Primer on Hepatitis C Virus Resistance to Direct-Acting Antiviral Treatment: A Practical Approach for the Treating Physician.

Treatment of hepatitis C virus has been vastly transformed by the arrival of all-oral, interferon-free, direct-acting antiviral regimens. Despite the high rate of success with these agents, a small portion of treated patients fail therapy and the emergence of viral resistance is the most common cause of treatment failure. Given the error-prone hepatitis C virus polymerase, baseline resistance-associated substitutions (RASs) may be present before direct-acting antiviral exposure. Clinicians need to understand the role of baseline RAS testing and the settings and manner in which the treatment regimens need to be customized based on the presence of RASs.