A Study on the Application of Recombinant Factor C (rFC) Assay Using Biopharmaceuticals.

Gram-negative bacterial endotoxins can cause pathophysiological effects such as high fever when introduced into the bloodstream. Therefore, endotoxin testing is necessary when producing injectable pharmaceuticals. The pharmaceutical industry has widely used Limulus amebocyte lysate (LAL) to certify product quality. However, ethical concerns have been raised and the increasing scarcity of Limulus polyphemus necessitates the development of novel testing techniques. Recombinant factor C (rFC) was developed using genetic engineering techniques. The aim of this study was to investigate the validity of rFC testing and compare it with the LAL method. The specificity, linearity, accuracy, precision, and robustness of the rFC assay were evaluated. After validation, the rFC assay was found to be suitable for endotoxin detection. We compared the accuracy of the rFC and LAL assays using reference standard endotoxin. The rFC assay was as accurate as the LAL assay. We also compared the two assays using biopharmaceuticals. Greater interference occurred in some samples when the rFC assay was used than when the LAL assay was used. However, the rFC assay overcame the interference when the samples were diluted. Overall, we suggest that rFC can be applied to test biopharmaceuticals.

Changes in the QTc interval after administration of flecainide acetate, with and without coadministered paroxetine, in relation to cytochrome P450 2D6 genotype: data from an open-label, two-period, single-sequence crossover study in healthy Korean male subjects.

BACKGROUND: Flecainide acetate is a class Ic antiarrythmic agent that is metabolized by the cytochrome P450 (CYP) 2D6 isozyme. A previous open-label, 2-period, single-sequence crossover study in healthy Korean male volunteers found differences in the pharmacokinetics of flecainide between subjects with the CYP2D6 wild-type allele and those with the CYP2D6*10 allele, as well as differences in the pharmacokinetic interaction between flecainide and the CYP2D6 inhibitor paroxetine between genotype groups. OBJECTIVE: This study evaluated QTc-interval changes after administration of a single oral dose of flecainide, with and without paroxetine, in relation to CYP2D6 genetic polymorphism. METHODS: This was a follow-on to the previous pharmacokinetic study and used data from the same group of healthy Korean male volunteers. Subjects were grouped by CYP2D6 genotype as follows: CYP2D6*1/*1 or CYP2D6*1/*2 (group 1, extensive metabolizers); CYP2D6*1/*10 (group 2, intermediate metabolizers); and CYP2D6*10/*010 or CYP2D6*10/*36 (group 3, poor metabolizers). Flecainide 200 mg was administered on day 1 (period 1); after a 7-day washout period, subjects received paroxetine 20 mg once daily from day 8 to day 14, and flecainide 200 mg on day 15 (period 2). On days 1 and 15, serial 12-lead ECGs were obtained before flecainide dosing and at 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours after dosing. Baseline ECGs were obtained at the same time points on days -1 and 14. Machine-read changes in the QT interval corrected using the Fridericia formula (QTcF) and manually read changes in the QT interval individually corrected using mixed-effects modeling (QTcI) from time-matched baseline were analyzed by genotype and by period (baseline and paroxetine-inhibited state). The QRS duration and JTc interval (QTcF - QRS) were also determined. RESULTS: Twenty-one healthy volunteers (mean [SD] age, 24.5 [3.0] years; mean height, 173.5 [4.6] cm; mean weight, 69.1 [4.5] kg), 7 in each group, were enrolled in and completed the study. In period 1, all genotype groups had significant increases from time-matched baseline in both the QTcF interval (group 1:17.4 milliseconds [90% CI, 9.9-24.9], P < 0.001; group 2: 11.1 milliseconds [90% CI, 7.9-14.3], P = 0.013; and group 3: 20.5 milliseconds [90% CI, 12.8-28.2], P < 0.001) and the QTcI interval (group 1:15.4 milliseconds [90 % CI, 8.0-22.9], P = 0.001; group 2: 9.1 milliseconds [90% CI, 6.5-11.8], P = 0.030; and group 3:16.4 milliseconds [90% CI, 9.3-23.5], P = 0.001); the extent of increase did not differ significantly between groups. In groups 1 and 2, the least squares mean difference between period 1 and period 2 was statistically significant for the change in QTcF interval (6.5 milliseconds [90 CI, 3.2-9.8], P = 0.002; and 6.7 milliseconds [90% CI, 3.6-9.7], P = 0.001, respectively) and QTcI interval (6.9 milliseconds [90% CI, 4.1-9.8], P < 0.001; and 5.8 milliseconds [90% CI, 3.4-8.3], P < 0.001). In group 3, the least squares mean difference between period 1 and period 2 was statistically significant for the change in QTcI interval (3.9 milliseconds [90% CI, 1.3-6.5], P = 0.015) but not for the change in QT cF interval. The changes in QRS duration did not differ significantly by genotype or period. Consistent with the findings for the QTc interval, the least squares mean difference between period 1 and period 2 was statistically significant for the change in JTc interval in groups 1 and 2 (6.9 milliseconds [90% CI, 3.7-10.2], P = 0.001; and 5.4 milliseconds [90% CI, 2.7-8.2], P = 0.001, respectively) but not in group 3. CONCLUSION: The extent of drug interaction between flecainide and paroxetine, as reflected in the change in QTc interval (used as a pharmacodynamic biomarker), was influenced by the CYP2D6*10 allele in these healthy Korean male volunteers.

Pharmacokinetic interaction of flecainide and paroxetine in relation to the CYP2D6*10 allele in healthy Korean subjects.

AIMS: The objectives were to evaluate the effect of CYP2D6 genetic polymorphism on the pharmacokinetics of flecainide, and also on the extent of drug interaction with paroxetine as a CYP2D6 inhibitor after a single oral administration in healthy subjects. METHODS: An open-label, two-period, single-sequence, cross-over study was performed in 21 healthy Korean male volunteers (seven for CYP2D6*1/*1 or *1/*2, group 1; seven for CYP2D6*1/*10, group 2; seven for CYP2D6*10/*10 or *10/*36, group 3). Subjects were administered 200 mg of flecainide on day 1. After a 7-day wash-out period, subjects were administered 20 mg of paroxetine from day 8 to 14, and 200 mg of flecainide on day 15. Blood sampling was performed up to 72 h after flecainide administration. RESULTS: Terminal elimination half-life and mean residence time (MRT) were significantly different among three genotype groups after a single oral administration of flecainide (P = 0.021, 0.011, respectively). Area under the concentration-time curve, terminal elimination half-life and MRT increased significantly after paroxetine co-administration only in groups 1 and 2. CONCLUSIONS: This study reports that the extent of drug interaction between flecainide and paroxetine is influenced by the CYP2D6*10 allele in healthy subjects, which is frequent in Asians.