Mutations in hepatitis B DNA polymerase associated with resistance to lamivudine do not confer resistance to adefovirin vitro

Xiong, Xiaofeng; Flores, Carmina; Yang, Huiling; Toole, John J.; Gibbs, Craig S.

doi:10.1002/hep.510280629

Cited by 230 publications

(189 citation statements)

References 31 publications

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“…We previously reported that the lamivudine-resistant mutations M552I, M552V, L528MϩM552I, and L528MϩM552V mutant HBV polymerases displayed resistance to LAMTP with K i values increased by 8-to 25-fold compared with that of wild-type HBV polymerase and that all these mutants remained sensitive to ADVDP. 30 In this study, we found that the M552I and L528MϩM552V mutants remained sensitive to PCVTP with K i values increased by 1.1-and 2.5-fold, respectively. However, the M552V mutant displayed moderately decreased sensitivity to PCVTP (3.1-fold) ( Table 2).…”

Section: Resultsmentioning

confidence: 49%

“…The V521L and L528M mutations only displayed 3.1-fold decreased sensitivity compared with 8-to 25-fold increases in K i values for LAMTP for mutations associated with lamivudine resistance in the same assay. 30 However, the 3-fold decreased sensitivity could be enough to cause clinical resistance to famciclovir. 33 Because suppression of HBV replication by famciclovir in chronically infected patients appears to be suboptimal, famciclovir has a low threshold to become clinically ineffective.…”

Section: Discussionmentioning

confidence: 99%

“…Human HBV polymerase (adw2 serotype, GenBank X02763) was cloned into a baculovirus transfer vector pBacPAK9 (Clontech) as described by Xiong et al 30 In this construct (pSX20) a FLAG affinity tag (Met-Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys) was fused to the Nterminal of the polymerase to facilitate protein purification. The V521L, P525L, T532S, L528M, and V555I mutations were generated by polymerase chain reaction mutagenesis 42 ; their codon sequences are shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…These mutations have been directly associated with a lamivudineresistant phenotype in several in vitro models of HBV replication. 27,[29][30][31][32] Several mutations, also in the subdomains B and C of HBV DNA polymerase, including V521L, P525L, L528M, T532S, and V555I, have been reported to arise in HBV patients during famciclovir treatment (Fig. 1).…”

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In vitro evaluation of hepatitis B virus polymerase mutations associated with famciclovir resistance

et al. 2000

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Several mutations (V521L, P525L, L528M, T532S, and V555I) in the gene for hepatitis B virus (HBV) polymerase have been identified in HBV isolated from patients that displayed break-through viremia during famciclovir treatment. To determine whether these mutations cause phenotypic resistance to famciclovir, we compared the inhibition constants (K i ) of penciclovir triphosphate (PCVTP, the active metabolite of famciclovir) for recombinant wild-type and mutant HBV polymerases containing these mutations. In in vitro enzymatic assays, the V555I mutation displayed the most resistance (with K i increased by 6.2-fold) to PCVTP. The V521L and L528M mutations showed moderately decreased sensitivity to PCVTP (K i increased by G3-fold). We also analyzed the cross-resistance profiles of these variants for adefovir and lamivudine, two other antiviral agents that also inhibit DNA replication by HBV polymerase. All 5 famciclovir-associated mutations were sensitive to adefovir diphosphate (ADVDP) in in vitro enzymatic assays (F2.3-fold decreased sensitivity). The V521L, L528M, and T532S mutations were also sensitive to lamivudine triphosphate (LAMTP); however, the P525L and V555I mutations displayed moderately decreased sensitivity to LAMTP in enzymatic assays (3.6-fold decreased sensitivity). The lamivudine-resistant mutations M552I, M552V, and L528M؉M552V, which were previously shown to display 8-to 25-fold resistance to LAMTP, were less resistant (I3.1-fold) to PCVTP. (HEPATOLOGY 2000;31:219-224.)Hepatitis B viral infection is a major cause of acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma, and it is one of the 10 most common causes of death worldwide. 1 Current treatment regimens rely primarily on interferon alfa therapy. However, interferon has limited efficacy, is expensive, requires parenteral administration, and is associated with frequent and unpleasant side effects. Nucleoside or nucleotide analogs, which inhibit DNA replication through hepatitis B virus (HBV) polymerase, represent a new class of promising anti-HBV therapeutics. In addition to lamivudine, 2-9 which was approved recently for the treatment of hepatitis B infection in the United States, several nucleoside and nucleotide analogs including famciclovir 5,10,11 and adefovir dipivoxil 12-14 are currently being evaluated in late stage clinical trials. These compounds have been shown to be well tolerated and can produce rapid and marked decreases in serum HBV-DNA levels.Famciclovir is the oral prodrug of penciclovir, which has to be converted to penciclovir triphosphate by cellular enzymes to become an active inhibitor against HBV polymerase by competing with the natural substrate deoxyguanosine triphosphate (dGTP). 15 Famciclovir was originally approved for the treatment of herpes simplex virus and herpes zoster virus. 16,17 Later, famciclovir was shown to have activity against human and duck hepatitis B viruses in enzymatic and cell culture assays and in animal models of infection. 15,[18][19][20][21] Clinical studies subsequently showed...

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Section: Resultsmentioning

confidence: 49%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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In vitro evaluation of hepatitis B virus polymerase mutations associated with famciclovir resistance

et al. 2000

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“…9 Adefovir dipivoxil (ADV), an oral pro-drug of adefovir, has an antiviral activity against not only wild-type HBV but also LAM-resistant HBV mutants in vitro and in vivo. [10][11][12][13] Therefore, a switch to ADV is usually recommended for patients with LAM-resistant CHB. 14 In contrast to LAM, ADV therapy in treatment-naïve patients is associated with delayed and infrequent emergence of drug-resistant mutations.…”

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

et al. 2006

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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 log 10 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 treatmentnaïve patients after 48 weeks of ADV therapy and was associated with reduced antiviral efficacy to drug treatment. (HEPATOLOGY 2006;43:1385-1391

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Novel patterns of amino acid mutations in the hepatitis B virus polymerase in association with resistance to lamivudine therapy in Japanese patients with chronic hepatitis B

et al. 1999

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Lamivudine is effective in suppressing replication of hepatitis B virus (HBV). However, the emergence of HBV variants resistant to lamivudine is a concern. Lamivudine resistance has been attributed mainly to a substitution of isoleucine or valine for methionine at residue 550 (M550I or M550V) in the catalytic site of the virus polymerase. A substitution of methionine for leucine at residue 526 (L526M) has also been identified. To examine such virus genotypic mutations in Japanese patients, we studied five patients with chronic hepatitis B, who showed HBV breakthrough while on a 1-year lamivudine treatment. The entire nucleotide and deduced amino acid sequences of the proposed reverse transcriptase domain of the polymerase gene were determined on HBV DNA amplified by polymerase chain reaction from patient sera collected at the start and at the end of therapy. The HBV sequences from all five patients were of genotype C. In four patients, a substitution of valine or isoleucine for leucine at residue 426, which has not been reported previously, emerged in combination with M550I. One also harbored L526M. In the remaining patient, an alteration of leucine to methionine at residue 428 co-occurred with M550V. Longitudinal study of the mutations showed that the two or three mutations in each patient emerged almost simultaneously 4 weeks before or at the time of breakthrough and were replaced by wild-type virus after completing the therapy. Our results indicate that occurrence of HBV polymerase mutations at residue 426 in combination with M550I is frequent in Japanese or genotype C virus-in- fected patients who develop resistance to lamivudine.

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Mutations in hepatitis B DNA polymerase associated with resistance to lamivudine do not confer resistance to adefovirin vitro

Cited by 230 publications

References 31 publications

In vitro evaluation of hepatitis B virus polymerase mutations associated with famciclovir resistance

In vitro evaluation of hepatitis B virus polymerase mutations associated with famciclovir resistance

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

Novel patterns of amino acid mutations in the hepatitis B virus polymerase in association with resistance to lamivudine therapy in Japanese patients with chronic hepatitis B

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