Defining the Role of Gut Bacteria in the Metabolism of Deleobuvir: In Vitro and In Vivo Studies

Abstract

Deleobuvir is a potent inhibitor of the hepatitis C virus nonstructural protein 5B polymerase. In humans, deleobuvir underwent extensive reduction to form CD 6168. This metabolite was not formed in vitro in aerobic incubations with human liver microsomes or cytosol. Anaerobic incubations of deleobuvir with rat and human fecal homogenates produced CD 6168. Using these in vitro formation rates, a retrospective analysis was conducted to assess whether the fecal formation of CD 6168 could account for the in vivo levels of this metabolite. The formation of CD 6168 was also investigated using a pseudo-germ free (pGF) rat model, in which gut microbiota were largely eradicated by antibiotic treatment. Plasma exposure (area under the curve from 0 to ') of CD 6168 was approximately 9-fold lower in pGF rats (146 6 64 ng·h/ml) compared with control rats (1,312 6 649 ng·h/ml). Similarly, in pGF rats, lower levels of CD 6168 (1.5% of the deleobuvir dose) were excreted in feces compared with control rats (42% of the deleobuvir dose). In agreement with these findings, in pGF rats, approximately all of the deleobuvir dose was excreted as deleobuvir into feces (105% of dose), whereas only 26% of the deleobuvir dose was excreted as deleobuvir in control rats. These differences in plasma and excretion profiles between pGF and control rats confirm the role of gut bacteria in the formation of CD 6168. These results underline the importance of evaluating metabolism by gut bacteria and highlight experimental approaches for nonclinical assessment of bacterial metabolism in drug development.

Drug Metabolism by the Host and Gut Microbiota: A Partnership or Rivalry?

“…This topic is undertaken by McCabe et al (2015) in this issue; they used a combination of approaches to elucidate the impact of the gut bacteria on the metabolism of deleobuvir, a non-nucleoside polymerase inhibitor used to treat hepatitis C infections. This study also provides insights into the limitations and challenges associated with the use of in vivo and in vitro approaches to be used for studying the cometabolism of drugs in the host and gut microbiota.…”

How to Determine the Role of the Microbiome in Drug Disposition

“…This method has the advantage of capturing a greater diversity of organisms and has been successfully applied to identify numerous drugs that are susceptible to microbial metabolism (Valerino et al, 1972;Caldwell and Hawksworth, 1973;Smith and Griffiths, 1974;Powis et al, 1979;Koch and Goldman, 1979;Koch et al, 1980;Lindenbaum et al, 1981;Elmer and Remmel, 1984;Harris et al, 1986;Strong et al, 1987;Shu et al, 1991;DH Kim et al, 1992;Lavrijsen et al, 1995;Watanabe et al, 1995;Kitamura et al, 1997;Sasaki et al, 1997;Basit and Lacey, 2001;Basit et al, 2002;Deng et al, 2011;Li et al, 2012;McCabe et al, 2015). However, when testing a community of microorganisms collectively, inter-strain antagonism may mask This article has not been copyedited and formatted.…”

Contribution of Major Metabolites toward Complex Drug-Drug Interactions of Deleobuvir: In Vitro Predictions and In Vivo Outcomes

“…Adjusted geometric means (%gCV) for pharmacokinetic parameters and relative bioavailability of caffeine, tolbutamide, 4-OH tolbutamide, midazolam, and 4-OH midazolam in HCV-infected patients before (day 1) and after (day 9) treatment of 8 days with 600 mg TID deleobuvir (McCabe et al, 2015), and an acyl glucuronide of deleobuvir (deleobuvir-AG) were circulating at peak exposures of 59 and 32% of the parent deleobuvir, respectively. CD 6168 exposure is higher upon multiple dosing despite a short half-life , probably owing to the unique site of formation in the GI tract.…”

“…This distinction was made because the glucuronide metabolite is formed in the hepatocytes and thus portal vein concentrations were not expected to be higher than maximal plasma concentrations. Since CD 6168 is formed presystemically in the gastrointestinal tract by gut bacteria, it was regarded as administration of a second parent drug McCabe et al, 2015). The fraction absorbed for deleobuvir was considered to be 0.5, as an absorption, distribution, metabolism, and excretion (ADME) study showed ;50% of the radioactivity in feces was accounted for by CD 6168 and its metabolites .…”

“…In a disposition study in which 14 Cdeleobuvir was administered to healthy male human volunteers, two major metabolites of deleobuvir were identified, an alkene reduction product (CD 6168) formed by gut bacteria and deleobuvir-acyl glucuronide (deleobuvir-AG) ( Fig. 1) McCabe et al, 2015). Following a single oral dose of 800 mg deleobuvir to healthy volunteers, CD 6168 and deleobuvir-AG exposure (AUC 0-' ) in the systemic circulation was 27 and 43%, respectively, of the parent deleobuvir.…”