Liver-to-Plasma Vaniprevir (MK-7009) Concentration Ratios in HCV-Infected Patients

Abstract

Background

Some drugs that are actively taken up into the liver exhibit greater than dose proportional increases in plasma exposure, although human liver-to-plasma concentration ratios have rarely been evaluated. Understanding these relationships has implications for drug concentrations at the target site for certain classes of compounds, such as direct-acting antivirals, targeted towards HCV.

Methods

Treatment-experienced, chronic HCV non-cirrhotic patients (n=3) received vaniprevir (600 mg or 300 mg twice daily) on days 1–3 and (600 mg or 300 mg single dose) on day 4. Core needle biopsy was performed at 6 or 12 h post-dose on day 4. Blood samples were collected pre-dose on days 1 and 4, and for 24 h post-dose on day 4. The primary study objective was the hepatic concentration of vaniprevir at 6 and 12 h post-dose.

Results

Vaniprevir plasma pharmacokinetic parameters increased in a greater than dose-proportional manner between the 300 mg and 600 mg doses, with approximately fivefold increases in AUC_0–12 and C_max associated with a twofold increase in dose (AUC_0–12, 10.6 μM/h to 59.5 μM/h; C_max, 2.60 μM to 13.5 μM). In the 300 mg and 600 mg dose groups, mean liver concentrations of vaniprevir were 84.6 μM and 169 μM at 6 h post-dose, and 29.4 μM and 53.7 μM at 12 h post-dose. Liver concentrations were higher than plasma with liver-to-plasma concentration ratios of approximately 20–280.

Conclusions

These data confirm higher vaniprevir concentrations in human liver compared with plasma and demonstrate that measurement of human liver drug concentration using needle biopsy is feasible.