The effect of rifampin on the pharmacokinetics of famitinib in healthy subjects

BACKGROUND: Famitinib is an oral, small-molecule, multi-targeted tyrosine kinase inhibitor under clinical investigation for the treatment of solid tumors. As famitinib is metabolized mainly by cytochrome P450 3A4 (CYP3A4), the study was conducted to investigate the effect of potent CYP3A4 inducer rifampin on the pharmacokinetics of famitinb. METHODS: This single-center, single-arm and fixed-sequence drug–drug interaction study enrolled 21healthy Chinese male subjects. Subjects received a single oral dose of famitinib 25 mg on days 1 and 16 and repeated administration of oral rifampin 600 mg once daily on days 10–23. Blood samples were collected and plasma concentrations of famitinib were measured by validated liquid chromatography-tandem mass spectrometry (LC–MS/MS) method. Pharmacokinetic parameters were calculated using noncompartmental analysis and safety was assessed. RESULTS: In the presence of rifampin, the famitinib geometric mean maximum plasma concentration (C(max)) and area under the plasma concentration–time curve from time zero to infinity (AUC(0–∞)) decreased by 48% and 69%, respectively, and the mean elimination half-life was shortened from 33.9 to 18.2 h. The geometric mean ratio (GMR) of famitinib C(max) and AUC(0–∞) and their 90% CI were 0.52 (0.50, 0.54) and 0.31 (0.29, 0.33). Single dose of famitinib 25 mg was well tolerated and eight subjects (38.1%) reported treatment emergent adverse events, which were all grade 1–2 in severity. CONCLUSION: Co-administration of rifampin considerably reduces plasma concentration of famitinb due to CYP3A4 induction. Concomitant administration of famitinib and strong CYP3A4 inducers should be avoided, whereas when simultaneous use with inducers of CYP3A4, dose adjustment of famitinb is recommended. CLINICAL TRIAL REGISTRATION NUMBER: NCT04494659 (July 31, 2020). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00280-022-04474-8.