Development of an UPLC-MS/MS method for quantification of donafenib and its metabolite in rat plasma: application to drug-drug interaction.

Donafenib is a deuterated drug used as a first-line treatment for unresectable hepatocellular carcinoma (HCC). And efavirenz is an antiretroviral for human immunodeficiency virus (HIV) treatment. Due to the high prevalence of HCC in HIV patients, the combination of the two drugs is increasingly common. This study developed an ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay for simultaneous quantitative determination of donafenib and its metabolite donafenib N-oxide, and assessed the impact of efavirenz on donafenib metabolism. In this bioanalytical method, good linearity (r = 0.99) was observed for donafenib (5-40,000 ng/mL) and donafenib N-oxide (2-400 ng/mL), with lower limit of quantification (LLOQ) of 5 ng/mL and 2 ng/mL, respectively. The precision (RSD%) and accuracy (RE%) of both compounds were less than ±15 %. In addition, the results of recovery, matrix effect, and stability were all in accordance with FDA guidelines. In vitro, efavirenz inhibited the metabolism of donafenib in rat liver microsomes (RLM) and human liver microsomes (HLM) with the half-maximum inhibitory concentration (IC) values of 5.87 μM and 39.14 μM, respectively, with no time-dependent inhibition (TDI). Moreover, the mechanism of inhibition was a mixture type in RLM. In vivo, the AUC, AUC and C of donafenib and donafenib N-oxide were significantly increased in the presence of efavirenz, which indicated that efavirenz increased the exposure of donafenib in rats. In short, this UPLC-MS/MS method was reliable for quantifying donafenib and its metabolite, and the findings suggested that efavirenz had an inhibitory effect on the metabolism of donafenib in vitro and in vivo.