New class of HIV integrase inhibitors that block viral replication in cell culture

To improve the existing combination therapies of infection with the human immunodeficiency virus (HIV) and to cope with virus strains that are resistant to multiple drugs, we initiated a search for effective inhibitors of HIV integrase, the enzyme responsible for inserting the viral cDNA into the host cell chromosome.

We have now identified a series of 5H-pyrano[2,3-d:-6,5-d']dipyrimidines that block the replication of various strains of HIV-1 and HIV-2. The most potent congener, 5-(4-nitrophenyl)-2,8-dithiol-4,6-dihydroxy-5H-pyrano[2,3-d:-6,5-d']dipyrimidine (V-165), inhibited the replication of HIV-1(III(B)) in MT-4 cells at a 50% effective concentration (EC(50)) of 8.9 microM, which is 14-fold below its cytotoxic concentration. V-165 was equally active against virus strains that were resistant toward inhibitors of viral entry or reverse transcriptase. In combination regimens in cell culture, V-165 acted subsynergistically with zidovudine or nelfinavir and synergistically with nevirapine. V-165 inhibited both reverse transcriptase and integrase activities in enzymatic assays at micromolar concentrations, but only a close correlation was found between the anti-HIV activity observed in cell culture and the inhibitory activity in the integrase strand transfer assays. Time-of-addition experiments indicated that V-165 interfered with the viral replication cycle at a time point coinciding with integration. Quantitative Alu-PCR corroborated that the anti-HIV activity of V-165 is based upon the inhibition of proviral DNA integration.

Based on their mode of action, which is different from that of clinically approved anti-HIV drugs, PDPs are good candidates for further development into new drugs and to be included in future combination regimens.