Telaprevir

Telaprevir (LY 570310; LY-570310; LY570310; MP 424; MP-424; VX 950; VX-950) is an orally administered peptidomimetic inhibitor of the hepatitis C virus (HCV) protease NS3/4A. It is being developed by Vertex Pharmaceuticals and its licensees for the treatment of HCV infections and has recently been submitted to the US FDA for approval. As the first ever HCV protease inhibitor in phase III development, it is being studied in trials in combination therapy with pegylated interferon alfa-2a and ribavirin in Europe, the US, Australia, Canada, and Puerto Rico in treatment-naive and treatment-experienced patients with HCV genotype 1 infection. Phase III trials of telaprevir as combination therapy are also in progress in Japan. This review discusses the key development milestones and therapeutic trials of this drug to date.

For a decade, standard therapy for patients with genotype 1 chronic HCV (HCV G1) consisted of pegylated interferon (Peg-IFN) alfa-2a or Peg-IFN alfa-2b, combined with ribavirin. Despite the improved efficacy of this therapy over others, the overall sustained virologic response rate in patients with HCV G1 was still low. This article discusses phase I, II, and III trials examining telaprevir's role in treating patients with HCV. We have now entered an era of combination therapy utilizing direct acting anti-virals, the start of which was marked by the FDA approval of HCV protease inhibitors.

This article provides an unbiased review of the pharmacokinetic, pharmacodynamic, and drug-drug interaction data of telaprevir, an NS3/4A protease inhibitor. Telaprevir is well absorbed with fatty food, moderately protein bound (59-76 %) with a large volume of distribution (~252 L), primarily metabolized by cytochrome P450 (CYP) 3A4 and P-glycoprotein, and is largely excreted into feces. Pharmacokinetic and pharmacodynamic parameters are well described in healthy subjects and individuals infected with hepatitis C virus (HCV), although only limited data are available in specific patient subpopulations. Telaprevir is recommended to be given at 750 mg by mouth every 8 h for 12 weeks, in combination with peginterferon and ribavirin (the standard care). The addition of telaprevir to the standard care regimen results in increased sustained virological response in treatment-naïve patients (30 %) and treatment-experienced patients (up to 50 %), and works synergistically to lower viral resistance. Telaprevir is a substrate and/or inhibitor of CYP3A4 and P-glycoprotein, and drug-drug interaction studies in humans have focused on these pathways. Based on our analysis, a few reported drug-drug interactions may be classified as clinically significant, but more experiments under dosing conditions that resemble those given in the clinic are needed to understand the relevance of some of the reported interactions. Future studies should focus on the pharmacokinetics/pharmacodynamics of telaprevir in special populations or patients with concomitant conditions that will likely co-exist with HCV infection, with an emphasis on establishing pharmacokinetic-pharmacodynamic relationships. In vitro characterization of other phase 1-3 metabolic pathways could assist in elucidating the mechanisms of the drug-drug interactions observed in humans.