Integrase inhibitors currently include raltegravir and elvitegravir. To date, there is considerably less data on the resistance characteristics of the integrase inhibitors, due to their limited use to date. However, some data have been gathered from the developmental clinical trials.

Analysis has shown that the majority of amino acids on the integrase gene are polymorphic; i.e., there is variability within the amino acids typically found at most of the sites, although some areas of the integrase gene are more conserved than others. This is in contrast to the much more "conserved" nature of the protease and reverse transcriptase genes. Integrase-inhibitor resistance mutations have been identified, many of which seem to appear among the naturally-occurring variations (polymorphisms) in the integrase gene. These include T97A and K156N.

Other mutations that do not appear as natural variants include: T66I, L74M, F121Y, T125K, G140S, S230R, V249I and C280Y^[1][2].

The Stanford database identifies E92Q, Q148HRK, and N155H as conferring significant resistance to both raltegravir and elvitegravir ^[3]. IAS-USA concurs that Q148HRK and N155H are major raltegravir mutations but omits E92 and does not provide data for elvitegravir ^[4].