Switching to boosted protease inhibitor plus a second antiretroviral drug (dual therapy) for treatment simplification: a multicenter analysis.

Background: To assess the role of drugs used in dual therapy (DT), as cART simplification, over the risk of treatment failure.
Materials and Methods: Patients starting DT regimen composed by a boosted protease inhibitor (PI/r): darunavir (DRV/r), lopinavir (LPVr) or atazanavir (ATV/r) plus a second drug: raltegravir (RAL), maraviroc (MRV) etravirine (ETR), lamivudine (3TC) or tenofovir (TDF), this one generally used in HBV co-infected patients, were included. The effect of each drug as well as other clinical and virological cofactors over treatment failure was assessed using survival analysis.
Results: Overall, 480 patients from six reference Italian centres were included: all switched to DT with HIV-RNA <500 cp/µL, 376 of them at <50 cp/µL. Patients who switched at <50 cp/µL showed a significant lower risk of treatment failure (13.3% versus 23.3% at 1 year and 28.0% versus 44.6% at 3 years, p=0.005), thus the analysis was focused on this subgroup. Among the patients who switched at <50 cp/µL, the proportion of drug used in DT was: DRV/r 63.0%, RAL 53.7%, ETR 19.4%, ATV/r 18.4%, MRV 17.3%, LPV/r 12.8%, TDF 6.4% and 3TC 5.9%; DRV/r-RAL was the most widely used combination: 32.5%. Treatment failure was observed in 78 patients, of whom 38 virological and 35 for toxicity/intolerance, one patient died during follow-up and four patients interrupted for personal decision with undetectable HIV-RNA. At Cox Model, adjusted by gender, age, non-Italian origin, AIDS diagnosis, time on cART, number of regimens, CD4 nadir, baseline CD4, all the drugs had a positive effect on probability of failure (Figure), however the effect was significant for DRV/r (HR:0.21, 95% CI 0.07-0.59, p=0.03), ATV/r (0.30, 0.09-0.97, p=0.044) and RAL (0.37, 0.15-0.93, p=0.034); higher CD4 count at baseline was also associated with lower risk of failure while number of previous regimens with a higher risk. Moreover, ATV/r was found significant associated with significant higher risk of failure by toxicity (as well as LPV/r) but lower risk of virological failure, while both 3TC and RAL with significant lower risk of toxicity.
Conclusions: Our analysis suggest that using PI/r-based DL is highly effective if switching from HIV-RNA <50 cp/µL; DL should be used with caution in patients with low CD4 count and longer history of treatment; DRV/r is the best compromise among PI/r, ATV/r is effective but is associate with frequent interruption by toxicity; RAL showed high tolerability so that its use is related to the lowest risk of failure as second drug.