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.

Aims: Cytochrome P450 (CYP450) 2D6 is an important member of the P450 enzyme superfamily and responsible for clearing 25% of clinically important drugs. The aim of this study was to assess the catalytic characteristics of 24 CYP2D6 allelic isoforms found in the Chinese population and their effects on the metabolism of risperidone in vitro. Methods: Insect microsomes expressing wild-type CYP2D6 and 24 CYP2D6 allelic variants were incubated with 20-1,000 μmol/l risperidone for 40 min at 37°C. After termination, risperidone and 9-OH risperidone, the metabolite of risperidone, were precipitated and used for signal collection by ultra-performance liquid-chromatography tandem mass spectrometry. Results: Among 24 CYP2D6 variants tested, 2 variants (CYP2D6*92 and CYP2D6*96) were found to be with no detectable activity. Two variants (E215K and R440C) exhibited higher intrinsic clearance values than the wild-type protein, while the remaining 20 CYP2D6 allelic variants exhibited significantly decreased clearance values (2.01-87.56%) compared to CYP2D6*1. Conclusion: These findings suggest that more attention should be directed to subjects carrying these infrequent CYP2D6 alleles when administering risperidone in the clinic. This is the first report of all these novel alleles for risperidone metabolism, providing fundamental data for further clinical studies on CYP2D6 alleles.

Objective: The aim of this article was to assess the catalytic activities of 24 cytochrome P450 2D6 (CYP2D6) variants found in the Chinese population toward atomoxetine in vitro as well as CYP2D6.1. Methods: In this study, the co-expression enzyme of human recombinant CYPOR, CYPb5, and CYP2D6.1 or other CYP2D6 variants with the baculovirus-mediated insect cells (Sf21) was used to study the catalytic activities of 24 CYP2D6 variants toward atomoxetine metabolism. The metabolite of atomoxetine (4-hydroxyatomoxetine) was detected by ultra-high performance liquid chromatography-mass spectrometry method. Results: The intrinsic clearance (Vmax/Km) values of most variants were significantly altered when compared with CYP2D6.1. CYP2D6.94, CYP2D6.D336N, CYP2D6.R440C exhibited marked increased values 172, 126, 121% respectively. CYP2D6.89 and CYP2D6.98 exhibited similar catalytic activity as the wild type, whereas 17 variants exhibited significantly decreased values (from 5 to 87%) due to increase Km and/or decrease Vmax values. However, CYP2D6.92 and CYP2D6.96 showed no or few activity because of producing nothing. Conclusions: Our results suggest that most of these newly found variants exhibit significantly changed catalytic activities compared with the wild type. And these findings provide valuable information for the growth and development of personalized medicine in China.