Assessment of the absorption, metabolism and absolute bioavailability of maraviroc in healthy male subjects

Abstract

AIMSTwo studies were conducted to: (i) quantify the amount of drug-related radioactivity in blood, plasma, urine and faeces following a 14 C-labelled dose of maraviroc; and (ii) investigate the pharmacokinetics, safety and tolerability of intravenous (i.v.) maraviroc and determine the absolute bioavailability of oral maraviroc. Metabolite profiling was also conducted. Data from both of these studies were used to construct a mass-balance model for maraviroc. METHODSStudy 1 was an open-label study in three healthy male subjects. All subjects received a single 300-mg oral solution dose of 14 C-labelled maraviroc. Study 2 included two cohorts of subjects. Cohort 1 involved a double-blind (third party open), four-way crossover study where eight subjects received escalating i.v. doses of maraviroc (3, 10 and 30 mg) with placebo insertion. Cohort 2 involved an open, two-way crossover study where 12 subjects received 30 mg maraviroc by i.v. infusion and 100 mg maraviroc orally in random order. In study 1, blood samples and all urine and faeces were collected up to at least 120 h postdose. In study 2, blood samples were taken at intervals up to 48 h postdose. Urine was also collected up to 24 h postdose in cohort 1 only. RESULTSAfter oral administration in study 1, maraviroc was rapidly absorbed with a plasma Tmax reached by 2 h postdose for all three subjects. The maximum concentrations of radioactivity also occurred within 2 h for all subjects. There was a higher amount of radioactivity in plasma than in blood (blood/plasma ratio~0.6 for AUCt and Cmax). Unchanged maraviroc was the major circulating component in plasma, accounting for~42% of the circulating radioactivity. Following a 300-mg 14 C-labelled maraviroc dose, means of 76.4% and 19.6% of radioactivity were recovered in the faeces and urine, respectively. The mean total recovery of dosed radioactivity was 96%, with the majority of radioactivity being recovered within 96 h postdose. Profiling of the urine and faeces showed similar and extensive metabolism in all subjects. Unchanged maraviroc was the major excreted component (33%). The major metabolic pathways were determined and involved oxidation and N-dealkylation. Intravenous doses of maraviroc (3-30 mg) were well tolerated in study 2, and drug exposure was approximately proportional to dose within the studied range. Approximately 23% of total clearance (44 l h ). Mean volume of distribution at steady state was 194 l. Absolute bioavailability of a 100-mg oral tablet dose, by comparison with a 30-mg i.v. dose, was calculated to be 23.1%. CONCLUSIONSMaraviroc is rapidly absorbed and extensively metabolized, although unchanged maraviroc is the major circulating component in plasma and is the major excreted component after oral dosing. The pharmacokinetics of maraviroc after i.v. administration is approximately proportional over the dose range studied. Renal clearance contributes 23% of total clearance. The absolute bioavailability of 100 mg oral maraviroc is 23%.

Cytochrome P450 3A5 Plays a Prominent Role in the Oxidative Metabolism of the Anti-Human Immunodeficiency Virus Drug Maraviroc

“…1D). A secondary amine product resulting from N-dealkylation of maraviroc has been previously found in plasma and excreta (Abel et al, 2008a;Hyland et al, 2008). Therefore, to gain a more comprehensive view of maraviroc biotransformation, we also monitored the formation of this metabolite using our assay.…”

“…In addition, there is increased interest in the development of maraviroc as an oral and/or topical microbicide for use in HIV prevention. Although maraviroc is known to be extensively metabolized to a number of products (Abel et al, 2008a), a comprehensive analysis of the biotransformation of maraviroc has yet to be reported. The cytochromes P450 (P450) are a superfamily of heme-containing monooxygenases that play a crucial role in drug clearance.…”

A population pharmacokinetic meta‐analysis of maraviroc in healthy volunteers and asymptomatic HIV‐infected subjects

“…constant clearance and first-pass) [8]. It was further assumed that an infinitely high dose would be completely absorbed.…”

Twenty-six years of HIV science: an overview of anti-HIV drugs metabolism

“…The metabolite profiling of plasma, urine and fecal samples showed that maraviroc is extensively metabolized with the major pathways involving oxidation and N-dealkylation reactions (Figure 15) (Walker et al, 2005;Abel et al, 2008). The most abundant metabolite detected in human plasma was a secondary amine product of N-dealkylation (74, Figure 15).…”