Resistance to adefovir dipivoxil in lamivudine resistant chronic hepatitis B patients treated with adefovir dipivoxil

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 (< 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.

Adding-on versus switching-to adefovir therapy in lamivudine-resistant HBeAg-negative chronic hepatitis B

We studied the long-term efficacy of adefovir dipivoxil (ADV) treatment in 42 HBeAg-negative patients with chronic hepatitis B (CHB) who had developed genotypical lamivudine (LAM) resistance with virological and clinical breakthroughs under long-term LAM treatment. Patients were allocated in 2 treatment groups. In the first (n = 14), LAM was switched to ADV monotherapy whereas in the second (n = 28) ADV was added to LAM. The two groups did not differ in patients' characteristics, all of them having HBV genotype D infection with the precore stop codon mutation. Within 12 months from start of ADV treatment, serum HBV DNA became nondetectable and ALT normalized in 71% and 90% of patients, respectively, with no difference between the 2 arms. Patients with baseline HBV DNA levels less than 10(7) copies/ml experienced a significantly earlier and more frequent decline in serum HBV DNA to nondetectable levels as compared with patients with greater than 10(7) HBV DNA copies/ml at baseline (P = 0.0013) This response has hitherto been maintained (median treatment duration 40 months) in all patients with ADV added to LAM, whereas virological and biochemical breakthroughs due to development of ADV signature resistance mutations occurred in 3 of 14 patients (21%) on ADV monotherapy 15 to 18 months from start of treatment (P = 0.0174).

CONCLUSION

Adding ADV to LAM in HBeAg-negative CHB patients with LAM resistance effectively suppresses HBV replication inmost of them and induces biochemical remission that can be maintained in all of them at least for 3 years without any evidence of development of resistance to ADV.

COBAS AmpliPrep-COBAS TaqMan hepatitis B virus (HBV) test: a novel automated real-time PCR assay for quantification of HBV DNA in plasma

Success in antiviral therapy for chronic hepatitis B is supported by highly sensitive PCR-based assays for hepatitis B virus (HBV) DNA. Nucleic acid extraction from biologic specimens is technically demanding, and reliable PCR results depend on it. The performances of the fully automatic system COBAS AmpliPrep-COBAS TaqMan 48 (CAP-CTM; Roche, Branchburg, NJ) for HBV DNA extraction and real-time PCR quantification were assessed and compared to the endpoint PCR COBAS AMPLICOR HBV monitor (CAHBM; Roche). Analytical evaluation with a proficiency panel showed that CAP-CTM quantitated HBV DNA levels in one single run over a wide dynamic range (7 logs) with a close correlation between expected and observed values (r = 0.976, interassay variability below 5%). Clinical evaluation, as tested with samples from 92 HBsAg-positive patients, demonstrated excellent correlation with CAHBM (r = 0.966, mean difference in quantitation = 0.36 log(10) IU/ml). CAP-CTM detected 10% more viremic patients and longer periods of residual viremia in those on therapy. In lamivudine (LAM)-resistant patients, the reduction of HBV DNA after 12 months of Adefovir (ADF) was higher in the combination (LAM+ADF) schedule than in ADF monotherapy (5.1 logs versus 3.5 logs), suggesting a benefit in continuing LAM. CAP-CTM detected HBV DNA in liver biopsy samples from 15% of HBsAg-negative, anti-HBcAg-positive graft donors with no HBV DNA in plasma. The amount of intrahepatic HBV DNA was significantly lower in occult HBV infection than in overt disease. CAP-CTM can improve the management of HBV infection and the assessment of antiviral therapy and drug resistance, supporting further insights in the emerging area of occult HBV infection.

Antiviral therapy and resistance with hepatitis B virus infection

Hepatitis B virus (HBV) infection is still the most common cause of hepatocellular carcinoma and liver cirrhosis world wide. Recently, however, there has been quite dramatic improvement in the understanding of HBV associated liver disease and its treatment. It has become clear that high viral replication is a major risk factor for the development of both cirrhosis and hepatocellular carcinoma. Early studies have shown lamivudine lowers the risk of HBV associated complications. There are currently three nucleos(t)ides licensed, in addition to interferon, and there are more drugs coming to the market soon. Interferon or its pegylated counterpart are still the only options for treatment with defined end points, while nucleos(t)ides therapy is used mostly for long term treatment. Combination therapies have not been shown to be superior to monotherapy in naïve patients, however, the outcome depends on how the end point is defined. Interferon plus lamivudine achieves a higher viral suppression than either treatment alone, even though Hbe-seroconversion was not different after a one year treatment. HBV-genotypes emerge as relevant factors, with genotypes "A" and "B" responding relatively well to interferon, achieving up to 20% HBsAg clearance in the case of genotype "A". In addition to having a defined treatment duration, interferon has the advantage of lacking resistance selection, which is a major drawback for lamivudine and the other nucleos(t)ides. The emergence of resistance against adefovir and entecavir is somewhat slower in naïve compared to lamivudine resistant patients. Adefovir has a low resistance profile with 3%, 9%, 18%, and 28% after 2, 3, 4, and 5 years, respectively, while entecavir has rarely produced resistance in naïve patients for up to 3 years.

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

Aim

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.

Methods

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.

Results

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).

Conclusions

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.

Two-year assessment of entecavir resistance in Lamivudine-refractory hepatitis B virus patients reveals different clinical outcomes depending on the resistance substitutions present

Entecavir (ETV) is a deoxyguanosine analog approved for use for the treatment of chronic infection with wild-type and lamivudine-resistant (LVDr) hepatitis B virus (HBV). In LVD-refractory patients, 1.0 mg ETV suppressed HBV DNA levels to below the level of detection by PCR (<300 copies/ml) in 21% and 34% of patients by Weeks 48 and 96, respectively. Prior studies showed that virologic rebound due to ETV resistance (ETVr) required preexisting LVDr HBV reverse transcriptase substitutions M204V and L180M plus additional changes at T184, S202, or M250. To monitor for resistance, available isolates from 192 ETV-treated patients were sequenced, with phenotyping performed for all isolates with all emerging substitutions, in addition to isolates from all patients experiencing virologic rebounds. The T184, S202, or M250 substitution was found in LVDr HBV at baseline in 6% of patients and emerged in isolates from another 11/187 (6%) and 12/151 (8%) ETV-treated patients by Weeks 48 and 96, respectively. However, use of a more sensitive PCR assay detected many of the emerging changes at baseline, suggesting that they originated during LVD therapy. Only a subset of the changes in ETVr isolates altered their susceptibilities, and virtually all isolates were significantly replication impaired in vitro. Consequently, only 2/187 (1%) patients experienced ETVr rebounds in year 1, with an additional 14/151 (9%) patients experiencing ETVr rebounds in year 2. Isolates from all 16 patients with rebounds were LVDr and harbored the T184 and/or S202 change. Seventeen other novel substitutions emerged during ETV therapy, but none reduced the susceptibility to ETV or resulted in a rebound. In summary, ETV was effective in LVD-refractory patients, with resistant sequences arising from a subset of patients harboring preexisting LVDr/ETVr variants and with approximately half of the patients experiencing a virologic rebound.

Hepatitis B in liver transplant recipients

1. The use of low-dose immunosuppressive therapy along with pre- and posttransplantation nucleos(t)ide therapy and posttransplantation hepatitis B immunoglobulin (HBIG) has yielded marked improvements in survival. 2. Lamivudine (Epivir-HBV), adefovir (Hepsera), entecavir (Baraclude), tenofovir (Viread), emtricitabine (Emtriva), and the combination drugs tenofovir + emtricitabine (Truvada) and abacavir + lamivudine (Epzicom) are effective nucleos(t)ide antiviral agents that, in some cases, may help reverse liver disease sufficiently to avoid transplant. 3. In posttransplantation patients, virus suppression with some combination of HBIG and the nucleos(t)ide agents may prevent graft loss and death or the need for a second transplant. 4. In both the pre- and posttransplantation setting, the goal of hepatitis B virus management is complete virus suppression. 5. The use of low-dose intramuscular HBIG is evolving, with studies showing that dosing and cost can be reduced by 50-300% with a customized approach. 6. Elimination of HBIG from the treatment paradigm is currently under evaluation and may be possible with the use of newer medications that have no or low resistance rates. 7. Although there is growing evidence that some types of combination therapy may decrease the chance that drug resistance will develop and increase the likelihood of long-term success in preventing graft loss and death, additional research will be required to determine which combinations will work well in the long term, and which will not.

Virological Response and Incidence of Adefovir Resistance in Lamivudine-Resistant Patients Treated with Adefovir Dipivoxil

Background and aims

The incidence of adefovir dipivoxil (ADV) resistance in patients with lamivudine (3TC)-resistant mutants who received ADV therapy remains unclear. The aims of this study were to determine the virological response to ADV, the incidence and the risk factors of ADV resistance, and the associated factors of initial virological response (IVR) in lamivudine-resistant patients.

Patients and methods

Forty-six consecutive lamivudine-resistant chronic hepatitis B patients treated with ADV for more than 12 months with or without 3TC overlapping were prospectively examined for virological response and adefovir resistance.

Results

IVR was documented in 24 (52.2%) of patients. Of the 46 patients, 11 had ADV resistance (5 rtN236T, 5 rtA181T, 1 rtA181T and rtN236T). The cumulative incidence of ADV resistance at month 6, 12, 18 and 24 was 0%, 6.5%, 24.6% and 38.3% respectively. Compared with those without ADV resistance, patients with ADV resistance had a significantly higher rate of liver cirrhosis. Based on Cox regression analysis, the significant risk factor of ADV resistance was younger age (OR=0.92, 95% CI=0.86–0.99, P=0.023) and liver cirrhosis (OR=5.3, 95% CI=1.12–25.09, P=0.036). In addition, patients with ADV resistance were associated with higher HBV DNA levels and lower HBV DNA reduction in first 6 months of ADV treatment than those without ADV resistance.

Conclusion

Only half of our patients achieved IVR on ADV treatment. The incidence of ADV resistance was high in 3TC-resistant patients treated with ADV.