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Antimicrobial Agents and Chemotherapy, October 2001, p. 2740-2745, Vol. 45, No. 10
North Carolina State University College of
Veterinary Medicine, Raleigh, North Carolina
27606,1 and Gilead Sciences, Foster
City, California 944042
Received 9 February 2001/Returned for modification 26 April
2001/Accepted 11 July 2001
The antiviral efficacy of orally administered adefovir dipivoxil
was evaluated in an 18-week study (12 weeks of treatment and 6 weeks of
recovery) conducted with woodchucks chronically infected with woodchuck
hepatitis virus (WHV). Adefovir dipivoxil is a prodrug of adefovir
designed to enhance its oral bioavailability. Following administration
of 15 mg of adefovir dipivoxil per kg of body weight in four
WHV-infected animals, the mean maximum concentration of adefovir in
serum was 0.462 µg/ml, with an elimination half-life of 10.2 h,
and the oral bioavailability of adefovir was estimated to be 22.9%
(±11.2%). To study antiviral efficacy, the animals were divided into
three groups. There were six animals each in a high-dose group (15 mg/kg/day) and a low-dose group (5 mg/kg/day). A vehicle control group
consisted of five animals because WHV DNA was detectable only by PCR at
the time of the study in one of the original six animals. Efficacy was
evaluated by determining the levels of WHV DNA in serum. The geometric
mean WHV DNA level for the high-dose group diminished by >40-fold
(>1.6 log10) after 2 weeks of treatment and >300-fold
(>2.5 log10) at 12 weeks. There was a >10-fold reduction
in five of six low-dose animals by 2 weeks, but levels were unchanged
in one animal. By 12 weeks of treatment there was a >45-fold (>1.6
log10) reduction of WHV DNA levels, and serum WHV DNA
levels were below the limit of quantification in three of six animals.
Viral DNA levels returned to pretreatment levels during the 6-week
recovery period. There were no clinically significant changes in body
weight, hematology, or serum chemistry values, including bicarbonate or
lactate, in any of the treated animals. No histologic evidence of liver
injury was apparent in the biopsies. Under the conditions of this
study, adefovir dipivoxil was an effective antihepadnaviral agent.
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.10.2740-2745.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Antiviral Efficacy and Pharmacokinetics of Oral Adefovir
Dipivoxil in Chronically Woodchuck Hepatitis Virus-Infected
Woodchucks
*
Corresponding author. Mailing address: College of
Veterinary Medicine, North Carolina State University, 4700 Hillsborough St., Raleigh, NC 27606. Phone: (919) 513-6350. Fax: (919) 513-6455. E-mail: john_cullen{at}ncsu.edu.
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