Pharmacokinetics and immunologic consequences of repeated administrations of purified heterologous and homologous butyrylcholinesterase in mice

AimTo assess the consequences of repeated administrations of purified human serum butyrylcholinesterase (Hu BChE) and mouse serum (Mo) BChE into mice.Main methodsPurified Hu BChE and Mo BChE isolated from the sera of CD-1 mice were administered into Balb/c or CD-1 mice. The enzymes were delivered by i.m. injections of ∼ 100 U (0.15 mg) on day 1 and on day 28, respectively. The effects of two injections were monitored by following blood BChE and anti-BChE IgG levels.Key findingsHu BChE displayed a mean residence time (MRT) of 50 h, and an area under the curve (AUC) of 1220 U/ml·h in Balb/c or CD-1 mice. Mo BChE exhibited an MRT of 78 h and an AUC of 1815 U/ml·h in Balb/c mice; the AUC increased to 2504 U/ml·h in CD-1 mice. A second injection of Hu BChE in both strains exhibited a marked reduction in circulatory stability. The circulatory stability of the second injection of Mo BChE was reduced in Balb/c mice, but was almost identical to the first injection in CD-1 mice. Consistent with these observations, circulating anti-BChE IgGs were observed in mice injected with Hu BChE; low levels of anti-BChE IgGs were observed only in Balb/c mice injected with Mo BChE. No antibody response was detected in CD-1 mice following either injection of homologous Mo BChE.SignificanceThe identical pharmacokinetic profiles and the absence of an immunologic response following a second administration of homologous BChE support the development of Hu BChE as a detoxifying drug in humans.