In Vitro Characterization of Ertugliflozin Metabolism by UDP-Glucuronosyltransferase and Cytochrome P450 Enzymes

Abstract

Ertugliflozin is primarily cleared through UDP-glucurosyltransferase (UGT)-mediated metabolism (86%) with minor oxidative clearance (12%). In vitro phenotyping involved enzyme kinetic characterization of UGTs or cytochrome P450 (CYP) enzymes catalyzing formation of the major 3-O-β-glucuronide (M5c) and minor 2-O-β-glucuronide (M5a), monohydroxy-ertugliflozin (M1 and M3), and des-ethyl ertugliflozin (M2) metabolites in human liver microsomes (HLM). Fractional clearance (fCL) from HLM intrinsic clearance (CLint) indicated a major role for glucuronidation (fCL 0.96; CLint 37 µL/min/mg) versus oxidative metabolism (fCL 0.04; CLint 1.64 µL/min/mg). Substrate concentration at half-maximal velocity (Km), maximal rate of metabolism (Vmax), and intrinsic clearance (CLint) for M5c and M5a formation were 10.8 µM, 375 pmol/min/mg, 34.7 µL/min/mg and 41.7 µM, 94.9 pmol/min/mg, 2.28 µL/min/mg, respectively. Inhibition of HLM CLint with 10 µM digoxin or tranilast (UGT1A9) and 3 µM 16βphenyllongifolol (UGT2B7/UGT2B4) resulted in fraction metabolism (fm) estimates of 0.81 and 0.19 for UGT1A9 and UGT2B7/UGT2B4, respectively. Relative activity factor scaling of recombinant enzyme kinetics provided comparable fm for UGT1A9 (0.86) and UGT2B7 (0.14). Km and Vmax for M1, M2, and M3 formation ranged 73.0-93.0 µM and 24.3-116 pmol/min/mg, respectively, and was inhibited by ketoconazole (M1, M2, and M3) and montelukast (M2). In summary, ertugliflozin metabolism in HLM was primarily mediated by UGT1A9 (78%) with minor contributions from UGT2B7/UGT2B4 (18%), CYP3A4 (3.4%), CYP3A5 (0.4%), and CYP2C8 (0.16%). Considering higher ertugliflozin oxidative metabolism (fCL 0.12) obtained from human mass balance, human systemic CL is expected to be mediated by UGT1A9 (70%), UGT2B7/UGT2B4 (16%), CYP3A4 (10%), CYP3A5 (1.2%), CYP2C8 (0.5%), and renal elimination (2%).

Physiologically‐Based Pharmacokinetic Modeling of the Drug–Drug Interaction of the UGT Substrate Ertugliflozin Following Co‐Administration with the UGT Inhibitor Mefenamic Acid

“…As selective inhibitors of UGT2B4 and UGT2B7 are not available, the minor UGT enzymes are reported as UGT2B4/2B7 (19%). 12,17,18 Because MFA inhibits UGT1A9 and UGT2B7, and not UGT2B4, the minor UGT responsible for metabolism of ertugliflozin was assigned to UGT2B7 in the PBPK model. This assignment provides a conservative assessment of the DDI following co-administration of ertugliflozin with the UGT1A9/2B7 inhibitor MFA.…”

“…The minor UGT enzymes were assigned based on studies with the UGT inhibitor 16β‐phenyllongifolol, which was recently shown to be a nonselective inhibitor of both UGT2B4 and UGT2B7. As selective inhibitors of UGT2B4 and UGT2B7 are not available, the minor UGT enzymes are reported as UGT2B4/2B7 (19%) 12,17,18 . Because MFA inhibits UGT1A9 and UGT2B7, and not UGT2B4, the minor UGT responsible for metabolism of ertugliflozin was assigned to UGT2B7 in the PBPK model.…”

“…The remaining CL int was assigned to glucuronidation (UGT CL int,u ) and scaled to give a systemic enzymatic clearance (UGT CL int,scaled,u ). In vitro studies in human liver and kidney microsomes showed that 10% of the systemic ertugliflozin UGT clearance occurs in the kidneys, whereas 90% occurs in the liver 18 . Thus, 10% of the UGT CL int,scaled,u was subtracted and the remaining CL int,scaled,u was assigned to liver UGTs.…”

“…18 Thus, 10% of the UGT CL int,scaled,u was subtracted and the remaining CL int,scaled,u was assigned to liver UGTs. In vitro ertugliflozin UGT reaction phenotyping studies 12,17,18 showed that the relative contribution of UGT1A9 was 81%, and the contribution of the UGT2B4/2B7 isozymes was 19%. For modeling purposes, the minor UGT contribution was assigned to UGT2B7.…”

“…12 The primary clearance mechanism is metabolism, mainly by glucuronidation (~ 86%) with oxidation playing a minor role (~ 12%) 12 ; renal excretion of unchanged ertugliflozin is low (~ 2%). 12 The main enzyme responsible for the major glucuronidation pathway, as determined by in vitro reaction phenotyping studies, 12,17,18 is the uridine 5'-diphospho-glucuronosyltransferase (UGT) [Correction added on 21 January 2021, after first online publication: the abbreviation for (UGT) has been corrected to uridine 5'-diphospho-glucuronosyltransferase throughout the article.] isozyme UGT1A9 (81%), with a lesser contribution from UGT2B4/2B7 (19%), leading to two pharmacologically inactive glucuronide metabolites.…”