Protease inhibitor monotherapy as maintenance regimen in patients with HIV infection

Despite the remarkable success of combination antiretroviral therapy, usually including the association of three antiretroviral drugs selected from two different classes, the possibility of treating HIV-infected patients with one single potent agent as simplified maintenance regimen has attracted clinicians and researchers over the past years. Monotherapy with one ritonavir-boosted protease inhibitor in subjects with persistently suppressed plasma HIV RNA offers several potential advantages, such as avoiding the long-term toxicity associated with nucleoside/nucleotide analog, reducing costs, preventing drug-drug interactions, and preserving future treatment options. Several controlled and uncontrolled studies have assessed efficacy and safety of this monotherapy strategy, and the majority of available data concern lopinavir/ritonavir and darunavir/ritonavir. The virological efficacy of these boosted protease inhibitors as monotherapy is slightly lower than that of standard therapy, but the risk of resistance development is minimal and the re-introduction of nucleoside analogues usually leads to a re-suppression of the plasma viral load. Even though currently there is no consensus about the clinical use of protease inhibitor monotherapy for the treatment of HIV infection, this strategy seems an option for selected patients on stable combination therapy, with persistently suppressed plasma viral load, and without a history of virologic failure while receiving protease inhibitors. The aim of this article is to review and summarize the most recent randomized and observational studies which have evaluated efficacy and safety of the protease inhibitor monotherapy.