Absorption and Bioavailabilty

Telaprevir is orally available, most likely absorbed in the small intestine, with no evidence for absorption in the colon. Maximum plasma concentrations after a single dose of telaprevir are generally achieved after 4 to 5 hours. In vitro studies performed with human Caco-2 cells indicated that telaprevir is a substrate of P-glycoprotein (P-gp). Exposure to telaprevir is higher during co-administration of peginterferon alfa and ribavirin than after administration of telaprevir alone.

Effects of Food on Oral Absorption

The systemic exposure (AUC) to telaprevir was increased by 237% when telaprevir was administered with a standard fat meal (containing 533 kcal and 21 g fat) compared to when telaprevir was administered under fasting conditions. In addition, the type of meal significantly affects exposure to telaprevir. Relative to fasting, when telaprevir was administered with a low-fat meal (249 kcal, 3.6 g fat) and a high-fat meal (928 kcal, 56 g fat), the systemic exposure (AUC) to telaprevir was increased by approximately 117% and 330%, respectively. Doses of INCIVEK were administered within 30 minutes of completing a meal or snack containing approximately 20 grams of fat in the Phase 3 trials. Therefore, INCIVEK should always be taken with food (not low fat).

Distribution

In vitro, within a concentration range of 0.1 µM (68 ng/mL) to 20 µM (13600 ng/mL), telaprevir is approximately 59% to 76% bound to plasma proteins. Telaprevir binds primarily to alpha 1-acid glycoprotein and albumin and the binding is concentration dependent, decreasing with increasing concentrations of telaprevir. After oral administration, the typical apparent volume of distribution (Vd/F) was estimated to be 252 L, with an inter-individual variability of 72%.

Metabolism

Telaprevir is extensively metabolized in the liver, involving hydrolysis, oxidation, and reduction. Multiple metabolites were detected in feces, plasma, and urine. After repeated-oral administration, the R-diastereomer of telaprevir (30-fold less active), pyrazinoic acid, and a metabolite that underwent reduction at the α-ketoamide bond of telaprevir (not active) were found to be the predominant metabolites of telaprevir. In vitro studies using recombinant human cytochrome P450 (CYP) isoforms indicated that CYP3A4 was the major CYP isoform responsible for telaprevir metabolism. However, non-CYP mediated metabolism likely plays a role after multiple dosing of telaprevir.