Effects of CYP2C19 inhibitors on mavacamten pharmacokinetics in rats based on UPLC-MS/MS

French-Speaking Network of Pharmacogenetics (RNPGx) Recommendations for Clinical Use of Mavacamten

Mavacamten, the first drug in the class of β-cardiac myosin modulator, is used for the treatment of patients with hypertrophic cardiomyopathy. This orally administered drug demonstrates wide interpatient variability in pharmacokinetics parameters, due in part to variant CYP2C19 alleles. Individuals who are CYP2C19 poor metabolizers have increased exposure and are at increased risk of reduced cardiac hypercontractility. To ensure the safety of all patients, European Medicines Agency recommends CYP2C19 preemptive genotyping, and consecutively, to adapt maintenance and initial mavacamten doses, and to manage drug-drug interactions, according to CYP2C19 phenotype. In this article, we summarize evidence from the literature supporting the association between CYP2C19 phenotype and pharmacological features of mavacamten and provide, beyond biologic guidelines, therapeutic recommendations for the use of mavacamten based on CYP2C19 and CYP3A4/CYP3A5 genotype.

Effects of two commonly used antidepressants amitriptyline and fluoxetine on the pharmacokinetics of abrocitinib in rats

Abrocitinib is approved to treat moderate-to-severe atopic dermatitis and eliminated mainly through cytochrome P450 (CYP450) enzyme. Two commonly used antidepressants, amitriptyline and fluoxetine, could inhibit the activities of CYP2C19 and CYP3A4. In this study, we developed a new and quick ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for quantitatively analyzing the plasma concentration of abrocitinib, and further investigated the effects of amitriptyline or fluoxetine on the pharmacokinetics of abrocitinib in rats. The selectivity, linearity, recovery, accuracy, precision, matrix effect and stability of UPLC-MS/MS assay were satisfied according to the United States Food and Drug Administration (FDA) and European Medicines Agency (EMA) guidelines. Our result showed that when co-administered with amitriptyline and fluoxetine, the CLz/F of abrocitinib was reduced by 44.4 % and 33.3 %, respectively, while the AUC(0-t) of abrocitinib was increased by 77.7 % and 49.4 %, respectively. It indicated that amitriptyline and fluoxetine could significantly increase the plasma concentration of abrocitinib in rats. Thus, dose adjustment of abrocitinib may be required when it is combined with amitriptyline or fluoxetine in ongoing clinical practice.

Simultaneous determination of iguratimod and its metabolite in rat plasma using a UPLC-MS/MS method: Application for drug-drug interaction

This aim of the work was to establish an acceptable sensitive assay based on ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) for quantitatively analyzing the plasma concentrations of iguratimod (IGR) and its metabolite M2 in rats, and to further investigate the effect of fluconazole on the pharmacokinetics of IGR and M2. The mobile phase consisted of acetonitrile and water with 0.1% formic acid, was used to separate IGR, M2 and internal standard (IS) fedratinib on a UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) with the flow rate of 0.4 mL/min. Positive ion mode and multiple reaction monitoring (MRM) were used to construct the quantitative analysis. The calibration standard of IGR and M2 covered 2-10000 and 1-1000 ng/mL respectively, with the lower limit of quantification (LLOQ) as 2 ng/mL and 1 ng/mL respectively. In addition, selectivity, recovery, accuracy, precision, matrix effect and stability of the method validation program were well accepted in this work. Subsequently, this approach was used to assess the effect of fluconazole on the pharmacokinetics of IGR and M2 in rats. In the presence of 20 mg/kg fluconazole (experimental group), we found the main pharmacokinetic parameters were significantly altered when compared with 2.5 mg/kg IGR alone (control group). Among them, AUC(0-∞) and Cmax of IGR in the experimental group was 1.43 and 1.08 times higher than that of the control group, respectively. Moreover, we also found that the other main pharmacokinetic parameters of M2 had no significant changes, except t1/2z and Tmax. In conclusion, fluconazole significantly altered the main pharmacokinetics of IGR and M2 in rats. It implys that we should pay more attention to the adverse reaction of IGR when the concomitant use of fluconazole and IGR occur in the future clinical practice.