Drug Interactions of Imperatorin and Curcumin on Macitentan in vitro and in vivo

The purpose of this study was to establish an in vitro incubation system and an in vivo model to investigate the potential kinetic interactions of macitentan with imperatorin and curcumin, and to validate the potential inhibitory mechanisms using molecular docking.

In vitro, the enzyme kinetic profile of macitentan was explored in rat liver microsomes (RLM) and human liver microsomes (HLM). Furthermore, molecular docking technique was used to study the sites of action of macitentan, imperatorin, and curcumin with CYP 3A4. In vivo, the pharmacokinetic parameters of macitentan were investigated in Sprague-Dawley (SD) rats administered the drug orally, both as a single agent and in combination with imperatorin and curcumin.

In vitro, the results indicated that imperatorin and curcumin could inhibit the metabolism of macitentan, with IC₅₀ values of 6.58 μM and 10.86 μM in RLM and 6.97 μM and 5.71 μM in HLM, respectively. And in the study of inhibition type, in RLM, the inhibition types of imperatorin and curcumin on macitentan were mixed and non-competitive, respectively; in HLM, the inhibition types of imperatorin and curcumin on macitentan were both mixed. Furthermore, additional molecular docking studies demonstrated that both imperatorin and curcumin occupied the CYP3A4 site. In vivo, the result showed significant increases in AUC_(0-t), AUC_(0-∞), T_max, t_1/2, and C_max for macitentan while a decrease in CL_z/F when combined with imperatorin. The metabolite ACT-132577 exhibited substantial increases in t_1/2, T_max, and C_max. Combined with curcumin, the AUC_(0-∞) and T_max of macitentan were significantly increased, while CL_z/F was significantly decreased. Conversely, the metabolite ACT-132577 exhibited a substantial decrease in CL_z/F, accompanied by notable increases in AUC_(0-∞) and T_max.

In vitro and in vivo studies revealed that imperatorin and curcumin exhibited inhibitory effects on the metabolism of macitentan. Furthermore, molecular docking revealed that the metabolic inhibition of macitentan by imperatorin and curcumin occurred through binding to the site on CYP3A4. However, further investigation is necessary to ascertain whether this phenomenon will occur in humans.