Binding of the second generation non-nucleoside inhibitor S-1153 to HIV-1 reverse transcriptase involves extensive main chain hydrogen bonding

S-1153 (AG1549) is perhaps the most promising nonnucleoside inhibitor of HI V-1 reverse transcriptase currently under development as a potential anti-A IDS drug, because it has a favorable profile of resilience to many drug res istance mutations. We have determined the crystal structure of S-1153 in a complex with HIV-1 reverse transcriptase, The complex possesses some novel features, including an extensive network of hydrogen bonds involving the ma in chain of residues 101, 103, and 236 of the p66 reverse transcriptase sub unit, Such interactions are unlikely to be disrupted by side chain mutation s. The reverse transcriptase/S-1153 complex suggests different ways in whic h resilience to mutations in the non-nucleoside inhibitors of reverse trans criptase binding site can be achieved.