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Antimicrobial Agents and Chemotherapy, July 1998, p. 1620-1628, Vol. 42, No. 7
Gilead Sciences, Inc., Foster City,
California 94404
Received 30 September 1997/Returned for modification 15 December
1997/Accepted 16 April 1998
Adefovir dipivoxil [bis(pivaloyloxymethyl)-ester prodrug], an
orally bioavailable prodrug of adefovir
[9-(2-phosphonylmethoxyethyl)adenine], is currently in phase III
clinical trials for the treatment of human immunodeficiency virus
(HIV). In vitro experiments demonstrated that either a K65R or a K70E
mutation in HIV reverse transcriptase (RT) was selected in the presence
of adefovir, conferring a 16- or 9-fold decrease in susceptibility to
adefovir, respectively. Previous data demonstrated that patients
receiving adefovir dipivoxil monotherapy (125 mg daily) for 12 weeks
experienced a median decrease in HIV RNA levels of 0.5 log10 copies/ml and that resistance to adefovir dipivoxil
did not arise during that period. In the present investigation, a
further study was undertaken to investigate whether RT mutations
developed among viruses from patients who completed the 12-week study
and who opted to enroll in a maintenance phase of prolonged (6- to
12-month) adefovir dipivoxil therapy (120 mg daily). Concomitant
treatment with antiretroviral agents was permitted during the
maintenance phase. The median decreases in HIV RNA levels for patients
who completed 6 or 12 months of maintenance-phase dosing were 0.6 and
1.14 log10 copies/ml, respectively. The reductions in the
HIV RNA levels were similar among patients who received adefovir
dipivoxil with or without concomitant treatment with antiretroviral
agents. Viruses from 8 of 29 patients dosed for up to 12 months
developed RT mutations that were not present at baseline; these
mutations may have been related to adefovir dipivoxil therapy. Viruses
from two of the eight patients developed the K70E mutation while the
patients were on therapy, but none of the viruses from patients
developed the K65R RT substitution. Despite the development of RT
mutations, sustained reductions (6 to 12 months) in viral load (
0066-4804/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Genotypic and Phenotypic Characterization of Human
Immunodeficiency Virus Type 1 Variants Isolated from AIDS Patients
after Prolonged Adefovir Dipivoxil Therapy
0.7
log10 copies/ml decrease from baseline) were observed in
all eight patients.
*
Corresponding author. Mailing address: Gilead Sciences,
Inc., 333 Lakeside Dr., Foster City, CA 94404. Phone: (650) 573-4837. Fax: (650) 573-4890. E-mail:
julie_cherrington{at}gilead.com.
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