The increasing incidence of resistance to current HIV-1 therapy underscores the need to develop antiretroviral agents with new mechanisms of action. Integrase, one of three viral enzymes essential for HIV-1 replication, presents an important yet unexploited opportunity for drug development. We describe here the identification and characterization of L-870,810, a small-molecule inhibitor of HIV-1 integrase with potent antiviral activity in cell culture and good pharmacokinetic properties. L-870,810 is an inhibitor with an 8-hydroxy-(1,6)-naphthyridine-7-carboxamide pharmacophore. The compound inhibits HIV-1 integrase-mediated strand transfer, and its antiviral activity in vitro is a direct consequence of this ascribed effect on integration. L-870,810 is mechanistically identical to previously described inhibitors from the diketo acid series; however, viruses selected for resistance to L-870,810 contain mutations (integrase residues 72, 121, and 125) that uniquely confer resistance to the naphthyridine. Conversely, mutations associated with resistance to the diketo acid do not engender naphthyridine resistance. Importantly, the mutations associated with resistance to each of these inhibitors map to distinct regions within the integrase active site. Therefore, we propose a model of the two inhibitors that is consistent with this observation and suggests specific interactions with discrete binding sites for each ligand. These studies provide a structural basis and rationale for developing integrase inhibitors with the potential for unique and nonoverlapping resistance profiles.A gents for the treatment of HIV-1 infection target two of the three virally encoded enzymes and belong to three mechanistic classes known as nucleoside reverse transcriptase, nonnucleoside reverse transcriptase (NNRTI), and protease inhibitors. Although treatment regimens comprising combinations of these agents have significantly reduced AIDS-related morbidity and mortality, it is estimated that 78% of treatment-naive patients harbor viruses that have evolved resistance to at least one of these drug classes (1, 2). The emergence of HIV-1 strains resistant to reverse transcriptase and protease inhibitors highlights the need to develop antiviral agents with novel mechanisms of action.Integrase (3, 4), one of the three virally encoded enzymes required for HIV-1 replication, catalyses the integration of viral DNA into the genome of the host cell. The integration reaction requires three discrete steps: assembly of a stable preintegration complex at the termini of the viral DNA and two sequential transesterification reactions. In the first reaction, 3Ј-end processing, endonucleolytic cleavage of the two 3Ј nucleotides at each DNA end generates 3Ј-hydroxyl groups that function as nucleophiles in the second reaction. The strand breakage of the cellular DNA and concomitant covalent linkage to the viral DNA is a consequence of the second transesterification reaction, strand transfer.The discovery of a series of diketo acids containing HIV-1 integrase i...

We describe the efficacy of L-870812, an inhibitor of HIV-1 and SIV integrase, in rhesus macaques infected with the simian-human immunodeficiency virus (SHIV) 89.6P. When initiated before CD4 cell depletion, L-870812 therapy mediated a sustained suppression of viremia, preserving CD4 levels and permitting the induction of virus-specific cellular immunity. L-870812 was also active in chronic infection; however, the magnitude and durability of the effect varied in conjunction with the pretreatment immune response and viral load. These studies demonstrate integrase inhibitor activity in vivo and suggest that cellular immunity facilitates chemotherapeutic efficacy in retroviral infections.

A series of HIV protease inhibitors possessing a hydroxylaminepentanamide transition state isostere have been developed. Incorporation of a basic amine into the backbone of the L-685,434 (2) series provided antiviral potency combined with a highly improved pharmacokinetic profile in animal models. Guided by molecular modeling and an X-ray crystal structure of the inhibited enzyme complex, we were able to design L-735,524. This compound is potent and competitively inhibits HIV-1 PR and HIV-2 PR with Ki values of 0.52 and 3.3 nM, respectively. It also stops the spread of the HIV-1IIIb-infected MT4 lymphoid cells at concentrations of 25-50 nM. To date, numerous HIV-PR inhibitors have been reported, but few have been studied in humans because they lack acceptable oral bioavailability. L-735,524 is orally bioavailable in three animals models, using clinically acceptable formulations, and is currently in phase II human clinical trials.

Naphthyridine 7 inhibits the strand transfer of the integration process catalyzed by integrase with an IC50 of 10 nM and inhibits 95% of the spread of HIV-1 infection in cell culture at 0.39 microM. It does not exhibit cytotoxicity in cell culture at < or =12.5 microM and shows a good pharmacokinetic profile when dosed orally to rats. The antiviral activity of 7 and its effect on integration were confirmed using viruses with specific integrase mutations.

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