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Antimicrobial Agents and Chemotherapy, January 2001, p. 229-235, Vol. 45, No. 1
Novirio Pharmaceuticals, Inc., Cambridge,
Massachusetts 021401; Department of
Pharmacology and Toxicology, Division of Clinical Pharmacology, The
Liver Center, University of Alabama at Birmingham, Birmingham, Alabama
352942; Novirio Pharmaceuticals, SARL,
75008 Paris,3 and Laboratoire de Chimie
Bioorganique, CNRS UMR 5625, Université de Montpellier II, 34095 Cedex 5 Montpellier,4 France; Department
of Clinical Sciences, College of Veterinary Medicine, Cornell
University, Ithaca, New York 148535;
Division of Molecular Virology and Immunology, Georgetown
University College of Medicine, Rockville, Maryland
208526; Divisions of Gastroenterology
and Infectious Diseases and Geographic Medicine, Stanford University
School of Medicine, Stanford, California 943057;
and Laboratory of Biochemical Pharmacology, Department of
Pediatrics, Emory University School of Medicine and Veterans
Affairs Medical Center, Decatur, Georgia 300338
Received 10 April 2000/Returned for modification 20 June
2000/Accepted 10 October 2000
A unique series of simple "unnatural" nucleosides has been
discovered to inhibit hepatitis B virus (HBV) replication. Through structure-activity analysis it was found that the 3'-OH group of the
Infection with hepatitis B
virus (HBV) is a major world health problem, affecting 5% of the
population. More than 2 billion people have been infected with the
virus, and 350 million of them are chronic carriers at risk of death
from cirrhosis and liver cancer (49).
Several strategies have been evaluated for the treatment of chronic HBV
infection with the goal of eliminating persistent viral replication and
preventing progression to chronic active hepatitis and liver failure.
Currently, the only approved treatment options are alpha interferon
(IFN) and lamivudine ( Since the Food and Drug Administration approved lamivudine for the
treatment of HIV infection in the United States in 1996 and for HBV in
1998, intensive studies on "unnatural" L-nucleosides as
agents against HIV, HBV, and herpesviruses (including Epstein-Barr virus [EBV]) and as anticancer agents have been conducted
(23). Now, through an extensive structure-activity
analysis, we have found that the 3'-OH group of the
Chemicals.
L-dC, L-dT, and
L-dA were synthesized as previously described (D. Dukhan,
C. Pierra, M. Bryant, J.-P. Sommadossi, J.-L. Imbach, and G. Gosselin,
Abstr. 13th Int. Conf. Antiviral Res., abstr. 89, 2000; C. Pierra, D. Dukhan, M. Bryant, J.-P. Sommadossi, J.-L. Imbach and G. Gosselin,
Abstr. 13th Int. Conf. Antivir. Res., abstr. 90, 2000). The
5'-triphosphates of L-dT, L-dC, and
L-dA were chemically synthesized and characterized using
previously described methods (16). Radiolabeled
nucleotides were obtained from Moravek Biochemicals, Inc. (Brea,
Calif.). All other chemicals were of the highest grade available.
Extracellular HBV DNA analysis.
Inhibition of HBV
replication in vitro was assessed using the 2.2.15 cell line as
previously described (26). Briefly, cells were cultured at
a density of 2 × 105 cells per ml in
24-well plates in Dulbecco minimal essential medium supplemented
with 4% dialyzed fetal bovine serum and 0.5 mM L-glutamine
for 9 days in the presence or absence of drug, with medium changes
every 3 days. The antiviral activities of L-dC,
L-dT, and L-dA were determined as the reduction
of extracellular virus-associated DNA. HBV DNA isolated from virions
was analyzed by Southern blot analysis. Inhibition of viral DNA
replication was assessed by comparison of HBV DNA from drug-treated and
untreated cultures using hybridization to a
32P-labeled HBV-specific probe followed by
autoradiography and densitometry (i.e., detection and quantitation).
HIV antiviral and cytotoxicity assays in PBM cells.
Anti-HIV-1 activity of the compounds was determined in human peripheral
blood mononuclear (PBM) cells as previously described (41). Cells were infected with
HIV-1LAI at a multiplicity of infection of 0.01. Virus obtained from cell culture supernatant was quantitated on day 6 after infection using a reverse transcriptase assay and
(rA)n · (dT)12-18 as
a template primer. The toxicity of the compounds was assessed in human
PBM cells as previously described (41). The antiviral 50%
effective concentration (EC50) and 50% cytotoxic
concentration were determined from the concentration-response
curve using the median effect method (1).
Virion-associated WHV DNA polymerase assay.
For the
woodchuck hepatitis virus (WHV) DNA polymerase assay, virus particles
were concentrated from sera of woodchucks chronically infected with
WHV. Briefly, virus-containing serum was ultracentrifuged at
55,000 × g using a 30% sucrose gradient supplemented
with 1% bovine serum albumin and 1 µM EDTA for 12 h at
4oC. The viral pellet was suspended in 400 µl
of Tris-HCl buffer (pH 7.6) containing 10% Nonidet P-40 and 15 mM
Drug cytotoxicity studies in human bone marrow progenitor
cells.
Human bone marrow cells were collected by aspiration from
the posterior iliac crest of normal healthy donors, and the mononuclear cell population was isolated by Ficoll-Hypaque gradient centrifugation (44). Assays of granulocyte-macrophage CFU (GM-CFU) and
erythroid burst-forming units (E-BFU) were performed using a bilayer
soft-agar-methylcellulose method described previously
(44). After incubation for 14 days in the presence or
absence of drug, GM-CFU and E-BFU were counted with an inverted microscope.
Human DNA polymerase assays.
Human DNA polymerases Mitochondrial and cytotoxicity studies in HepG2 cells.
To
measure lactic acid production in drug-treated cultures, HepG2
cells (2.5 × 104 cells/ml) were plated in
12-well culture plates and treated with 10 µM L-dC,
L-dT, or L-dA as previously described
(8). Briefly, cells were cultured in minimal essential
medium with nonessential amino acids supplemented with 10%
heat-inactivated dialyzed fetal bovine serum and 1% sodium pyruvate.
Cells were cultured for 14 days with medium changes every 4 days.
Lactic acid content in the culture media was measured using a lactic
acid assay kit (Boehringer Mannheim Corp., Mannheim, Germany). Cell
number was determined with a hemocytometer. The effect of the
Woodchucks.
Chronically infected 16- to 18-month-old male
and female woodchucks were stratified into comparable groups of three
animals each (four animals in the control group) based on sex, weight, levels of WHV DNA in serum, and Viral load determinations.
Serum WHV DNA levels were
measured by a dot blot hybridization technique using a full-length
(3.2-kb) gel-purified WHV DNA probe as previously described
(47). Amounts of viral DNA were determined by reference to
a known amount of cloned viral DNA. Serum samples with WHV DNA levels
below the limit of detection using the dot blot procedure were
reanalyzed by PCR as previously described (34). The WHV
core region, nucleotides 2041 to 2411, was amplified with the forward
primer 5'-CATTGTTCACCTCACCATACTGCAC-3' and the reverse
primer 5'-GATTGAGACCTTCGTCTGCGAG-3'. The amplified product
was bound to nitrocellulose membranes using a 96-well dot blot manifold
and quantitated using a genomic WHV probe. A reference serum sample
containing 7 × 1010 WHV genomes was used to
calibrate the PCRs and to quantitate the amount of WHV DNA present in
the woodchuck serum samples. The limit of detection of the WHV DNA
detection procedure was approximately 300 WHV genome equivalents/ml of
woodchuck serum.
The
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.1.229-235.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Antiviral L-Nucleosides Specific for
Hepatitis B Virus Infection
ABSTRACT
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
References
-L-2'-deoxyribose of the
-L-2'-deoxynucleoside confers specific antihepadnavirus
activity. The unsubstituted nucleosides -L-2'-deoxycytidine, -L-thymidine, and
-L-2'-deoxyadenosine had the most potent, selective, and
specific antiviral activity against HBV replication. Human DNA
polymerases (
, , and 
) and mitochondrial function were not
affected. In the woodchuck model of chronic HBV infection, viral load
was reduced by as much as 108 genome equivalents/ml of
serum and there was no drug-related toxicity. In addition, the decline
in woodchuck hepatitis virus surface antigen paralleled the decrease in
viral load. These investigational drugs, used alone or in
combination, are expected to offer new therapeutic options for patients
with chronic HBV infection.
INTRODUCTION
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
References
-L-2',3'-dideoxy-3'-thiacytidine [3TC]). Unfortunately, the rate of response to IFN is low, and drug-associated side effects are significant (24, 55).
Individuals who are immunosuppressed (e.g., transplant recipients or
those coinfected with the human immunodeficiency virus [HIV]) rarely respond to IFN therapy (13). Lamivudine is a well-known
example of the class of -L-nucleoside analogs that has
recently drawn attention as antiviral and anticancer agents
(52). As with IFN, however, a complete antiviral response,
as assessed by HBe seroconversion, is seen in only a minority of
patients after 1 year of treatment (27). In addition,
cessation of lamivudine therapy or development of viral resistance may
lead to a marked rebound in viral replication which can be life
threatening (hepatitis flare) in HIV-HBV-coinfected patients (2,
30). Lamivudine resistance is now recognized in 16 to 32% of
HBV-infected patients after 1 year of treatment and in as many as 58%
after 2 to 3 years (14, 27, 30).
-L-2'-deoxyribose of the
-L-2'-deoxynucleoside series confers unique specificity
for anti-HBV activity. In this chemical series,
-L-2'-deoxycytidine (L-dC),
-L-thymidine (L-dT), and
-L-2'-deoxyadenosine (L-dA) had the most
potent, selective, and specific activity against HBV replication.
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
References
-mercaptoethanol. Reaction mixtures in a final volume of 50 µl
contained 80 mM Tris-HCl (pH 7.6); 20 mM MgCl2;
60 mM NH4Cl; 100 µM concentrations of dGTP, dATP, dCTP, and TTP with substitution of 0.75 µM
[3H]TTP, [3H]dCTP, or
[3H]dATP; and various concentrations of the
-L-2'-deoxynucleoside 5'-triphosphate
derivative (e.g., L-TTP was assayed in the
presence of 0.75 µM [3H]TTP and 100 µM
concentrations each of dGTP, dATP, and dCTP). The reaction was started
by adding the disrupted virus particles. The mixture was incubated for
2 h at 37oC, and aliquots were spotted onto
Whatman DE81 filters. The filters were washed three times with 125 mM
Na2HPO4 buffer (pH 7.0) and rinsed once with water and once with ethanol. The filters were dried
and counted in 4 ml of scintillation liquid (Econo-safe liquid;
Research Products International [RPI], Mount Prospect, Ill.) using a
Beckman LS TA 5000 scintillation counter.
and
were a generous gift from William Parker (Southern Research
Institute, Birmingham, Ala.) and human DNA polymerase was purchased
from Molecular Biology Resources, Inc. (Milwaukee, Wis.). Reaction
mixtures for DNA polymerase contained 50 mM Tris-HCl (pH 8.0); 10 mM MgCl2; 1.0 mg of bovine serum albumin/ml; 1.0 mM dithiothreitol; 10 µg of activated calf thymus DNA; 50 µM
concentrations of dGTP, dATP, dCTP, and TTP with substitution of 0.75 µM [3H]dCTP, [3H]TTP,
or [3H]dATP; and various concentrations of the
-L-2'-deoxynucleoside 5'-triphosphate derivative (e.g.,
L-dCTP was assayed in the presence of 0.75 µM
[3H]dCTP and 100 µM concentrations each of
dGTP, dATP, and TTP). The DNA polymerase assay was carried out in
the same buffer as for DNA polymerase except that 60 mM Tris-HCl at
pH 8.7, 100 mM KCl, and 15% (vol/vol) glycerol were used. Reactions
for the DNA polymerase assay were carried out in the buffer used for DNA polymerase except that 100 mM KCl was added. Reactions were
initiated by the addition of 1.5 U of DNA polymerase , , or .
All reaction mixtures were incubated for 60 min at
37oC, and 40-µl aliquots were spotted onto
Whatman DE81 filters. The filters were washed and counted as described above.
-L-2'-deoxynucleosides on mitochondrial DNA (mtDNA)
content in HepG2 cells was determined essentially as described
previously (8). Briefly, after 14 days of incubation in
the presence or absence of drug with medium changes every 4 days, cells
were lysed, and the DNA was immobilized on nylon membranes. The DNA
slot blots were probed with a specific mitochondrial probe to
quantitate mtDNA levels. A -actin probe was used to standardize
total DNA loading. For morphological evaluation, HepG2 cells (2.5 × 104 cells/ml) were plated in 35- by 10-mm
culture dishes and incubated in the absence or presence of 10 µM
L-dA, L-dT, or L-dC for 14 days
with medium changes every 4 days. For electron microscopic examination
(Hitachi 7000), the cells were fixed, postfixed, dehydrated, embedded,
and sectioned as previously described (8). The effect of
the -L-2'-deoxynucleosides on cell growth relative to
that of untreated cells was determined by the neutral red dye technique as described previously (39).
-glutamyl transpeptidase levels were
measured 30 days prior to the start of the study. Each drug was
dissolved in water (30 mg/ml), and woodchucks in the treatment group received a daily oral dose of 10 mg of drug/kg of body weight in
approximately 5 ml of liquid woodchuck control diet (Dyets, Inc.,
Bethlehem, Pa.) by dose syringe. The control group received an
equivalent volume of water administered with liquid woodchuck control
diet. The woodchucks were anesthetized (50 mg of ketamine/kg and 5 mg
of xylazine/kg), and body weights were determined and serum samples
were taken at the indicated time points.
RESULTS AND DISCUSSION
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
References
-L-2'-deoxynucleoside series is specific
for HBV.
The structure-activity relationships (SARs) established
among the L-dC, L-dT, and L-dA
series are presented in Table 1.
Substitution of a halogen atom at the 5 position (R1) in the pyrimidine
ring of L-dC, without modification of the deoxyribose
sugar (e.g., -L-2'-deoxy-5-fluorocytidine
[L-5-FdC] and
-L-2'-deoxy-5-chlorocytidine [L-5-CldC]), decreased the potency against HBV but
did not affect the specificity for HBV. In contrast, analogs of
L-dC which lacked the 3'-OH group (R3) on the
deoxyribose sugar (e.g., -L-2',3'-dideoxycytidine [L-ddC], 3TC, and
-L-2',3'-didehydro-2',3'-dideoxycytidine
[L-d4C]) lost antiviral specificity for HBV and showed
activity against HIV. Similarly, replacement of the 3'-OH group with
a 3'-fluoro- moiety (e.g.,
-L-2',3'-dideoxy-3'-fluorocytidine
[L-3'-FddC]) eliminated the antiviral specificity,
although antiviral potency against HBV and HIV was retained.
TABLE 1.
SARs of L-dC, L-dT, and
L-dA
analogs
-L-2',3'-dideoxy-5-fluorocytidine [L-5-FddC],
-L-2',3'-dideoxy-5-chlorocytidine
[L-5-ClddC],
-L-2',3'-dideoxy-3'-thia-5-fluorocytidine [FTC],
-L-2',3'-didehydro-2',3'-dideoxy-5-fluorocytidine
[L-d4FC], -L-2',3'-dideoxy-3'-fluoro-5-fluorocytidine
[L-3'-F-5-FddC], and
-L-2',3'-dideoxy-3'-azido-5-fluorocytidine
[L-3'-azido-5-FddC]) further affected the antiviral
potency of these analogs against HBV as well as HIV. These studies
suggest that the 3'-OH of the -L-2'-deoxyribose of
L-dC plays a crucial role in inhibiting virus replication,
possibly by specific interaction with the HBV DNA polymerase.
The SARs for the L-dT and L-dA series (Table 1)
were similar to those observed for the L-dC series. The
specific anti-HBV activity of L-dT and L-dA
was lost upon removal or substitution of the 3'-OH group (R3).
-L-2'-Deoxy-xylo-thymidine (L-xylo-dT), which is identical to L-dT except that the 3'-OH group is
in the opposite orientation (R2), also lost anti-HBV activity, further emphasizing the importance of the 3'-OH group in the interaction with
the HBV DNA polymerase. An L-dT analog with a fluorine
substitution at the 2'
up position (-L-2'-deoxy-2'-fluoro-5-methyl-arabinofuranosyl uracil
[L-FMAU]) has been reported to have activity against both HBV and EBV (6). Thus, it is possible that modification of the 2' position in addition to the 3' position of L-dT may
also change antiviral specificity for HBV.
Substitution at the 2 position (R1) on the purine base of
L-dA (e.g., -L-2'-deoxy-2-chloroadenosine
[L-2-CldA]) had a negative effect on anti-HBV activity.
The analogs of L-dA lacking the 3'-OH group with or without
further modification of the deoxyribose sugar lost specificity and were
not as potent against HBV. The marginal antiviral activity of
-L-2',3'-dideoxyadenosine (L-ddA), despite
its potent inhibitory activity against both HIV reverse transcriptase
and WHV DNA polymerase (Placidi et al., unpublished data), can
be explained by the low intracellular concentrations of the
phosphorylated form due to rapid and extensive catabolism (36). This conclusion is also supported by recent studies
that demonstrated potent antiviral activity of an L-ddA
5'-monophosphate prodrug
(-L-2',3'-ddAMP-terbutyl-S-acyl-2-thioethyl
[L-ddAMP-bis(terbutyl-SATE)]). The prodrug form
decreases the intracellular catabolism of the parent molecule (L. Placidi et al., Proc. 2nd Int. Conf. Ther. Vir. Hepatitis, abstr. A22,
1998 [Antivir. Ther. 3, Suppl. 3]) and releases the
5'-monophosphate derivative inside the cell. When used in this
pronucleotide form, L-ddA was active against both
HIV and HBV, further supporting the importance of the 3'-OH group for
antiviral specificity. As in the L-dC and
L-dT series, unmodified
-L-2'-deoxyadenosine most potently and
specifically inhibited HBV replication.
To further assess their antiviral specificities, L-dC,
L-dT, and L-dA were screened against 15 different RNA and DNA viruses. The
-L-2'-deoxynucleosides inhibited hepadnavirus
replication as previously defined by the SAR but had no activity
against HIV-1, herpes simplex virus types 1 and 2, varicella-zoster
virus, EBV, human cytomegalovirus, adenovirus type 1, influenza A and B
viruses, measles virus, parainfluenzavirus type 3, rhinovirus type 5, or respiratory syncytial virus type A at concentrations as high as 200 µM. Potent antiviral activity against WHV, determined using an in
vivo model of chronic HBV infection, is described below. Thus,
the unmodified -L-2'-deoxynucleosides L-dC,
L-dT, and L-dA are uniquely specific for the
hepadnaviruses HBV, duck HBV (DHBV), and WHV.
Selectivity of -L-2'-deoxynucleosides.
Since
long-term treatment is expected for chronic HBV infection, drug
selectivity is a critical issue. Toxic side effects have been a major
problem, limiting the clinical use of some nucleoside analogs
(17, 25, 53, 54). The 5'-triphosphates of
L-dC, L-dT, and L-dA did not
inhibit human DNA polymerases , , and at concentrations up to
100 µM. Semizarov and coworkers also reported that the
5'-triphosphates of L-dC and L-dT were not
substrates for human DNA polymerases (42).
L-dC, L-dT, and L-dA had no cytotoxic effect on the human hepatoma cell line 2.2.15 (50% cytotoxic concentration > 1,000 µM), primary human PBM cells, human
foreskin fibroblasts, or other cell types of mammalian and avian
origin. In addition, studies by Verri et al. demonstrated that
L-dC was not cytotoxic toward lymphoblastoid T cells
(51). Human bone marrow stem cells in primary culture have
been shown to be a good predictor of potential nucleoside
analog-induced hematotoxicity in patients (15, 45). GM-CFU
and E-BFU precursors exposed to L-dC, L-dT, and
L-dA in clonogenic assays at concentrations up to 10 µM
were not affected. These results suggest that L-dC, L-dT, and L-dA are highly selective and that
their phosphorylated forms will be nontoxic in vivo.
-L-2'-dUTP
(L-dUTP) which also inhibited WHV DNA polymerase, with a
50% inhibitory concentration of 5.26 µM (Faraj et al. and Placidi et
al., 3rd Int. Conf. Ther. Vir. Hepatitis, abstr. A119 and A122, 1999 [Antivir. Ther. 4, Suppl. 4]). Similar to
-L-cytidine analogs (4, 19, 31, 51),
L-dC was not a substrate for cytosolic cytidine deaminase,
which suggested that the 5'-monophosphate metabolite of
L-dC may be susceptible to deamination through
deoxycytidylate deaminase. The inhibition of HBV replication by these
-L-2'-deoxynucleosides and inhibition of hepadnaviral
polymerase by their corresponding 5'-triphosphates suggested that, like
most nucleoside analogs, L-dC, L-dT, and L-dA may act by inhibiting the reverse transcription of HBV
pregenomic RNA. Demonstration that L-deoxynucleoside
triphosphate analogs inhibit HBV reverse transcriptase and/or
DNA polymerase activity does not preclude other mechanisms of action.
Inhibition of other important activities of the polymerase (which
include RNase H activity, priming of reverse transcription, and
coordination of intracellular virion assembly) and the possibility of
internal incorporation of L-deoxynucleoside monophosphates
into viral DNA as a mechanism of inhibition are currently under investigation.
-L-2'-Deoxynucleosides have no effect on
mitochondrial function or morphology.
Nucleoside analogs used in
AIDS therapy, such as zidovudine
(-D-3'-azido-3'-deoxythymidine), stavudine
(-D-2',3'-didehydro-2',3'-dideoxythymidine [d4T]),
didanosine (-D-2',3'-dideoxyinosine [ddI]), and
zalcitabine (-D-2',3'-dideoxycytidine [ddC]), have
shown clinically limiting delayed toxicities such as peripheral
neuropathy, myopathy, and pancreatitis (17, 25, 53, 54).
This nucleoside analog-related cellular toxicity has been attributed to
decreased mtDNA content and altered mitochondrial function, leading to
increased lactic acid production (5, 9-12, 28, 35).
Concomitant morphological changes in mitochondria (e.g., loss of
cristae, matrix dissolution and swelling, and lipid droplet formation)
can be observed with ultrastructural analysis using transmission
electron microscopy (10, 29, 35). In HepG2 cells incubated
with 10 µM fialuridine (FIAU;
1,2'-deoxy-2'-fluoro-1--D-arabinofuranosly-5-iodo-uracil), a substantial increase in lactic acid production was observed (data not shown). Electron micrographs of these cells showed the presence of enlarged mitochondria with morphological changes consistent with mitochondrial dysfunction. Lamivudine (10 µM) did not affect mitochondrial structure or function. Under similar conditions, exposure
of HepG2 cells to 10 µM L-dC, L-dT, or
L-dA for 14 days had no effect on lactic acid production,
mtDNA content, or morphology (data not shown).
In vivo antiviral activity and toxicity.
The woodchuck model
of chronic HBV infection has proven to be a positive predictor of the
antiviral activity and safety of antiviral drug candidates for the
treatment of human chronic HBV infection (47, 48).
L-dC, L-dT, and L-dA were given
orally to woodchucks once daily at 10 mg/kg/day. The levels of WHV DNA in serum during 4 weeks of drug treatment and 8 weeks of posttreatment follow-up were determined by DNA dot blot hybridization (detection limit, approximately 107 genome equivalents/ml of
serum) and by quantitative PCR (detection limit, 300 genome
equivalents/ml of serum). The WHV DNA replication was significantly
inhibited within the first few days of treatment and this inhibition
was maintained throughout the treatment period. Notably, serum WHV DNA
levels (HBV viremia) decreased in the L-dT-treated animals
by as much as 8 logs (Fig. 1). Following
drug withdrawal, viral rebound reached near-pretreatment levels between
week 4 and week 8. In the L-dC-treated animals, serum WHV
DNA levels decreased by up to 6 logs by the third week of therapy.
Viral rebound was detected within the first week posttreatment. Animals receiving L-dA showed a decrease in serum WHV DNA levels of
approximately 1.5 logs within the first week of treatment, and this
decrease was also followed by viral rebound. In addition to the
determination of viral load, WHV surface antigen (WHsAg), which is
assumed to represent the level of intercellular gene expression, was
measured using the method of Cote et al. (7). In general,
the serologic profiles paralleled the decrease in viral load and
continued to fall for several weeks after drug removal.
|
-L-2'-deoxynucleosides L-dC, L-dT, and L-dA were well
tolerated and caused no drug-related toxicity through 12 weeks of
treatment and 4 weeks of follow-up (data not shown).
In summary, this is the first report of
-L-2'-deoxynucleosides with potent, selective, and
specific activity against HBV replication. This series of drug
candidates has in common the presence of a hydroxyl group in the 3'
position that determines specific activity against hepadnavirus. In the
woodchuck model of chronic HBV infection, oral administration of these
-L-2'-deoxynucleosides reduced serum viral load by as
much as 108 genome equivalents/ml without
toxicity. These -L-2'-deoxynucleosides are highly
attractive clinical development candidates for the treatment of
chronic HBV infection.
| |
FOOTNOTES |
|---|
* Corresponding author. Mailing address: Novirio Pharmaceuticals, Inc., 125 Cambridge Park Dr., Cambridge, MA 02140. Phone: (617) 250-3100. Fax: (617) 250-3101. E-mail: bryant.martin{at}novirio.com.
| |
REFERENCES |
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Top
Abstract
Introduction
Materials and Methods
Results and Discussion
References
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Antimicrobial Agents and Chemotherapy, January 2001, p. 229-235, Vol. 45, No. 1
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.1.229-235.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
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