Xue Zhi Zhao

MK-0536 inhibits HIV-1 integrases resistant to raltegravir

ABSTRACT With the U.S. Food and Drug Administration approval of raltegravir (RAL; MK-0518; Merck & Co.), HIV-1 integrase (IN) is the newest therapeutic target for AIDS and HIV infections. Recent structural analyses show that IN strand transfer inhibitors (INSTIs) share a common binding mode in the enzyme active site. While RAL represents a therapeutic breakthrough, the emergence of IN resistance mutations imposes the development of new INSTIs. We report here the biochemical and antiviral activities of MK-0536, a new IN inhibitor. We demonstrate that, like RAL, MK-0536 is highly potent against recombinant IN and viral replication. It is also effective against INs that carry the three main RAL resistance mutations (Y143R, N155H, and to a lesser extent G140S-Q148H) and against the G118R mutant. Modeling of IN developed from recent prototype foamy virus structures is presented to account for the differences in the drug activities of MK-0536 and RAL against the IN mutants.

Diketoacid – Genre HIV-1 Integrase Inhibitors Containing Enantiomeric Arylamide Functionality

Using our recently disclosed 2,3-dihydro-6,7-dihydroxy-1H-isoindol-1-one and 4,5-dihydroxy-1H-isoindole-1,3(2H)-dione integrase inhibitors, we report differential effects on inhibitory potency induced by introduction of an alpha-chiral center into a key aryl substituent. We show that introduction of the chiral center is uniformly deleterious to binding, with the (R)-enantiomer being more deleterious than the (S)-enantiomer. A greater enantiomeric difference in potency is shown by inhibitors that have restricted rotation of the aryl ring, with the larger difference being due to poorer potency of the (R)-enantiomer rather than higher potency of the (S)-enantiomer. The potency difference for enantiomers based on the isoindoline-1,3-dione ring system is less than for those derived from the isoindol-1-one ring system. Our findings provide useful information that should aid in understanding molecular binding interactions of DKA-derived IN inhibitors.

Activities, Crystal Structures and Molecular Dynamics of Dihydro-1H-Isoindole Derivatives, Inhibitors of HIV-1 Integrase.

On the basis of a series of lactam and phthalimide derivatives that inhibit HIV-1 integrase, we developed a new molecule, XZ-259, with biochemical and antiviral activities comparable to raltegravir. We determined the crystal structures of XZ-259 and four other derivatives in complex with the prototype foamy virus intasome. The compounds bind at the integrase-Mg(2+)-DNA interface of the integrase active site. In biochemical and antiviral assays, XZ-259 inhibits raltegravir-resistant HIV-1 integrases harboring the Y143R mutation. Molecular modeling is also presented suggesting that XZ-259 can bind in the HIV-1 intasome with its dimethyl sulfonamide group adopting two opposite orientations. Molecular dynamics analyses of the HIV-1 intasome highlight the importance of the viral DNA in drug potency.

Bicyclic 1-Hydroxy-2-oxo-1,2-dihydropyridine-3-carboxamide-Containing HIV-1 Integrase Inhibitors Having High Antiviral Potency against Cells Harboring Raltegravir-Resistant Integrase Mutants

Integrase (IN) inhibitors are the newest class of antiretroviral agents developed for the treatment of HIV-1 infections. Merck’s Raltegravir (RAL) (October 2007) and Gilead’s Elvitegravir (EVG) (August 2012), which act as IN strand transfer inhibitors (INSTIs), were the first anti-IN drugs to be approved by the FDA. However, the virus develops resistance to both RAL and EVG, and there is extensive cross-resistance to these two drugs. New “2nd-generation” INSTIs are needed that will have greater efficacy against RAL- and EVG-resistant strains of IN. The FDA has recently approved the first second generation INSTI, GSK’s Dolutegravir (DTG) (August 2013). Our current article describes the design, synthesis, and evaluation of a series of 1,8-dihydroxy-2-oxo-1,2-dihydroquinoline-3-carboxamides, 1,4-dihydroxy-2-oxo-1,2-dihydro-1,8-naphthyridine-3-carboxamides, and 1-hydroxy-2-oxo-1,2-dihydro-1,8-naphthyridine-3-carboxamides. This resulted in the identification of noncytotoxic inhibitors that exhibited single digit nanomolar EC50 values against HIV-1 vectors harboring wild-type IN in cell-based assays. Importantly, some of these new inhibitors retain greater antiviral efficacy compared to that of RAL when tested against a panel of IN mutants that included Y143R, N155H, G140S/Q148H, G118R, and E138K/Q148K.

Examination of halogen substituent effects on HIV-1 integrase inhibitors derived from 2,3-dihydro-6,7-dihydroxy-1H-isoindol-1-ones and 4,5-dihydroxy-1H-isoindole-1,3(2H)-diones

Using 2,3-dihydro-6,7-dihydroxy-1H-isoindol-1-one and 4,5-dihydroxy-1H-isoindole-1,3(2H)-dione based HIV-1 integrase inhibitors as display platforms, we undertook a thorough examination of the effects of modifying the halogen substituents on a key benzyl ring that is hypothesized to bind in a hydrophobic pocket of the integrase.DNA complex. Data from this study suggest that in general dihalo-substituted analogues have higher potency than monohalo-substituted compounds, but that further addition of halogens is not beneficial.

HIV Integrase Inhibitors Block Replication of Alpha-, Beta-, and Gammaherpesviruses

ABSTRACT The catalytic site of the HIV integrase is contained within an RNase H-like fold, and numerous drugs have been developed that bind to this site and inhibit its activity. Herpes simplex virus (HSV) encodes two proteins with potential RNase H-like folds, the infected cell protein 8 (ICP8) DNA-binding protein, which is necessary for viral DNA replication and exhibits recombinase activity in vitro, and the viral terminase, which is essential for viral DNA cleavage and packaging. Therefore, we hypothesized that HIV integrase inhibitors might also inhibit HSV replication by targeting ICP8 and/or the terminase. To test this, we evaluated the effect of 118-D-24, a potent HIV integrase inhibitor, on HSV replication. We found that 118-D-24 inhibited HSV-1 replication in cell culture at submillimolar concentrations. To identify more potent inhibitors of HSV replication, we screened a panel of integrase inhibitors, and one compound with greater anti-HSV-1 activity, XZ45, was chosen for further analysis. XZ45 significantly inhibited HSV-1 and HSV-2 replication in different cell types, with 50% inhibitory concentrations that were approximately 1 µM, but exhibited low cytotoxicity, with a 50% cytotoxic concentration greater than 500 µM. XZ45 blocked HSV viral DNA replication and late gene expression. XZ45 also inhibited viral recombination in infected cells and ICP8 recombinase activity in vitro. Furthermore, XZ45 inhibited human cytomegalovirus replication and induction of Kaposi’s sarcoma herpesvirus from latent infection. Our results argue that inhibitors of enzymes with RNase H-like folds may represent a general antiviral strategy, which is useful not only against HIV but also against herpesviruses. IMPORTANCE The herpesviruses cause considerable morbidity and mortality. Nucleoside analogs have served as effective antiviral agents against the herpesviruses, but resistance can arise through viral mutation. Second-line anti-herpes drugs have limitations in terms of pharmacokinetic properties and/or toxicity, so there is a great need for additional drugs for treatment of herpesviral infections. This study showed that the HIV integrase inhibitors also block herpesviral infection, raising the important potential of a new class of anti-herpes drugs and the prospect of drugs that combat both HIV and the herpesviruses. The herpesviruses cause considerable morbidity and mortality. Nucleoside analogs have served as effective antiviral agents against the herpesviruses, but resistance can arise through viral mutation. Second-line anti-herpes drugs have limitations in terms of pharmacokinetic properties and/or toxicity, so there is a great need for additional drugs for treatment of herpesviral infections. This study showed that the HIV integrase inhibitors also block herpesviral infection, raising the important potential of a new class of anti-herpes drugs and the prospect of drugs that combat both HIV and the herpesviruses.

Bicyclic hydroxy-1H-pyrrolopyridine-trione containing HIV-1 integrase inhibitors.

HIV‐1 integrase (IN) is a validated therapeutic target for the treatment of AIDS. However, the emergence of resistance to raltegravir, the sole marketed FDA‐approved IN inhibitor, emphasizes the need to develop second‐generation inhibitors that retain efficacy against clinically relevant IN mutants. We report herein bicyclic hydroxy‐1H‐pyrrolopyridine‐triones as a new family of HIV‐1 integrase inhibitors that were efficiently prepared using a key ‘Pummerer cyclization deprotonation cycloaddition’ cascade of imidosulfoxides. In in vitro HIV‐1 integrase assays, the analogs showed low micromolar inhibitory potencies with selectivity for strand transfer reactions as compared with 3′‐processing inhibition. A representative inhibitor (5e) retained most of its inhibitory potency against the three major raltegravir‐resistant IN mutant enzymes, G140S/Q148H, Y143R, and N155H. In antiviral assays employing viral vectors coding these IN mutants, compound 5e was approximately 200‐ and 20‐fold less affected than raltegravir against the G140S/Q148H and Y143R mutations, respectively. Against the N155H mutation, 5e was approximately 10‐fold less affected than raltegravir. Thus, our new compounds represent a novel structural class that may be further developed to overcome resistance to raltegravir, particularly in the case of the G140S/Q148H mutations.

HIV-1 Integrase Strand Transfer Inhibitors with Reduced Susceptibility to Drug Resistant Mutant Integrases.

HIV integrase (IN) strand transfer inhibitors (INSTIs) are among the newest anti-AIDS drugs; however, mutant forms of IN can confer resistance. We developed noncytotoxic naphthyridine-containing INSTIs that retain low nanomolar IC50 values against HIV-1 variants harboring all of the major INSTI-resistant mutations. We found by analyzing crystal structures of inhibitors bound to the IN from the prototype foamy virus (PFV) that the most successful inhibitors show striking mimicry of the bound viral DNA prior to 3′-processing and the bound host DNA prior to strand transfer. Using this concept of “bi-substrate mimicry,” we developed a new broadly effective inhibitor that not only mimics aspects of both the bound target and viral DNA but also more completely fills the space they would normally occupy. Maximizing shape complementarity and recapitulating structural components encompassing both of the IN DNA substrates could serve as a guiding principle for the development of new INSTIs.

6,7-Dihydroxy-1-oxoisoindoline-4-sulfonamide-containing HIV-1 Integrase Inhibitors

Although an extensive body of scientific and patent literature exists describing the development of HIV-1 integrase (IN) inhibitors, Mercks raltegravir and Gileads elvitegravir remain the only IN inhibitors FDA-approved for the treatment of AIDS. The emergence of raltegravir-resistant strains of HIV-1 containing mutated forms of IN underlies the need for continued efforts to enhance the efficacy of IN inhibitors against resistant mutants. We have previously described bicyclic 6,7-dihydroxyoxoisoindolin-1-ones that show good IN inhibitory potency. This report describes the effects of introducing substituents into the 4- and 5-positions of the parent 6,7-dihydroxyoxoisoindolin-1-one platform. We have developed several sulfonamide-containing analogs that enhance potency in cell-based HIV assays by more than two orders-of-magnitude and we describe several compounds that are more potent than raltegravir against the clinically relevant Y143R IN mutant.

Comparison of metal-dependent catalysis by HIV-1 and ASV integrase proteins using a new and rapid, moderate throughput assay for joining activity in solution.

BackgroundHIV-1 integrase (IN) is an attractive target for the development of drugs to treat AIDS, and inhibitors of this viral enzyme are already in the clinic. Nevertheless, there is a continuing need to devise new approaches to block the activity of this viral protein because of the emergence of resistant strains. To facilitate the biochemical analysis of wild-type IN and its derivatives, and to measure the potency of prospective inhibitory compounds, a rapid, moderate throughput solution assay was developed for IN-catalyzed joining of viral and target DNAs, based on the detection of a fluorescent tag.ResultsA detailed, step-by-step description of the new joining assay is provided. The reactions are run in solution, the products captured on streptavidin beads, and activity is measured by release of a fluorescent tag. The procedure can be scaled up for the analysis of numerous samples, and is substantially more rapid and sensitive than the standard radioactive gel methods. The new assay is validated and its utility demonstrated via a detailed comparison of the Mg++- and Mn++-dependent activities of the IN proteins from human immunodeficiency virus type 1 (HIV-1) and the avian sarcoma virus (ASV). The results confirm that ASV IN is considerably more active than HIV-1 IN, but with both enzymes the initial rates of joining, and the product yields, are higher in the presence of Mn++ than Mg++. Although the pH optima for these two enzymes are similar with Mn++, they differ significantly in the presence of Mg++, which is likely due to differences in the molecular environment of the binding region of this physiologically relevant divalent cation. This interpretation is strengthened by the observation that a compound that can inhibit HIV-1 IN in the presence of either metal cofactors is only effective against ASV in the presence of Mn++.ConclusionA simplified, assay for measuring the joining activity of retroviral IN in solution is described, which offers several advantages over previous methods and the standard radioactive gel analyses. Based on comparisons of signal to background ratios, the assay is 10–30 times more sensitive than gel analysis, allows more rapid and accurate biochemical analyses of IN catalytic activity, and moderate throughput screening of inhibitory compounds. The assay is validated, and its utility demonstrated in a comparison of the metal-dependent activities of HIV-1 and ASV IN proteins.