Interferon (IFN) has long been used as an antiviral therapy to treat patients with chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infection. In the case of chronic hepatitis C infection, peg-IFN plus ribavirin therapy is able to eradicate the virus in about half of genotype 1b HCV-infected patients. The eradication rate was much improved following the advent of protease inhibitors. Later development of direct acting antiviral agents (DAAs), such as NS5A and polymerase inhibitors, has led to very high sustained virological response (SVR) rates without requiring IFN.
In contrast, treatment of HBV infected patients has not achieved the same success. Forty-eight weeks of peg-IFN alpha is administered to both HBe antigen (HBeAg)-positive and HBeAg-negative patients. For patients treated with 180 micrograms of peg-IFN alpha for 48 weeks, HBeAg seroconversion and HBV DNA negativity were seen in 19.5% of 41 HBeAg-positive patients, whereas suppression of HBV DNA to less than 4.3 log/ml was obtained in 93.1% of 29 HBeAg-negative patients. However, such suppression continued for more than 24 weeks in only 37.9% of patients. HBs antigen seroconversion was observed in less than 10% of treated patients. The recently introduced peg-IFN beta has shown comparable-to-superior anti-viral activity against HBV.
The role of IFN in treatment of HCV-infected patients has nearly come to an end due to the efficacy of interferon-free alternatives, whereas IFN continues to play a role in treatment of HBV infection. However, as the effect of IFN against HBV is limited, combination therapies with cytokines or other compounds should be developed to improve future prospects for treatment of HBV.