Partial response to entecavir and tenofovir in naïve patients with chronic hepatitis B : clinical relevance and management

Entecavir and tenofovir are the currently recommended first line analogues for treatment of naïve patients with chronic hepatitis B. Despite their overall efficacy and high genetic barrier granting for a low risk of resistance, both regimens will fail to completely suppress HBV DNA at week 48 in 10% of HBeAg-negative and 30% of HBeAgpositive patients. A pre-treatment level >8 log10 IU/mL HBV DNA and poor medication adherence were the most significant predictors of a partial virological response (PVR). While the clinical relevance of PVR is still poorly understood, nucleos(t)ide (NUC)-naive PVR patients who maintained detectable levels of viremia in follow up, were at risk of developing resistance to ETV. Patients with a suboptimal decline of viremia during the first 48 weeks of therapy with ETV and/or a residual viremia >1,000 IU/mL, can be protected by a rescue switch to TDF. Resistance to TDF has not been described so far, yet the long-term risk of PVR in TDF-treated patients remains unclear