ADV-resistant Mutations Research Articles

Combination of Lamivudine and adefovir therapy in HBeAg-positive chronic hepatitis B patients with poor response to adefovir monotherapy

At present, there is no consensus treatment for patients who have poor response to Adevofir dipivoxil (ADV) monotherapy and no ADV-associated mutation. The purpose of this study was to evaluate the effect of a new therapeutic strategy combining Lamivudine (LAM) and ADV in patients with HBeAg-positive chronic hepatitis B (CHB) and poor response to ADV monotherapy. Thirty-one patients with chronic hepatitis B with HBV DNA > or = 10(4) copies/mL after 48 weeks of ADV monotherapy were included and received ADV plus LAM for 24 weeks. Compared with ADV monotherapy, ADV + LAM had an improved response rate at weeks 12 and 24 - compared with baseline, the median decrease in HBV-DNA level at week 12 and 24 were 1.27 and 2.03 log respectively. The virological response (VR) rate (HBV-DNA level <10(3) copies/mL) was 6.5% and 35.5% at weeks 12 and 24, respectively; the biochemical response (BR) rate (normalization of alanine aminotransferase levels) was 67.8% and 100%, respectively; the HBeAg loss rate was 6.9% and 34.5%, respectively; and the seroconversion rate (from HBeAg to HBeAb) was 3.5% and 6.9% respectively. No ADV-associated mutation was detected at baseline. After combination therapy for 24 weeks, no LAM-resistant or ADV-resistant mutations were detected. Only one patient had a mild adverse reaction. In conclusion, optimization of therapy combining LAM and ADV may be a good choice for patients with hepatitis B who have a poor response to ADV monotherapy.

Prevalence, viral replication efficiency and antiviral drug susceptibility of rtQ215 polymerase mutations within the hepatitis B virus genome

The rtQ215S mutation in the hepatitis B virus (HBV) polymerase has been described as a secondary mutation associated with resistance to lamivudine (LAM) and adefovir (ADV). We aimed at assessing the prevalence of substitutions at rtQ215 of the HBV polymerase and determining the molecular and functional consequences using phenotypic analyses in vitro. The polymerase region was directly sequenced in HBV isolates from a cohort of 249 HBV genotype D-infected patients from Iran (174 males/75 females, 194 treatment-nai ve/ 55 LAM-treated). Replication-competent HBV constructs containing the naturally occurring rtQ215H, rtQ215P and rtQ215S mutations were generated, and compared to wild-type, LAM- (rtM204I, rtL180M/rtM204V) and ADV-resistant (rtN236T) clones. In an Iranian cohort of 249 HBV infected patients, 14.5% (36/249) showed mutations in the rtQ215 locus, namely 6.8% rtQ215S, 3.6% rtQ215P and 4.1% rtQ215H. The frequency of rtQ215 substitutions was higher in LAM-treated than treatment-nai ve patients (25% vs. 11%), but not associated with clinical complications. In phenotypic assays, rtQ215S, rtQ215P and rtQ215H constructs showed equivalent levels of viral replication as wild-type HBV, whereas LAM- and ADV-resistant mutants had significantly impaired replicative capacities. Furthermore, rtQ215S, rtQ215P and rtQ215H harbouring constructs remained susceptible towards treatment with LAM or ADV in vitro. Our study reveals that rtQ215 substitutions in the HBV polymerase frequently occur in chronic hepatitis B, even without exogenous selection pressures. As these substitutions do neither impair the viral replication efficiency nor susceptibility to LAM or ADV in vitro, rtQ215 substitutions likely represent background polymorphisms rather than resistance mutations with clinical implications.

A short course of add‐on adefovir dipivoxil treatment in lamivudine‐resistant chronic hepatitis B patients

The aims of the study were to investigate the efficacy of rescue therapy with lamivudine (LAM) and adefovir (ADV) combination for 6 months followed by ADV monotherapy in lamivudine-resistant chronic hepatitis B (LAM-R CHB) patients, and to analyze the frequency of ADV resistance mutant development in such patients. A total of 170 consecutive LAM-R CHB patients (male/female: 130/40, mean age: 42.9+/-13.4 years) with viral breakthrough under LAM therapy were analyzed. A total of 68 had HBeAg-positive. Patients received rescue therapy with LAM [100 mg (qd)]+ADV [10 mg (qd)] for 6 months after which LAM was discontinued. HBV-DNA was assessed with the HBV-DNA 3.0 bDNA assay. ADV-resistant mutations were identified by sequencing the reverse transcriptase region. The median duration of rescue therapy was 24 months. Cumulative probability of becoming HBV-DNA undetectable was 33.8%, 59.6% and 68.2% after 24, 48 and 96 weeks of treatment, respectively. These figures were 43.2%, 58.0% and 73.1% for ALT normalization. Among 68 HBeAg-positive CHB patients, 10 patients had an e-antigen seroconversion. Low baseline HBV-DNA level (<10(7) copies/mL) was a significant predictor of response to ADV treatment (P<0.01). Cumulative probability of ADV resistance was 1.2%, 15.1% and 37.3% at 12, 24 and 36 months of therapy, respectively. By multivariate analysis, baseline high viral load and primary nonresponse to treatment at week 24 predicted ADV resistance. The data indicate that a time limited add-on strategy does not provide benefit over the switch strategy with respect emergence of ADV resistant mutants in LAM-R CHB patients.

On‐treatment monitoring of adefovir therapy in chronic hepatitis B: virologic response can be assessed at 24 weeks

Patients with chronic hepatitis B (CHB) who will and those who will not respond to adefovir (ADV) monotherapy need to be identified at an early stage in order to adjust treatment and prevent future development of antiviral resistance. In a single-centre cohort study, we investigated 76 CHB patients [50% hepatitis B e antigen (HBeAg)-positive] treated with long-term ADV monotherapy. During a median follow-up of 122 (24-185) weeks, 42 (55%) patients achieved virologic response (VR), defined as HBV-DNA levels <10(3) copies/mL, and 10 patients (13%) developed genotypic ADV resistance. Independent baseline predictors of VR were HBeAg negativity [hazard ratio (HR) 2.98; 95% confidence interval (CI) 1.24-7.19; P = 0.02], high alanine aminotransferase (ALT) levels (HR 1.11; 95% CI 1.05-1.18; P = 0.001), and low HBV-DNA levels (HR 0.56; 95% CI 0.41-0.75; P < 0.001). HBV-DNA at week 24 demonstrated a higher predictive value for VR than HBV-DNA at week 48. Important predictors of genotypic resistance were presence of cirrhosis (HR 6.54; 95% CI 1.39-30.9; P = 0.018), and not achieving VR during treatment (HR 6.60; 95% CI 1.35-32.4; P = 0.008). Patients without VR at week 24 already demonstrated a trend towards the emergence of ADV resistance (P = 0.07). HBV-DNA at week 24 was a better on-treatment predictor of VR than HBV-DNA at week 48, and ADV-resistant mutations developed more frequently in patients without VR at week 24. Therefore, our study suggests that virologic response to ADV therapy can be assessed at 24 weeks, instead of the generally recommended 48 weeks.

Emergence of adefovir‐resistant mutants after reversion to YMDD wild‐type in lamivudine‐resistant patients receiving adefovir monotherapy

To evaluate the effect of reversion to YMDD wild-type on emergence of adefovir (ADV)-resistant mutation and antiviral activity of ADV in lamivudine (LAM)- resistant patients. We determined YMDD mutations and ADV-resistant mutations before and every 3 months during ADV monotherapy in 33 LAM-resistant patients using the restriction fragment mass polymorphism (RFMP) method. Reversion to pure YMDD wild-type hepatitis B virus (HBV) occurred in 6% (2/33), 9% (3/33), 20% (4/20) and 35% (6/17) of patients after 12, 24, 36 and 48 weeks, respectively. Five (29%) patients were found to have pure YMDD mutants at 48 weeks of therapy. Among 33 patients, 4 (12%) patients developed ADV-resistant mutations at 48 weeks of therapy. Adefovir-resistant mutants emerged in all patients after reversion to YMDD wild-type HBV. The mean serum HBV reductions, evaluated at 24 weeks of therapy, were not different between patients with and without reversion to YMDD wild-type HBV (-3.1 log(10) copies/mL vs-3.4 log(10) copies/mL, P > 0.05). ADV-resistant mutations emerged after reversion to YMDD wild-type in LAM-resistant patients who received ADV monotherapy. Thus, ADV add-on therapy may be necessary to reduce the incidence of developing ADV resistance in patients with LAM resistance.

Tenofovir plus lamivudine as rescue therapy for adefovir‐resistant chronic hepatitis B in hepatitis B e antigen‐positive patients with liver cirrhosis

There is no consensus on the management of patients with adefovir (ADV)-resistant hepatitis B virus (HBV) infection. The aim of this study was to investigate whether tenofovir disoproxil fumarate (TDF) combined with lamivudine (LMV) is effective and safe in patients with resistance to or non-response to ADV. Six patients with HBV-related cirrhosis, viral breakthrough during LMV therapy and viral breakthrough or non-response during ADV therapy were treated daily with TDF plus LMV for at least 6 months. The HBV DNA level, alanine aminotransferase (ALT), the Child-Pugh score and serum creatinine were monitored. Genotypic LMV- or ADV-resistant mutations were measured in stored samples. In five of six patients, ADV-resistant mutations at rt181 or rt236 were detected during ADV therapy. At 6 months of starting TDF/LMV combination, HBV DNA levels became undetectable (detection limit, 400 copies/ml) in four of six patients. Within 12 months, HBV DNA levels became undetectable in all patients, and ALT levels were normalized in four of six patients. These responses persisted up to the end of the observation period (median duration 16.5 months, range 6-21 months). The Child-Pugh scores improved in two of three patients with hepatic decompensation. No significant changes in serum creatinine were observed. Our data demonstrated that TDF plus LMV safely and markedly suppressed HBV replication in patients with resistance to or non-response to ADV. This study suggests that this combination may be a promising rescue therapy for these patients, particularly those with liver cirrhosis or pre-existing LMV resistance.

Low risk of adefovir resistance in lamivudine-resistant chronic hepatitis B patients treated with adefovir plus lamivudine combination therapy: Two-year follow-up

We studied the long-term efficacy (median follow-up of 28 months) of adefovir (ADV) in combination with lamivudine (LAM) in 132 LAM-resistant Japanese patients with chronic genotype C-dominant hepatitis B virus (HBV) infection. The viral response (undetectable HBV-DNA by PCR assay) and the predictor of viral response were evaluated. The emergence of ADV-resistant mutants was investigated during the combination therapy. The cumulative probability of viral response was 69% at 12 months, and 81% at 24 months. Multivariate analysis identified baseline HBe antigen status (P=0.0001), aspartate aminotransferase level (AST) (P=0.001) and HBV-DNA level (P=0.002) as determinants of viral response to treatment. At the beginning of ADV therapy, substitutions at rtA181 (rtA181T and rtA181S) were identified in 3 patients (2.3%). In the remaining 129 patients, the rtM204 mutants were identified at baseline, and two (1.6%) of the 129 patients developed new ADV-resistant mutants; one was rtA181S and another was rtA181T plus rtN236T mutation. Adefovir and lamivudine combination therapy effectively suppressed viral replication and maintained the efficacy well in LAM-resistant patients with chronic HBV infection. Genotypic analysis indicated that the emergence of ADV-resistant mutants is rare, at least over a period of 2 years, in patients with combination therapy.

Tenofovir monotherapy is effective in hepatitis B patients with antiviral treatment failure to adefovir in the absence of adefovir-resistant mutations

We sought to identify mutations associated with treatment failure to adefovir (ADV) and to determine virologic response to tenofovir (TDF) alone and in combination with emtricitabine (FTC) in these patients. Serum samples prior to and after the change in treatment to TDF/TDF+FTC from 13 patients were analyzed by direct sequencing and clonal analysis. ADV-resistant mutations, rtA181V and rtN236T, were detected on direct sequencing in 3 of 8 patients who had virologic breakthrough. Among patients with suboptimal virologic response, rtA181T, rtI233V, and rtN236T were present on clonal analysis in 3 patients. Ten patients received TDF, 8 achieved virologic response. One had ADV-resistance at baseline and persistence of ADV-resistant mutations during TDF treatment, addition of FTC resulted in a further decrease in HBV DNA. Another patient had no ADV-resistance at baseline, and selection of ADV-resistant mutations during TDF treatment. All 3 patients who received TDF+FTC had undetectable HBV DNA within 3-12 months including 2 who had ADV-resistance at baseline. TDF monotherapy is effective for patients with virologic breakthrough or suboptimal response to ADV, but combination therapy with a nucleoside analogue should be considered in patients with ADV-resistance. No novel mutations were detected.

Evaluation of initial virological response to adefovir and development of adefovir-resistant mutations in patients with chronic hepatitis B

The aims of the present study were to assess initial virological response (IVR) to adefovir (ADV) treatment for chronic hepatitis B, to identify patients with suboptimal response and to determine the incidence of ADV-resistant mutants. All patients treated with ADV for at least 12 months were evaluated for virological response and ADV resistance. IVR was defined as a reduction > or = 4 log10 IU/mL in hepatitis B virus (HBV)-DNA at month 6. Forty-two patients were analysed. Mean treatment duration was 23 +/- 7 months; 50% had prior lamivudine (LAM) therapy (LAM resistance 62%); 88% were hepatitis B e antigen (HBeAg)-negative; and 76% carried genotype D. IVR was seen in 40.5% of patients. Higher baseline ALT level was the only factor associated with IVR (P = 0.043). Patients with IVR achieved undetectable HBV-DNA at month 12 in 77% of cases compared with only 5% of those without IVR (P < 0.001). Five (12%) patients developed ADV-resistant mutations: rtN236T in four cases and one case with an rtV207L change, which has not been previously reported. This mutation was accompanied by viral rebound and alanine aminotransferase (ALT) flare. The cumulative probability of ADV-resistant mutations at 12 and 24 months was 5% and 17% respectively. IVR defined as a reduction > or = 4 log10 IU/mL in HBV-DNA at month 6 is a useful tool to predict virological response at month 12 and to identify patients with suboptimal response to ADV. Cumulative probability of ADV resistance is higher than previously reported for nucleos(t)ide-naïve patients.

Adefovir dipivoxil treatment of lamivudine-resistant chronic hepatitis B

Adefovir dipivoxil (ADV)-resistant mutations have been identified in treating hepatitis B virus (HBV) infection. This study aimed to analyze the response, the incidence of ADV resistance and the virologic characteristics of ADV therapy. A total of 29 CHB patients with confirmed lamivudine (LAM)-resistant HBV were treated with ADV for more than 52 weeks. Serum HBV DNA, HBV genotypes and sequences of HBV polymerase reverse-transcriptase domain were determined. Rates for the biochemical response, HBeAg loss, HBeAg seroconversion and virologic response (<200copies/mL of HBV DNA) were 82.8, 23.5, 11.8, and 48.3%, respectively, at week 52 of treatment. Lower pre-treatment mean HBV DNA level was the only significant factor associated with negative HBV DNA after ADV therapy. Six (20.7%) patients had clearance of LAM-resistant YMDD variants with replacement by the wild type HBV at week 52. The rtN236T, rtA181V/T and rtI233V were not identified before ADV therapy and the genotypic mutation of rtN236T was detected in one (3.4%) patient. In conclusion, the 52-week ADV treatment for patients with LAM-resistant HBV variants significantly achieved normalization of ALT levels, reduced serum HBV DNA levels and induced HBeAg loss and seroconversion. The emergence of ADV-resistant mutations seemed rare at weeks 52.

Effect of Initial Virologic Response to Adefovir on the Development of Resistance to Adefovir in Lamivudine-resistant Chronic Hepatitis B

Adefovir dipivoxil (ADV) resistance in patients with lamivudine-resistant chronic hepatitis B is not well understood. This study examined the initial virologic response (IVR) to ADV, the rate of ADV resistance and the factors associated with ADV resistance. Eighty one lamivudine-resistant HBeAg-positive patients were enrolled in this study. IVR was defined as HBV DNA < 4 log10 copies/mL after 6 months of therapy. IVR was observed in 37/81(45.7%) patients and it was associated with higher pretreatment ALT (P=0.002), and low pretreatment HBV DNA level (P=0.015). The HBV DNA levels were significantly higher in the non-IVR patients than the IVR patients at 12, 18 and 24 months (4.73 vs 2.59, 4.53 vs 2.31, 4.39 vs 2.40 log10 copies/mL, respectively; P<0.01). During the follow-up period, 17(21.0%) patients showed phenotypic resistance to ADV and 9 (11.1%) patients had ADV-resistant mutations. The cumulative probabilities of the phenotypic resistance to ADV at 12 and 24 months were 8.7% and 32.5%, respectively. The cumulative probabilities of the genotypic resistance to ADV at 12 and 24 months were 0% and 14.6%, respectively. Resistance to ADV was associated with a higher pretreatment HBV DNA (P=0.019), and non-IVR (P<0.001). The cumulative probabilities of the phenotypic and genotypic resistance to ADV at 24 months were 32.5% and 14.6%. The high pretreatment HBV DNA and non-IVR (HBV DNA >/= 4 log10 copies/mL after 6 months of therapy) were associated with ADV resistance.

Adefovir Dipivoxil Monotherapy and Combination Therapy with Lamivudine for the Treatment of Chronic Hepatitis B in an Asian Population

To determine differences in Chinese patients treated with adefovir (ADV) monotherapy or ADV in combination with lamivudine (3TC) after development of resistance to 3TC, with respect to biochemical improvement, HBV DNA suppression and development of subsequent ADV resistance. All hepatitis B patients with 3TC resistance treated with ADV for 3 months or more at our centre were included, and monitored 3-6 monthly for biochemical and virological response, and development of ADV resistance. A total of 56 patients were included, 50% switched to ADV monotherapy and 50% received combination 3TC/ADV therapy. Median follow-up was 15.5 months. Normalization of alanine aminotransferase (ALT) occurred in 25 (89%) patients in the ADV group compared with 24 (86%) in the 3TC/ADV group (P = 0.686). Virological response (VR) was achieved in seven (35%) patients in the ADV group at 12 months compared with five (28%) in the 3TC/ADV group (P = 0.637). By 24 months, seven (64%) patients in the ADV group achieved VR compared with two (40%) in the 3TC/ADV group (P = 0.377). Cumulative probability of developing genotypic ADV resistance in the ADV group at 24 months was 18% compared with 7% in the 3TC/ADV group (P = 0.94). There was no obvious improvement in ALT normalization and virological suppression or reduction in the development of ADV-resistant mutations with 3TC/ADV therapy compared with ADV monotherapy. Further studies with longer follow-ups are required to determine whether combination 3TC/ADV therapy will reduce the emergence of ADV resistance compared with ADV monotherapy.

Increased risk of adefovir resistance in patients with lamivudine‐resistant chronic hepatitis B after 48 weeks of adefovir dipivoxil monotherapy†

Although adefovir dipivoxil (ADV) has a unique profile of delayed and infrequent resistance in treatment-naïve chronic hepatitis B patients, the association of ADV resistance with previous lamivudine (LAM) resistance is not well understood. We compared the emergence of the ADV-resistant mutations rtA181V/T and rtN236T between LAM-resistant patients and treatment-naïve patients at 48 weeks of ADV monotherapy. Fifty-seven LAM-resistant patients and 38 treatment-naïve patients were treated with 10 mg/d ADV for more than 48 weeks. Both baseline and 48-week blood samples were analyzed for ADV-resistant mutations via restriction fragment mass polymorphism analysis. Antiviral responses were evaluated according to changes in serum HBV DNA (measured via real-time polymerase chain reaction) and alanine aminotransferase (ALT) levels and loss of hepatitis B e antigen (HBeAg). After 48 weeks, 10 (18%) of the 57 LAM-resistant patients were found to have developed ADV-resistant mutations, whereas none of the 38 treatment-naïve patients developed such mutations (P < .01). Among LAM-resistant patients, the reduction in serum HBV DNA levels was significantly lower in patients with ADV-resistant mutations than in those without such mutations (-1.04 vs. -2.63 log10 copies/mL) (P = .01). However, the rates of serum ALT normalization (60% vs. 55%) and HBeAg loss (14% vs. 21%) were not significantly different between the 2 groups (P > .05). In conclusion, the emergence of the rtA181V/T and rtN236T mutations was more common in LAM-resistant patients than in treatment-naïve patients after 48 weeks of ADV therapy and was associated with reduced antiviral efficacy to drug treatment.

Tenofovir for patients with lamivudine-resistant hepatitis B virus (HBV) infection and high HBV DNA level during adefovir therapy

Incomplete virological response to adefovir dipivoxil (ADV) has been observed in patients with lamivudine-resistant hepatitis B virus (HBV) infection and may be associated with developing resistance and disease progression. We therefore investigated whether the efficacy of viral suppression could be improved by replacing ADV with tenofovir disoproxil fumarate (TDF). Twenty patients with chronic HBV infection (18 HBeAg+), viral breakthrough during lamivudine therapy, and persistent viral replication (>10(4) copies/mL) after 15 months of ADV monotherapy (range 4-28 months) were treated with TDF 300 mg daily and were retrospectively analyzed. A screening for nucleoside/nucleotide analogue resistance mutations within the HBV polymerase gene was performed in all patients by direct sequencing. Within a median of 3.5 months, application of TDF led to undetectable HBV DNA in 19 of 20 patients, as demonstrated by suppression of HBV DNA below the detection limit of 400 copies/mL. Initially elevated ALT levels had normalized in 10 of 14 patients by the end of follow-up (median 12 months, range 3-24 months). Four patients lost HBeAg, after 3, 4, 5, and 16 months, and one patient seroconverted to anti-HBs after 16 months of TDF therapy. Lamivudine-associated mutations (rtV173L, rtL180M, rtM204V/I) could be detected in 6 patients at baseline of TDF, but this obviously did not influence the response. ADV-resistant mutations were not detected. No side effects were reported. In conclusion, these preliminary observations strongly suggest that TDF might be a highly effective rescue drug for HBV-infected patients with altered responsiveness to treatment with lamivudine and ADV.

P.104 Durability of HBeAg seroconversion following adefovir dipivoxil treatment for chronic hepatitis B (CHB)

Adefovir dipivoxil (ADV)-resistant mutations have been identified in treating hepatitis B virus (HBV) infection. This study aimed to analyze the response, the incidence of ADV resistance and the virologic characteristics of ADV therapy. A total of 29 CHB patients with confirmed lamivudine (LAM)-resistant HBV were treated with ADV for more than 52 weeks. Serum HBV DNA, HBV genotypes and sequences of HBV polymerase reverse-transcriptase domain were determined. Rates for the biochemical response, HBeAg loss, HBeAg seroconversion and virologic response (<200 copies/mL of HBV DNA) were 82.8, 23.5, 11.8, and 48.3%, respectively, at week 52 of treatment. Lower pre-treatment mean HBV DNA level was the only significant factor associated with negative HBV DNA after ADV therapy. Six (20.7%) patients had clearance of LAM-resistant YMDD variants with replacement by the wild type HBV at week 52. The rtN236T, rtA181V/T and rtI233V were not identified before ADV therapy and the genotypic mutation of rtN236T was detected in one (3.4%) patient. In conclusion, the 52-week ADV treatment for patients with LAM-resistant HBV variants significantly achieved normalization of ALT levels, reduced serum HBV DNA levels and induced HBeAg loss and seroconversion. The emergence of ADV-resistant mutations seemed rare at weeks 52.

Management of chronic hepatitis B in the liver transplant setting

Chronic viral hepatitis is the leading indication for orthotopic liver transplantation worldwide. Hepatitis B immunoglobulin and lamivudine (LAM) have been widely adopted as an effective treatment strategy against recurrent hepatitis B virus (HBV) infection in posttransplant patients. However, immunosuppression and the anti-hepatitis B surface (anti-HBs)–mediated immune pressure on HBV may culminate in the emergence and/or selection of immune escape HBV mutants. The emergence of mutations in the tyrosine methionine, aspartate, aspartate motif of the DNA polymerase represents a significant problem of long-term LAM therapy. Newer nucleoside analogs, such as adefovir dipivoxil (ADV) and entecavir, may provide a rescue therapy for LAM-resistant strains to avoid potential aggressive courses of HBV graft reinfection in liver transplant recipients. Previously, the selection of novel ADV-resistant mutations has been described in approximately 2% of patients over a 2-year treatment period. Five-year resistance surveillance programs are currently ongoing to monitor the emergence of ADV-resistant mutants in the long-term. Because of significant advances in detection, monitoring, and treatment options of hepatitis B, patient and graft survival have become excellent over the last years.