Evaluation of 24 CYP2D6 Variants on the Metabolism of Nebivolol In Vitro

Abstract

CYP2D6 is an important cytochrome P450 (P450) enzyme that metabolizes approximately 25% of therapeutic drugs. Its genetic polymorphisms may significantly influence the pharmacokinetics and pharmacodynamics of clinically used drugs. Studying the effects of CYP2D6 on drug metabolism can help reduce adverse drug reactions and therapeutic failure to some extent. This study aimed to investigate the role of CYP2D6 in nebivolol metabolism by evaluating the effect of 24 CYP2D6 variants on the metabolism of nebivolol in vitro. CYP2D6 variants expressed by insect cell systems were incubated with 0.1-80 μM nebivolol for 30 minutes at 37°C and the reaction was terminated by cooling to -80°C immediately. An ultra-performance liquid chromatography-tandem mass spectrometry system was used to analyze nebivolol and its metabolite 4-hydroxy nebivolol. Compared with CYP2D6.1, the intrinsic clearance values of most variants were significantly altered, and most of these variants exhibited either reduced V and/or increased K values. Variant R440C showed much higher intrinsic clearance than the wild type (219.08%). Five variants (CYP2D6.88, CYP2D6.89, R344Q, V342M, and D336N) exhibited no difference from the wild type. CYP2D6.92 and CYP2D6.96 displayed weak or no activity, whereas the intrinsic clearance values of the remaining 16 variants were significantly reduced to various degrees (ranging from 4.07% to 71%). As the first report of 24 CYP2D6 alleles for nebivolol metabolism, these results are valuable to interpreting in vivo studies and may also serve as a reference for rational clinical administration.

Functional characterization of wild-type and 24 CYP2D6 allelic variants on gefitinib metabolism in vitro

“…Furthermore, the most meaningful difference between our study and previous reports19,21–24 is that gefitinib exhibited a substrate inhibition trend of metabolic ability by CYP2D6 in vitro. Twenty-three tested CYP2D6 allelic variants showed this substrate inhibition trend toward gefitinib and their K si values varied from ~6 to 158 μM.…”

“…In addition, different from the previous studies,19,21–24 the metabolic ability toward gefitinib in vitro exhibited substrate inhibition trend, the inhibition constant of 25 tested CYP2D6 variants varied from nearly 5.9 to 158.1 μM.…”

“…In our study, both CYP2D6.92 and CYP2D6.96 had undetectable enzyme activity in gefitinib metabolism, similar to previous reports 19,21,23,24. The reason for this may be because both of these variants were expressed as truncated proteins due to the premature termination in protein translation process, which led to the function loss of enzymatic activity.…”

“…Particularly, only one variant CYP2D6.94, with a decrease K m and an increase V max , showed significant increased relative clearance compared with CYP2D6.1, suggesting higher catalytic activity than CYP2D6.1. On the contrary, as reported in other studies, CYP2D6.94 exhibited markedly different decreased catalytic activity toward propranolol (31.37%), nebivolol (58.23%), dextromethorphan (67.03%), venlafaxine (71.9%), and bufuralol (74.96%) in vitro 19,21,23,24. These data suggest that CYP2D6.94 may be reclassified as an ultrarapid metabolizer phenotype for gefitinib.…”

Functional characterization of CYP2C19 variants in nebivolol 4‐hydroxlation in vitro

“…It has been proven that nebivolol bioavailability was greater for the CYP2D6 poor metabolizers in comparison with CYP2D6 extensive metabolizers, suggesting the potential need for individualized treatment strategies . Most studies have concentrated primarily on the influence of the CYP2D6 genotype/phenotype on the clinical response and metabolism of nebivolol, which is a metabolic pathway that is under polymorphic regulation . However, our previous study showed that CYP2C19 and CYP3A4 can contribute, to some extent, to this pathway for the metabolism of nebivolol 4‐hydroxylation .…”