Development and validation of an enzyme-linked immunosorbent assay for the quantification of cytochrome 3A4 in human liver microsomes

Development of a highly sensitive and specific monoclonal antibody based enzyme-linked immunosorbent assay for the detection of a new β-agonist, phenylethanolamine A, in food samples

BACKGROUND

All β-agonists are banned as feed additives for growth promotion in animals due to toxic effects on humans after consuming the β-agonist contaminated meats. Phenylethanolamine A (PA) is a newly emerged β-agonist. Thus there is a need to develop highly sensitive and specific analytical methods for the detection of PA in food samples. In this study, the monoclonal antibody (mAb) against PA was produced by hybridoma technology and used for the development of enzyme-linked immunosorbent assay (ELISA).

RESULTS

The IC₅₀ values and limits of detection (LODs) of the ELISA using homogeneous combination of coating antigen/antibody for PA were 0.16 ng mL^-1 and 0.011 ng mL^-1 , respectively. The cross-reactive (CR) values of the assay with 14 structurally related β-agonists were lower than 0.59%. Swine liver and meat samples were spiked with PA at different content and analysed by ELISA. Acceptable recovery rates of 91.40-105.51% and intra-assay coefficients of variation of 1.56-9.92% (n = 3) were obtained. The ELISA for seven spiked samples was confirmed by LC-MS/MS with a high correlation coefficient of 0.9881.

CONCLUSION

The proposed mAb-based ELISA was highly sensitive and specific for PA and could be used as a quantitative/screening method for PA analysis in food samples. © 2016 Society of Chemical Industry.

Physiology-based IVIVE predictions of tramadol from in vitro metabolism data

PURPOSE

To predict the tramadol in vivo pharmacokinetics in adults by using in vitro metabolism data and an in vitro-in vivo extrapolation (IVIVE)-linked physiologically-based pharmacokinetic (PBPK) modeling and simulation approach (Simcyp®).

METHODS

Tramadol metabolism data was gathered using metabolite formation in human liver microsomes (HLM) and recombinant enzyme systems (rCYP). Hepatic intrinsic clearance (CLintH) was (i) estimated from HLM corrected for specific CYP450 contributions from a chemical inhibition assay (model 1); (ii) obtained in rCYP and corrected for specific CYP450 contributions by study-specific intersystem extrapolation factor (ISEF) values (model 2); and (iii) scaled back from in vivo observed clearance values (model 3). The model-predicted clearances of these three models were evaluated against observed clearance values in terms of relative difference of their geometric means, the fold difference of their coefficients of variation, and relative CYP2D6 contribution.

RESULTS

Model 1 underpredicted, while model 2 overpredicted the total tramadol clearance by -27 and +22%, respectively. The CYP2D6 contribution was underestimated in both models 1 and 2. Also, the variability on the clearance of those models was slightly underpredicted. Additionally, blood-to-plasma ratio and hepatic uptake factor were identified as most influential factors in the prediction of the hepatic clearance using a sensitivity analysis.

CONCLUSION

IVIVE-PBPK proved to be a useful tool in combining tramadol's low turnover in vitro metabolism data with system-specific physiological information to come up with reliable PK predictions in adults.

In vitro cytochrome p450 activity decreases in children with high pediatric end-stage liver disease scores

To improve the modeling and simulation of pharmacokinetics in pediatric patients, research into developmental and disease-specific determinants is needed. This article describes the evaluation of the activity of in vitro cytochrome P450 (P450), an important enzyme family in drug metabolism, in children with hepatic dysfunction. The activity of six P450 isoforms (CYP1A2, 2C9, 2C19, 2D6, 2E1, and 3A4) was evaluated in 31 patients with different pathologies, predominantly biliary atresia (n = 23). Hypervariable activity was observed for all the isoforms. Compared with average adult activity, low activity levels were seen for CYP1A2, 2C19, 2E1, and 3A4. For CYP2E1 and 3A4, a positive correlation between activity and abundance was observed. Age, comedication, and genotype could not be used as predictors for P450 activity in this patient population. In contrast, the pediatric end-stage liver disease score was negatively correlated with the ln(activity). This finding suggests a decrease in P450 activity with deteriorating hepatic function. Moreover, the activity of all isoforms was correlated, demonstrating a concomitant decrease of all isoforms in young patients with liver disease. To our knowledge, this is the first study to evaluate P450 activity in children with hepatic impairment. The presented data may provide support in the further optimization of a disease-specific model in this patient population.