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. Here, CD4 is linked to AIDS.