Mechanistic Assessment of Extrahepatic Contributions to Glucuronidation of Integrase Strand Transfer Inhibitors

Abstract

Integrase strand transfer inhibitor (INSTI)-based regimens dominate initial human immunodeficiency virus treatment. Most INSTIs are metabolized predominantly via UDP-glucuronosyltransferases (UGTs). For drugs predominantly metabolized by UGTs, including INSTIs, in vitro data recovered from human liver microsomes (HLMs) alone often underpredict human oral clearance. While several factors may contribute, extrahepatic glucuronidation may contribute to this underprediction. Thus, we comprehensively characterized the kinetics for the glucuronidation of INSTIs (cabotegravir, dolutegravir, and raltegravir) using pooled human microsomal preparations from liver (HLMs), intestine (HIMs), and kidney (HKMs) tissues; human embryonic kidney 293 cells expressing individual UGTs; and recombinant UGTs. In vitro glucuronidation of cabotegravir (HLMsHKMs>>>HIMs), dolutegravir (HLMs>HIMs>>HKMs), and raltegravir (HLMs>HKMs>> HIMs) occurred in hepatic and extrahepatic tissues. The kinetic data from expression systems suggested the major enzymes in each tissue: hepatic UGT1A9 > UGT1A1 (dolutegravir and raltegravir) and UGT1A1 (cabotegravir), intestinal UGT1A3 > UGT1A8 > UGT1A1 (dolutegravir) and UGT1A8 > UGT1A1 (raltegravir), and renal UGT1A9 (dolutegravir and raltegravir). Enzymes catalyzing cabotegravir glucuronidation in the kidney and intestine could not be identified unequivocally. Using data from dolutegravir glucuronidation as a prototype, a "bottom-up" physiologically based pharmacokinetic model was developed in a stepwise approach and predicted dolutegravir oral clearance within 4.5-fold (hepatic data only), 2-fold (hepatic and intestinal data), and 32% (hepatic, intestinal, and renal data). These results suggest clinically meaningful glucuronidation of dolutegravir in tissues other than the liver. Incorporation of additional novel mechanistic and physiologic underpinnings of dolutegravir metabolism along with in silico approaches appears to be a powerful tool to accurately predict the clearance of dolutegravir from in vitro data.

Assessment of Maternal and Fetal Dolutegravir Exposure by Integrating Ex Vivo Placental Perfusion Data and Physiologically‐Based Pharmacokinetic Modeling

“…Although the PBPK model in the current work did not incorporate any metabolism apart from the liver, and also because the effect of pregnancy on extrahepatic clearance is unknown, it is expected that accounting for metabolism in the kidneys and gut could improve oral clearance predictions. 40 On the other hand, the amount of DTG available for metabolism may yet be underestimated. Active basolateral uptake of the drug into hepatocytes via yet unknown routes or an underestimation of the fraction unbound present within the hepatocytes may be a cause for the underestimation of clearance in our model.…”

Characterization of Hepatic UDP-Glucuronosyltransferase Enzyme Abundance-Activity Correlations and Population Variability Using a Proteomics Approach and Comparison with Cytochrome P450 Enzymes

“…(dolutegravir and raltegravir), 1A4 (lamotrigine), and 1A9 (mycophenolic acid). The tested drugs showed comparable correlations with expression as the probe substrates, supporting that they are predominantly conjugated by the respective UGT1A enzymes, with minor contributions by other UGTs (Picard et al, 2005;Rowland et al, 2006;Kassahun et al, 2007;Argikar and Remmel, 2009;Reese et al, 2013;Liu et al, 2019). Correlation of UGT1A9 abundance with mycophenolic acid glucuronidation was reasonable (rs = 0.63), but with propofol, an accepted probe substrate for UGT1A9, the degree of correlation was lower than expected (rs = 0.52).…”

Characterization of Seasonal Pharmacokinetic Variability in Woodchucks

“…Anti-HIV Phase II glucuronidation by UGT1A1 (Kassahun et al, 2007;Liu et al, 2019) Lamivudine 3TCAnti-HIV Active transport and renal clearance by MDR1, MRP1, MRP2, MRP3, MRP4 and BCRP (Johnson et al, 1999) Indocyanine Green (ICG)…”

“…The final version may differ from this version. 8 changes in: oxidative metabolism with AP (Balani et al, 2002), phase II glucuronidation with RTG (Kassahun et al, 2007;Liu et al, 2019), renal clearance with 3TC (Johnson et al, 1999) and hepatic function with ICG (Cooke et al, 1963;Huang and Vore, 2001;de Graaf et al, 2011;Hwang et al, 2017).…”