A naphthyridine carboxamide provides evidence for discordant resistance between mechanistically identical inhibitors of HIV-1 integrase

Abstract

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...

Biochemical Analysis of HIV-1 Integrase Variants Resistant to Strand Transfer Inhibitors

“…The N155H, Q148R, and E92Q enzymes were all between 4 and 15% as efficient as WT, with N155H being the weakest single variant (4%). The N155S virus has been reported to be less fit than WT (42,43), and the N155E, N155K, and N155L variants were reported to have 6% of WT strand transfer activity (44), similar to the N155H results reported here. T66I had a relative efficiency of 36%, indicating that this enzyme is not much altered catalytically, as compared with WT, similar to what has been reported previously (38).…”

The Terminal (Catalytic) Adenosine of the HIV LTR Controls the Kinetics of Binding and Dissociation of HIV Integrase Strand Transfer Inhibitors

“…Published models of HIV IN (19,22) suggest that these specific STIs bind to the IN active site in a pocket flanked by the end of the LTR such that the diketoacid moiety, or its mimic, is positioned to coordinate with both of the catalytic magnesium atoms (23)(24)(25) (14,19,22,(26)(27)(28)(29). Amino acid substitutions which confer resistance to STIs cluster around the IN active site (30)(31)(32)(33)(34)(35)(36)(37), and changes to the 5′ end of the LTR reduce the affinity of a specific STI for its binding site (16). Published models do not address the issue of the precise placement of the 3′ terminus of the viral LTR in the inhibitor-bound state.…”

Novel fused tetrathiocines as antivirals that target the nucleocapsid zinc finger containing protein of the feline immunodeficiency virus (FIV) as a model of HIV infection

“…The activity of AZT and Raltegravir are consistent with previous reports in FIV/HIV. 51,52 Overall, these results indicate that the nucleocapsid protein of FIV can be targeted effectively with symmetrical dual functionality compounds with high efficacy. The relative simplicity and tractability of the synthetic approach makes these compounds attractive for further development and optimization.…”