Background of study: LPV/r and APV have recently been used as dual PI-containing salvage ARV therapy. However, when coadministered with LPV/r, APV levels have been observed to be lower in some patients as compared to historical controls. Limited clinical data is available on the LPV/r and APV PI combination.
Objective: To compare the HIV RNA viral load (VL) and CD4 immunologic responses between ARV-experienced patients on salvage therapy containing both LPV/r and APV versus LPV/r as the sole PI.
Design: A retrospective cohort study of HIV-infected patients with virologic failure who were switched to a LPV/r-containing salvage regimen. Patients were analysed in two groups: those who received APV (750 mg bid) plus LPV/r (400mg/100mg bid or 533mg/133mg bid if on NNRTI) and those who received LPV/r as the sole PI. Patient demographics, baseline clinical and laboratory markers were compared. Continuous variables were compared using the student t-test and categorical variables using chi-square. The proportion of patients who achieve a VL < 50 copies/mL and those who achieve a > one log VL decrease was compared between the two groups using an on-treatment analysis using chi-square. The change in CD4 count between the groups was
compared using the Wilcoxon rank sum test. The virologic and immunologic responses were compared at multiple time periods: 1-2 months, 3-5 months and 6-12 months.
Results: 33 patients were initiated on a salvage regimen that contained APV and LPV/r while 35 were on LPV/r as the sole PI for a mean of 5.6 months (1-11 months). The groups were equivalent in gender, age, HIV risk factors, baseline VL, baseline CD4 count and proportion who were NNRTI-naïve. A larger proportion of Caucasians received APV and LPV/r (p=0.02). The APV/LPV/r group had been diagnosed with HIV for longer (11.7 vs. 9.9 years, p=0.03) and had received more ARV agents previously (9.2 vs. 8.2, p=0.11). The on-treatment analysis revealed that the virologic responses were the same in the two groups at all time periods with 33.3% of patients receiving APV/LPV/r achieving a VL < 50 copies/mL at any one time period compared
to 37.1% in the LPV/r only group (p=0.74). By 3-5 months the APV/LPV/r group had a CD4 count increase of 76 cells/µL compared to 32 cells/µL (p=0.12).
Conclusion: In this retrospective cohort study, the combination of APV and LPV/r in salvage therapy had no virologic disadvantage over LPV/r alone. However, a larger sample size would be required to determine if there was a statistically significant difference in the virologic or CD4 response to the combination PI.
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