Efficacy and safety of entecavir versus lamivudine over 5 years of treatment: A randomized controlled trial in Korean patients with hepatitis B e antigen-negative chronic hepatitis B

Study design

This Phase IV randomized trial was conducted in 16 hospitals across South Korea from 30 January 2007 to 4 March 2013, in accordance with the International Conference of Harmonisation Guidelines for Ethical Conduct and approved by the Clinical Trials Review committee of each institution (this study has been registered at ClinicalTrials. gov under registration number NCT00393484). The study was double-blinded for 96 weeks followed by open-label treatment until Week 240. Randomized block design stratification was employed, wherein a unique identification code was assigned to each patient during registration. Patients, investigators and the sponsor’s staff were blinded during allocation of the study medication and during the 96-week treatment period. Patients who were willing to participate in the open-label phase of the study were unblinded on an individual basis to determine further management. As this study was planned from 2005 when LAM was the standard of care in chronic hepatitis B treatment in Korea, no data on the use of ETV in Korean patients with HBeAg-negative chronic HBV infection had been released at the time. HBeAg-negative disease represents an important segment of the Korean adult population with chronic HBV infection, thus additional information was needed regarding the efficacy of ETV with long-term use in these HBeAg negative patients.

Patients

Adult (>16 years old) Korean patients with CHB who were HBeAg-negative (i.e. HBeAg-negative and anti-HBe-positive) and hepatitis B surface antigen (HBsAg)-positive for ≥6 months were included in the study. These patients were NUC-naive with compensated liver function and HBV DNA levels ≥10⁵ copies/mL (≥1 occurrence and more than 4 weeks prior to screening). Additional inclusion criteria included elevated ALT 1.3–10 × upper limit of normal (ULN; ≥1 occurrence at the time of screening and 4 weeks prior to screening), international normalised ratio ≤1.5, serum albumin levels ≥3 g/dL (≥30 g/L) and serum bilirubin levels ≤2.5 mg/dL (≤42.75 μmol/L).

Patients treated with IFNs within 24 weeks of randomization were excluded from the study. Women who were pregnant or breastfeeding, those of childbearing potential, and those who were unable to use contraceptives during the study period and up to 8 weeks post-study completion; patients with pre-existing diseases such as variceal bleeding, hepatic encephalopathy, ascites, hepatorenal syndrome, human immunodeficiency virus, co-infection with hepatitis C or D; patients with hepatocellular carcinoma; patients awaiting liver transplantation; and patients with serum alpha fetoprotein >100 ng/mL were not included. Concurrent medications that could lead to liver or kidney toxicity were contraindicated throughout the study.

Written informed consent was obtained from all patients who participated in the study. These patients were randomly assigned to receive ETV (0.5 mg/day) or LAM (100 mg/day). The first medication dose was administered within 72 hours of randomization. During the double-blind period, patients in the ETV group received one ETV tablet and one tablet of LAM placebo, while patients in the LAM group received one LAM tablet and one tablet of ETV placebo. Patients were instructed to take their medication at the same time every day, typically 2 hours before or after a meal.

Endpoints and assessments

The primary efficacy endpoint was the proportion of patients who achieved virologic response (VR; HBV DNA <300 copies/mL) at week 24 of treatment with ETV and LAM. Secondary endpoints included the proportion of patients with VR at weeks 96 and 240; mean log reduction in HBV DNA levels through to week 240; serum ALT levels until week 96 and emergence of resistance to ETV. Development of resistance was defined as manifestation of amino acid substitutions conferring ETV resistance in patients who met the criterion for virologic rebound (>1 log₁₀ increase in HBV DNA from nadir on blinded treatment determined by two sequential HBV DNA measurements by polymerase chain reaction [PCR] assay, or last on-treatment measurement). Since genotypic resistance to LAM is well documented based on previous clinical trial data, we did not include this evaluation in our study [8,9]. Virologic breakthrough was defined according to the American Association for the Study of Liver Diseases (AASLD) guidelines as increase in serum HBV DNA by ≥1 log₁₀ (10-fold) above nadir after achieving virologic response, during continued treatment. The frequency of AEs, serious adverse events (SAEs), discontinuations due to AEs and laboratory abnormalities were reported as safety outcomes.

HBV DNA was analysed at weeks 24, 48, 96, 192 and 240 using the Roche COBAS Amplicor PCR assay (Roche Diagnostics Systems Inc., Pleasanton, CA, USA) until the year 2010, followed by COBAS Taqman^® HBV Real-Time PCR assay (Roche Molecular Systems Inc., Branchburg, NJ, USA) from 2011 using the same endpoint for VR (HBV DNA <300 copies/mL). Other laboratory tests were performed at Weeks 24, 48 and 96 in accordance with standardised procedures in a centralised location.

Therapy was discontinued if one of the following criteria were met: (1) cancellation of written consent by patient; (2) upon investigators’ judgement that continuing medication was not appropriate for patients due to clinical adverse reaction, abnormal lab test results or concurrent disease; (3) pregnancy; or (4) confinement of patients due to physical (such as infectious disease) or mental treatments.

Statistical analysis

A two-stage evaluation, using a non-completer equals failure analysis for the efficacy of ETV compared with LAM was conducted. The first stage test was carried out to establish the non-inferiority of ETV over LAM, while the second stage analysis was a test for treatment superiority. Since the superiority test was carried out only after establishing non-inferiority, the significance levels were not adjusted for the first stage of testing. Non-inferiority was established when the lower limit of the 90% confidence interval (CI) was above –10%, while superiority was established when the 90% CI was above 0% at week 24.

A sample size of 60 patients per group was considered sufficient to yield 83% power to demonstrate non-inferiority for the difference in the primary endpoint, as well as to establish the superiority of ETV over LAM. Categorical data are presented as frequency and percentages, and statistical significance was calculated using the Pearson’s chi-square test or Fisher’s exact test. Continuous data are presented as mean±standard deviation and/or median values. Statistical significance was determined using the unpaired t-test, paired t-test, Wilcoxon rank-sum test, or Wilcoxon signed-rank test depending on the Gaussian satisfaction criteria. All analytical data were set at a double-sided significance level of 0.05.

Patient disposition and baseline characteristics

A total of 200 patients were screened, of whom 122 met the inclusion criteria and were randomized to receive ETV 0.5 mg/day (n=57) or LAM 100 mg/day (n=65). Patient disposition until week 240 is presented in Figure 1. The most common reason for study discontinuation in the ETV group was withdrawal of consent, while in the LAM group, treatment failure/lack of efficacy was the most common reason cited (Fig. 1). Demographic and baseline characteristics were comparable between the two groups (Table 1).

Figure 1.

Flow diagram depicting the enrolment, allocation and progress of patients through the phases of the trial. HBV, hepatitis B virus; ETV, entecavir; LAM, lamivudine; ITT, intent-to-treat.

Table 1.

Baseline demographics and disease characteristics

Efficacy outcomes

A significantly higher proportion of patients treated with ETV achieved VR compared with those receiving LAM at week 24 (92.9% vs. 67.2%; P=0.0006) (Fig. 2) and week 96 (94.6% vs. 48.4%; P<0.0001). After 240 weeks of treatment, VR was observed in 95.0% of ETV-treated patients and 47.6% of LAMtreated patients (P<0.0001) (Fig. 2).

Figure 2.

Proportion of patients with virologic response (HBV DNA <300 copies/mL) at weeks 24, 96 and 240. P-values calculated using Pearson’s chi-square test (Weeks 24 and 96) or Fisher’s exact test (week 240). HBV, hepatitis B virus; ETV, entecavir; LAM, lamivudine.

The mean log reduction in HBV DNA throughout the study duration is shown in Figure 3. Patients treated with ETV had a significantly higher log reduction in HBV DNA (–3.6±0.8 log₁₀ copies/mL) compared with those receiving LAM (–2.5±1.5 log₁₀ copies/mL, P<0.0001) at week 240.

Figure 3.

Mean log reduction in HBV DNA levels from week 1 to week 240 in ETV- and LAM-treated patients. HBV, hepatitis B virus; ETV, entecavir; LAM, lamivudine.

ALT normalization was observed in a higher proportion of ETVtreated patients than LAM-treated patients in the double-blind period: week 24 (ETV, 43 [76.8%] patients vs. LAM, 37 [57.8%] patients; P=0.03) and week 96 (ETV, 49 [87.5%] patients vs. LAM, 33 [51.6%] patients; P<0.0001). Virologic breakthrough occurred in one (1.8%) ETV-treated patient and 26 (42.6%) LAMtreated patients (P<0.0001) at week 96 (Table 2). No emergent resistance was detected in this one ETV-treated patient.

Table 2.

Virologic breakthrough profile

Safety outcomes

Overall, both treatments were well tolerated. AEs reported in both groups up to week 240 are presented in Table 3. Serious AEs (SAEs) were reported in seven ETV-treated patients and 17 LAMtreated patients; however, no event was found to be related to the study medications. The most common SAEs in the ETV group were classified under ‛injury, poisoning and procedural complications,’ while ‛neoplasms’ were the most frequent SAEs in the LAM group (Table 3). Death, reported for one patient in the ETV group, occurred due to subarachnoid haemorrhage in a road accident and was unrelated to the study medication. One patient in the LAM group discontinued due to an SAE (cellulitis) that was not considered likely to be related to LAM treatment.

Table 3.

Summary of safety outcomes

Laboratory abnormalities reported until week 96 have been summarized in Table 3. Grade 3/4 increase in ALT and aspartate aminotransferase (AST) was observed in six (9.7%) and three (4.8%) LAM-treated patients, respectively. None of the patients in the ETV-treated cohort experienced grade 3/4 abnormalities in ALT or AST. At Week 96, eight (12.9%) LAM-treated patients reported ALT and AST >2 × the baseline levels. Additionally, ALT flare (ALT >2 × baseline and >10 × ULN) was noted in one patient.