The Impact of Sialylation Linkage Type on the Pharmacokinetics of Recombinant Butyrylcholinesterases

Chinese hamster ovary (CHO) cells typically produce glycoproteins with N-glycans terminating in alpha-2,3 sialylation. Human cells produce glycoproteins that include alpha-2,3 and alpha-2,6 sialic acids. To examine the impact of altering protein sialylation on pharmacokinetic properties, recombinant human butyrylcholinesterase (BChE) was produced in CHO cells by knocking out the alpha-2,3 sialyltransferase genes followed by overexpression of the alpha-2,6 sialyltransferase (26BChE) enzyme. The N-glycan composition of 26BChE was compared to BChE with alpha-2,3 sialylation (23BChE) derived from wild-type CHO cells. Both 23BChE and 26BChE exhibited comparable antennarity distributions with bi-antennary di-sialylated glycans representing the most abundant glycoform. CD-1 mice were intravenously injected with the 23BChE or 26BChE, and residual BChE activities from blood collected at various time points for pharmacokinetic analyses. Although 23BChE contained a slightly lower initial sialylation level compared to 26BChE, the molecule exhibited higher residual activity between 5 and 24 hr postinjection. Pharmacokinetic analyses indicated that 23BChE exhibited an increase in area under the curve and a lower volume of distribution at steady state than that of 26BChE. These findings suggest that the type of sialylation linkage may play a significant role in the pharmacokinetic behavior of a biotherapeutic when tested in in vivo animal models.