Aiming for cure in HBV and HDV infection

Chronic hepatitis B virus (HBV) infection continues to be a major health burden worldwide. Currently available antiviral treatment options for chronic hepatitis B include pegylated interferon alpha2a (PegIFN) or nucleos(t)ide analogues (NAs). The major advantages of NAs are good tolerance and potent antiviral activity associated with high rates of sustained on-treatment response to therapy. The advantages of PegIFN include a finite course of treatment, the absence of drug resistance, and an opportunity to obtain a durable post-treatment response to therapy. Furthermore, PegIFN is the only approved agent known to be active against hepatitis D virus (HDV). The use of these two antiviral agents with different mechanisms of action in combination against hepatitis B is theoretically an attractive approach for treatment. Although several studies have confirmed certain virological advantages of combination therapies, data supporting a long-term clinical benefit for patients are lacking and monotherapy with PegIFN or NAs remains the therapy of choice. Moreover, with the current treatment approaches, only a limited number of patients achieve hepatitis B surface antigen (HBsAg) loss. HBsAg loss is considered a "functional cure", but does not mean viral eradication. There is a need for novel therapeutic approaches that enable not only suppression of viral replication, but resolution of HBV infection. A key challenge is to target covalently closed circular DNA (cccDNA) in the nucleus of infected hepatocytes. The recent development and availability of innovative in vitro and in vivo systems and sensitive molecular techniques has opened new possibilities to study the complex network of interactions that HBV establishes with the host in the course of infection and to define new targets for antiviral strategies. Several new antiviral or immunomodulatory compounds have reached preclinical or clinical testing with the aim of silencing or eradicating cccDNA to achieve functional cure. Many of these strategies may also be effective for the treatment of HDV, which is dependent on HBsAg for its life cycle. This Clinical Trial Watch summarizes the most recent therapeutic strategies designed to directly target the viruses B and D or to improve immune responses during chronic HBV infection.