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Viread
(tenofovir) Is As Potent as Norvir (ritonavir) in Monotherapy Study
By
Brian Boyle, MD
The underlying potency
of individual antiretrovirals is an important factor in selecting
the antiretrovirals that will be used in an effective highly active
antiretroviral therapy (HAART) regimen.
However,
since most trials involve a combination of at least 3 antiretrovirals,
only limited data exist regarding the potency of monotherapy with
a particular, individual antiretroviral.
In an open-label, single-site
study published in AIDS, investigators at Rockefeller University
evaluated the efficacy of Viread
(tenofovir disoproxil fumarate) monotherapy. The study followed
the initial rate of decline in plasma viral load – a measure of
the efficacy of the antiretroviral at blocking viral replication
– that resulted from 21 days of Viread monotherapy in 10 antiretroviral-naïve,
chronically HIV-1-infected patients. The data collected from these
patients was then compared with those previously collected in a
Norvir (ritonavir) monotherapy study.
The investigators found
that during the 21 days of Viread monotherapy, the patients experienced
a mean plasma HIV-1 RNA level decrease of 1.5 log10 copies/ml
(range, 0.7–2.0). The initial rates of decline in plasma HIV-1 RNA
in the Viread treated patients and in 20 protease inhibitor-naive
subjects treated with Norvir monotherapy were nearly identical,
with average viral decay slopes for Viread and Norvir of 0.39/day
and 0.34/day, respectively.
Finally, in 8 of the
10 patients post-treatment resistance testing could be performed
and none were found to have developed new mutations following the
21 days of Viread monotherapy.
The authors conclude,
“The reduction in plasma HIV-1 RNA with [Viread] monotherapy was
comparable with the decline observed in previous studies of protease
inhibitor monotherapy. [Viread] is a potent antiretroviral agent
and has comparable inherent antiviral activity with that of [Norvir],
a potent protease inhibitor.
“These data support further
study of [Viread]-based regimens in simplified combinations of antiviral
agents as initial treatment for chronic HIV-1 infection.”
05/23/03
Reference
M Louie and others. Determining
the antiviral activity of tenofovir disoproxil fumarate in treatment-naive
chronically HIV-1-infected individuals AIDS 2003, 17:1151–1156.
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