Purpose / DescriptionHAART is generally based on the combination of three active drugs. Two of them, usually defined the backbone, belong to the nucleosidic analogues class (NRTI). In the last years, drugs of this class have been associated to several long-term adverse events of HAART such as lipoatrophy, cardiovascular diseases, bone and kidney toxicity. Furthermore the need of a triple drug regimen has recently been questioned as maintenance therapy in well controlled chronically treated subjects. In this setting, less drug regimens (LDR) have been proposed. LDR would allow a reduced exposure to drugs and eventually limit drug-drug interactions, drug-related toxicities and would allow treatment simplification so to enhance HAART acceptability, tolerability and persistence.