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PubMed1999

Novel modifications in the alkenyldiarylmethane (ADAM) series of non-nucleoside reverse transcriptase inhibitors.

In an effort to obtain more insight into the interaction between HIV-1 reverse transcriptase and the alkenyldiarylmethanes (ADAMs), a new series of compounds has been synthesized and evaluated for inhibition of HIV-1 replication. The modifications reported in this new series include primarily changes to the alkenyl chain. The most potent compound proved to be methyl 3',3' '-dibromo-4',4' '-dimethoxy-5',5' '-bis(methoxycarbonyl)-6,6-diphenyl-5-hexenoate (28), which displayed an EC(50) of 1.3 nM for inhibition of the cytopathic effect of HIV-1(RF) in CEM-SS cells. ADAM 28 inhibited HIV-1 reverse transcriptase with an IC(50) of 0.3 microM. Mutations that conferred greater than 10-fold resistance to ADAM 28 clustered at residues Val 106, Val 179, Tyr 181, and Tyr 188. Results derived from this series indicate that ADAMs containing chlorines in the aromatic rings might bind to HIV-1 reverse transcriptase in a slightly different mode when compared with those analogues incorporating bromine in the aromatic rings.

Anti-HIV Agents↗

PubMed2002

Advances in QSAR studies of HIV-1 reverse transcriptase inhibitors.

A review is presented of the recent advances in quantitative structure-activity relationship (QSAR) studies of HIV-1 reverse transcriptase (RT) inhibitors. These inhibitors have been put into two classes: nucleoside RT inhibitors (NRTIs), which are 2',3'-dideoxynucleoside analogues (ddNs), and non-nucleoside RT inhibitors (NNRTIs). For NRTIs (ddNs), which act as competitive inhibitors or alternate substrates of RT and hence interact at the substrate binding site of the enzyme, QSARs have pointed out the major role of the electronic factors governing their activity. For NNRTIs, which bind to a site entirely distinct from the substrate binding site, the activity has been shown to be largely dependent upon the hydrophobic nature of the compounds or substituents. The hydrophobic nature of the active site in the receptor with which the NNRTIs interact provides relatively few possibilities for the molecules to have polar interactions or hydrogen bondings, but QSARs have indicated that NNRTIs do involve some polar interactions and hydrogen bondings with some pockets of the enzyme. QSARs also indicate the significant roles of steric interactions and conformational shape of the molecule.

Algorithms↗

PubMed1998

Synthesis and biological evaluation of 5H-indolo [3,2-b][1,5]benzothiazepine derivatives, designed as conformationally constrained analogues of the human immunodeficiency virus type 1 reverse transcriptase inhibitor L-737,126.

In the presence of sodium hydride, reaction of aryl-disulphides with ethyl esters of indole-2-carboxylic acids furnished ethyl 3-arylthioindole-2-carboxylates, which were cyclized intramolecularly to afford 5H-indolo[3,2-b][1,5]benzothiazepin-6(7H)-ones or hydrolysed in alkaline medium to give 3-arylthioindole-2-carboxylic acids. These acids, also obtained by the action of aryldisulphides on indole-2-carboxylic acids, afforded tetracyclic 5H-indolo [3,2-b][1,5]benzothiazepin-6(7H)-ones upon treatment with EDCI-DMAP. Transformation of cyclic sulphides into the required sulphones was achieved by treatment with hydrogen peroxide or with m-chloroperbenzoic acid. The title derivatives are conformationally constrained analogues of the potent human immunodeficiency virus type 1 (HIV-1) reverse transcriptase inhibitor 3-benzene-sulphonyl-5-chloroindole-2-carboxamide (L-737, 126). Although the indolobenzothiazepine derivatives, as well as the indolyl aryl sulphones used for their synthesis, were endowed with anti-HIV-1 activities in the submicromolar and micromolar range, none of them proved more potent than L-737,126.

Anti-HIV Agents↗

PubMed2003

Metabolism of (S)-5,6-difluoro-4-cyclopropylethynyl-4-trifluoromethyl-3, 4-dihydro-2(1H)-quinazolinone, a non-nucleoside reverse transcriptase inhibitor, in human liver microsomes. Metabolic activation and enzyme kinetics.

(S)-5, 6-Difluoro-4-cyclopropylethynyl-4-trifluoromethyl-3, 4-dihydro- 2-(1H)-quinazolinone (DPC 963), a specific non-nucleoside inhibitor of human immunodeficiency virus-1 reverse transcriptase, is primarily metabolized in humans to the glucuronide conjugate of 8-OH DPC 963 (M8). Electrospray ionization-liquid chromatography/mass spectrometry analyses of urine from subjects dosed with DPC 963 also revealed the presence of other minor metabolites including glucuronide conjugate of 6-OH DPC 963 (M7). An oxidative defluorination pathway involving a putative p-benzoquinone imine capable of being reduced to the hydroquinone (M7) is postulated. The formation of the benzoquinone imine [detected as a glutathione (GSH) adduct, M5] was primarily carried out by CYP3A4, whereas M8 was formed mainly by the polymorphic CYP2B6. The kinetic studies with human liver microsomes showed that the apparent K(m) and V(max) values for the formation of M5 were 65.8 microM and 25.6 pmol/min/mg of protein, respectively. The formation of M8 showed K(m) and V(max) values of 15.1 microM and 22.9 pmol/min/mg of protein, respectively. The microsomal studies also revealed the occurrence of a possible oxirene intermediate that was trapped as GSH adducts M3 and M4. It was demonstrated, for the first time, that CYP3A4 was capable of directly oxidizing the triple bond of the cyclopropyl ethynyl group to an unstable oxirene. The apparent K(m) and V(max) values for the formation of an oxirene (detected as the GSH adduct M3) were 1.9 mM and 10.2 pmol/min/mg of protein, respectively. These results suggest that CYP2B6 has a higher affinity than CYP3A4 toward DPC 963. This consequently leads to greater levels of CYP2B6-catalyzed product, M8, than CYP3A4-mediated bioactivation of DPC 963 to benzoquinone imine or oxirene intermediates.

Biotransformation↗

PubMed1995

Sensitivity/resistance profile of a simian immunodeficiency virus containing the reverse transcriptase gene of human immunodeficiency virus type 1 (HIV-1) toward the HIV-1-specific non-nucleoside reverse transcriptase inhibitors.

To develop an animal model for the therapy of AIDS with human immunodeficiency virus type 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors, we recently constructed a hybrid simian immunodeficiency virus (SIV)/HIV-1 in which the RT gene of SIV was replaced by the RT gene of HIV-1. This chimaeric virus, designated RT-SHIV, was found to be markedly sensitive to the inhibitory effects of both nucleoside (ddN) and non-nucleoside RT inhibitors (NNRTIs). In contrast, SIV was inhibited only by ddNs (i.e., 3TC and AZT), but not NNRTIs. When RT-SHIV was grown in the presence of 3TC, nevirapine, TSAO-m3T or the thiocarboxanilide UC-42 drug-resistant mutant virus strains emerged in cell culture as rapid as for HIV-1(IIIB). The antiviral sensitivity/resistance spectrum of the mutant RT-SHIV strains against NNRTIs and ddNs, and the nature of the mutations that appeared in their RT were similar to those of the mutant HIV-1 strains that were selected under identical experimental conditions. Infection of macaques with RT-SHIV may be a useful tool for studying the mechanism of NNRTI-resistance development and the therapy of NNRTI-resistant viruses in an animal model.

Acquired Immunodeficiency Syndrome↗

PubMed1999

Synthesis and anti-HIV activity of 1,1,3-trioxo-2H,4H-thieno[3,4-e][1,2,4]thiadiazines (TTDs): a new family of HIV-1 specific non-nucleoside reverse transcriptase inhibitors.

The anti-HIV activity of a novel series of 1,1,3-trioxo-2H,4H-thieno[3,4-e][1,2,4]thiadiazines (TTDs) has been described. The compounds were synthesized via Curtius rearrangement of appropriate sulfamoylcarboxy azides which, in turn, were prepared from known starting materials. Several 4-substituted-2-benzyl-derivatives were found to selectively inhibit human immunodeficiency virus type 1 [HIV-1 (IIIB)] replication in MT-4 and CEM cells. These TTDs were also effective against other strains of HIV-1 (RF, HE, MN, NDK), including those that are resistant to AZT, but not against HIV-2 (ROD) or simian immunodeficiency virus [SIV(MAC251)] at subtoxic concentrations. Some of the test compounds exhibited antiviral activity against L100I RT mutant virus, but significantly lost antiviral activity against K103N, V106A, E138K, Y181C and Y188H RT mutant viruses. Compounds 6d, 6f and 6g were inhibitory to HIV-1 RT at concentrations that rank between 16.4 and 59.8 microM (nevirapine: IC50 = 4.5 microM against HIV-1 RT). Inhibition of HIV-1 RT by compound 6g was purely non-competitive with respect to the natural substrate (dGTP), which is in agreement with the nature of inhibition shown by other NNRTIs such as nevirapine and delarvidine. A structure-activity relationship was established for the anti-HIV activity of these heterocyclic compounds. TTDs represent a new chemical class of non-nucleoside HIV-1 reverse transcriptase inhibitors (NNRTIs).

Anti-HIV Agents↗

PubMed2000

Immunogenicity of mutations induced by nucleoside reverse transcriptase inhibitors for human immunodeficiency virus type 1-specific cytotoxic T cells.

The impact of drug resistance mutations induced by nucleoside reverse transcriptase (RT) inhibitors (NRTI) on cytotoxic T-lymphocyte (CTL) recognition of human immunodeficiency virus type 1 strain LAI (HIV-1(LAI)) RT was addressed in 35 treated or untreated patients. Two HIV-1(LAI) RT regions encompassing mutation M41L, L74V, M184V, and T215Y/F were recognized in 75 and 83% mutated and in 33 and 42% unmutated samples, respectively. A total of 41 new CTL epitopes overlapping these mutations were predicted. Mutations enhanced HLA-binding scores of 17 epitopes, decreased scores of 5, and had no effect in 19. Four predicted epitopes containing mutations 41, 74, and 184 were tested and recognized by CD8 cells from mutated or unmutated samples, with frequencies up to 270 gamma interferon spot-forming cells per 10(6) peripheral blood mononuclear cells. Therefore, RT mutations induced by NRTI can increase the immunogenicity of RT for CTL and might allow a better immune control of resistant viruses in vivo, suggesting that specific immune therapy might help prevent these mutations.

Anti-HIV Agents↗

PubMed1990

Inhibition of HIV-1 replication by a nonnucleoside reverse transcriptase inhibitor.

A series of dipyridodiazepinones have been shown to be potent inhibitors of human immunodeficiency virus-1 (HIV-1) reverse transcriptase (RT). One compound, BI-RG-587, had a Ki of 200 nanomolar for inhibition of HIV-1 RT that was noncompetitive with respect to deoxyguanosine triphosphate. BI-RG-587 was specific for HIV-1 RT, having no effect on feline and simian RT or any mammalian DNA polymerases. BI-RG-587 inhibited HIV-1 replication in vitro as demonstrated by in situ hybridization, inhibition of protein p24 production, and the lack of syncytia formation in cultured human T cell lines and freshly isolated human peripheral blood lymphocytes. Cytotoxicity studies of BI-RG-587 on human cells showed a high therapeutic index (greater than 8000) in culture.

Animals↗

PubMed1994

Design of structure-based reverse transcriptase inhibitors.

Based on the crystallographic structure of the active site in the reverse transcriptase (RT) of human immunodeficiency virus (HIV), a group of hydrophobic polyadenylic acid (5') derivatives were designed and synthesized as inhibitors of the enzyme. These compounds were found to inhibit all six of the RTs tested, with IC50 = 10(-11)-10(-8) M, but did not inhibit either RNA polymerase II (even at 10(-5) M) or DNA polymerase I up to 10(-6) M inhibitor concentration. The underivatized poly(A) did not inhibit any of the RTs tested under the same conditions. In aqueous solutions of purified HIV-1 RT, poly-2'-O-(2,4-dinitrophenyl)-oligo(A) was found to inhibit the enzyme reversibly and compete with the primer-template poly(A)-(dT)12, whereas poly-2'-O-(3-fluoro-4,6-dinitrophenyl)-poly(A) was found to inactivate HIV-1 RT irreversibly by covalent labeling. A comparison of physicochemical properties of the hybrids poly(A)-poly(dT) and dinitrophenyl-poly(A)-poly(dT) shows that the hydrophobic dinitrophenyl groups stabilize double helical structures. These inhibitors were also found to be effective in keeping susceptible lymphocytes viable in the presence of HIV-1 (wild type). The effective inhibitor concentrations (EC50) were found to be 0.2-2.6 microgram/ml. No toxic effect on the host cells was found even at 100-1000-fold higher inhibitor concentrations.

Animals↗

PubMed2003

Structure-activity relationship studies on a novel family of specific HIV-1 reverse transcriptase inhibitors.

We have previously reported the discovery and preliminary structure-activity relationships of a new class of specific HIV-1 reverse transcriptase (RT) inhibitors whose prototype compound is the 1-[2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3-N-[(carboxy) methyl]-thymine. In an attempt to increase the inhibitory efficacy against HIV-1 RT of this new class of nucleosides, and to further explore the structural features required for anti-HIV-1 activity, different types of modifications have been carried out on the prototype compound. These include substitution of the tert-butyldimethylsilyl groups by other liphophilic groups, replacement of the carboxy group at the N-3 position of the nucleobase by other functional groups, change in the length of the spacer between the thymine and the carboxylic acid residue and substitution of the thymine moiety by other pyrimidine (uracil, 5-ethyluracil) or purine (hypoxanthine) nucleobases. In addition, the most salient structural features of this new class of HIV-1-specific nucleosides have been incorporated into classical HIV RT nucleoside inhibitors such as ddl, AZT, d4T. Our studies demonstrate that both the carboxymethyl moiety at the nucleobase and tert-butyldimethylsilyl groups at the sugar are important structural components since deletion of either of them is detrimental to the antiviral activity.

Anti-HIV Agents↗

PubMed2006

A comparison between abacavir and efavirenz as the third drug used in combination with a background therapy regimen of 2 nucleoside reverse-transcriptase inhibitors in patients with initially suppressed viral loads.

BACKGROUND: Our objective was to compare the rate of viral rebound and therapy failure in patients receiving abacavir or efavirenz as the third drug (in addition to 2 non-abacavir nucleosides) in combination antiretroviral therapy (cART) and to compare the rate of metabolic alteration associated with these regimens. METHODS: We conducted a multicohort prospective observational study of human immunodeficiency virus-infected patients who had attained viral loads < or = 80 copies/mL while receiving cART, without having previously received antiretrovirals. The rates of virological rebound, therapy failure, and lipid-level alteration during follow-up were calculated as the number of events divided by person-years of follow-up (PYFU). A multivariable analysis was performed using a Poisson regression model. RESULTS: We studied a total of 744 patients; the median age was 37 years, 27% of the patients were female, and 41% were heterosexual. There was a total of 854 PYFU spent receiving efavirenz and 285 spent receiving abacavir. The nucleoside reverse-transcriptase inhibitor pairs most frequently used were zidovudine/lamivudine (66% of PYFU), stavudine/lamivudine (17.6%), and stavudine/didanosine (5.4%). The adjusted relative rates of virological failure and therapy failure for abacavir, compared with those for efavirenz, were 2.17 (95% confidence interval [CI], 1.12-4.18; P = .02) and 1.41 (95% CI, 1.01-2.01; P = .05), respectively. CONCLUSIONS: Patients with virological suppression while receiving regimens containing abacavir appear more likely to experience virological and therapy failure than those receiving efavirenz as their third drug. Although this is a selected group of adherent patients, bias cannot be ruled out, because this is a nonrandomized comparison.

Acquired Immunodeficiency Syndrome↗

PubMed1995

The inhibition of human immunodeficiency virus type 1 in vitro by a non-nucleoside reverse transcriptase inhibitor MKC-442, alone and in combination with other anti-HIV compounds.

MKC-442, a derivative of the non-nucleoside reverse transcriptase (RT) inhibitor 1-[(2-hydroxyethoxy)methyl)-6-(phenylthio)thymidine (HEPT), showed potent and selective inhibition of human immunodeficiency virus type 1 (HIV-1) replication in vitro, using a range of host-cell/virus systems including human peripheral blood mononuclear cells infected with primary clinical isolates. MKC-442 was evaluated in combination with the nucleoside analogues AZT, ddI and ddC, the non-nucleoside RT inhibitor nevirapine, the HIV-1 proteinase inhibitor Ro-31-8959, and the alpha-glucosidase 1 inhibitor, MDL-28,574, using a cell viability assay. Drug interactions were evaluated by the isobologram technique and by calculating combination indices. Notable synergistic inhibition of HIV-1 replication was observed when MKC-442 was combined with AZT and MDL-28,574 and moderate synergy with ddI. In combination with ddC, nevirapine or Ro-31-8959, only a slightly better than additive effect was observed. Impressive synergy was seen using the three-drug combinations of MKC-442, AZT and MDL-28,574 or MKC-442, AZT and Ro-31-8959. No additional cytotoxicity was observed as measured by [3H]thymidine incorporation by concanavalin A-stimulated peripheral blood mononuclear cells, when MKC-442 was combined with any of the above-mentioned compounds. The use of MKC-442 in a two- or three-drug combination regimen with other RT inhibitors, a proteinase inhibitor or an alpha-glucosidase 1 inhibitor should be considered for HIV-1-related chemotherapy.

Antiviral Agents↗

PubMed2000

Resistance profile of the human immunodeficiency virus type 1 reverse transcriptase inhibitor abacavir (1592U89) after monotherapy and combination therapy. CNA2001 Investigative Group.

Abacavir (1592U89) is a nucleoside inhibitor of human immunodeficiency virus (HIV) type 1 reverse transcriptase (RT). Resistance to abacavir was studied with abacavir alone and with abacavir in combination with other nucleoside analogues in cell culture, in virus isolates from zidovudine/lamivudine clinical trials, and in the first dose-escalating 12-week clinical trial (CNA2001) to evaluate abacavir clinical potency. Abacavir alone in vitro selected for mutations at HIV RT codons K65R, L74V, Y115F, and M184V. However, abacavir combined with zidovudine selected against virus with the M184V mutation. Abacavir therapy in vivo resulted in large decreases in HIV load (>1 log), even in 1 subject who had the M184V mutation at baseline. A total of 51% of subjects showed new mutations at any of codons K65R, L74V, and M184V after abacavir monotherapy, compared with 11% who received zidovudine/abacavir. Small changes (2- to 4-fold) in abacavir susceptibility were detected. On stopping therapy, reselection of the pretherapy sequence occurred within 4 weeks.

Acquired Immunodeficiency Syndrome↗

PubMed2001

SJ-3366, a unique and highly potent nonnucleoside reverse transcriptase inhibitor of human immunodeficiency virus type 1 (HIV-1) that also inhibits HIV-2.

We have identified and characterized a potent new nonnucleoside reverse transcriptase (RT) inhibitor (NNRTI) of human immunodeficiency virus type 1 (HIV-1) that also is active against HIV-2 and which interferes with virus replication by two distinct mechanisms. 1-(3-Cyclopenten-1-yl)methyl-6-(3,5-dimethylbenzoyl)-5-ethyl-2,4-pyrimidinedione (SJ-3366) inhibits HIV-1 replication at concentrations of approximately 1 nM, with a therapeutic index of greater than 4 x 10(6). The efficacy and toxicity of SJ-3366 are consistent when evaluated with established or fresh human cells, and the compound is equipotent against all strains of HIV-1 evaluated, including syncytium-inducing, non-syncytium-inducing, monocyte/macrophage-tropic, and subtype virus strains. Distinct from other members of the pharmacologic class of NNRTIs, SJ-3366 inhibited laboratory and clinical strains of HIV-2 at a concentration of approximately 150 nM, yielding a therapeutic index of approximately 20,000. Like most NNRTIs, the compound was less active when challenged with HIV-1 strains possessing the Y181C, K103N, and Y188C amino acid changes in the RT and selected for a virus with a Y181C amino acid change in the RT after five tissue culture passages in the presence of the compound. In combination anti-HIV assays with nucleoside and nonnucleoside RT and protease inhibitors, additive interactions occurred with all compounds tested with the exception of dideoxyinosine, with which a synergistic interaction was found. Biochemically, SJ-3366 exhibited a K(i) value of 3.2 nM, with a mixed mechanism of inhibition against HIV-1 RT, but it did not inhibit HIV-2 RT. SJ-3366 also inhibited the entry of both HIV-1 and HIV-2 into target cells. On the basis of its therapeutic index and multiple mechanisms of anti-HIV action, SJ-3366 represents an exciting new compound for use in HIV-infected individuals.

Drug Resistance, Microbial↗

PubMed2005

Newer aminopyrimidinimino isatin analogues as non-nucleoside HIV-1 reverse transcriptase inhibitors for HIV and other opportunistic infections of AIDS: design, synthesis and biological evaluation.

Human immuno deficiency virus (HIV) weakens the immune system so that many opportunistic infections (OIs) like tuberculosis, hepatitis, bacterial infections etc can develop. In this paper, we designed aminopyrimidinimino isatin lead compound as a novel non-nucleoside reverse transcriptase inhibitor (NNRTI) with broad-spectrum chemotherapeutic properties for the effective treatment of AIDS and AIDS-related OIs. Compound 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-[[N4-[3'-(4'-amino-5'-trimethoxybenzyl pyrimidin-2'-yl)imino-1'-(5-methylisatinyl)]methyl]-N1-piperazinyl]-3-quinoline carboxylic acid (10) emerged as the most potent broad-spectrum chemotherapeutic agent active against HIV, HCV, Mycobacterium tuberculosis and various pathogenic bacteria.

AIDS-Related Opportunistic Infections↗

PubMed1999

Structure-based design of non-nucleoside reverse transcriptase inhibitors of drug-resistant human immunodeficiency virus.

A computer model of reverse transcriptase (RT) from human immunodeficiency virus type 1 (HIV-1) was used to design thiourea compounds that were predicted to inhibit RT. The RT model was used to approximate how changes in binding pocket shape, volume and chemical properties resulting from residue mutations would affect inhibitor binding. Our lead compound, N-[2-(2,5-dimethoxyphenylethyl)]-N'-[2-(5-bromopyridyl)]-thi ourea (HI-236) was tested against clinically observed non-nucleoside inhibitor (NNI)-resistant mutated strains of HIV. HI-236 was more potent than trovirdine, MKC-442 and zidovudine against the drug-sensitive HIV-1 strain IIIB, 50-100 times more effective than delavirdine or nevirapine and twice as effective as our recently reported lead compound N-[2-(2-fluorophenethyl)]-N'-[2-(5-bromopyridyl)]-thiourea (HI-240) against the NNI-resistant Y181C mutant HIV-1 strain A17. HI-236 was highly effective against the multidrug-resistant HIV-1 strain RT-MDR containing multiple mutations involving the RT residues 74V, 41L, 106A and 215Y. In general, thiourea compounds such as HI-236 and HI-240 showed better inhibition of drug-resistant strains of HIV-1 than thioalkylbenzyl-pyrimidine compounds such as HI-280 and HI-281. The improved activity of thioureas against RT mutants is consistent with a structural analysis of the NNI binding pocket model of RT. The activity of HI-236 against RT-MDR was superior to that of other anti-HIV agents tested, in the following order, from high to low activity; HI-236 (IC50 5 nM), HI-240 (IC50 6 nM), trovirdine (IC50 20 nM), zidovudine (IC50 150 nM), MKC-442 (IC50 300 nM), delavirdine (IC50 400 nM) and nevirapine (IC50 5 microM).

Alanine↗

PubMed2006

Molecular mechanism by which the K70E mutation in human immunodeficiency virus type 1 reverse transcriptase confers resistance to nucleoside reverse transcriptase inhibitors.

The K70E mutation in human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) has become more prevalent in clinical samples, particularly in isolates derived from patients for whom triple-nucleoside regimens that include tenofovir (TNV), abacavir, and lamivudine (3TC) failed. To elucidate the molecular mechanism by which this mutation confers resistance to these nucleoside RT inhibitors (NRTI), we conducted detailed biochemical analyses comparing wild-type (WT), K70E, and K65R HIV-1 RT. Pre-steady-state kinetic experiments demonstrate that the K70E mutation in HIV-1 RT allows the enzyme to discriminate between the natural deoxynucleoside triphosphate substrate and the NRTI triphosphate (NRTI-TP). Compared to the WT enzyme, K70E RT showed 2.1-, 2.3-, and 3.5-fold-higher levels of resistance toward TNV-diphosphate, carbovir-TP, and 3TC-TP, respectively. By comparison, K65R RT demonstrated 12.4-, 12.0-, and 13.1-fold-higher levels of resistance, respectively, toward the same analogs. NRTI-TP discrimination by the K70E (and K65R) mutation was primarily due to decreased rates of NRTI-TP incorporation and not to changes in analog binding affinity. The K65R and K70E mutations also profoundly impaired the ability of RT to excise 3'-azido-2',3'-dideoxythymidine monophosphate (AZT-MP) and other NRTI-MP from the 3' end of a chain-terminated primer. When introduced into an enzyme with the thymidine analog mutations (TAMs) M41L, L210W, and T215Y, the K70E mutation inhibited ATP-mediated excision of AZT-MP. Taken together, these findings indicate that the K70E mutation, like the K65R mutation, reduces susceptibility to NRTI by selectively decreasing NRTI-TP incorporation and is antagonistic to TAM-mediated nucleotide excision.

Adenine↗

PubMed2000

Structure-based design, synthesis, and biological evaluation of novel pyrrolyl aryl sulfones: HIV-1 non-nucleoside reverse transcriptase inhibitors active at nanomolar concentrations.

Pyrrolyl aryl sulfones (PASs) have been recently reported as a new class of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) inhibitors acting at the non-nucleoside binding site of this enzyme (Artico, M.; et al. J. Med. Chem. 1996, 39, 522-530). Compound 3, the most potent inhibitor within the series (EC(50) = 0.14 microM, IC(50) = 0.4 microM, and SI > 1429), was then selected as a lead compound for a synthetic project based on molecular modeling studies. Using the three-dimensional structure of RT cocrystallized with the alpha-APA derivative R95845, we derived a model of the RT/3 complex by taking into account previously developed structure-activity relationships. Inspection of this model and docking calculations on virtual compounds prompted the design of novel PAS derivatives and related analogues. Our computational approach proved to be effective in making qualitative predictions, that is in discriminating active versus inactive compounds. Among the compounds synthesized and tested, 20 was the most active one, with EC(50) = 0.045 microM, IC(50) = 0.05 microM, and SI = 5333. Compared with the lead 3, these values represent a 3- and 8-fold improvement in the cell-based and enzyme assays, respectively, together with the highest selectivity achieved so far in the PAS series.

Cell Survival↗