Acacetin is a natural flavonoid that is widely distributed in plants and possesses numerous pharmacological activities. The aim of the present study was to investigate the effects of acacetin on the activities of the cytochrome P450 family members CYP1A2, CYP2B1, CYP2C11, CYP2D1, CYP2E1, and CYP3A2 in rat liver microsomes in vitro and rats in vivo to evaluate potential herb-drug interactions by using a cocktail approach. Phenacetin, bupropion, tolbutamide, dextromethorphan, chlorzoxazone, and midazolam were chosen as the probe substrates. An ultra-performance liquid chromatography-tandem mass spectrometry method was developed for the simultaneous detection of the probe substrates and their metabolites. In vitro, the mode of acacetin inhibition of CYP2B1, CYP2C11, and CYP2E1 was competitive, while mixed inhibition was observed for CYP1A2 and CYP3A2. The Ki values in this study were less than 8.32 μM. In vivo, the mixed probe substrates were administered by gavage after daily intraperitoneal injection with 50 mg/kg acacetin or saline for 2 weeks. The main pharmacokinetic parameters, area under the plasma concentration-time curve (AUC), plasma clearance (CL), and maximum plasma concentration (C_max) of the probe substrates were significantly different in the experimental group than in the control group. Overall, the in vitro and in vivo results indicated that acacetin would be at high risk to cause toxicity and drug interactions via cytochrome P450 inhibition.

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_max and/or increased K_m 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.

Poziotinib and vonoprazan are two drugs mainly metabolized by CYP3A4. However, the drug-drug interaction between them is unknown.To study the interaction mechanism and pharmacokinetics of poziotini...

Cytochrome P450 2C9 (CYP2C9) participates in about 15% of clinical drug metabolism, and its polymorphism is associated with individual drug metabolism differences, which may lead to the adverse drug reactions (ADRs). In this study, 1163 Chinese Han individuals were recruited to investigate their distribution pattern of CYP2C9 gene and find out the variants that may affect their drug metabolic activities. We successfully developed a multiplex PCR amplicon sequencing method and used it for the genetic screening of CYP2C9 in a large scale. Besides the wild type CYP2C9*1, totally 26 allelic variants of CYP2C9 were detected, which included 16 previously reported alleles and 10 new non-synonymous variants that had not been listed on the PharmVar website. The characteristics of these newly detected CYP2C9 variants were then evaluated after co-expressing them with CYPOR in S. cerevisiae microsomes. Immunoblot analysis revealed that except for Pro163Ser, Glu326Lys, Gly431Arg and Ile488Phe, most of newly detected variants showed comparable protein expression levels to wild type in yeast cells. Two typical CYP2C9 probe drugs, losartan and glimepiride, were then used for the evaluation of metabolic activities of variants. As a result, 3 variants Thr301Met, Glu326Lys, and Gly431Arg almost lost their catalytic activities and most of other variants exhibited significantly elevated activities for drug metabolism. Our data not only enriches the knowledge of naturally occurring CYP2C9 variants in the Chinese Han population, but also provides the fundamental evidence for its potential clinical usage for personalized medicine in the clinic.

Cytochrome 2C9 (CYP2C9), one of the most important drug metabolic enzymes in the human hepatic P450 superfamily, is required for the metabolism of 15% of clinical drugs. Similar to other CYP2C family members, CYP2C9 gene has a high genetic polymorphism which can cause significant racial and inter-individual differences in drug metabolic activity. To better understand the genetic distribution pattern of CYP2C9 in the Chinese Han population, 931 individuals were recruited and used for the genotyping in this study. As a result, seven synonymous and 14 non-synonymous variations were identified, of which 4 missense variants were designated as new alleles CYP2C9*72, *73, *74 and *75, resulting in the amino acid substitutions of A149V, R150C, Q214H and N418T, respectively. When expressed in insect cell microsomes, all four variants exhibited comparable protein expression levels to that of the wild-type CYP2C9 enzyme. However, drug metabolic activity analysis revealed that these variants exhibited significantly decreased catalytic activities toward three CYP2C9 specific probe drugs, as compared with that of the wild-type enzyme. These data indicate that the amino acid substitution in newly designated variants can cause reduced function of the enzyme and its clinical significance still needs further investigation in the future.