Functional characterization of 27 CYP3A4 variants on macitentan metabolism in vitro

Objective Macitentan is a new choice for pulmonary hypertension treatment which is converted to active metabolite ACT132577 by human cytochrome P450 3A4. Human cytochrome P450 3A4 often occurred gene mutations. Gene polymorphism might cause a variety of changes of protein expression and thus give rise to metabolic difference. The aim of this study was to investigate the catalytic characteristics of 27 CYP3A4 protein variants on the metabolism of macitentan in vitro. Method The incubation mixtures (final volume of 200 mu l in 1 m PBS) consisted of 1 pmol wild-type CYP3A4.1 or other CYP3A4 protein variants, 2.38 pmol CYP b5 and macitentan (10-600 mu m) with 1 mm NADPH. All specimens were processed using same approach with acetonitrile precipitation. The metabolite of macitentan was analysed by ultra performance liquid chromatography-tandem mass spectrometry. Key finding Most CYP3A4 protein variants (CYP3A4.9, .11, .12, .13, .17, .20, .23, .24, .28, .29, .33, .34) exhibited a sharp decrease, meanwhile nearly one in five variants (CYP3A4.3, .4, .5, .10, .15, .16) showed a significant rise in intrinsic clearance. The relative clearance of CYP3A4 protein variants was ranged from 5.53 to 501.00%. Conclusion Twenty-seven CYP3A4 protein variants displayed different catalytic characteristics towards macitentan in vitro, especially CYP3A4.5, .17, .20, .23. It is important to pay more attention to the dosage of macitentan in order to get better treatment for pulmonary arterial hypertension.