Success in treating hepatitis B virus (HBV) infection with nucleoside analog drugs like lamivudine is limited

No abstract

The combination of elotuzumab, lenalidomide, and low-dose dexamethasone was generally well tolerated and showed encouraging response rates in patients with relapsed or refractory MM.

Therapy of chronic hepatitis B virus (HBV) infection with the polymerase inhibitor lamivudine frequently is associated with the emergence of viral resistance. Genotypic changes in the YMDD motif (reverse transcriptase[rt] mutations rtM204V/I) conferred resistance to lamivudine as well as reducing the in vitro replication efficiency of HBV. A second mutation, rtL180M, was previously reported to partially restore replication fitness as well as to augment drug resistance in vitro. Here we report the functional characterization of a third polymerase mutation (rtV173L) associated with resistance to lamivudine and famciclovir. rtV173L was observed at baseline in 9 to 22% of patients who entered clinical trials of adefovir dipivoxil for the treatment of lamivudine-resistant HBV. In these patients, rtV173L was invariably found as a third mutation in conjunction with rtL180M and rtM204V. In vitro analyses indicated that rtV173L did not alter the sensitivity of wild-type or lamivudine-resistant HBV to lamivudine, penciclovir, or adefovir but instead enhanced viral replication efficiency. A molecular model of HBV polymerase indicated that residue rtV173 is located beneath the template strand of HBV nucleic acid near the active site of the reverse transcriptase. Substitution of leucine for valine at this residue may enhance polymerization either by repositioning the template strand of nucleic acid or by affecting other residues involved in the polymerization reaction. Together, these results suggest that rtV173L is a compensatory mutation that is selected in lamivudine-resistant patients due to an enhanced replication phenotype.Until the recent approval of adefovir dipivoxil, lamivudine (a dideoxycytidine analog in the unnatural L configuration) was the only approved oral therapy for the treatment of chronic hepatitis B. Antiviral therapy for chronic hepatitis B with famciclovir and lamivudine has been limited by the emergence of viral resistance in significant proportions of patients. Although lamivudine therapy results in potent reductions in viremia, relapse is common, as resistant viruses emerge in approximately 24% of patients after 1 year of therapy and 70% after 4 years of therapy (20). Sequencing of hepatitis B virus (HBV) isolates from patients for whom lamivudine treatment failed revealed a mutation of methionine to valine or isoleucine at position rt204 (rtM204V/I) in the YMDD motif of the C subdomain of HBV polymerase (3, 21); amino acid residues in HBV polymerase are numbered according to the consensus nomenclature developed by Stuyver et al. (34). A second mutation, of leucine 180 to methionine (rtL180M), in the upstream B subdomain of HBV polymerase frequently accompanies rtM204 mutations. The rtM204V mutation almost invariably occurs in tandem with rtL180M, while rtM204I can occur as a single mutation or in conjunction with rtL180M.In vitro analyses have confirmed and characterized the role of the major HBV polymerase mutations in lamivudine resistance. Cell culture and enzyme assays have revealed that rtM20...

Three-hundred and twenty-four patients were enrolled in an open-label, multicenter, international study in which pre- and post-liver transplantation (LT) patients with recurrent chronic hepatitis B (CHB) and evidence of lamivudine-resistant HBV were treated with adefovir dipivoxil 10 mg once daily. In the pre- and post-LT cohorts, 128 and 196 patients were treated for a median duration of 18.7 and 56.1 weeks, respectively. In patients who received 48 weeks of treatment, 81% of the pre-LT and 34% of the post-LT cohort achieved undetectable serum hepatitis B virus (HBV) DNA (Roche Amplicor Monitor polymerase chain reaction [PCR] assay lower limit of quantification [LLQ] < 400 copies/mL) with a median change in serum HBV DNA from baseline of -4.1 log(10) and -4.3 log(10) copies/mL, respectively. Serum alanine aminotransferase (ALT), albumin, bilirubin, and prothrombin time normalized in 76%, 81%, 50%, and 83% of pre-LT patients and 49%, 76%, 75%, and 20% of post-LT patients. The Child-Pugh-Turcotte (CPT) score improved in over 90% of patients in both cohorts. Genotypic analysis of 122 HBV baseline samples revealed that 98% of these patients had lamivudine-resistant mutant HBV. No adefovir resistance mutations were identified in patients after 48 weeks of therapy. One-year survival was 84% for pre-LT and 93% for post-LT patients (Kaplan-Meier analysis). Treatment-related adverse effects associated with adefovir dipivoxil in this setting were primarily mild to moderate in severity. In conclusion, 48 weeks of adefovir dipivoxil resulted in significant improvements in virologic, biochemical, and clinical parameters in CHB patients pre- and post-LT with lamivudine-resistant HBV.