1The Texas Liver Institute, University of Texas Health Science Center at San Antonio, 607 Camden, San Antonio, TX 78215, USA.
On-treatment responses to antiviral therapy are used to determine duration of therapy in patients being treated for genotype 1 hepatitis C virus (HCV) infection. Such use of response-guided therapy has successfully reduced exposure of patients to the side effects of pegylated interferon (PegIFN) and ribavirin (RBV) without jeopardizing overall treatment success. Response-guided therapy is an integral part of treatment using the current standard treatments involving the direct-acting antiviral (DAA) agents-boceprevir or telaprevir-combined with PegIFN/RBV. Improvements in our understanding of the kinetics of viral load during antiviral therapy have shown us that more potent suppression of viral replication increases the rate of viral eradication, providing impetus for the development of more potent DAAs. Emerging results from clinical trials of these agents-including trials of interferon-free DAA combinations-suggest that very high rates of viral eradication are achievable, even in patients who failed to respond to previous courses of interferon-based therapy. Furthermore, because of these high rates of treatment success, on-treatment assessment of viral response may become unnecessary. The field of HCV therapy is evolving rapidly and current trends indicate that the era of simple treatment regimens with high rates of success and good tolerability are near.