INTRODUCTION: Resistance in nucleoside/nucleotide analog (NA) therapy has always been a challenge in the management of chronic hepatitis B (CHB).
CLINICAL STUDIES: Initially developed for the treatment of HIV infection, early in vitro and clinical observational studies had shown tenofovir disoproxil fumarate (TDF) to be also active against CHB. Recent data from various multicenter phase 3 and 4 clinical trials have confirmed TDF being able to achieve a high viral suppression in both NA-naive and -experienced CHB patients. There are also emerging data on the efficacy of TDF in decompensated CHB. Although there are in vitro studies identifying certain mutation loci associated with a reduced susceptibility to TDF, there have so far been no reports of virologic resistance to TDF in clinical studies. TDF has a favorable safety profile, although more long-term data would be needed.