December 16, 2005
What is the role of dual-boosted protease inhibitors (PIs) in HIV therapy? Initially devised as a strategy for treatment-experienced patients with drug resistant virus, dual-boosted PIs have also drawn interest as potential nucleoside reverse transcriptase inhibitor (NRTI)-sparing treatment options. In this pilot study, a dual-boosted PI was compared with a standard two NRTI/boosted PI approach.
Sixteen treatment-naive patients were enrolled; all received lopinavir/ritonavir (LPV/r, Kaletra) at standard doses, and were randomized to receive either zidovudine/lamivudine (AZT/3TC, Combivir) one tablet twice daily or saquinavir (SQV, Invirase) four 200-mg capsules twice daily.
At baseline, the HIV RNA was approximately 5 log copies/mL in both groups; by chance, the zidovudine/lamivudine group had a significantly lower CD4+ cell count (120) than the saquinavir group (269).
At the end of 48 weeks, 50% of the zidovudine/lamivudine-treated patients and 63% of the dual-boosted PI patients had an undetectable HIV RNA, a non-significant difference. CD4+ responses were also similar. Treatment discontinuations due to adverse effects occurred in 3 patients in the zidovudine/lamivudine group and 1 patient in the saquinavir group. No differences between the groups were seen with regards to changes in lipids or fasting glucose.
A strength of this study is that it was prospective and randomized; most studies of dual-boosted PIs have been single-arm or retrospective. However, given the small sample size, no definitive conclusions can be made about the relative success of dual-boosted PIs vs. standard therapy, or even about whether using two PIs is more effective than one PI boosted with ritonavir.
Over time, as our NRTI choices have become less toxic, the need for NRTI-sparing therapies has somewhat declined. Of note, since the conduct of this study, a 500-mg tablet of saquinavir and an improved formulation of lopinavir/ritonavir have now become available -- this would reduce the daily pill burden of the PI-only strategy from 14 to 8 pills a day.
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