Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

For AIDS therapy, there are currently a number of compounds available for multiple targets already approved by the FDA and in clinic, e.g. protease inhibitors, reverse transcriptase inhibitors (NRTI, NNRTI), fusion inhibitors, CCR4, CCR5 among others. Some pharmaceuticals act against the virus before the entrance of HIV into the host cells. One of these targets is the glucosidase protein. This novel fusion target has been recently explored because the synthesis of viral glycoproteins depends on the activity of enzymes, such as glucosidase and transferase, for the elaboration of the polysaccharides. In this work we have built an homology model of Saccharomyces cerevisiae glucosidase and superimposed all relevant glucosidase-like enzymes in complex with carbohydrates, and calculated as well molecular interaction fields in our S. cerevisiae active site model. Our results suggest that there are two saccharide binding sites which are the most important for the binding of inhibitors with this family of enzymes which supports the possibility of inhibitors containing only two sugar units. Based on these results, we have proposed a novel pseudo-dissacharide which is a potential pharmaceutical for AIDS treatment.
...
PMID:Homology modeling and molecular interaction field studies of alpha-glucosidases as a guide to structure-based design of novel proposed anti-HIV inhibitors. 1607 3

Combinatorial chemistry has been well recognized as an important tool of drug discovery. An ongoing hand is to integrate the combinatorial approach with fundamentals of medicinal chemistry and rational drug design. The last five years has seen an explosion in the exploration and adoption of combinatorial techniques. Indeed, it is difficult to identify any other topic in chemistry that has ever caught the imagination of chemists with such fervor and with the continuous development of high throughput screening methods. There is a growing need for the synthesis of a large number of molecules. Compound libraries designed to produce specific inhibitors of therapeutic target proteins have generated significant interest in drug discovery research. Combinatorial chemistry provides the opportunity to generate large libraries of compounds for biological testing. A literature search revealed that many lead compounds have indeed been discovered from libraries and this review presents a survey of combinatorial synthesis of HIV-1 reverse transcriptase inhibitors, protease inhibitors, HIV-1 function inhibitors such as adsorption inhibitors, CCR5 antagonists and HIV-1 Tat-tar inhibitors that can be developed as potential anti-HIV drugs.
...
PMID:Combinatorial synthesis of anti-HIV agents--a review. 1610 78

Current targets for antiretroviral therapy (ART) include the viral enzymes reverse transcriptase and protease. The use of a combination of inhibitors targeting these enzymes can reduce viral load for a prolonged period and delay disease progression. However, complications of ART, including the emergence of viruses resistant to current drugs, are driving the development of new antiretroviral agents targeting not only the reverse transcriptase and protease enzymes but novel targets as well. Indeed, enfuvirtide, an inhibitor targeting the viral envelope protein (Env) was recently approved for use in combination therapy in individuals not responding to current antiretroviral regimens. Emerging drug targets for ART include: (i) inhibitors that directly or indirectly target Env; (ii) the HIV enzyme integrase; and (iii) inhibitors of maturation that target the substrate of the protease enzyme. Env mediates entry of HIV into target cells via a multistep process that presents three distinct targets for inhibition by viral and cellular-specific agents. First, attachment of virions to the cell surface via nonspecific interactions and CD4 binding can be blocked by inhibitors that include cyanovirin-N, cyclotriazadisulfonamide analogues, PRO 2000, TNX 355 and PRO 542. In addition, BMS 806 can block CD4-induced conformational changes. Secondly, Env interactions with the co-receptor molecules can be targeted by CCR5 antagonists including SCH-D, maraviroc (UK 427857) and aplaviroc (GW 873140), and the CXCR4 antagonist AMD 070. Thirdly, fusion of viral and cellular membranes can be inhibited by peptides such as enfuvirtide and tifuvirtide (T 1249). The development of entry inhibitors has been rapid, with an increasing number entering clinical trials. Moreover, some entry inhibitors are also being evaluated as candidate microbicides to prevent mucosal transmission of HIV. The integrase enzyme facilitates the integration of viral DNA into the host cell genome. The uniqueness and specificity of this reaction makes integrase an attractive drug target. However, integrase inhibitors have been slow to reach clinical development, although recent contenders, including L 870810, show promise. Inhibitors that target viral maturation via a unique mode of action, such as PA 457, also have potential. In addition, recent advances in our understanding of cellular pathways involved in the life cycle of HIV have also identified novel targets that may have potential for future antiretroviral intervention, including interactions between the cellular proteins APOBEC3G and TSG101, and the viral proteins Vif and p6, respectively. In summary, a number of antiretroviral agents in development make HIV entry, integration and maturation emerging drug targets. A multifaceted approach to ART, using combinations of inhibitors that target different steps of the viral life cycle, has the best potential for long-term control of HIV infection. Furthermore, the development of microbicides targeting HIV holds promise for reducing HIV transmission events.
...
PMID:Emerging drug targets for antiretroviral therapy. 1611 75

The first small-molecule CCR5 antagonist, TAK-779, could not be developed as an anti-human immunodeficiency virus type (anti-HIV-1) agent because of its poor oral bioavailability. TAK-652 is an orally bioavailable TAK-779 derivative with potent anti-HIV-1 activity. TAK-652 inhibited the binding of RANTES (regulated on activation, normal T-cell expressed and secreted), macrophage inflammatory protein 1alpha (MIP-1alpha), and MIP-1beta to CCR5-expressing cells at nanomolar concentrations. TAK-652 could also suppress the binding of monocyte chemotactic protein 1 (MCP-1) to CCR2b-expressing cells. However, its inhibitory effect on ligand binding to other chemokine receptors was limited. TAK-652 was active against CCR5-using (R5) HIV-1 but totally inactive against CXCR4-using (X4) HIV-1. The compound was active against R5 HIV-1 clinical isolates containing reverse transcriptase and protease inhibitor-resistant mutations, with a mean 50% effective concentration (EC50) and EC90 of 0.061 and 0.25 nM, respectively. In addition, recombinant R5 viruses carrying different subtype (A to G) envelope proteins were equally susceptible to TAK-652. A single oral administration of TAK-652 up to 100 mg was safe and well tolerated in humans. The compound displayed favorable pharmacokinetics, and its plasma concentration was 7.2 ng/ml (9.1 nM) even 24 h after the administration of 25 mg. Thus, TAK-652 is a promising candidate as a novel entry inhibitor of HIV-1.
...
PMID:TAK-652 inhibits CCR5-mediated human immunodeficiency virus type 1 infection in vitro and has favorable pharmacokinetics in humans. 1625 Dec 99

Since the introduction of the nucleoside reverse transcriptase inhibitor zidovudine in 1987, the number of the available antiretroviral medications has grown to about 20. Despite the efficacy of these medications, treatment-limiting adverse events are frequent. During the last several years, a new class of antiretroviral drugs often referred to as entry inhibitors, specifically the CCR5 blockers, have moved from the basic science laboratories and are now in the clinical phases of drug development. There are three agents in phase 2/3 development that inhibit viral entry by binding to CCR5, disrupting the interaction between the co-receptor and viral glycoprotein (gp) 120. They are aplaviroc (GW-873140), maraviroc (UK-427,857), and vicriviroc (SCH 417690). The development of these new antiviral agents that target different aspects of the viral life cycle is likely to make it possible to suppress viral strains that are resistant to the currently available antiretroviral drugs. There is a growing need for a new class of antiretrovirals with reduced toxicity and improved tolerability. However, currently available information suggests further pharmacokinetics, resistance, safety, and efficacy data are needed to understand how these agents may be effectively used in the clinical setting.
...
PMID:Human immunodeficiency virus (HIV) entry inhibitors (CCR5 specific blockers) in development: are they the next novel therapies? 1630 33

The persistence of human immunodeficiency virus type 1 (HIV-1) in memory CD4+ T cells is a major obstacle to the eradication of the virus with current antiretroviral therapy. Here, we investigated the effect of the activation status of CD4+ T cells on the predominance of R5 and X4 HIV-1 variants in different subsets of CD4+ T cells in ex vivo-infected human lymphoid tissues and peripheral blood mononuclear cells (PBMCs). In these cell systems, we examined the sensitivity of HIV replication to reverse transcriptase inhibitors. We demonstrate that R5 HIV-1 variants preferentially produced productive infection in HLA-DR- CD62L- CD4+ T cells. These cells were mostly in the G1b phase of the cell cycle, divided slowly, and expressed high levels of CCR5. In contrast, X4 HIV-1 variants preferentially produced productive infection in activated HLA-DR+ CD62L+ CD4+ T cells, which expressed high levels of CXCR4. The abilities of the nucleoside reverse transcriptase inhibitors (NRTI) zidovudine and lamivudine to stop HIV-1 replication were 20 times greater in activated T cells than in slowly dividing HLA-DR- CD62L- CD4+ T cells. This result, demonstrated both in a highly physiologically relevant ex vivo lymphoid tissue model and in PBMCs, correlated with higher levels of thymidine kinase mRNA in activated than in slowly dividing HLA-DR- CD62L- CD4+ T cells. The non-NRTI nevirapine was equally efficient in both cell subsets. The lymphoid tissue and PBMC-derived cell systems represent well-defined models which could be used as new tools for the study of the mechanism of resistance to HIV-1 inhibitors in HLA-DR- CD62L- CD4+ T cells.
...
PMID:R5 variants of human immunodeficiency virus type 1 preferentially infect CD62L- CD4+ T cells and are potentially resistant to nucleoside reverse transcriptase inhibitors. 1637 87

Entry inhibitors represent a new generation of antivirals for the treatment of HIV infection. Several compounds which block the attachment of HIV gp120 to either the CD4 T cell receptor or the CCR5/CXCR4 co-receptors are currently in clinical development. Most of these compounds have different molecular structures and specific mechanisms of action. These agents are eagerly awaited by a growing number of patients carrying viruses resistant viruses to many of the current available reverse transcriptase and protease inhibitors. For enfuvirtide, the first and, so far, only entry inhibitor approved for clinical use, the main mechanism of resistance is the selection of changes within a 10 amino acid segment encompassing residues 36-45 within the HR1 region of gp41. For other entry inhibitors, multiple changes in different gp120 domains (V1, V2, V3, C2 and C4) have been associated with loss of susceptibility to these agents, although in most cases with limited cross-resistance.
...
PMID:HIV entry inhibitors: mechanisms of action and resistance pathways. 1646 88

Human immunodeficiency virus (HIV) infection affects close to 40 million individuals worldwide. Since 1981 when the first case reports of individuals dying from a then rare opportunistic infection were published, twenty million people have died from this epidemic. With 3 or more antiretrovirals as the standard of care, the prevalence of single, double and triple-class resistant HIV strains has increased significantly over the last 5 years due to the tremendous replicative capacity of HIV and selective drug pressure. With greater resistance comes the need for novel and effective antiretrovirals to treat these resistant strains. The purpose of this review is to highlight the most promising agents and classes in Phase II-III drug development by assessing the clinical efficacy, pharmacology, resistance and tolerability. Three out of the four existing antiretroviral classes (nucleosides, non-nucleosides, protease inhibitors) with agents in clinical trials will be discussed such as nucleoside reverse transcriptase inhibitors (D-d4FC, SPD754), non-nucleoside reverse transcriptase inhibitors (capravirine, TMC125) and protease inhibitors (tipranavir, TMC114). In the next several years, antiretrovirals from novel pharmacologic classes will enter the HIV armamentarium. Based on the early clinical studies, these promising agents will be reviewed from the following classes: attachment inhibitors (TNX-355, BMS-488043), CCR5 coreceptor antagonists (SCH-D, UK-427857, GW 873140) and a maturation inhibitor (PA-457). It is hoped that these agents will represent a therapeutic advance and better activity against HIV resistant strains by providing effective therapy that will reduce viral load, increase the CD4+ cell count and ultimately, prolong survival with minimal adverse effects.
...
PMID:On the horizon: promising investigational antiretroviral agents. 1651 88

The new generation of antiviral drugs intended to counter HIV-1 entry into susceptible cells is emerging swiftly. The antiviral agents that inhibit HIV entry to the target cells (denoted as HIV entry inhibitors) are already in different phases of clinical trials. Operating early in the viral life cycle, they prevent viral entry, and have a novel, highly specific mechanism of action with a low toxicity profile. Entry inhibitors have different toxicity and resistance profiles than the existing reverse transcriptase and protease inhibitors. Some of these compounds demonstrated in vitro synergism with other classes of antivirals, thus offering the rationale for their combination in therapies for HIV-infected individuals. It is worth focusing on recent developments in HIV entry inhibitors, as most of the current drug regimens suffer from the events of developing resistance against existing combination therapies. Recent advances in the understanding of the cellular and molecular mechanisms of HIV-1 entry provide the basis for novel therapeutic strategies that prevent viral penetration of the target cell-membrane, while reducing detrimental virus and treatment effects on cells and prolonging virion exposure to immune defenses. A number of potential sites for therapeutic intervention become accessible during the narrow window between virus attachment and the subsequent fusion of viral envelope with the cell membrane. The HIV-1 coreceptors are particularly attractive from the perspective of identifying new antiviral compounds, since they are seven-transmembrane motif G protein-coupled receptors (GPCRs), a family of proteins that is a well-validated target for drug development. Among the many chemokine receptors that can mediate HIV-1 entry in vitro, only CCR5 and CXCR4 are of frontline pharmacological importance. In particular, CCR5 is essential for viral transmission and replication during the early and clinically latent phase of disease. Several small-molecule antagonists of CCR5 and CXCR4 that block chemokine binding and HIV-1 entry have been identified in recent years. Considerable advances have been made in the last years in the design of derivatives acting as inhibitors of HIV entry. The molecular mechanism involved in viral entry, the structural and functional aspects of entry inhibitors are reviewed here. We have also summarized the recent insights into how small-molecule antagonists interact with CCR5 and CXCR4, focusing on drug development programs that are well documented in the scientific literature. An overview of the entry inhibitors that are in preclinical or early clinical development, and the Quantitative Structure-Activity Relationships (QSAR) studies reported for the coreceptor antagonists are also be presented.
...
PMID:The HIV entry inhibitors revisited. 1661 Oct 75

Oligonucleotide agents (ODN) are emerging as attractive alternatives to chemical drugs. However, the clinical use of ODNs as therapeutics has been hindered by their susceptibility to degradation by cellular enzymes and their limited ability to penetrate intact cells. We have used various liposome-mediated transfection agents, for the in vitro delivery of DNA thioaptamers into U373-MAGI-CCR5 cells. Our lead thioaptamer, R12-2, targets the RNase H domain of the HIV-1 reverse transcriptase (RT) and inhibits viral infection in U373-MAGI-CCR5 cells. R12-2, a 62-base-pair, double-stranded DNA molecule with a monothio-phosphate modified backbone, was selected through a novel combinatorial selection method. We studied the use of oligofectamine (OF), TFX-20, Transmessenger (TM), and Gene Jammer (GJ) for transfection of the thio-modified DNA aptamers. OF-transfected U373-MAGI-CCR5 cells resulted in 68% inhibition of HIV infection in the treated cells compared to the untreated control. Inhibition was observed in a dose-dependent manner with maximal inhibition of 83%. In this report, we demonstrate that monothioate-modified DNA duplex oligonucleotides can be efficiently delivered into cells by liposome-based transfection agents to inhibit HIV replication.
...
PMID:Delivery of double-stranded DNA thioaptamers into HIV-1 infected cells for antiviral activity. 1663 Nov 18


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---