Lamivudine-resistant Hepatitis B Virus Research Articles

Management of chronic hepatitis B virus infection: a new era of disease control

When assessing patients with chronic hepatitis B virus (HBV) infection, consider the state of viral replication, the immune response and whether viral mutations could be present, as well as evidence for liver disease or extrahepatic manifestations. In wild-type infections, loss of hepatitis B e antigen (HBeAg), gain of anti-HBe and disappearance of HBV DNA from serum indicate immunosuppression of viral replication, or 'nonreplicative chronic HBV infection'. This 'healthy carrier' state must be distinguished from HBeAg-negative chronic hepatitis B (CHB) resulting from precore and core promoter mutations. HBeAg-negative CHB is common with genotypes D (Mediterranean region, south Asia) and C (north Asia) infections. Age, disease activity (alanine aminotransferase level) and severity (fibrosis stage, cirrhosis) influence treatment decisions. Following the marginal effectiveness of interferon and often temporary effectiveness of lamivudine due to drug resistance, treatment of CHB is entering a new era. Adefovir, entecavir, tenofovir, telbivudine and clevudine have equal or superior antiviral efficacy to lamivudine, whereas several agents are effective against lamivudine-resistant HBV. Pegylated-interferon (peginterferon) is superior to conventional interferon for obtaining sustained immunosuppression of HBV without drug resistance. Antiviral suppression of HBV replication for 2-5 years reverses hepatic fibrosis, prevents cirrhosis and, when cirrhosis is established, improves liver function, prevents hepatic decompensation and lowers the risk of liver cancer. Before embarking on immunosuppressive chemotherapy or organ transplantation in patients with chronic HBV infection, it is important to start antiviral therapy to prevent hepatitis flares. Antiviral therapy can be effective against membranous glomerulonephritis and polyarteritis nodosa caused by HBV. Further improvements in treatment of CHB are needed to prevent drug resistance and permanently suppress viral replication by eradicating viral templates or stimulating host immune responsiveness to HBV.

O.180 Longer survival of liver transplant recipients with hepatitis virus coinfections

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 MonitorTM 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 log10 and −4.3 log10 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. (Hepatology 2003;38:1419-1427.)

O.072 Antiviral-resistant HBV: Can we prevent this monster from growing?

Background & Aims: Lamivudine treatment is associated with frequent development of resistant hepatitis B virus (HBV) and loss of treatment benefit. In preclinical and phase II studies, entecavir demonstrated potent antiviral activity against lamivudine-resistant HBV. Methods: In this phase III, double-blind trial, hepatitis B e antigen-positive patients who were refractory to lamivudine therapy (persistent viremia or documented YMDD mutations while receiving lamivudine) were randomized to switch to entecavir 1 mg daily (n = 141) or continue lamivudine 100 mg daily (n = 145) for a minimum of 52 weeks. Two coprimary end points were assessed at 48 weeks: histologic improvement and a composite end point (HBV branched DNA <0.7 MEq/mL and alanine aminotransferase [ALT] <1.25 times the upper limit of normal). Results: Histologic improvement occurred in 55% (68/124) of entecavir-treated vs 28% (32/116) of lamivudine-treated patients (P < .0001). More patients on entecavir than lamivudine achieved the composite end point: 55% (77/141) vs 4% (6/145), respectively (P < .0001). Mean change from baseline in HBV DNA was −5.11 log10 copies/mL for entecavir-treated patients and −0.48 log10 copies/mL for lamivudine-treated patients (P < .0001). Virologic rebound because of entecavir resistance substitutions occurred in 2 of 141 of entecavir-treated patients, and genotypic evidence of resistance was detected in 10 patients. The safety profile of entecavir was comparable to lamivudine with fewer ALT flares on treatment. Conclusions: In patients with lamivudine-refractory chronic hepatitis B, switching to entecavir provides superior histologic improvement, viral load reduction, and ALT normalization compared with continuing lamivudine, with a comparable adverse event profile.

Outcome of patients with hepatitis B virus and human immunodeficiency virus infections referred for liver transplantation

The outcome of patients with hepatitis B virus (HBV) and human immunodeficiency virus (HIV) referred for liver transplantation (LT) is unknown. A high frequency of lamivudine-resistant (LAM-R) HBV infection may increase the risk of liver-related death pre-transplantation and prophylaxis failure post-transplantation. We evaluated the association of LAM-R HBV on pre-transplant survival and post-transplant outcomes in 35 consecutive HIV-HBV coinfected patients referred for LT between July 2000 and September 2002. At the time of referral, the median CD4 count was 273/mm, MELD was 14, and LAM-R HBV infection was present in 67%. Among these referred patients, 26% were listed, 29% not listed due to relative/absolute contraindications; 26% not listed as too early for LT; 9% not listed as too sick for LT; and 11% died during transplant evaluation. Of the 9 listed patients, 4 remained listed, 1 died 18 months post-referral, and 4 were transplanted (11% of total) 3 to 40 months after listing. Of 17 evaluated but not listed patients, 5 died (p=0.38 compared to listed group) and all deaths were liver-related. All the HBV-HIV coinfected patients, who were transplanted, are HBsAg negative and have undetectable HBV DNA levels on prophylactic therapy using hepatitis B immune globulin (HBIG) plus lamivudine, with and without tenofovir or adefovir, with median 33.1 months follow-up. Late referral and the presence of LAM-R HBV pre-transplantation are common in referred HIV-HBV patients. In HIV-HBV coinfected patients undergoing LT, HBV recurrence is successfully prevented with combination prophylaxis using HBIG and antivirals.

Evolution of multi-drug resistant hepatitis B virus during sequential therapy

Multi-drug resistant hepatitis B virus (HBV) has been reported in hepatitis B patients who received sequential antiviral therapy. In vitro studies showed that HBV constructs with mutations resistant to lamivudine and adefovir have marked reduction in sensitivity to combination of lamivudine and adefovir, whereas constructs with mutations resistant to either drug remain sensitive to the other drug. We conducted this study to determine whether mutations conferring resistance to multiple antiviral agents co-locate on the same HBV genome in vivo and to describe the evolution of these mutations. Sera from six patients who had been found to have multi-drug resistant HBV mutations to lamivudine+adefovir, lamivudine+hepatitis B immunoglobulin (HBIG), or lamivudine+entecavir on direct sequencing were cloned after nested polymerase chain reaction (PCR). Analysis of 215 clones from 11 samples with multi-drug resistant mutations on direct sequencing showed that 183 (85%) clones had mutations to both therapies on the same genome; 31 clones had lamivudine-resistant mutants only. Clonal analysis of serial samples from three patients showed progressive evolution from all clones with lamivudine-resistant HBV mutations only to mixtures of clones that have multi-drug resistant mutations and clones that have lamivudine-resistant HBV mutations only, and ultimately all clones having multi-drug resistant HBV mutations. In conclusion, mutations conferring resistance to multiple antiviral agents co-locate on the same viral genome, suggesting that combination therapy directed against mutants resistant to each treatment may not be adequate in suppressing multi-drug resistant HBV. De novo combination therapy may prevent the emergence of multi-drug resistant mutants.

Study on the Efficacy and Safety of Adefovir Dipivoxil Treatment in Post–Liver Transplant Patients With Hepatitis B Virus Infection and Lamivudine-Resistant Hepatitis B Virus

Hepatitis B virus (HBV) recurrence and de novo HBV infection are frequent events in liver transplantation recipients. Treatment with lamivudine is initially efficient in both infections but the incidence of lamivudine-resistant HBV emergence increases over time. Adefovir appears to be promising in post–liver transplantation patients with recurrent HBV infection and lamivudine-resistant HBV. This study analyzed adefovir treatment in 42 post–liver transplantation patients who developed recurrent HBV or de novo HBV infection with lamivudine-resistant HBV (54.8% HCV-coinfected). Patients received 10 mg of oral adefovir once daily for a mean period of time of 21.5 months (range from 12 to 31 months). In 62.9% of patients, ALT levels decreased significantly. Serum HBV-DNA was undetectable in 64% of the cases. Twenty percent of patients lost HBeAg marker and 13.3% of them developed anti-HBe. In 9.5% of recipients, HBsAg became negative. There was no significant change in serum creatinine levels. In only one patient was worsening of the renal function detected, making dose adjustment necessary. No other side effects were reported. Our results confirm the efficacy and safety of adefovir treatment in post–liver transplantation patients with lamivudine-resistant HBV, neither were adefovir-resistant mutations identified in patients after 21 months of therapy, nor were there adverse events, especially renal toxicity.

Efficacy and Safety of Adefovir Dipivoxil in Kidney Recipients, Hemodialysis Patients, and Patients with Renal Insufficiency

This study analyzes the biochemical, serological, and virological efficacy and the safety of adefovir dipivoxil in patients with renal disturbances. Twelve patients with lamivudine-resistant hepatitis B virus (HBV) chronic infection were treated for a median time of 15 (3-19) months. The daily dosage was 10 mg initially and then adjusted according to renal function. Median (range) ALT values remained stable: 55 (13-117) and 37 (17-266) UI/L. After the 12th month, the median decline in serum HBV DNA was from 8.76 (6.3-9.7) to 2.97 (1.15-5.65) log10 Eq/ml (median decline of -5.5 log10). No virologic breakthrough was observed. One of the six HBeAg-positive patients lost HBe Ag but without HBe seroconversion; none had HBs Ag loss. There were no significant clinical and biochemical adverse effects. In the 11 nonhemodialysed patients, the creatinine clearance significantly improved from 70 (30-100) to 88 (38-125) ml/mn (P=0.01) and the mean serum creatinine levels increased only slightly from 114 (91-839) to 130 (81-561) micromol/ml (NS). Serum phosphorus remained stable. The urinary level of protein decreased from 0.16 (0.08-8.63) to 0.12 (0.01-0.74) g/day (NS). Adefovir dipivoxil is safe for the treatment of chronic hepatitis B in patients with varying degrees of renal dysfunction and lamivudine-resistant HBV and results in biochemical and virological efficacy similar to that reported in the general population.

Cross-Resistance Testing of Next-Generation Nucleoside and Nucleotide Analogues against Lamivudine-Resistant HBV

Several next-generation nucleoside and nucleotide analogues are currently in clinical development for the treatment of chronic hepatitis B. However, the efficacy of newer agents against lamivudine-resistant hepatitis B virus (HBV) has not been fully explored. To investigate this in vitro, we generated novel stable cell lines expressing HBV encoding the four major patterns of lamivudine resistance mutations (rtL180M+rtM204V, rtV173L+rtL180M+rtM204V, rtM204I and rtL180M+ rtM204I). Using these cell lines, we assessed the susceptibility of all four strains of lamivudine-resistant HBV to eleven nucleoside analogues in various stages of clinical development. Our studies indicate that lamivudine-resistant HBV remain sensitive to acyclic phosphonate nucleotides (adefovir, tenofovir, and alamifovir), have reduced susceptibility to entecavir, and have high-level cross-resistance to all L-nucleosides tested including emtricitabine, telbivudine, clevudine, and torcitabine.

Antiviral Effect of Oral Administration of Tenofovir Disoproxil Fumarate in Woodchucks with Chronic Woodchuck Hepatitis Virus Infection

Tenofovir disoproxil fumarate (TDF) is a nucleotide analogue approved for treatment of human immunodeficiency virus (HIV) infection. TDF also has been shown in vitro to inhibit replication of wild-type hepatitis B virus (HBV) and lamivudine-resistant HBV mutants and to inhibit lamivudine-resistant HBV in patients and HBV in patients coinfected with the HIV. Data on the in vivo efficacy of TDF against wild-type virus in non-HIV-coinfected or lamivudine-naïve chronic HBV-infected patients are lacking in the published literature. The antiviral effect of oral administration of TDF against chronic woodchuck hepatitis virus (WHV) infection, an established and predictive animal model for antiviral therapy, was evaluated in a placebo-controlled, dose-ranging study (doses, 0.5 to 15.0 mg/kg of body weight/day). Four weeks of once-daily treatment with TDF doses of 0.5, 1.5, or 5.0 mg/kg/day reduced serum WHV viremia significantly (0.2 to 1.5 log reduction from pretreatment level). No effects on the levels of anti-WHV core and anti-WHV surface antibodies in serum or on the concentrations of WHV RNA or WHV antigens in the liver of treated woodchucks were observed. Individual TDF-treated woodchucks demonstrated transient declines in WHV surface antigen serum antigenemia and, characteristically, these woodchucks also had transient declines in serum WHV viremia, intrahepatic WHV replication, and hepatic expression of WHV antigens. No evidence of toxicity was observed in any of the TDF-treated woodchucks. Following drug withdrawal there was prompt recrudescence of WHV viremia to pretreatment levels. It was concluded that oral administration of TDF for 4 weeks was safe and effective in the woodchuck model of chronic HBV infection.

Inhibition of Hepatitis B Virus Gene Expression and Replication by Helioxanthin and its Derivative

Chronic hepatitis B virus (HBV) infection continues to be an important worldwide cause of morbidity and mortality. All the currently approved therapeutic drugs have their limitations: interferon-alpha (IFN-alpha) has limited efficacy and a high incidence of adverse effects; nucleoside analogues are very efficient HBV DNA inhibitors, but resistance occurs eventually. Therefore, it is important to develop new non-nucleoside/nucleotide agents with different modes of action that can be used for antiviral combination therapy. Here, we report on a novel class of compounds, helioxanthin and its derivative 5-4-2, which had potent anti-HBV activities in HepG2.2.15 cells, with the EC50s of 1 and 0.08 microM, respectively. The lamivudine-resistant HBV, L526M/M550V double mutant strain, was also sensitive to helioxanthin and 5-4-2. This class of compounds not only inhibited HBV DNA, but also decreased HBV mRNA and HBV protein expression. The EC50 of HBV DNA inhibition was consistent with the EC50 of HBV 3.5 Kb transcript inhibition, which was 1 and 0.09 microM for helioxanthin and 5-4-2 respectively. Western blot analysis of cell lysate from HepG2.2.15 cells showed that the core protein expression decreased in a dose-dependent manner after drug treatment. In conclusion, helioxanthin and 5-4-2 are potentially unique new anti-HBV agents, which possess a different mechanism of action from existing therapeutic drugs. Both compounds inhibited HBV RNA and protein expression in addition to inhibiting HBV DNA.

Intrahepatic Hepatitis B Virus Covalently Closed Circular DNA Can Be a Predictor of Sustained Response to Therapy

This study aimed to determine whether intrahepatic hepatitis B virus (HBV) covalently closed circular (ccc) DNA and total HBV DNA levels at the end of therapy would predict sustained response to therapy. Hepatitis B e antigen (HBeAg)-positive chronic hepatitis B patients receiving either lamivudine monotherapy or combination of peginterferon and lamivudine had liver biopsy at the end of 1 year therapy and were followed for 52 more weeks after cessation of therapy. Serum HBV DNA, intrahepatic HBV ccc DNA, and total HBV DNA levels were determined. Forty-seven patients, including 34 males and 13 females, were studied. Twenty-seven patients received combination therapy, and 20 patients received lamivudine monotherapy. Twenty-nine patients had end-of-treatment virologic response, and 15 patients had sustained response 52 weeks after therapy. At the end of treatment, log serum HBV DNA levels correlated well with log intrahepatic HBV cccDNA and log intrahepatic total HBV DNA levels. Log intrahepatic cccDNA and log intrahepatic total DNA levels were significantly lower among patients with sustained virologic response. The adjusted odds ratio for log cccDNA was 5.3 (95% CI: 1.5-18.2, P = .009) and, for log intrahepatic HBV DNA, was 4.4 (95% CI: 1.3-14.7, P = .015) to predict sustained virologic response. Using log cccDNA at -0.80 copies/genome equivalent as cutoff, the sensitivity, specificity, and positive and negative predictive values and accuracy of predicting sustained virologic response were 73%, 78%, 56%, 86%, and 77% respectively. Intrahepatic HBV cccDNA and intrahepatic total HBV DNA levels at the end of therapy are superior to serum HBV DNA as surrogates of sustained virologic response.

Adefovir Dipivoxil Therapy in Liver Transplant Recipients With Lamivudine-Resistant Hepatitis B Virus

Hepatitis B virus (HBV) infection is the leading cause of cirrhosis worldwide. One effective strategy to prevent recurrence or transmission of HBV infection after liver transplantation exists is prescription of Lamivudine, although it is associated with high resistance rates. Adefovir dipivoxil (AD) is a nucleotide analogue of adenosine that has achieved significant results in virologic, biochemical, and clinical parameters in lamivudine-resistant HBV-infected patients. Between 1990 and 2003 7 adult recipients of ortothopic liver transplants who experienced lamivudine-resistant HBV infection (pretransplantation or posttransplantation) were enrolled in a prospective study to administer AD for 48 weeks. At baseline they showed serum HBV DNA between 2.2 × 10 6 and 1.1 × 10 8 copies/mL. After 48 weeks of AD treatment, the median time-weighted average change in serum HBV DNA (log 10 copies/mL) was −3.19 (SD, 1.65). In 3 patients with HBV, DNA was undetectable (<400 copies/mL) at the end of the follow-up. HBe antigen seroconversion was observed in 1 patient. No significant adverse effects were recorded, except for renal functional impairment in 1 patient who had previous renal insufficiency. In our study, adefovir was an effective drug to suppression HBV replication in liver transplant recipients with lamivudine-resistant HBV. Excluding renal function abnormalities, tolerance of the drug was excellent. None of the patients developed resistance to adefovir. Therapy with AD in liver transplant recipients is effective and safe, although renal function should be monitored closely.

Evaluation of Methods for Monitoring Drug Resistance in Chronic Hepatitis B Patients during Lamivudine Therapy Based on Mass Spectrometry and Reverse Hybridization

A matrix-assisted laser desorption/ionization time-of-flight mass spectrometry-based genotyping assay, termed restriction fragment mass polymorphism (RFMP) has been recently developed for detecting hepatitis B virus (HBV) mutants. The assay is based on PCR amplification and mass measurement of oligonucleotides containing sites of mutations that confer resistance to lamivudine. We compared the efficacy and usefulness of the RFMP assay with a commercial assay using a reverse hybridization line probe technology, namely INNO-LiPA HBV DR (referred to henceforth as the LiPA assay), for the detection of lamivudine-resistant HBV mutants. A total of 60 patient samples were analysed for the presence of mutations at rtL1 80M and rtM204I/V of HBV polymerase by the LiPA and RFMP assays. The ability to detect mutations at rtM204I/V was compared with defined mixtures of wild-type and mutant HBV cloned in plasmids at relative concentrations ranging from 1-25%. Concordance between methods was found to be 95.0% (57/60) when only the presence of resistance mutations was considered, regardless of quasispecies. In three cases, additional minor populations of resistant viruses were identified by RFMP. Defined mixtures were consistently successfully identified at a 1% relative concentration of mutant versus wild-type viruses by the RFMP assay and 4% by the LiPA assay. The RFMP assay proved to be an accurate and reliable tool for detection of lamivudine-resistant mutations and was more sensitive than the LiPA assay in detecting mixtures of mutant and wild-type viruses. The improved sensitivity of the RPMP assay can help monitor drug resistance as it develops, enabling early intervention and prevention.

Quantification of the relative levels of wild‐type and lamivudine‐resistant mutant virus in serum of HBV‐infected patients using microarray

During the course of lamivudine administration in hepatitis B virus (HBV)-infected patients, a dynamic development of the viral population in serum is observed. Total HBV level is initially reduced, then lamivudine-resistant mutants appear, and finally, the viral level is increased. All methods of mutant detection so far described can only identify mutants in the serum, and cannot determine the proportion of those mutants. In this paper, we report the development of a novel technique that can quantify the relative proportion of mutants in serum utilizing gene microarray technology. Based on the nucleotide sequence at the loci of the mutations in lamivudine-resistant HBV mutants, 28 probes were designed and dotted on glass film to prepare the oligonucleotide microarray. Ten standard curves were established by employing 15 reference plasmids as templates. Ten standard math functions were simulated, which allowed quantification of the proportion of mutants in the sample by measuring the value of fluorescent intensity on the microarray. By utilizing the standard math function, the relative proportion of two different mutation sequences in the mixed template could be detected with an error <10%. The HBV-lamivudine oligonucleotide microarray is reliable to quantify the relative proportion of wild-type HBV vs HBV mutants in patient's sera.

Liver transplantation for patients with lamivudine-resistant HBV: What is the optimal prophylactic strategy?

The use of hepatitis B immune globulins (HBIG) revolutionized liver transplantation for hepatitis B. In the landmark paper by Samuel et al. in 1993, recurrence of hepatitis B virus (HBV) infection 3 years after liver transplantation was reduced from 75% in patients who received no HBIG to 36% in those who received HBIG for at least 6 months.1 However, the benefit of HBIG was mainly seen in patients with fulminant hepatitis or coexistent hepatitis D virus infection, clinical conditions associated with low HBV replication. Among patients with HBV cirrhosis, the HBV recurrence rate was 83% in those with detectable serum HBV DNA at the time of transplantation and 58% in those with undetectable HBV DNA or hepatitis B e antigen. These results stimulated efforts to reduceHBV replication in patients with HBV cirrhosis while waiting for liver transplantation. Early studies using interferon2 failed to reduce HBV recurrence because of poor tolerability and low efficacy. The availability of lamivudine, a nucleoside analog that is safe and effective in suppressing HBV replication, in the 1990s rekindled efforts to treat patients with HBV cirrhosis. Several studies have shown that lamivudine is safe in patients with decompensated cirrhosis and effective not only in suppressing HBV replication, but also in stabilizing or in improving liver disease.3-7 However, long-term use of lamivudine was limited by the high rate of drug resistance; resistant mutations involving the YMDD motif in HBV polymerase can be detected in 15% to 30% of patients after 1 year of treatment and in 50% after 3 years of treatment.7-9 Although in vitro studies showed that lamivudine-resistant mutants have decreased replication compared to wild-type HBV,10 clinical studies found that over timemost patients with lamivudine resistance have increasing serum HBV DNA and alanine aminotransferase (ALT) levels, some patients develop hepatitis flares, and occasional patients experience hepatic decompensation.9,11,12 In the late 1990s, the concern about fatal hepatitis flares associated with lamivudine resistance led many transplant centers to reserve lamivudine until transplantation was imminent. Around the same time, it was also recognized that while reduction in serum HBV DNA levels can be observed within 4 weeks of treatment, improvement in liver function and clinical status takes 3 to 6 months.3,6,7 Thus, delaying treatment until transplantation is imminent may not benefit patients who have advanced liver failure. The dilemma regarding when to initiate lamivudine treatment in the late 1990s and early 2000 was related to the unavailability of a salvage treatment that can suppress lamivudineresistant HBV. Patients with lamivudine-resistant HBV may experience rapid worsening of liver failure leading to death or removal from the transplant waiting list. Additionally, the risk of HBV recurrence after transplantationmay be increased because of high serum HBV DNA levels at the time of transplantation. Since 2002, adefovir dipivoxil, a nucleotide analog that is effective in suppressing wild-type and lamivudine-resistant HBV, has been approved in the United States and subsequently in Europe and many other countries. However, its use as a first-line antiviral agent, particularly in patients with decompensated cirrhosis, has evolved slowly. Thus, lamivudine continues to be a first-line antiviral agent in patients with decompensated HBV cirrhosis in many transplant centers. With the move to initiate treatment earlier and the increase in waiting time on the transplant list, many transplant centers now face a rising number of patients who have lamivudine-resistant HBV prior to transplantation. Abbreviations: HBIG, hepatitis B immune globulins; HBV, hepatitis B virus; ALT, alanine aminotransferase; PCR, polymerase chain reaction. From the Division of Gastroenterology, University of Michigan, Ann Arbor, MI. Address reprint requests to Anna S.F. Lok, MD, Division of Gastroenterology, University of Michigan Medical Center, 3912 Taubman Center, Ann Arbor, MI 48109-0362. Telephone: 734-615-4628; FAX: 734-936-7392; E-mail: aslok@umich.edu Copyright © 2005 by the American Association for the Study of Liver Diseases Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/lt.20409

Adefovir Dipivoxil Alone or in Combination with Ongoing Lamivudine in Patients with Decompensated Liver Disease and Lamivudine-resistant Hepatitis B Virus

The purpose of this prospective study was to evaluate the efficacy and safety of adefovir dipivoxil with or without ongoing lamivudine in decompensated lamivudine-resistant chronic hepatitis B patients. Forty-six hepatitis B e antigen (HBeAg)-positive patients with decompensated liver function and lamivudine-resistant hepatitis B virus (HBV) were assigned to adefovir dipivoxil monotherapy (n=18) or combination therapy with ongoing lamivudine (n=28) according to their own preference. After 24 weeks of treatment, 83% of monotherapy and 86% of combination therapy showed serum HBV DNA below detection limit (<0.5 pg/mL). Alanine aminotransferase (ALT) normalized in 78% and 82% respectively. Median Child-Pugh-Turcotte (CPT) score or Model for End-Stage Liver Disease (MELD) score reduced significantly by 3 or 5 point in monotherapy and 2 or 2 point in combination therapy respectively. There were no significant differences in rate of undetectable serum HBV DNA, median change of ALT and median reduction of CPT or MELD scores between the two groups. In conclusion, both adefovir dipivoxil monotherapy and combination therapy with ongoing lamivudine result in comparable virologic, biochemical, and clinical improvements in HBeAg-positive patients with decompensated liver function and lamivudine-resistant HBV. Combination with lamivudine showed no additional benefit over monotherapy during 24 weeks of treatment in these patients.

Management of HBV Infection in Liver Transplantation Patients

In the absence of preventative therapy, reinfection of allografts with hepatitis B virus (HBV) after orthotopic liver transplantation (OLT) resulted in dismal allograft and patient survival. Major advances in the management of HBV-infected recipients of OLT during the past 15 years have steadily reduced the rate of reinfection, resulting in improved outcomes. Initially, long-term use of hepatitis B immune globulin (HBIG) as a source of anti-HBs antibodies was effective in preventing or delaying reinfection. Lamivudine monotherapy made it possible to suppress HBV replication prior to OLT, markedly decreasing the risk of reinfection. Although lamivudine monotherapy used before and after OLT could prevent reinfection, its effectiveness was limited by progressive development of lamivudine-resistant mutant infections. Combination therapy with HBIG and lamivudine after OLT reduced both HBV recurrence and the risk of lamivudine resistance even in patients with active HBV replication. Introduction of adefovir provided a safe, alternative oral antiviral able to treat effectively lamivudine-resistant mutants HBV. Available strategies to prevent reinfection have resulted in OLT outcomes for HBV-infected patients comparable to those for patients transplanted for non-HBV indications. In the future, combination therapies of HBIG and both nucleoside and/or nucleotide agents will undoubtedly be optimized. Development of new drugs to treat HBV will increase opportunities to combine agents to enhance safety, efficacy and prevent emergence of HBV escape mutants. New vaccines and adjuvants may make it possible to generate anti-HBs in immunosuppressed patients, eliminating the need for HBIG.

Activity of adefovir dipivoxil against all patterns of lamivudine‐resistant hepatitis B viruses in patients

One hundred and thirty-one post-liver transplantation patients with chronic hepatitis B and failing lamivudine therapy with detectable serum hepatitis B virus (HBV) deoxyribonucleic acid by hybridization assays or > or =1 x 10(6) copies/mL by polymerase chain reaction, and elevated alanine transaminase levels despite continuous lamivudine, were enrolled in an open-label study of adefovir dipivoxil. The B and C domains of HBV polymerase were sequenced for baseline samples to determine the presence of lamivudine resistance mutations. The results showed that 98% of the samples had tyrosine-methionine-aspartate-aspartate (YMDD) mutations, indicating a strong correlation between the above clinical definition of lamivudine treatment failure and the presence of YMDD mutations. In addition to the rtM204V/I and the rtL180M mutations, the mutation rtV173L was identified in 19% of patients. Four major patterns of lamivudine-resistant HBV were identified: rtL180M + rtM204V (60%), rtV173L + rtL180M + rtM204V (19%), rtM204I (9%) and rtL180M + rtM204I (9%). Treatment with adefovir dipivoxil showed similar antiviral efficacy in patients with lamivudine-resistant virus from all four patterns.

Chronic hepatitis B

Interferon alpha, lamivudine, and adefovir are the three drugs currently approved for the treatment of chronic hepatitis B virus (HBV). There are pros and cons associated with the use of each drug. Individualization of therapy, based upon factors such as patient comorbidities, response to prior therapies, and stage of disease, is recommended. Patients with abnormal liver enzymes, indices of active viral replication (HBV DNA positive hepatitis B early antigen positive) or evidence of necroinflammatory activity on liver biopsy, and compensated liver disease are potential candidates for treatment with interferon, lamivudine, or adefovir. Patients with abnormal liver enzymes, indices of active viral replication (HBV DNA positive HB(e)Ag positive), and decompensated liver disease are candidates for treatment with lamivudine or adefovir. Consideration of liver transplantation should occur concurrently. Interferon alpha treatment results in hepatitis B surface antigen loss and sustained suppression of HBV DNA replication in 30% to 40% of treated patients. Loss of HBsAg occurs in nearly 10% of patients and a higher than expected frequency of HBsAg loss occurs long-term. The main limitation of therapy is the side effects and the need for parenteral administration. Additionally, interferon therapy is not applicable to all patient groups. Lamivudine achieves HB(e)Ag seroconversion in 15% to 20% of patients treated for 12 months, but (HBsAg) loss is rare. Reduction in HBV DNA to undetectable levels (by hybridization assay) during treatment is nearly universal, and histologic improvement is seen in about 55% of patients. The main limitation of lamivudine therapy is the development of drug resistance, which occurs in 20% of patients after 12 months and increases with duration of therapy (55% at 3 years). Adefovir achieves HB(e)Ag seroconversion in 12% of patients treated for 12 months, but HBsAg loss is rare. An average 3.5 log reduction in HBV DNA levels is and histologic improvement occurs in 50% to 60% of patients. It is effective against both wild-type and lamivudine-resistant HBV. The risk of drug resistance is low and estimated to be approximately 2% to 3% after 2 years of treatment. Several new antiviral agents are currently under evaluation in clinical trials. In addition, there are two drugs (tenofovir and emtricitabine) that have been approved for HIV infection and that have anti-HBV activity. In the future, combination therapy for chronic HBV infection can be anticipated. Utilization of two or more anti-HBV drugs would be predicted to enhance efficacy and reduce the likelihood of emergence of drug resistance.

Lamivudine therapy for chronic hepatitis B in renal transplant recipients

Chronic liver disease due to hepatitis B virus (HBV) infection remains a significant cause of morbidity and mortality after renal transplantation. Administration of immunosuppressive drugs facilitates viral replication and may lead to increased frequency of progressive chronic hepatitis, cirrhosis and hepatocellular carcinoma. Chronic HBV infection adversely affects both patient and graft survival. Because of increased risk of death HBV-seropositive renal graft recipients require prophylaxis and treatment of hepatitis B. Interferon due to its immunomodulating effects, risk of activation of rejection is not recommended for transplant recipients. Lamivudine seems to be efficacious and useful for treating hepatitis B in renal transplant recipients. The main disadvantages of lamivudine are relapse after withdrawal of the agent and emergence of lamivudine resistant strains due to mutations in the YMDD locus of the HBV polymerase gene during prolonged lamivudine therapy. Optimal lamivudine treatment regimen for HBsAg-positive renal transplant recipients should be defined. It seems better to initiate lamivudine therapy before or immediately after transplantation to prevent viral replication. The clinical course of hepatitis in most patients with lamivudine resistant HBV mutants seems relatively benign and long-term resistance was well tolerated. Discontinuation of lamivudine in order to minimize the emergence of drug resistant HBV mutants is safe in selected groups of patients. Lamivudine therapy has become the treatment of choice in HBV positive renal transplant recipients and improves prognosis and outcome of infected patients.