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Abstract
Resistance profile after treatment with an atazanavir-containing regimen: first interim analysis results from the IMPACT study (BMS AI424-128)
A. Zolopa1, W. Towner2, C. Zurawski3, G. Crofoot4, D. Butcher5, S. Wang5, J.F. Maa5, D. Seekins5
Background: The I50L substitution, previously shown to maintain or increase the susceptibility of HIV-1 to other protease inhibitors (PIs), was observed in treatment-naive patients developing resistance at virologic failure (VF) on atazanavir (ATV)-containing regimens. Treatment-naive patients treated with ATV/ritonavir (ATV/r) were not observed to evolve primary PI mutations. Treatment-experienced patients were observed to evolve resistance through alternate pathways. To expand upon these clinical trial observations, a large observational study is being conducted.
Methods: IMPACT is an observational, cross-sectional study of patients experiencing VF while on an atazanavir-containing regimen. This planned interim analysis includes patients enrolled from September 2004 through October 2005 at 230 US centers. VF was defined as confirmed HIV-1 RNA by PCR (VL) ³1000 copies/mL after either (1) VL ³1000 copies/mL after achieving a confirmed VL <400 copies/mL, or (2) VL ³1000 copies/mL after ³24 weeks of ATV therapy. Demographic information, complete antiretroviral history, CD4, VL, and genotype were collected.
Results: Among 128 patients enrolled, most had advanced disease: median HIV duration 13.1 years, median CD4 187 cells/mm3, and 55% CDC stage C. Median ATV exposure was 16 months. Overall, 12 (9.4%) had I50L. 116/128 (91%) were PI-experienced, including all 12 I50L patients. Among 12 with VF on initial PI therapy with ATV or ATV/r, no primary PI mutations developed, including I50L. I50L prevalence was 3/24 (12.5%) for ATV and 9/104 (8.7%) for ATV/r at VF, regardless of treatment experience. Ritonavir-boosted PI (PI/r) use prior to ATV was associated with a lower prevalence of I50L (p = 0.033).
Conclusions: In this cohort, primary PI mutations, including I50L, were not seen at VF in patients on initial PI-based therapy with ATV/r. The prevalence of I50L in PI-experienced patients experiencing VF on an ATV-containing regimen was 10%. Use of PI/r prior to ATV/r appeared to reduce the prevalence of I50L.
AIDS 2006 - XVI International AIDS Conference
Abstract no.
THPE0099
Suggested Citation
"A.Zolopa, et al.
Resistance profile after treatment with an atazanavir-containing regimen: first interim analysis results from the IMPACT study (BMS AI424-128).
:
AIDS 2006 - XVI International AIDS Conference:
Abstract no.
THPE0099"
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