Triple therapy with first generation HCV protease inhibitors: lead-in or no lead-in phase?

The standard therapeutic approach currently recommended for patients infected with genotype 1 hepatitis C virus (HCV) is the triple therapy combining pegylated interferon (PEG-IFN), ribavirin (RBV)and NS3/NS4 protease inhibitors, boceprevir or telaprevir [1]. Protease inhibitors (PIs) are direct acting antiviral drugs (DAA) which, when added to PEG-IFN and RBV, are able to achieve a significant gain in terms of sustained virological response (SVR), both in naïve and treatment-experienced patients [2–5]. The use of these new molecules, despite its in contestable benefits, reveals on the other hand new challenges: the emergence of variants with reduced sensitivity to PIs, the development of new or higher rate of side effects, drug to drug interactions, and significant increase in the overall cost of antiviral therapy. Among the two DAAs commonly used in combination with PEG-IFN and RBV (PEG-IFN/RBV) for the treatment of genotype 1 HCV patients, boceprevir has been licensed with a lead-in phase, while telaprevir has been licensed without. EMA approved regimens of both drugs are reported in Figs. 1 and 2. The lead-in phase represents an initial period of 4 weeks of dual therapy with PEG-IFN/RBV, in standard doses, followed by triple therapy. The concept of lead-in phase was initiated by the Schering–Plough company in order to improve efficacy of boceprevir-based triple therapy. Indeed, by lowering HCV RNA level, a short course of PEG-IFN/RBV may theoretically reduce the risk of viral breakthrough or resistance. However, there is still much controversy regarding the utility of the lead-in phase, some authors advocating its role in improving, and/or predicting triple therapy effectiveness, while others view it as a useless complication of the therapeutic regimen, its chief disadvantage being the inconvenience to the patient.