Purpose: Regorafenib is an orally administered multi-kinase inhibitor used in the treatment of hepatocellular carcinoma, colorectal cancers and advanced gastrointestinal tumors. The contribution of hepatic uptake transporters such as OATP1B2 to the pharmacokinetic profile and disposition mechanism of regorafenib remains poorly understood. In the study, we developed a population pharmacokinetic model for regorafenib and its major metabolites regorafenib-N-oxide (M2; RO) and regorafenib-N-β-glucuronide (M7; RG) in mice with and without OATP1B2
Methods: A total of 120 concentration-time profiles were obtained from 40 wild-type and OATP1B2-knockout [OATP1B2(-/-)] mice, female and male mice (1:1) in each group. Mice received a single 10 mg/kg oral dose of regorafenib, and plasma levels of regorafenib, RO and RG were measured by a validated UPLC-MS/MS method with a lower limit of quantification of 5 ng/mL. Estimates of pharmacokinetic and variability parameters as well as model covariate identification (P<0.01) were obtained through nonlinear mixed effects modeling. Expression levels of CYP3A11 and UGT1A9, the main enzymes involved in the formation of RO and RG were obtained by RT-PCR, and enzymatic activity was confirmed in liver microsomes through in vitro metabolite profiling.
Results: The population pharmacokinetics of regorafenib, RO and RG were best described with a two-compartment model for regorafenib, a one-compartment model for RO, and an enterohepatic circulation (EHC) model for RG, assuming complete conversion of regorafenib to RO and RG. The model parameters displayed acceptable goodness-of-fit, stability, and predictive ability in both wild-type and OATP1B2(-/-) mice. The apparent volumes of distribution of regorafenib (V2/F and V3/F) in wild-type and OATP1B2(-/-) mice were 37.9 vs 33.2 mL and 36.6 vs 35.2 mL, with an inter-compartment clearance Q/F of 13.1 vs 16 mL/h, and an apparent clearance CL/F of 1.4 vs 1.27 mL/h, respectively. The respective apparent metabolic clearance (CLM1/F and CLM2/F) for RO and RG were 1.32 vs 1.24 mL/h and 1.3 vs 0.45 mL/h, respectively. OATP1B2 deficiency was associated with a significant decrease in RG clearance by 65%, and increased the systemic expose to RG by 7-fold. In covariate evaluation, sex was found to be a significant covariate that impacted CLM2/F (P<0.01) in wild-type and OATP1B2(-/-) mice. Metabolic studies revealed that the liver microsomal expression of CYP3A11 was 2-fold lower in female mice, whereas UGT1A9 levels and function were not sex-dependent.
Conclusion: The developed parent-metabolite model suggests that OATP1B2 strongly impacts RG exposure in mice receiving oral regorafenib, and that sex was significant covariate on the metabolic clearance of RG. This finding is consistent with the metabolism of regorafenib occurring via two competing pathways, and where RG is preferentially formed when CYP3A11 activity is low. The described model provides mechanistic insights into the in vivo handling of regorafenib, and can be applied to evaluate the potential for transporter-mediated drug interactions with xenobiotics undergoing extensive glucuronidation.
Qiang Fu
– Research Scientist, Ohio State University, Columbus, OhioMingqing Chen
– The Ohio State UniversityCollege Of Pharmacy - Columbus, OH, OhioJason T Anderson
– The Ohio State UniversityCollege Of Pharmacy - Columbus, OH, OhioXinxin Sun
– The Ohio State UniversityCollege Of Pharmacy - Columbus, OH, OhioShuiying Hu
– Research Assistant Professor, The Ohio State UniversityCollege Of Pharmacy - Columbus, OH, OhioAlex Sparreboom
– Professor, The Ohio State UniversityCollege Of Pharmacy - Columbus, OH, OhioSharyn Baker
– Professor and Chair of Pharmaceutics, Ohio State University, Columbus, OhioQiang Fu
– Research Scientist, Ohio State University, Columbus, Ohio321 Views