Past
studies have shown that NRTI-only regimens are less potent overall that PI- or
NNRTI-based regimens, but may be suitable for certain patients such as those with
low baseline viral loads.
At
the 8th Annual International Congress on Drug Therapy in HIV Infection (HIV8)
held last week in Glasgow, researchers presented data from a 48-week study of
122 treatment-experienced patients taking a single-class regimen consisting of
tenofovir DF (Viread) plus the
AZT/3TC/abacavir fixed-dose combination
pill (Trizivir).
Of
the 122 subjects, 35 were initially on Trizivir alone, and tenofovir was added
to intensify the regimen. Others had achieved virological suppression on other
regimens, but switched to the NRTI-only combination due to toxicity.
Results
•
At baseline, participants
had a median viral load of 406 copies/mL and a median CD4 cell count of 281 cells/mm3.
•
In an intent-to-treat
analysis at Week 48, the median viral load was 78 copies/mL and the median CD4
count was 321 cells/mm3.
•
These included 11 out
of 27 subjects with HIV RNA above 100,000 copies/mL at baseline.
•
Only 3 patients experienced
virological failure after Week 24.
•
For the 80 patients
who remained on therapy, viral load continued to drop after Week 24, to a sustained
suppression below 50 copies/mL, and CD4 count rose to 402 cells/mm3.
•
24 of the 35 patients
failing Trizivir alone responded to Trizivir plus tenofovir.
•
54 of 61 patients who
switched to Trizivir plus tenofovir due to toxicity (baseline viral load 400 copies/mL
or less) experienced stable or improved virological suppression.
•
Significant predictors
of virological response were: - baseline viral load below 5000 copies/mL (P
< 0.001); - baseline CD4 count of 200 cells/mm3 or greater (P < 0.001).
•
Among the 85 subjects
for whom genotypic resistance results were available, the only predictor of virological
failure was the 41L+210W+215Y/F mutational pattern (P = 0.03).
Conclusion
"Patients
on a failing NRTI-only regimen showed virologic response after tenofovir intensification,"
the researchers concluded. "Patients who failed virologically did so early.
Baseline viral load < 5000 copies was a significant predictor for response.
Mono-class tenofovir plus Trizivir therapy showed increasing efficacy even after
24 weeks, which was maintained out to 48 weeks."
11/21/06
Reference B
Dauer, P Khaykin, P Gute, and others. Response to mono-class nucleoside regimen
of tenofovir DF + trizivir in antiretroviral-experienced patients: 48 week results
and predictors of response. 8th Annual International Congress on Drug Therapy
in HIV Infection. Glasgow, UK. November 12-16, 2006. Abstract P27.
