 R100943, in the horseshoe mode of binding, is located at a distance of approximately 6.0 Å from G190.When compared with nevirapine and loviride which bind in the butterfly shape the ITU derivatives revealed improved activity against Tyr-181C and Tyr-188L mutants.A structural study suggested that a potent TIBO compound could partly supplement for the effects of the Tyr-181C mutation by moving itself in the non-nucleoside inhibitor binding pocket (NNIBP) of the mutant RT.