Anti-human immunodeficiency virus type 1 activity of the nonnucleoside reverse transcriptase inhibitor GW678248 in combination with other antiretrovirals against clinical isolate viruses and in vitro selection for resistance

Potent inhibition of HIV replication in primary human cells by novel synthetic polyketides inspired by Aureothin

Overcoming the global health threat of HIV infection requires continuous pipelines of novel drug candidates. We identified the γ-pyrone polyketides Aureothin/Neoaureothin as potent hits by anti-HIV screening of an extensive natural compound collection. Total synthesis of a structurally diverse group of Aureothin-derivatives successfully identified a lead compound (#7) superior to Aureothin that combines strong anti-HIV activity (IC₉₀<45 nM), photostability and improved cell safety. Compound #7 inhibited de novo virus production from integrated proviruses by blocking the accumulation of HIV RNAs that encode the structural components of virions and include viral genomic RNAs. Thus, the mode-of-action displayed by compound #7 is different from those of all current clinical drugs. Proteomic analysis indicated that compound #7 does not affect global protein expression in primary blood cells and may modulate cellular pathways linked to HIV infection. Compound #7 inhibited multiple HIV genotypes, including HIV-type 1 and 2 and synergistically inhibited HIV in combination with clinical reverse transcriptase and integrase inhibitors. We conclude that compound #7 represents a promising new class of HIV inhibitors that will facilitate the identification of new virus-host interactions exploitable for antiviral attack and holds promise for further drug development.

Patterns of emergent resistance-associated mutations after initiation of non-nucleoside reverse-transcriptase inhibitor-containing antiretroviral regimens in Taiwan: a multicenter cohort study

Background

Increasing trends of resistance-associated mutations (RAMs) to non-nucleoside reverse-transcriptase inhibitors (nNRTIs) have raised concerns about the effectiveness of the regimens in the national HIV treatment programs in resource-limited countries. We aimed to retrospectively investigate the incidence and patterns of emergent RAMs of HIV-1 in HIV-positive adults experiencing virological failure to first-line nNRTI-containing combination antiretroviral therapy (cART) in Taiwan.

Patients and methods

Between June 2012 and March 2016, 1138 antiretroviral-naïve HIV-positive adults without baseline RAMs who initiated nNRTI-containing regimens were included for analysis. Virological failure was defined as plasma viral load (PVL) ≥200 copies/mL after 6 months of cART or confirmed PVL ≥200 copies/mL after achieving PVL <50 copies/mL. Population sequencing was retrospectively performed to detect baseline and emergent RAMs. RAMs were interpreted using the International AIDS Society-USA 2016 mutations list.

Results

Seventy-one patients (6.2%) developed virological failure, which occurred in 14.8% (43/291), 3.9% (26/675), and 1.2% (2/172) of patients receiving 2 nucleoside reverse-transcriptase inhibitors (NRTIs) plus nevirapine, efavirenz, and rilpivirine, respectively. Among those, 53 (74.6%) had emergent RAMs identified, which included 43 (81.1%), 53 (100.0%), and 1 (1.9%) with RAMs to NRTIs, nNRTIs, and protease inhibitors, respectively; and 43 (81.1%) had multi-drug resistance. The most common emergent RAMs to NRTIs were M184V/I (42.3%) and K65R (28.2%), and those to nNRTIs were Y181C (42.3%), K103N (15.5%), G190A/E/Q (12.7%), V179D/E (12.7%), and V108I (9.9%).

Conclusion

While the rates of virological failure varied with the nNRTI used, the rate of emergent RAMs of HIV-1 to NRTIs and nNRTIs among the antiretroviral-naïve patients who failed nNRTI-containing cART remained low.

Cell-permeable stapled peptides based on HIV-1 integrase inhibitors derived from HIV-1 gene products

HIV-1 integrase (IN) is an enzyme which is indispensable for the stable infection of host cells because it catalyzes the insertion of viral DNA into the genome and thus is an attractive target for the development of anti-HIV agents. Earlier, we found Vpr-derived peptides with inhibitory activity against HIV-1 IN. These Vpr-derived peptides are originally located in an α-helical region of the parent Vpr protein. Addition of an octa-arginyl group to the inhibitory peptides caused significant inhibition against HIV replication associated with an increase in cell permeability but also relatively high cytotoxicity. In the current study, stapled peptides, a new class of stabilized α-helical peptidomimetics were adopted to enhance the cell permeability of the above lead peptides. A series of stapled peptides, which have a hydrocarbon link formed by a ruthenium-catalyzed ring-closing metathesis reaction between successive turns of α-helix, were designed, synthesized, and evaluated for biological activity. In cell-based assays some of the stapled peptides showed potent anti-HIV activity comparable with that of the original octa-arginine-containing peptide (2) but with lower cytotoxicity. Fluorescent imaging experiments revealed that these stapled peptides are significantly cell permeable, and CD analysis showed they form α-helical structures, whereas the unstapled congeners form β-sheet structures. The application of this stapling strategy to Vpr-derived IN inhibitory peptides led to a remarkable increase in their potency in cells and a significant reduction of their cytotoxicity.

Synthesis, structure-activity relationships, and docking studies of N-phenylarylformamide derivatives (PAFAs) as non-nucleoside HIV reverse transcriptase inhibitors

A series of N-phenylarylformamide derivatives (PAFAs) with anti-wild-type HIV-1 activity (EC(50) values) ranging from 0.3 nM to 5.1 nM and therapeutic index (TI) ranging from 10 616 to 271 000 were identified as novel non-nucleoside reverse transcriptase inhibitors. Among them, compound 13g (EC(50) = 0.30 nM, TI = 184 578), 13l (EC(50) = 0.37 nM, TI = 212 819), 13m (EC(50) = 0.32 nM, TI = 260 617) and 13r (EC(50) = 0.27 nM, TI = 271 000) displayed the highest activity against this type virus nearly as potent as lead compound GW678248. Moreover, all of them were also active to inhibit the double mutant strain A(17) (K103N + Y181C) with EC(50) values of 0.29 μM, 0.14 μM, 0.10 μM and 0.27 μM, respectively. In particular, compound 13m, which showed broad-spectrum anti-HIV activity, was also effective to inhibit the HIV-2 ROD replication within 4.37 μM concentration.

EASY-HIT: HIV full-replication technology for broad discovery of multiple classes of HIV inhibitors

HIV replication assays are important tools for HIV drug discovery efforts. Here, we present a full HIV replication system (EASY-HIT) for the identification and analysis of HIV inhibitors. This technology is based on adherently growing HIV-susceptible cells, with a stable fluorescent reporter gene activated by HIV Tat and Rev. A fluorescence-based assay was designed that measures HIV infection by two parameters relating to the early and the late phases of HIV replication, respectively. Validation of the assay with a panel of nine reference inhibitors yielded effective inhibitory concentrations consistent with published data and allowed discrimination between inhibitors of early and late phases of HIV replication. Finer resolution of the effects of reference drugs on different steps of HIV replication was achieved in secondary time-of-addition assays. The EASY-HIT assay yielded high Z' scores (>0.9) and signal stabilities, confirming its robustness. Screening of the LOPAC(1280) library identified 10 compounds (0.8%), of which eight were known to inhibit HIV, validating the suitability of this assay for screening applications. Studies evaluating anti-HIV activities of natural products with the EASY-HIT technology led to the identification of three novel inhibitory compounds that apparently act at different steps of HIV-1 replication. Furthermore, we demonstrate successful evaluation of plant extracts for HIV-inhibitory activities, suggesting application of this technology for the surveillance of biological extracts with anti-HIV activities. We conclude that the EASY-HIT technology is a versatile tool for the discovery and characterization of HIV inhibitors.

Virologic, immunologic, clinical, safety, and resistance outcomes from a long-term comparison of efavirenz-based versus nevirapine-based antiretroviral regimens as initial therapy in HIV-1-infected persons

PURPOSE

To compare long-term virologic, immunologic, and clinical outcomes in antiretroviral-naïve persons starting efavirenz (EFV)- versus nevirapine (NVP)-based regimens.

METHOD

The FIRST study randomized patients into three strategy arms: PI+NRTI, NNRTI+NRTI, and PI+NNRTI+NRTI. NNRTI was determined by optional randomization (NVP or EFV) or by choice. For this randomized substudy, the primary endpoint was HIV RNA >50 copies/mL after 8 months or death. Genotypic resistance testing was done at virologic failure (VF; HIV RNA >1,000 copies/mL at or after 4 months).

RESULTS

228 persons (111 randomized to EFV, 117 to NVP) were followed for median 5 years. Rates per 100 person years for the primary endpoint were 41.2 (EFV) and 42.8 (NVP; p = .59). The percent of persons with HIV RNA <50 copies/mL was similar throughout follow-up (p = .24), as were average increases in CD4+ cells (p = .30). 423 persons declining the substudy chose EFV; 264 chose NVP. There were 915 persons in the combined cohort (randomized and choice). In the combined cohort, the risk of VF and VF with any NNRTI or NRTI resistance or resistance of any class was significantly less for EFV compared to NVP.

CONCLUSIONS

EFV-based regimens as initial therapy resulted in a lower risk of VF and VF with resistance than did NVP-based regimens, although immunologic and clinical outcomes were similar.

Structural basis for the improved drug resistance profile of new generation benzophenone non-nucleoside HIV-1 reverse transcriptase inhibitors

Owing to the emergence of resistant virus, next generation non-nucleoside HIV reverse transcriptase inhibitors (NNRTIs) with improved drug resistance profiles have been developed to treat HIV infection. Crystal structures of HIV-1 RT complexed with benzophenones optimized for inhibition of HIV mutants that were resistant to the prototype benzophenone GF128590 indicate factors contributing to the resilience of later compounds in the series (GW4511, GW678248). Meta-substituents on the benzophenone A-ring had the designed effect of inducing better contacts with the conserved W229 while reducing aromatic stacking interactions with the highly mutable Y181 side chain, which unexpectedly adopted a "down" position. Up to four main-chain hydrogen bonds to the inhibitor also appear significant in contributing to resilience. Structures of mutant RTs (K103N, V106A/Y181C) with benzophenones showed only small rearrangements of the NNRTIs relative to wild-type. Hence, adaptation to a mutated NNRTI pocket by inhibitor rearrangement appears less significant for benzophenones than other next-generation NNRTIs.

Mechanisms of inhibition of HIV replication by non-nucleoside reverse transcriptase inhibitors

The non-nucleoside reverse transcriptase (RT) inhibitors (NNRTIs) are a therapeutic class of compounds that are routinely used, in combination with other antiretroviral drugs, to treat HIV-1 infection. NNRTIs primarily block HIV-1 replication by preventing RT from completing reverse transcription of the viral single-stranded RNA genome into DNA. However, some NNRTIs, such as efavirenz, have been shown to inhibit the late stages of HIV-1 replication by interfering with HIV-1 Gag-Pol polyprotein processing, while others, such as the pyrimidinediones, have been shown to inhibit both HIV-1 RT-mediated reverse transcription and HIV-1/HIV-2 viral entry. Accordingly, in this review we describe the multiple mechanisms by which NNRTIs inhibit HIV-1 reverse transcription (and in some cases HIV-2 reverse transcription) and other key steps involved in HIV-1/HIV-2 replication.

The dolabellane diterpene Dolabelladienetriol is a typical noncompetitive inhibitor of HIV-1 reverse transcriptase enzyme

We recently described that a dollabelane diterpene isolated from the marine algae Dictyota pfaffii (Dolabelladienetriol) inhibits the human immunodeficiency virus type 1 (HIV-1) enzyme reverse transcriptase (RT), and HIV-1 replication in primary cells. Based on these findings, we investigated additional antiretroviral properties of Dolabelladienetriol. Here, we describe that Dolabelladienetriol blocked the synthesis and integration of HIV-1 provirus and completely abrogated viral replication in primary cells. Also, studies of kinetic mode of action revealed that the Dolabelladienetriol is a nonnucleoside RT inhibitor (NNRTI), acting as a noncompetitive inhibitor, with a K(i) value equal to 7.2 microM. To assess whether Dolabelladienetriol could potentiate the anti-HIV-1 effects of other HIV-1 inhibitors, HIV-1-infected cells were treated with Dolabelladienetriol at its EC(50) dose plus sub-optimal concentrations of classical antiretrovirals. Dolabelladienetriol provided an additive effect with the nucleoside RT inhibitor AZT, and a synergistic effect with the protease inhibitor atazanavir sulphate. There was no increment of the anti-HIV-1 effect resulting from the combination between Dolabelladienetriol and the NNRTI nevirapine. Using a large panel of HIV-1 isolates harboring NNRTI resistance mutations, we found no cross-resistance between Dolabelladienetriol and clinical available NNRTIs. Thus, Dolabelladienetriol is an NNRTI, with potent activity against HIV-1 isolates carrying common NNRTI-associated resistance mutations. Dolabelladienetriol may be considered as a potential new agent for anti-HIV-1 therapy.

Dual enzyme-linked immunosorbent assay system for detection of endogenous kinase activities of mitogen- and stress-activated protein kinase-1/2

The kinase signaling cascades related to mitogen- and stress-activated protein kinase-1 and -2 (MSK1 and MSK2, respectively) are attractive targets for pharmaceutical intervention, especially for neural injury. Therefore, we have developed a high throughput and cost-effective detection platform for measuring selective activity of MSK1/MSK2 in cells. Through the serial monitoring of both the p38 mitogen-activated protein kinase (stress-activated protein kinase 2B)-MSK1/MSK2- cyclic AMP response element binding protein (CREB)/activating transcription factor 1 (ATF1) pathway and the p38-mammalian heat shock protein 27 (Hsp27) pathway in HeLa cells treated with anisomycin, two selective MSK1 inhibitors showed inhibition of CREB (Ser-133) and ATF1 (Ser-63) phosphorylation and no interference with Hsp-27 phosphorylation (Ser-82). On the other hand, the p38 inhibitor SB-220025 showed equipotent inhibition of CREB/ATF1 and Hsp27 phosphorylation. This study demonstrated that the specific inhibition of a target kinase could be subsequently monitored by a secondary assay that measures the intervention arising from the modulation of off-target kinases. Our established system is applicable to inhibitor screening and drug discovery related to MSK1/MSK2.

Effective program against mother-to-child transmission of HIV at Saint Camille Medical Centre in Burkina Faso

The present research was aimed to prevent mother-to-child transmission of HIV; to use RT-PCR in order to detect, 6 months after birth, infected children; and to test the antiretroviral resistance of both children and mothers in order to offer them a suitable therapy. At the Saint Camille Medical Centre, 3,127 pregnant women (aged 15-44 years) accepted to be enrolled in the mother-to-child transmission prevention protocol that envisages: (i) Voluntary Counselling and Testing for all the pregnant women; (ii) Antiretroviral therapy for HIV positive pregnant women and for their newborns; (iii) either powdered milk feeding or short breast-feeding and RT-PCR test for their children; (iv) finally, pol gene sequencing and antiretroviral resistance identifications among HIV positive mothers and children. Among the patients, 227/3,127 HIV seropositive women were found: 221/227 HIV-1, 4/227 HIV-2, and 2/227 mixed HIV infections. The RT-PCR test allowed the detection of 3/213 (1.4%) HIV infected children: 0/109 (0%) from mothers under ARV therapy and 3/104 (2.8%) from mothers treated with Nevirapine. All children had recombinant HIV-1 strain (CRF06_CPX) with: minor PR mutations (M36I, K20I) and RT mutations (R211K). Among them, two twins had Non-Nucleoside Reverse Transcriptase Inhibitor mutation (Y18CY). Both mothers acquired a major PR mutation (V8IV), investigated 6 months after a single-dose of Nevirapine. Prevention by single-dose of Nevirapine reduced significantly mother-to-child transmission of HIV, but caused many mutations and resistance to antiretroviral drugs. Based on present study the antiretroviral therapy protocol, together with the artificial-feeding, might represent the ideal strategy to avoid transmission of HIV from mother-to-child.

Inhibition of HIV‐1 or bacterial activation of macrophages by products of HIV‐1‐resistant human cells

We have recently described the molecular basis of HIV-1 resistance factor (HRF)-mediated anti-viral activity in primary and transformed CD4 T cells. HRF+ cell culture supernatants or partially purified HRF were found to incapacitate the formation of the NF-kappaB/DNA complex, which is indispensable for long terminal promoter-driven transcription of virus genes. In this study, we tested whether HRF might have much broader activity against other organisms whose pathogenesis is linked to NF-kappaB activation. Specifically, we tested the effects of HRF on the NF-kappaB-mediated responses of primary macrophages to HIV-1 or several bacterial antigens. We found that exposure to HRF inhibited HIV-1 expression in macrophages and also induced the production of HRF-like activity by macrophages, which prevented replication of virus in HIV-1-infected peripheral blood lymphocytes cultured in the adjacent compartment. We investigated the mechanism of this inhibition and found that HRF impeded NF-kappaB/DNA binding in macrophages induced by either HIV-1 or lipopolysaccharide from several bacteria species, resulting in impaired tumor necrosis factor-alpha responses to these organisms.

Characterization of novel non-nucleoside reverse transcriptase (RT) inhibitor resistance mutations at residues 132 and 135 in the 51 kDa subunit of HIV-1 RT

Several rare and novel NNRTI [non-nucleoside reverse transcriptase (RT) inhibitor] resistance mutations were recently detected at codons 132 and 135 in RTs from clinical isolates using the yeast-based chimaeric TyHRT (Ty1/HIV-1 RT) phenotypic assay. Ile132 and Ile135 form part of the beta7-beta8 loop of HIV-1 RT (residues 132-140). To elucidate the contribution of these residues in RT structure-function and drug resistance, we constructed twelve recombinant enzymes harbouring mutations at codons 132 and 135-140. Several of the mutant enzymes exhibited reduced DNA polymerase activities. Using the yeast two-hybrid assay for HIV-1 RT dimerization we show that in some instances this decrease in enzyme activity could be attributed to the mutations, in the context of the 51 kDa subunit of HIV-1 RT, disrupting the subunit-subunit interactions of the enzyme. Drug resistance analyses using purified RT, the TyHRT assay and antiviral assays demonstrated that the I132M mutation conferred high-level resistance (>10-fold) to nevirapine and delavirdine and low-level resistance (approximately 2-3-fold) to efavirenz. The I135A and I135M mutations also conferred low level NNRTI resistance (approximately 2-fold). Subunit selective mutagenesis studies again demonstrated that resistance was conferred via the p51 subunit of HIV-1 RT. Taken together, our results highlight a specific role of residues 132 and 135 in NNRTI resistance and a general role for residues in the beta7-beta8 loop in the stability of HIV-1 RT.

A selective cellular screening assay for B-Raf and c-Raf kinases

The Ras/Raf signaling pathway has been recognized as an important process in cancer biology. Recently, activating mutations in the BRAF gene were reported to be present in approximately 66% of malignant melanomas as well as other malignancies such as colon cancer. Here, the authors report the development of a B-Raf-specific cellular assay to profile cell-active B-Raf inhibitors. Expression of the active B-Raf mutant (V600E) and the kinase-inactive form of its substrate, MEK1, was regulated by mifepristone, and the catalytic activity of B-Raf was monitored by following MEK1 phosphorylation. Target specificity was ensured because the phosphorylation of MEK1 was significantly inhibited when kinase-inactive B-Raf was used in place of the active kinase. A cellular c-Raf assay was similarly established to monitor the selectivity between B-Raf and c-Raf. Z' factor values were consistently above 0.50 with either kinase, indicating that assay performance was sufficiently robust for use as cellular profiling assays. The authors used this system to demonstrate that the selectivity profile of compounds targeted against B-Raf and c-Raf kinases could be quantitatively determined. This platform provides a quantitative cellular readout for a spectrum of specific inhibitors of B-Raf and c-Raf kinases that is particularly suitable for use in drug discovery.

A robust, target-driven, cell-based assay for checkpoint kinase 1 inhibitors

Checkpoint kinase 1 (Chk1), a serine/threonine kinase, plays an important role in DNA damage checkpoint control and is an attractive target for cancer treatment. To develop a Chk1-specific cell-based assay, stable clones were established in which Chk1 kinase domain fused at its N-terminus with p53 through 4 tandem repeats of Gly-Gly-Gly-Gly-Ser was expressed in an inducible manner. Chk1 kinase specificity of the phosphorylation of fused p53 was confirmed by the experiments with a kinase-inactive Chk1. Only in the presence of an inducer molecule was phosphorylation of p53 at Ser-15 in the stable clones induced. Furthermore, its assay performance proved acceptable for high-throughput screening applications, judging from the Z' factor values (> 0.77). Finally, the cell-based assay thus established yielded structure-activity relationship data for a small set of test inhibitors of Chk1 within cells. Collectively, these results demonstrate that the established cell-based assay provides a novel and highly sensitive cellular platform for Chk1 inhibitor discovery.

Relationship of Potency and Resilience to Drug Resistant Mutations for GW420867X Revealed by Crystal Structures of Inhibitor Complexes for Wild-Type, Leu100Ile, Lys101Glu, and Tyr188Cys Mutant HIV-1 Reverse Transcriptases†

The selection of drug resistant viruses is a major problem in efforts to combat HIV and AIDS, hence, new compounds are required. We report crystal structures of wild-type and mutant HIV-1 RT with bound non-nucleoside (NNRTI) GW420867X, aimed at investigating the basis for its high potency and improved drug resistance profile compared to the first-generation drug nevirapine. GW420867X occupies a smaller volume than many NNRTIs, yet accesses key regions of the binding pocket. GW420867X has few contacts with Tyr188, hence, explaining the small effect of mutating this residue on inhibitor-binding potency. In a mutated NNRTI pocket, GW420867X either remains in a similar position compared to wild-type (RT(Leu100Ile) and RT(Tyr188Cys)) or rearranges within the pocket (RT(Lys101Glu)). For RT(Leu100Ile), GW420867X does not shift position, in spite of forming different side-chain contacts. The small bulk of GW420867X allows adaptation to a mutated NNRTI binding site by repositioning or readjustment of side-chain contacts with only small reductions in binding affinity.

Nevirapine clearance from plasma in African adults stopping therapy: a pharmacokinetic substudy

OBJECTIVE

To measure nevirapine elimination in African adults undertaking a structured treatment interruption (STI) in the DART trial.

DESIGN

Cohort (16 women, 5 men; median weight 61 kg) within a randomized trial of management strategies.

METHODS

Plasma nevirapine was measured by validated high performance liquid chromatography at 0,1,2,3 and 4 weeks after stopping the drug in a subset of patients undertaking an STI. All patients continued lamivudine plus zidovudine/stavudine for a further 7 days.

RESULTS

Two patients with no or low plasma nevirapine concentration at baseline were excluded. Geometric mean plasma concentration when nevirapine was stopped in the remaining 19 patients was 6421 ng/ml (range, 3724-9473). Nevirapine was detected in 15/18 (83%) patients at 1 week, and 5/19 (26%) patients at 2 weeks but was not found any samples collected after 2 weeks. Only one patient had > 100 ng/ml (limit of quantification) at 2 weeks (415 ng/ml, female). The median times to reach thresholds of 200, 100 and 20 ng/ml (limit of detection) were estimated to be 7.6 [interquartile range (IQR), 7.0-10.1], 9.3 (IQR, 8.7-13.0) and 13.2 (IQR, 12.3-18.4) days, respectively, with 3/19 (16%) and 14/19 (74%) estimated to have reached < 20 ng/ml by 7 and 14 days, respectively.

CONCLUSION

Although elimination of nevirapine was faster than previously published after a single dose, the data suggest that an additional staggered period of 7-10 days with dual nucleotide reverse transcriptase inhibitor cover is necessary for African patients discontinuing nevirapine.

Status Presens of Antiviral Drugs And Strategies: Part I: DNA Viruses and Retroviruses

More than 40 compounds have been formally licensed for clinical use as antiviral drugs, and half of these are used for the treatment of HIV infections. The others have been approved for the therapy of herpesvirus (HSV, VZV, CMV), hepadnavirus (HBV), hepacivirus (HCV) and myxovirus (influenza, RSV) infections. New compounds are in clinical development or under preclinical evaluation, and, again, half of these are targeting HIV infections. Yet, quite a number of important viral pathogens (i.e. HPV, HCV, hemorrhagic fever viruses) remain in need of effective and/or improved antiviral therapies.

Viruses and Viral Diseases

More than 40 compounds have been formally licensed for clinical use as antiviral drugs, and half of these are used for the treatment of human immunodeficiency virus (HIV) infections. The others have been approved for the therapy of herpesvirus (herpes simplex virus (HSV), varicella-zoster virus (VZV), cytomegalovirus (CMV)), hepadnavirus (hepatitis B virus (HBV)), hepacivirus (hepatitis C virus (HCV)), and myxovirus (influenza, respiratory synctural virus (RSV)) infections. New compounds are in clinical development or under preclinical evaluation, and, again, half of these target HIV infections. Yet, quite a number of important viral pathogens (i.e., human papilloma virus (HPV), HCV, hemorrhagic fever viruses) remain in need of effective and/or improved antiviral therapies.

Antiviral activity of GW678248, a novel benzophenone nonnucleoside reverse transcriptase inhibitor

The compound GW678248 is a novel benzophenone nonnucleoside reverse transcriptase inhibitor (NNRTI). Preclinical assessment of GW678248 indicates that this compound potently inhibits wild-type (WT) and mutant human immunodeficiency virus type 1 (HIV-1) reverse transcriptase in biochemical assays, with 50% inhibitory concentrations (IC(50)s) between 0.8 and 6.8 nM. In HeLa CD4 MAGI cell culture virus replication assays, GW678248 has an IC(50) of < or =21 nM against HIV-1 isogenic strains with single or double mutations known to be associated with NNRTI resistance, including L100I, K101E, K103N, V106A/I/M, V108I, E138K, Y181C, Y188C, Y188L, G190A/E, P225H, and P236L and various combinations. An IC(50) of 86 nM was obtained with a mutant virus having V106I, E138K, and P236L mutations that resulted from serial passage of WT virus in the presence of GW678248. The presence of 45 mg/ml human serum albumin plus 1 mg/ml alpha-1 acid glycoprotein increased the IC(50) approximately sevenfold. Cytotoxicity studies with GW678248 indicate that the 50% cytotoxicity concentration is greater than the level of compound solubility and provides a selectivity index of >2,500-fold for WT, Y181C, or K103N HIV-1. This compound exhibits excellent preclinical antiviral properties and, as a prodrug designated GW695634, is being developed as a new generation of NNRTI for the treatment of HIV-1 in combination with other antiretroviral agents.