Inadequacy of Current Therapy for HDV

Current therapy for HDV infections is suboptimal. Although efficacy of interferon in obtaining a biochemical and virologic response has been demonstrated by randomized controlled trial, even with prolonged treatment, most patients who respond initially relapse after cessation of therapy (Farci et al. 1994). Even among patients followed for more than 12 years, only those in whom HBV surface antigen could be eradicated were able to be cleared of their delta infection (Farci et al. 2004).

A more drastic approach such as orthotopic liver transplantation of HDV patients can, like for HBV, yield good long term results when appropriate immunoprophylaxis with anti-HBsAg antibodies (anti-Hbs) is used (Samuel et al. 1995). Moreover, HDV has been associated with decreased rates of graft re-infection compared to HBV alone (Zignego et al. 1993).

Because of HDV's dependence on HBV for providing a source of HBsAg, anti-HBV agents which completely eradicate HBV would be expected to eventually lead to clearance of HDV as well. Unfortunately, if the drug is only effective at decreasing HBV DNA levels, but leaves HBsAg largely unaffected, it would be predicted to have little effect on HDV. Indeed, when used as a single agent or in combination with high dose interferon, lamivudine does not improve disease activity or lower HDV-RNA levels in HDV patients (Lau et al. 1999; Wolters et al. 2000). Similarly, famciclovir which can inhibit HBV (Cirelli et al. 1996), was shown to be ineffective in the setting of HDV infection. In particular, no therapeutic effect on serum HDV RNA, alanine aminotransferase, or liver histology could be observed (Yurdaydin et al. 2002).

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