Reverse Transcriptase Activity of Hepatitis B Virus (HBV) DNA Polymerase within Core Capsid: Interaction with Deoxynucleoside Triphosphates and Anti-HBV l-Deoxynucleoside Analog Triphosphates

2004 ◽  
Vol 65 (2) ◽  
pp. 400-406 ◽  
Author(s):  
Wing Lam ◽  
Ying Li ◽  
Jieh-Yuan Liou ◽  
Ginger E. Dutschman ◽  
Yung-chi Cheng
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Reverse Transcriptase ◽  
Dna Polymerase ◽  
Reverse Transcriptase Activity ◽  
Hbv Dna ◽  
Transcriptase Activity ◽  
B Virus

Inhibitory Effects of Acyclic Nucleoside Phosphonate Analogues on Hepatitis B Virus DNA Synthesis in HB611 Cells

1994 ◽  
Vol 5 (2) ◽  
pp. 57-63 ◽  
Author(s):  
T. Yokota ◽  
K. Konno ◽  
S. Shigeta ◽  
A. Holy ◽  
J. Balzarini ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Dna Synthesis ◽  
Dna Polymerase ◽  
Hbv Dna ◽  
Inhibitory Effects ◽  
B Virus ◽  
Acyclic Nucleoside ◽  
Cellular Dna ◽  
Acyclic Nucleoside Phosphonate

By using an assay system based on a human hepatoblastoma cell line (HB611) that continuously synthesizes hepatitis B virus (HBV) DNA, 56 acyclic nucleoside phosphonate analogues were examined for their inhibitory effects on HBV DNA synthesis. The following compounds were found to inhibit HBV DNA synthesis at concentrations that were significantly lower than their minimum cytotoxic concentrations; 9-(2-phosphonylmethoxyethyl)adenine (PMEA), 9-(2-phosphonylmethoxyethyl) guanine(PMEG), 9-(2-phosphonylmethoxyethyl) guanine ethyl ester (PMEGEE), 9 - (2 - phosphonylmethoxyethyl) - 1 - deazaadenine (PMEC1A), 9-(2-phosphonylmethoxyethyl)-2,6-diaminopurine (PMEDAP), ( S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA), 9-(3-isopropoxy-2-phosphonylmethoxypropyl)adenine (IPPMPA), 9-( RS)-(2-phosphonylmethoxypropyl)adenine (PMPA) and 9-(3-hydroxy-2-phosphonylmethoxypropyl)-2, 6-diaminopurine (HPMPDAP). The most selective compounds (with indexes greater than 100) were PMEDAP, PMEA, IPPMPA, and PMPA. Acyclic pyrimidine nucleoside phosphonate analogues did not prove markedly selective as anti-HBV agents. Diphosphoryl derivatives of some acyclic purine nucleoside phos-phonates (i.e. PMEA, PMEDAP, HPMPA) were prepared. They proved inhibitory to HBV DNA polymerase but not cellular DNA polymerase α.

scholarly journals Entecavir for Treatment of Hepatitis B Virus Displays No In Vitro Mitochondrial Toxicity or DNA Polymerase Gamma Inhibition

2007 ◽  
Vol 52 (2) ◽  
pp. 598-605 ◽  
Author(s):  
Charles E. Mazzucco ◽  
Robert K. Hamatake ◽  
Richard J. Colonno ◽  
Daniel J. Tenney
Keyword(s):  
Mitochondrial Dna ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Reverse Transcriptase ◽  
Dna Polymerase ◽  
Mitochondrial Proteins ◽  
Mitochondrial Toxicity ◽  
Chronic Hepatitis B Virus ◽  
B Virus

ABSTRACT Therapy with nucleoside reverse transcriptase inhibitors (NRTIs) can be associated with mitochondrial toxicity. In vitro studies have been used to predict the predisposition for and characterize the mechanisms causing mitochondrial toxicity. Entecavir (ETV) is an approved deoxyguanosine nucleoside for the treatment of chronic hepatitis B virus (HBV) infection that exhibits potent activity against viral reverse transcriptase. We assessed the potential for mitochondrial toxicity of ETV in long-term cultures of HepG2 hepatoma cells by measuring mitochondrial function (through lactate secretion), levels of mitochondrial DNA (mtDNA), and levels of mitochondrial proteins COX II and COX IV. Furthermore, we tested the activity of ETV-triphosphate (ETV-TP) against mitochondrial DNA polymerase γ (Pol γ) in vitro. ETV concentrations as high as 100 times the maximal clinical exposure (C max) did not affect cell proliferation, levels of lactate, mitochondrial DNA, or mitochondrial proteins throughout the 15-day culture. The lack of mitochondrial toxicity was consistent with the finding that ETV-TP was not recognized by mitochondrial DNA Pol γ and failed to be incorporated into DNA or inhibit the polymerase assay at the highest levels tested, 300 μM. Combinations of ETV with each of the other HBV NRTI antivirals, adefovir, tenofovir, and lamivudine at 10 times their respective C max levels also failed to result in cellular or mitochondrial toxicity. In summary, cell culture and enzymatic studies yielded no evidence that would predict mitochondrial toxicity of ETV at exposure levels in excess of those expected to be achieved clinically.

scholarly journals Inhibition of Hepatitis B Virus Polymerase by Entecavir

2007 ◽  
Vol 81 (8) ◽  
pp. 3992-4001 ◽  
Author(s):  
David R. Langley ◽  
Ann W. Walsh ◽  
Carl J. Baldick ◽  
Betsy J. Eggers ◽  
Ronald E. Rose ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Reverse Transcriptase ◽  
Kinetic Studies ◽  
Hbv Dna ◽  
Cross Resistance ◽  
Significant Activity ◽  
B Virus ◽  
Dna Chain

ABSTRACT Entecavir (ETV; Baraclude) is a novel deoxyguanosine analog with activity against hepatitis B virus (HBV). ETV differs from the other nucleoside/tide reverse transcriptase inhibitors approved for HBV therapy, lamivudine (LVD) and adefovir (ADV), in several ways: ETV is >100-fold more potent against HBV in culture and, at concentrations below 1 μM, displays no significant activity against human immunodeficiency virus (HIV). Additionally, while LVD and ADV are obligate DNA chain terminators, ETV halts HBV DNA elongation after incorporating a few additional bases. Three-dimensional homology models of the catalytic center of the HBV reverse transcriptase (RT)-DNA-deoxynucleoside triphosphate (dNTP) complex, based on the HIV RT-DNA structure, were used with in vitro enzyme kinetic studies to examine the mechanism of action of ETV against HBV RT. A novel hydrophobic pocket in the rear of the RT dNTP binding site that accommodates the exocyclic alkene moiety of ETV was predicted, establishing a basis for the superior potency observed experimentally. HBV DNA chain termination by ETV was accomplished through disfavored energy requirements as well as steric constraints during subsequent nucleotide addition. Validation of the model was accomplished through modeling of LVD resistance substitutions, which caused an eightfold decrease in ETV susceptibility and were predicted to reduce, but not eliminate, the ETV-binding pocket, in agreement with experimental observations. ADV resistance changes did not affect the ETV docking model, also agreeing with experimental results. Overall, these studies explain the potency, mechanism, and cross-resistance profile of ETV against HBV and account for the successful treatment of naive and LVD- or ADV-experienced chronic HBV patients.

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