M A J O R A R T I C L E
Sustained Hepatitis B e Antigen Seroconversion in
Patients with Chronic Hepatitis B after Adefovir
Dipivoxil Treatment: Analysis of Precore and Basal
Core Promoter Mutants
I-Chin Wu,1,2Mitchell L. Shiffman,4Myron J. Tong,5Patrick Marcellin,7Elsa Mondou,6David Frederick,6 Andrea Snow-Lampart,6Jeff Sorbel,6Franck Rousseau,6and Ting-Tsung Chang1,2,3
1Department of Internal Medicine, National Cheng Kung University Hospital, and2Institute of Clinical Medicine and3Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China;4Virginia Commonwealth University Medical Center, Richmond;5Huntington Medical Research Institute, Pasadena, and6Gilead Sciences, Foster City, California; and7Hopital Beaujon, Clichy, France
(See the editorial commentary by Nguyen and Keeffe on pages 1312–4)
Background. This study evaluated the persistence of hepatitis B e antigen (HBeAg) seroconversion (which is considered to be an important therapeutic end point) after adefovir dipivoxil treatment.
Methods. Forty-five patients who experienced confirmed HBeAg seroconversion and had a serum hepatitis B virus DNA level!105copies/mL while receiving 10 mg of adefovir dipivoxil in a prior study were enrolled in the present study. At the time of the last dose of adefovir dipivoxil (baseline), the median age of the patients was 35 years, 64% were male, 73% were Asian, 27% were white, the median alanine aminotransferase level was 25 IU/L, and the median serum hepatitis B virus DNA level was 3.0 log copies/mL. The median follow-up time was 150 weeks (range, 13–252 weeks).
Results. Forty-one patients maintained sustained seroconversion at the last 2 assessments, and 4 experienced seroreversion at weeks 12 (3 patients) and 16 (1 patient) of follow-up. Approximately 50% of patients had a hepatitis B virus DNA level!1000 copies/mL at the last visit of the study period. Of 13 patients who were viremic and had available samples at the last visit, 11 had basal core promoter and/or precore mutations. Notably, 8 of these 11 patients had basal core promoter and/or precore mutations before adefovir dipivoxil therapy despite being HBeAg positive. The median duration of adefovir dipivoxil treatment was shorter before seroconversion (48 vs.
108 weeks; P p .03) and longer after seroconversion (41 vs. 22 weeks;P p .02) for patients who experienced sustained seroconversion, compared with the patients who experienced seroreversion.
Conclusions. Prolonged adefovir dipivoxil therapy after HBeAg seroconversion appeared to increase the likelihood of sustained HBeAg seroconversion. Most patients who experienced HBeAg seroconversion and had viremia had precore and/or basal core promoter mutants, which usually existed before initiation of adefovir dipivoxil therapy.
More than 350 million people worldwide are chroni- cally infected with hepatitis B virus (HBV). HBV car- riers are at risk of developing cirrhosis and hepatocel- lular carcinoma, and 15%–40% will develop cirrhosis, liver failure, or hepatocellular carcinoma during their
Received 31 January 2008; accepted 8 July 2008; electronically published 7 October 2008.
Reprints or correspondence: Dr. Ting-Tsung Chang, Dept. of Internal Medicine, National Cheng Kung University Hospital, No. 138, Sheng-Li Rd., Tainan City 704, Taiwan, Republic of China (ttchang@mail.ncku.edu.tw).
Clinical Infectious Diseases 2008; 47:1305–11
2008 by the Infectious Diseases Society of America. All rights reserved.
1058-4838/2008/4710-0009$15.00 DOI: 10.1086/592570
lifetime. An estimated 500,000–1,200,000 people per year die of HBV–related diseases [1–3].
The goal of treatment of chronic hepatitis B is to prevent progression of liver disease to cirrhosis, hepatic failure, or hepatocellular carcinoma. Loss of hepatitis B surface antigen and seroconversion to antibody to hepatitis B surface antigen, indicating resolution of hep- atitis B, is the most desired end point but rarely occurs with current therapies [4]. Loss of hepatitis B e antigen (HBeAg) and seroconversion to antibody to HBeAg (anti-HBe; i.e., HBeAg seroconversion) may reduce the risk of disease progression and are commonly consid- ered to be favorable outcomes of therapy; however, in
some patients, HBeAg seroconversion ultimately evolves into the selection of precore mutants [2].
Treatment with IFN results in HBeAg seroconversion in ap- proximately one-third of patients chronically infected with HBV but is associated with a number of adverse effects that limit its tolerability. Follow-up studies involving patients who experienced HBeAg seroconversion during IFN or pegylated IFN-a-2a therapy revealed that HBeAg seroconversion was du- rable in 80%–90% of patients [5–10].
Viral suppression with lamivudine, an L-nucleoside analog, has been associated with improvements in liver histologic find- ings and HBeAg seroconversion and has an excellent safety profile. HBeAg seroconversion is observed in 16%–18% of pa- tients after 1 year of lamivudine therapy. HBeAg seroconversion rates increased to 50% after 5 years of treatment [11–15].
Among the patients who experienced HBeAg seroconversion during lamivudine treatment, the durability of response after cessation of therapy has ranged from 50% to 77% [16–21].
The efficacy of lamivudine is limited by the emergence of drug- resistant HBV mutants. The proportion of patients with drug resistant virus increased from 23% after 1 year of treatment to 65% after 5 years of treatment [22].
Entecavir, a nucleoside analog of guanosine, is a potent in- hibitor of viral replication. HBeAg seroconversion occurred in 21% of patients after 1 year of treatment. Among the patients who achieved seroconversion at week 48, 82% had a sustained response 24 weeks after discontinuation of treatment [23].
Adefovir dipivoxil, a nucleotide analog of adenosine mon- ophosphate, has potent activity against wild-type and lami- vudine-resistant HBV. HBeAg seroconversion was observed in 12% of patients after 1 year of treatment. A progressive increase in the frequency of HBeAg seroconversion has been docu- mented over 240 weeks of adefovir treatment [24, 25]. The objective of this study was to investigate the durability of HBeAg seroconversion after discontinuation of therapy in patients who had experienced HBeAg seroconversion in a previous study of adefovir dipivoxil therapy (10 mg per day).
PATIENTS AND METHODS
Patients and study design. This was a long-term, observa- tional study of the durability of HBeAg seroconversion in pa- tients who had experienced confirmed HBeAg seroconversion (loss of HBeAg and appearance of anti-HBe at 2 consecutive visits that were at least 4 weeks apart) while receiving adefovir dipivoxil therapy (10 mg per day) in a prior study (study 437) [24, 25]. All patients tested HBeAg positive when they began the prior study (study 437). Patients who were HBeAg negative and anti-HBe positive and had a serum HBV DNA level!105 copies/mL at the 2 study visits before the final visit of the prior study were eligible. Patients were excluded if they received con- comitant systemic drugs with possible activity against HBV,
such as lamivudine, ganciclovir, lobucavir, famciclovir, ente- cavir, diaminopurine dioxolane, emtricitabine, clevudine, tel- bivudine, IFN, or thymosin-a. The study was conducted in accordance with the Declaration of Helsinki and was approved by local institutional review boards. All patients provided writ- ten informed consent.
Patients did not receive study drug in the present study. Visits were scheduled every 4 weeks for the first 16 weeks and every 24 weeks thereafter. Sustained HBeAg seroconversion was de- fined as a patient being HBeAg negative and anti–HBe positive at the last available measurement in the current study. Liver function tests (to determine total protein, albumin, aspartate aminotransferase, alanine aminotransferase [ALT], g-glutamyl- transferase, alkaline phosphatase, and total bilirubin levels) were performed every 24 weeks. Study participants who en- rolled within 16 weeks after discontinuation of adefovir dipi- voxil therapy received visits every 4 weeks, with a chemistry panel performed for the first 16 weeks, to monitor for post- treatment hepatitis flares. Serial ultrasonography and a-feto- protein monitoring were not performed as part of this study.
The duration of adefovir dipivoxil treatment before HBeAg seroconversion was defined as the duration of adefovir dipivoxil treatment before confirmed HBeAg seroconversion in the prior trial. The duration of adefovir dipivoxil treatment after HBeAg seroconversion was defined as the duration of adefovir dipivoxil treatment after confirmed HBeAg seroconversion in the prior trial. The duration of follow-up was defined as the period from discontinuation of use of adefovir dipivoxil in the prior trial to the last visit in the present study (i.e., the sum of the period from discontinuation of adefovir dipivoxil therapy in the prior trial to enrollment in the present study and the period from enrollment to the last visit in the present study).
HBV reactivation was defined as (1) a serum HBV DNA level of at least 105copies/mL and a serum ALT concentration 12 times the upper limit of normal and/or (2) reappearance of HBeAg that had previously been cleared and absence of anti–
HBe. These criteria were to be confirmed at 2 consecutive visits at least 3 months apart. If HBV reactivation was confirmed by 1 or both of the criteria, patients were to return for a final study evaluation and permanently discontinue participation in the study.
Serologic and virologic measurements. Serum HBeAg and anti–HBe levels were measured with use of commercially avail- able assays (ETI-EBK-PLUS and ETI-AB-EBK-PLUS assays, re- spectively; DiaSorin). Serum HBV DNA levels were measured with use of a PCR assay (Roche Amplicor Monitor; Roche) and a PCR HBV DNA assay (Roche TaqMan; Roche). The lower limits of quantification for the PCR assay and the PCR HBV DNA assay were 1000 copies/mL and 169 copies/mL, respec- tively. Values from the PCR assay and the PCR HBV DNA assay
Table 1. Baseline characteristics of the patients at the time of the last dose of adefovir dipivoxil.
Characteristic
Patients (n p 45)
Age, median years (range) 35 (21–63)
Sex
Male 29
Female 16
Ethnicity
Asian 33
White 12
ALT level, median IU/L (range) 25 (9–110)
HBV DNA level, median log10copies/mL (range) 3.0 (3.0–3.2) HBV genotype
A 10
B 9
C 21
D 4
G 1
NOTE. Data are no. of patients, unless otherwise indicated. ALT, al- anine aminotransferase; HBV, hepatitis B virus.
that were!1000 copies/mL were set to 999 copies/mL for cal- culating summary statistics.
Genotypic analyses were performed with use of dideoxy se- quencing (sensitivity, 25%) to identify changes within the pre- core and/or core promoter region of the HBV genome in viral isolates from patients with detectable viral replication (HBV DNA level, 11000 copies/mL). A nucleotide fragment (∼300 base pairs) encoding the precore or core promoter region of the HBV genome was sequenced and aligned to a known wild- type sequence. Changes within the core promoter region (po- sitions 1762 and 1764) and the precore region (position 1896) were noted.
Statistical analysis. The distributions of categorical vari- ables were compared by the x2 test and Fisher’s exact test.
Continuous variables were compared by the Wilcoxon rank- sum test. Results were considered to be statistically significant atP!.05.
RESULTS
During the previous study, 82 patients met the criteria for confirmed HBeAg seroconversion. Forty-five patients who had previously experienced seroconversion while receiving adefovir dipivoxil (10 mg per day) were enrolled in the present study;
the other 37 patients did not choose to participate in the present study, and no additional follow-up information was available after discontinued participation in the previous study.
With regard to the baseline characteristics at the time of the last dose of adefovir dipivoxil, the median age of the patients was 35 years (range, 21–63 years), 64% were male, 73% were Asian, 27% were white, the median ALT level was 25 IU/L (range, 9–110 IU/L), and the median serum HBV DNA level was 3.0 log copies/mL (range, 3.0–3.2 copies/mL) (table 1). The median follow-up time from the end of treatment in the prior study to the last visit in the current study was 150 weeks (range, 13–252 weeks).
Forty-one patients maintained sustained HBeAg serocon- version at the last 2 assessments, and 4 patients did not maintain seroconversion at weeks 12 (3 patients) and 16 (1 patient) of follow-up. Of the 41 patients who experienced sustained HBeAg seroconversion, 21 (51%) had an HBV DNA level!1000 copies/
mL and 32 (78%) had a normal ALT level at the last available follow-up measurement. Thirty-eight (84%) of patients had received follow-up for the minimum of 1 year after their last dose of adefovir dipivoxil; 18 (40%) had received follow-up for 2–3 years, and 15 (33%) had received follow-up for 13 years. The reasons for discontinuation from the study were loss to follow-up (6 patients), protocol-defined HBV reactivation (6), investigator’s request because of increases in serum HBV DNA level (2), death from metastatic hepatocellular carcinoma (1), concomitant medication prohibited by protocol (1), patient
noncompliance (1), pregnancy (1), and change of residence to another state (1).
The median duration of adefovir dipivoxil treatment was shorter before seroconversion (48 vs. 108 weeks;P p .03) and longer after seroconversion (41 vs. 22 weeks;P p .02) for pa- tients who experienced sustained HBeAg seroconversion, com- pared with the 4 patients who experienced seroreversion. No statistically significant difference was found with regard to age, sex, ethnicity, ALT level, serum HBV DNA level, and viral ge- notype between patients who did and did not experience sus- tained seroconversion (table 2).
Testing for the presence of precore and/or core promoter mutations was attempted for all patients with an HBV DNA level11000 copies/mL at the last study visit. However, only 13 of the 20 patients with an HBV DNA level11000 copies/mL had stored serum samples available for testing to determine whether precore (change from G to A at nucleotide 1896) and/
or core promoter (change from A to T at nucleotide 1764 and change from G to A at nucleotide 1764) mutations were present.
Of 7 patients with an HBV DNA level11000 copies/mL, 6 did not have a stored sample available for testing and 1 patient had a sample that could not be amplified. Core promoter mutations and/or precore mutations were observed in 11 (85%) of the 13 clinical isolates evaluated, and single nucleotide insertions were found in 2 of the 13 clinical isolates (table 3). Four patients were shown to harbor virus with the precore mutation (1 with G1896G/A and 3 with G1896A), 1 patient harbored a single core promoter mutation (A1762A/T), 5 patients harbored both the A1762T and G1764A mutations, and 1 patient harbored both precore (G1896G/A) and core promoter (G1764G/A) mu-
Table 2. Baseline characteristics of patients and duration of treatment, by hepatitis B e antigen (HBeAg) seroconversion status.
Variable
Patients
P Sustained HBeAg
seroconversion (n p 41)
HBeAg seroreversion
(n p 4)
Age, median years (range) 34 (21–63) 39 (29–52) NS
Sex NS
Male 26 3
Female 15 1
Ethnicity NS
Asian 29 4
White 12 0
ALT level, median IU/L (range)a,b 25 (9–110) 26 (19–32) NS
HBV DNA level, median log10copies/mL (range)a 3.0 (3.0–3.2) 3.0 (3.0–3.0) NS
HBV genotype NS
A 10 0
B 9 0
C 17 4
D 4 0
G 1 0
Duration of adefovir dipivoxil treatment
Before HBeAg seroconversion, median weeks (range) 48.1 (4.1–212.6) 107.7 (72.3–130.3) .03 After HBeAg seroconversion, median weeks (range) 40.7 (9.1–143.6) 22.3 (20.4–32.0) .02 NOTE. Data are no. of patients, unless otherwise indicated. ALT, alanine aminotransferase; HBV, hepatitis B virus; NS, not statistically significant.
aAt the time of the last dose of adefovir dipivoxil.
b The normal ranges of ALT level for men and women are 6–43 IU/L and 6–34 IU/L, respectively.
tations. Genotypic analysis of serum samples before adefovir dipivoxil therapy was also performed for these 13 patients.
Notably, 8 of the 11 patents with basal core promoter and/or precore mutations at the last visit had these mutations before initiation of adefovir dipivoxil therapy (table 4).
DISCUSSION
HBeAg seroconversion has generally been considered to be a favorable indicator of response in the treatment of chronic hepatitis B infection. In this study, HBeAg seroconversion at the last dose of adefovir dipivoxil was sustained in 41 patients over a median follow-up period while not receiving treatment of 150 weeks. Four patients experienced seroreversion within 16 weeks after discontinuation of adefovir dipivoxil therapy.
The only differences between patients who did and did not experience sustained HBeAg seroconversion were the median durations of adefovir dipivoxil treatment before and after se- roconversion; the duration was shorter before seroconversion and longer after seroconversion for patients who experienced sustained seroconversion, compared with 4 patients who ex- perienced seroreversion.
Previous studies assessing the durability of lamivudine-in- duced HBeAg seroconversion have suggested that longer treat-
ment after seroconversion increased sustained response. Song et al. [21] reported that14 months of additional lamivudine therapy significantly decreased the seroreversion rate. Another lamivudine trial conducted by Lee et al. [20] revealed that two- thirds of the patients who experienced seroreversion had re- ceived!10 months of additional therapy. In a study of deter- minants for sustained HBeAg seroconversion, at least 8 months of additional lamivudine treatment was required to ensure a significantly higher sustained response [16]. This finding had also been noted by other authors and prompted management guidelines to recommend continuing oral therapy for at least 6 months after confirmed HBeAg seroconversion to reduce posttreatment seroreversion [2]. The results of the present study support the continuation of adefovir dipivoxil therapy for a longer time after confirmed HBeAg seroconversion and, in view of the precore and/or core promoter mutation findings, possibly 11 year. Because hepatitis B surface antigen loss is generally prefaced by HBeAg seroconversion, the subset of patients who experience seroconversion may represent those most likely to clear hepatitis B surface antigen while continuing to receive treatment.
Of the patients who experienced sustained HBeAg serocon- version, approximately one-half had an HBV DNA level!1000
Table 3. Genotypic analysis of hepatitis B virus (HBV) DNA in 13 patients with active viral replication.
Patient
HBV DNA level at the final visit,
copies/mL
Viral
genotype Mutations observed Classification
1 1129 A A1762A/T Core promoter mutation
2 2372 C A1762T, G1764A Core promoter mutations
3 33257371 B G1896A Precore mutation
4 1046 B G1896A Precore mutation
5 1246869 C A1762T, G1764A Core promoter mutations
6 11535 B A1762T, G1764A Core promoter mutations
7 255195 B ⫺1839A Single nucleotide insertion
8 3079 C G1764G/A, G1896G/A Core promoter and precore mutation
9 17344 C A1762T, G1764A Core promoter mutations
10 44852 C A1762T, G1764A Core promoter mutations
11 2288 B G1896G/A Precore mutation
12 2413 B G1896A Precore mutation
13 36447 B ⫺1846A Single nucleotide insertion
NOTE. HBV DNA levels at the final visit in the 7 study participants without samples available for testing for mutations were 1017, 1412, 5448, 6649, 7481, 7852, and 3,421,647 copies/mL.
Table 4. Comparison of genotypic analysis of hepatitis B virus before initiation of adefovir dipivoxil therapy and at the final study visit for 13 patients with active viral replication.
Genotype classification before adefovir dipivoxil therapy, genotype classification at the final visit
No. (%) of patients
Core promoter mutations: core promoter mutations 5 (38)
Precore mutation: precore mutation 2 (15)
Core promoter and precore mutations: core promoter and precore mutations 1 (8) Wild type
Precore mutation 2 (15)
Core promoter mutations 1 (8)
1 nucleotide insertion 2 (15)
NOTE. The precore mutation occurs at position 1896, and the core promoter mutations occur at positions 1762 and 1764. The single nucleotide insertions occurred at positions 1839 and 1846.
copies/mL at last the follow-up visit when they were not re- ceiving treatment. However, among the remaining patients with active viremia, basal core promoter and/or precore mutations were present in 11 of the 13 patients with available samples for testing, which demonstrates that these patients had experienced progression to HBeAg–negative disease despite experiencing sustained HBeAg seroconversion. Interestingly, 8 of the 11 pat- ents with basal core promoter and/or precore mutations at the last visit also had these mutations before initiation of adefovir dipivoxil therapy. Of note, 6 of these 11 patients had an HBV DNA level!104copies/mL (range, 1046–3079 copies/mL), and 5 were viremic (HBV DNA level,1104copies/mL); thus, more than one-half harbored precore and/or core promoter muta- tions but did not have high-level viremia, and even low levels of replication can potentially lead to escape mutations and, probably, disease progression. Recent studies [26, 27] have re-
vealed that presence of serum HBV DNA was a risk factor for cirrhosis and hepatocellular carcinoma, even if the patients had low serum HBV DNA levels. In addition, the risk of accu- mulating accessory mutations may exist. The relatively small sample of patients and the number of patients lost to follow- up are limitations of this study. These data show that HBeAg seroconversion might be an inadequate therapeutic end point for stopping therapy. The patients who have experienced HBeAg seroconversion and have viremia may consider contin- ued antiviral treatment or adding a more potent drug that is not cross-resistant—a suggestion that is derived from the report by Keeffe et al. [28].
Some guidelines for the treatment of HBeAg–positive chronic hepatitis B recommend that nucleoside analog treatment should be continued until the patient has achieved HBeAg serocon- version and completed at least 6 months of additional treatment
after the appearance of anti–HBe (with a serum HBV DNA level!105 copies/mL [29] or without mention of serum HBV DNA levels [2]). The present study revealed that, despite ex- periencing sustained HBeAg seroconversion after discontinu- ation of antiviral therapy, most of the patients with viremia developed precore and/or basal core promoter mutants, even at a low viral titer. Therefore, HBeAg seroconversion alone may not be an adequate treatment end point. Regular HBV DNA monitoring may be needed for patients who discontinue an- tiviral treatment when HBeAg seroconversion is confirmed.
The possible influence of viral genotype on durability of HBeAg seroconversion has also been studied. Chien et al. [16]
found that viral genotype C was associated with a higher relapse rate than viral genotype B in patients receiving lamivudine therapy. In the present study, all 4 patients who experienced seroreversion were infected with viral genotype C. However, because viral genotype C was the most predominant viral ge- notype in this group of patients who experienced seroconver- sion, no statistically significant association was found between HBV viral genotype and loss of seroconversion.
In conclusion, most patients experienced sustained HBeAg seroconversion after discontinuation of adefovir dipivoxil ther- apy for a median of 3 years. Prolonged antiviral therapy after HBeAg seroconversion appeared to increase the likelihood of sustained HBeAg seroconversion, and a longer duration of an- tiviral therapy might be needed in patients who experience seroconversion late after initiation of therapy. However, one- half of the patients who experienced sustained HBeAg sero- conversion had viremia, and most of them had precore and/
or basal core promoter mutants, which usually existed before initiation of adefovir dipivoxil therapy. The clinical outcome of these patients needs to be illustrated in the future.
Acknowledgments
Potential conflicts of interest. T.-T.C. has received research funding from Gilead Sciences, Bristol-Myers Squibb, GlaxoSmithKline, Schering- Plough, and Pfizer. M.L.S. has received research funding from Gilead Sci- ences, Roche, and Bristol-Myers Squibb. E.M., D.F., A.S.-L., J.S., and F.R.
are employees of Gilead Sciences. All other authors: no conflicts.
References
1. Lavanchy D. Hepatitis B virus epidemiology, disease burden, treatment, and current and emerging prevention and control measures. J Viral Hepat 2004; 11:97–107.
2. Lok AS, McMahon BJ. Chronic hepatitis B. Hepatology 2007; 45:
507–39.
3. Keeffe EB, Dieterich DT, Han SH, et al. A treatment algorithm for the management of chronic hepatitis B virus infection in the United States:
an update. Clin Gastroenterol Hepatol 2006; 4:936–62.
4. Hoofnagle JH, Doo E, Liang TJ, Fleischer R, Lok AS. Management of hepatitis B: summary of a clinical research workshop. Hepatology 2007; 45:1056–75.
5. Lau GK, Piratvisuth T, Luo KX, et al. Peginterferon a-2a, lamivudine, and the combination for HBeAg-positive chronic hepatitis B. N Engl J Med 2005; 352:2682–95.
6. Lin SM, Sheen IS, Chien RN, Chu CM, Liaw YF. Long-term beneficial effect of interferon therapy in patients with chronic hepatitis B virus infection. Hepatology 1999; 29:971–5.
7. Krogsgaard K; The Long-Term Follow-up Investigator Group; The Eu- ropean Study Group on Viral Hepatitis (EUROHEP); Executive Team on Anti-Viral Treatment. The long-term effect of treatment with in- terferon-a 2a in chronic hepatitis B. J Viral Hepat 1998; 5:389–97.
8. Lau DT, Everhart J, Kleiner DE, et al. Long-term follow-up of patients with chronic hepatitis B treated with interferon a. Gastroenterology 1997; 113:1660–7.
9. Niederau C, Heintges T, Lange S, et al. Long-term follow-up of HBeAg- positive patients treated with interferon a for chronic hepatitis B. N Engl J Med 1996; 334:1422–7.
10. Lau GK, Piratvisuth T, Luo KX, et al. Durability of response and occurrence of late response to peginterferon a-2a (40kD) [Pegasys]
one year post-treatment in patients with HBeAg-positive chronic hep- atitis B. J Hepatol 2006; 44:S23.
11. Lai CL, Chien RN, Leung NW, et al.; Asia Hepatitis Lamivudine Study Group. A one-year trial of lamivudine for chronic hepatitis B. N Engl J Med 1998; 339:61–8.
12. Dienstag JL, Schiff ER, Wright TL, et al. Lamivudine as initial treatment for chronic hepatitis B in the United States. N Engl J Med 1999; 341:
1256–63.
13. Leung NW, Lai CL, Chang TT, et al. Extended lamivudine treatment in patients with chronic hepatitis B enhances hepatitis B e antigen seroconversion rates: results after 3 years of therapy. Hepatology 2001; 33:1527–32.
14. Liaw YF, Leung NW, Chang TT, et al.; Asia Hepatitis Lamivudine Study Group. Effects of extended lamivudine therapy in Asian patients with chronic hepatitis B. Gastroenterology 2000; 119:172–80.
15. Chang TT, Lai CL, Chien RN, et al. Four years of lamivudine treatment in Chinese patients with chronic hepatitis B. J Gastroenterol Hepatol 2004; 19:1276–82.
16. Chien RN, Yeh CT, Tsai SL, Chu CM, Liaw YF. Determinants for sustained HBeAg response to lamivudine therapy. Hepatology 2003;
38:1267–73.
17. Dienstag JL, Cianciara J, Karayalcin S, et al. Durability of serologic response after lamivudine treatment of chronic hepatitis B. Hepatology 2003; 37:748–55.
18. van Nunen AB, Hansen BE, Suh DJ, et al. Durability of HBeAg se- roconversion following antiviral therapy for chronic hepatitis B: re- lation to type of therapy and pretreatment serum hepatitis B virus DNA and alanine aminotransferase. Gut 2003; 52:420–4.
19. Lee CM, Ong GY, Lu SN, et al. Durability of lamivudine-induced HBeAg seroconversion for chronic hepatitis B patients with acute ex- acerbation. J Hepatol 2002; 37:669–74.
20. Lee KM, Cho SW, Kim SW, Kim HJ, Hahm KB, Kim JH. Effect of virological response on post-treatment durability of lamivudine-in- duced HBeAg seroconversion. J Viral Hepat 2002; 9:208–12.
21. Song BC, Suh DJ, Lee HC, Chung YH, Lee YS. Hepatitis B e antigen seroconversion after lamivudine therapy is not durable in patients with chronic hepatitis B in Korea. Hepatology 2000; 32:803–6.
22. Lok AS, Lai CL, Leung N, et al. Long-term safety of lamivudine treat- ment in patients with chronic hepatitis B. Gastroenterology 2003; 125:
1714–22.
23. Chang TT, Gish RG, de Man R, et al. A comparison of entecavir and lamivudine for HBeAg-positive chronic hepatitis B. N Engl J Med 2006; 354:1001–10.
24. Marcellin P, Chang TT, Lim SG, et al. Adefovir dipivoxil for the treat- ment of hepatitis B e antigen–positive chronic hepatitis B. N Engl J Med 2003; 348:808–16.
25. Marcellin P, Chang TT, Lim SG, et al. Long-term efficacy and safety of adefovir dipivoxil for the treatment of HBeAg-positive chronic hep- atitis b (CHB) patients. Hepatology 2006; 44:548A.
26. Iloeje UH, Yang HI, Su J, Jen CL, You SL, Chen CJ. Predicting cirrhosis risk based on the level of circulating hepatitis B viral load. Gastro- enterology 2006; 130:678–86.
27. Chen CJ, Yang HI, Su J, et al. Risk of hepatocellular carcinoma across a biological gradient of serum hepatitis B virus DNA level. JAMA 2006; 295:65–73.
28. Keeffe EB, Zeuzem S, Koff RS, et al. Report of an international work- shop: roadmap for management of patients receiving oral therapy for chronic hepatitis B. Clin Gastroenterol Hepatol 2007; 5:890–7.
29. de Franchis R, Hadengue A, Lau G, et al. Consensus statement (long version) from the EASL International Consensus Conference on Hep- atitis B. 13–14 September, 2002 Geneva, Switzerland. J Hepatol 2003; 39(Suppl 1):S3–25.
