggest that exposed Gal on the desialylated BR3-Fc led to rapid clearance due to uptake and degradation in the liver that was associated with nonparenchymal cells. It is interesting to note that the data indicated a decreased clearance and increased exposure of BR3-Fc as the sialic acid levels increased, even though increased sialic acid was associated with increased asialo GalNAc. Therefore, the exposed GalNAc did not seem to play a role in the clearance of BR3-Fc; although the Gal linked to the hydroxyl group at position 3 may have prevented an interaction. Because we did not see uptake of desialylated BR3-Fc in hepatocytes where the asialoglycoprotein receptor is localized, this nonparenchymal cell lectin may have preference for O-linked glycoproteins.
B细胞活化因子受体3（BR3）-Fc是一种IgG1受体二聚体融合蛋白，具有多个O-连接糖基化位点，其唾液酸化水平在生产过程中可能会有所不同。唾液酸水平的增加是由于O-连接的N-乙酰半乳糖胺（GalNAc-Gal）占据位点增加所致，但由于每摩尔寡糖中唾液酸的比例仍约为1，这导致了去唾液酸末端GalNAc的增加。先前的研究表明，末端去唾液酸Gal或GalNAc会因肝脏中凝集素受体的摄取和降解而影响糖蛋白的清除。然而，先前的研究检测的是N-连接寡糖，关于O-连接寡糖的数据较少。这些研究的目的是确定去唾液酸末端GalNAc和不同数量的唾液酸残基对BR3-Fc的药代动力学和分布的影响。此处呈现的数据结果表明，去唾液酸化的BR3-Fc上暴露的Gal由于在与非实质细胞相关的肝脏中被摄取和降解而导致快速清除。值得注意的是，数据表明随着唾液酸水平的增加，BR3-Fc的清除率降低且暴露增加，尽管唾液酸增加与去唾液酸GalNAc增加有关。因此，暴露的GalNAc似乎在BR3-Fc的清除中不起作用；尽管与3位羟基相连的Gal可能阻止了相互作用。由于我们在定位有去唾液酸糖蛋白受体的肝细胞中未观察到去唾液酸化BR3-Fc的摄取，这种非实质细胞凝集素可能对O-连接糖蛋白有偏好。
