Pathobiology of HBV mutants and clinical impact for treatment monitoring.

HBV is the leading cause of liver cancer and frequently leads to cirrhosis and liver failure. The goals of nucleos(t)ide analog treatments are to suppress viral replication to as low as possible, to halt disease progression and to prevent the onset of complications. Due to the mechanism of viral genome persistence, chronic hepatitis B requires long-term therapy that exposes patients to the risk of selection of resistant mutants and treatment failure. Genotypic resistance is defined as the detection of resistant mutations that are known to confer resistance to antiviral drugs. Virologic rebound is defined as an increase in viral load of at least 1 log(10) copies/ml compared with the lowest value during therapy. Clinical breakthrough is defined as a rise in alanine aminotransferase levels and liver disease progression following the emergence of resistant mutants and the rise in viral load. Currently, the management of antiviral therapy should be based on precise virologic monitoring to enable an early diagnosis of partial response and treatment failure. An early treatment adaptation is recommended at least at the time of virologic breakthrough or in the case of insufficient viral suppression. The choice of drug for second-line therapy should be based on cross-resistance data to tailor therapy to the virologic situation of the patient. The addition of a complementary drug is the preferred strategy. Clinical experience shows that an optimal management of antiviral therapy allows the control of viral replication in the majority of patients in whom liver disease progression is halted.