Proteomics‐informed physiologically‐based pharmacokinetic (PBPK) modeling revealed differential effects of UGT2B17 variability on the pharmacokinetics of diclofenac following intravenous and oral administration

Uridine 5'-diphospho-glucuronosyltransferase 2B17 (UGT2B17) demonstrates dramatic inter-individual variability (>3000-fold) in the activity and expression in humans, which is associated with age, sex, genotype, and ethnicity.1 We recently found that diclofenac is a UGT2B17 substrate, however, the quantitative contribution of UGT2B17 in the metabolism and pharmacokinetics (PK) of diclofenac is not well studied. Moreover, we hypothesized that the higher intestinal abundance of UGT2B17 could further amplify the magnitude and variability in its in vivo PK. We first investigated diclofenac glucuronide (DG) formation kinetics in human liver microsomes (HLM) and human intestinal microsomes (HIM) that were isolated from human donors containing the deletion genotype and the highest-expressor of UGT2B17 in our tissue bank. Diclofenac showed 4- and 16-fold difference in maximum DG formation rate (Vmax ) in UGT2B17 highest-expressor versus deletion in HLM and HIM, respectively (Fig. 1). Proteomics-informed PBPK modeling2 estimated the quantitative contribution (fm ) of UGT2B17 in the intestinal and hepatic glucuronidation of diclofenac, which revealed fm of 0.77, 0.24, and 0.0 in the highest, average, and null UGT2B17 expressors, respectively. Interestingly, intestinal fm of UGT2B17 was 0.94, 0.90, and 0.0 in the highest, average, and null expressors, respectively. The organ-specific changes in the fm were also substantiated by the predicted fraction gut escaped (fg ), which was primarily associated with UGT2B17 abundance in the enterocytes. A PBPK model was first developed and validated in the UGT2B17 average expressor and then extended to other populations utilizing UGT2B17 abundance data. Predicted plasma levels (AUC) of diclofenac were 20 % and 100 % higher following an IV dose (50 mg) in UGT2B17 deletion versus the average and the highest expressor subjects, respectively. Similalry, after 50 mg oral dose, ~2-fold and 8.5-fold higher AUC was observed in UGT2B17 deletion as compared to that in the average and the highest UGT2B17 expressors, respectively. Sex differences in UGT2B17 abundance explained ~2-fold higher diclofenac AUC in females after oral administration. In summary, the unique intestinal abundance and the highly prevalent gene deletion of UGT2B17 could likely contribute to the variable bioavailability of its substrate drugs. Similarly, poor metabolism of diclofenac in children and in UGT2B17 deletion subjects could predispose these patients to high GI discomfort. REFERENCES: Bhatt et al., Drug Metab. Dispos. (2018). Parvez Md M et al., Drug Metab. Dispos.(2021).