Treatment strategies using adefovir dipivoxil for individuals with lamivudine-resistant chronic hepatitis B

AIM:To investigate retrospectively the long-term efficacy of various treatment strategies using adefovir dipivoxil(adefovir) in patients with lamivudine-resistant chronic hepatitis B.METHODS:We included 154 consecutive patients in two treatment groups:the "add-on" group(n = 79),in which adefovir was added to ongoing lamivudine treatment due to lamivudine resistance,and the "switch/combination" group(n = 75),in which lamivudine was first switched to adefovir and then re-added later as needed.The "switch/combination" group was then divided into two subgroups depending on whether participants followed(group A,n = 30) or violated(group B,n = 45) a proposed treatment strategy that determined whether to add lamivudine based on the serum hepatitis B virus(HBV) DNA levels(< 60 IU/mL or not) after 6 mo of treatment(roadmap concept).RESULTS:The cumulative probability of virologic response(HBV DNA < 60 IU/mL) was higher in group A than in the "add-on" group and in group B(P < 0.001).In contrast,the cumulative probability of virologic breakthrough was lower in the "add-on" group than in group B(P = 0.002).Furthermore,the risk of virologic breakthrough in the multivariate analysis was significantly lower in the "add-on" group than in group A(hazard ratio = 0.096;95%CI,0.015-0.629;P = 0.015).CONCLUSION:The selective combination of adefovir with lamivudine based upon early treatment responses increased the odds of virologic breakthrough relative to the use of uniform combination therapy from the beginning of treatment.

Construction and expression of eukaryotic plasmids containing lamivudine-resistant or wild-type strains of Hepatitis B Virus genotype C

AIM:To construct eukaryotic expression plasmids of full-length Hepatitis B Virus(HBV) genotype C genome,which contain lamivudine-resistant mutants(YIDD,YVDD) or wild-type strain(YMDD) ,and to observe the expression of HBV DNA and antigens [hepatitis B surface antigen(HBsAg) and hepatitis B e antigen(HBeAg) ] of the recombinant plasmids in HepG2 cells. METHODS:Three HBV full-length genomes were amplified from the plasmids pMD18T-HBV/YIDD,pMD18T-HBV/YVDD and pMD18T-HBV/YMDD,using PCR. Three recombinant plasmids were generated by inserting each of the PCR products into the eukaryotic expression vector pcDNA3.1(+) ,between the EcoRI and HindⅢ sites. After being characterized by restriction endonuclease digestion,and DNA sequence analysis,the recombinant plasmids were transfected into HepG2 cells. At 48 and 72 h post-transfection,the levels of intracellular viral DNA replication were detected by real-time PCR,and the expression of HBsAg and HBeAg in the cell culture supernatant was determined by ELISA. RESULTS:Restriction endonuclease digestion and DNA sequence analysis confirmed that the threerecombinant plasmids were correctly constructed. After transfecting the plasmids into HepG2 cells,high levels of intracellular viral DNA replication were observed,and HBsAg and HBeAg were secreted into the cell culture supernatant. CONCLUSION:Eukaryotic expression plasmids pcDNA3.1(+) -HBV/YIDD,pcDNA3.1(+) -HBV/YVDD or pcDNA3.1(+) -HBV/YMDD,which contained HBV genotype C full-length genome,were successfully constructed. After transfection into HepG2 cells,the recombinant plasmids efficiently expressed HBV DNA,HBsAg and HBeAg. Our results provide an experimental basis for the further study of HBV lamivudine-resistant mutants.

Lamivudine resistance in children with chronic hepatitis B

Currently, although lamivudine(LAM) has a low genetic barrier, only interferon-alpha and LAM are available as a first-line treatment in children with chronic hepatitis B(CHB). LAM is a potent inhibitor of hepatitis B virusdeoxyribonucleic acid(HBV-DNA) polymerase replication by termination of the proviral HBV-DNA chain. LAM has a good safety and tolerability profile in CHB patients with hepatic decompensation. However, the main disadvantages of this HBV reverse transcriptase inhibitor are:(1) pre-existing covalently closed circular DNA cannot be eradicated by LAM, thus relapse after therapy withdrawal is frequent; and(2) although the longer LAMtreatment induced the higher seroconversion rate, the risk of viral resistance increased through the selection of YMDD(tyrosine, methionine, aspartate, aspartate) motif. Insufficient suppression of viral replication leads to the emergence of resistant strains that could result in virological breakthrough which is usually followed by biochemical breakthrough. Mutant strains affects additional resistance and cross resistance, leading to drug resistance in a significant number of CHB patients. In this case, efficacy of more powerful anti-viral agents with higher genetic barrier against development of resistance is diminished. Furthermore, strains that are resistant to LAM could bring about vaccine escape mutants, decreasing the efficacy of HBV vaccine. A more potent drug with a high genetic barrier to resistance needs to be approved as the first-line treatment option for CHB in children.

Phase Ⅱb trial of in vivo electroporation mediated dualplasmid hepatitis B virus DNA vaccine in chronic hepatitis B patients under lamivudine therapy

AIM To assess the efficacy and safety of in vivo electroporation(EP)-mediated dual-plasmid hepatitis B virus(HBV) DNA vaccine vs placebo for sequential combination therapy with lamivudine(LAM) in patients with chronic hepatitis B. METHODS Two hundred and twenty-five patients were randomized to receive either LAM + vaccine(vaccine group, n = 109) or LAM + placebo(control group, n = 116). LAM treatment lasted 72 wk. Patients received the DNA vaccine or placebo by intramuscular injection mediated by EP at weeks 12(start of treatment with vaccine or placebo, SOT), 16, 24, and 36(end of treatment with vaccine or placebo, EOT). RESULTS In the modified intent-to-treat population, morepatients had a decrease in HBV DNA > 2 log10 IU/m L in the vaccine group at week 12 after EOT compared with the control group. A trend toward a difference in the number of patients with undetectable HBV DNA at week 28 after EOT was obtained. Adverse events were similar. In the dynamic per-protocol set, which excluded adefovir(ADV) add-on cases at each time point instantly after ADV administration due to LAM antiviral failure, more patients had a decrease in HBV DNA > 2 log10 IU/mL in the vaccine group at week 12 and 28 after EOT compared with the control group. More patients with undetectable HBV DNA at week 28 after EOT in the vaccine group were also observed. Among patients with a viral load < 1000 copies/mL at week 12, more patients achieved HBeA g seroconversion in the vaccine group than among controls at week 36 after EOT, as well as less virological breakthrough and YMDD mutations. CONCLUSION The primary endpoint was not achieved using the HBV DNA vaccine. The HBV DNA vaccine could only be beneficial in subjects that have achieved initial virological response under LAM chemotherapy.

Impact of Lamivudine plus Adefovir therapy in chronic hepatitis B Iranian patients, resistant to Lamivudine treatment alone, on disease inhibition: A pilot study

AIM: To evaluate the impact of combination therapy with Lamivudine and Adefovir for treatment of chronic hepatitis B in Lamivudine-resistant patients. METHODS: Among the 110 adult chronic hepatitis B Iranian patients whom were treated with Lamivudine, for 36 months, nineteen patients (17%) with no any biochemical and viral responses to Lamivudine alone, were selected and enrolled in the study. Due to resistancy, Adefovir was added to Lamivudine, and continued for 30 months. We measured HBV_DNA viral load and serum AST, ALT in 0, 12, 24, 30 and 0, 6, 12, 18, 24, 30 months, respectively. RESULTS: Between biochemical and viral characteristics, Repeated Measure analysis identified just biochemical markers— Aspartate Aminotransferase level (AST) (P = 0.002) and Alanine Aminotransferase level (ALT) (P = 0.007) —as predictors of response to treatment, while, viral marker—HBV DNA load—was not statistically significant (P = 0.128). CONCLUSIONS: Treatment for a long time, such as 21.5 ± 8.8 months, with Lami- vudine and Adefovir, can cause liver enzymes including AST and ALT, decreasing and being normal. But, this finding is not indicative, for HBV-DNA viral load.