Mass balance, metabolite profile, and in vitro-in vivo comparison of clearance pathways of deleobuvir, a hepatitis C virus polymerase inhibitor

Abstract

The pharmacokinetics, mass balance, and metabolism of deleobuvir, a hepatitis C virus (HCV) polymerase inhibitor, were assessed in healthy subjects following a single oral dose of 800 mg of [(14)C]deleobuvir (100 μCi). The overall recovery of radioactivity was 95.2%, with 95.1% recovered from feces. Deleobuvir had moderate to high clearance, and the half-life of deleobuvir and radioactivity in plasma were ∼ 3 h, indicating that there were no metabolites with half-lives significantly longer than that of the parent. The most frequently reported adverse events (in 6 of 12 subjects) were gastrointestinal disorders. Two major metabolites of deleobuvir were identified in plasma: an acyl glucuronide and an alkene reduction metabolite formed in the gastrointestinal (GI) tract by gut bacteria (CD 6168), representing ∼ 20% and 15% of the total drug-related material, respectively. Deleobuvir and CD 6168 were the main components in the fecal samples, each representing ∼ 30 to 35% of the dose. The majority of the remaining radioactivity found in the fecal samples (∼ 21% of the dose) was accounted for by three metabolites in which deleobuvir underwent both alkene reduction and monohydroxylation. In fresh human hepatocytes that form biliary canaliculi in sandwich cultures, the biliary excretion for these excretory metabolites was markedly higher than that for deleobuvir and CD 6168, implying that rapid biliary elimination upon hepatic formation may underlie the absence of these metabolites in circulation. The low in vitro clearance was not predictive of the observed in vivo clearance, likely because major deleobuvir biotransformation occurred by non-CYP450-mediated enzymes that are not well represented in hepatocyte-based in vitro models.

FIG 1

Structure of the sodium salt of deleobuvir. The asterisk denotes the location of the ¹⁴C label.

FIG 2

Geometric mean (and standard deviation) cumulative excretion of radioactivity in urine and feces (% of dose) at specified time intervals after a single target 800-mg (100-μCi) oral dose of [¹⁴C]deleobuvir to healthy male subjects.

FIG 3

(A) Geometric mean radioactivity in blood and plasma and mean deleobuvir concentrations in plasma over time after a single target 800-mg (100-μCi) oral dose of [¹⁴C]deleobuvir to healthy male subjects (% coefficient of variation [%CV] for the geometric mean concentrations are not shown in order to enable a visual comparison of the central tendencies; the geometric %CV [gCV%] range for radioactivity is 33 to 56%, and that for deleobuvir is 41 to 97%). (B) Geometric mean plasma concentrations of deleobuvir and its metabolites over time after a single-target 800-mg (100-μCi) oral dose of [¹⁴C]deleobuvir to healthy male subjects (%CV for the geometric mean concentrations are not shown in order to enable visual comparison of the central tendencies. The gCV% ranges for individual plasma concentrations are as follows: 41 to 97% for deleobuvir, 33 to 56% for deleobuvir-AG, 34 to 97% for CD 6168, and 42 to 82% for CD 6168-AG).

FIG 4

Radiochromatograms for plasma samples showing deleobuvir and metabolites detected in plasma at 2 h (a), 8 h (b), and 12 h (c) (pooled sample) after the administration of [¹⁴C]deleobuvir.

FIG 5

Radiochromatogram of fecal sample pool after the administration of [¹⁴C]deleobuvir.

FIG 6

Proposed metabolic pathways of deleobuvir in humans.

FIG 7

Positive MS/MS of [MH]⁺ ion at m/z 653 (top) and MS³ of its fragment at m/z 382 (bottom) from deleobuvir standard.

FIG 8

MS/MS of M655/1 [MH]⁺ ion at m/z 655 from fecal pool (top) and MS/MS of M829/2 [MH]⁺ ion at m/z 829 from 6-h plasma pool (bottom).

FIG 9

Positive MS/MS of [MH]⁺ ion at m/z 671 (top) and MS³ of its fragment at m/z 398 (bottom) from fecal pool.

FIG 10

Schematic for metabolism and disposition of deleobuvir.