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Intravenous delivery of GS-441524 is efficacious in the African green monkey model of SARS-CoV-2 infection. Antiviral Res 2022; 203:105329. [PMID: 35525335 PMCID: PMC9068261 DOI: 10.1016/j.antiviral.2022.105329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 04/26/2022] [Accepted: 04/29/2022] [Indexed: 01/17/2023]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the COVID-19 pandemic, has infected over 260 million people over the past 2 years. Remdesivir (RDV, VEKLURY®) is currently the only antiviral therapy fully approved by the FDA for the treatment of COVID-19. The parent nucleoside of RDV, GS-441524, exhibits antiviral activity against numerous respiratory viruses including SARS-CoV-2, although at reduced in vitro potency compared to RDV in most assays. Here we find in both human alveolar and bronchial primary cells, GS-441524 is metabolized to the pharmacologically active GS-441524 triphosphate (TP) less efficiently than RDV, which correlates with a lower in vitro SARS-CoV-2 antiviral activity. In vivo, African green monkeys (AGM) orally dosed with GS-441524 yielded low plasma levels due to limited oral bioavailability of <10%. When GS-441524 was delivered via intravenous (IV) administration, although plasma concentrations of GS-441524 were significantly higher, lung TP levels were lower than observed from IV RDV. To determine the required systemic exposure of GS-441524 associated with in vivo antiviral efficacy, SARS-CoV-2 infected AGMs were treated with a once-daily IV dose of either 7.5 or 20 mg/kg GS-441524 or IV RDV for 5 days and compared to vehicle control. Despite the reduced lung TP formation compared to IV dosing of RDV, daily treatment with IV GS-441524 resulted in dose-dependent efficacy, with the 20 mg/kg GS-441524 treatment resulting in significant reductions of SARS-CoV-2 replication in the lower respiratory tract of infected animals. These findings demonstrate the in vivo SARS-CoV-2 antiviral efficacy of GS-441524 and support evaluation of its orally bioavailable prodrugs as potential therapies for COVID-19.
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Toll-Like Receptor 8 Agonist GS-9688 Induces Sustained Efficacy in the Woodchuck Model of Chronic Hepatitis B. Hepatology 2021; 73:53-67. [PMID: 32246499 PMCID: PMC7898792 DOI: 10.1002/hep.31255] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 02/27/2020] [Accepted: 03/18/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND AND AIMS GS-9688 (selgantolimod) is an oral selective small molecule agonist of toll-like receptor 8 in clinical development for the treatment of chronic hepatitis B. In this study, we evaluated the antiviral efficacy of GS-9688 in woodchucks chronically infected with woodchuck hepatitis virus (WHV), a hepadnavirus closely related to hepatitis B virus. APPROACH AND RESULTS WHV-infected woodchucks received eight weekly oral doses of vehicle, 1 mg/kg GS-9688, or 3 mg/kg GS-9688. Vehicle and 1 mg/kg GS-9688 had no antiviral effect, whereas 3 mg/kg GS-9688 induced a >5 log10 reduction in serum viral load and reduced WHV surface antigen (WHsAg) levels to below the limit of detection in half of the treated woodchucks. In these animals, the antiviral response was maintained until the end of the study (>5 months after the end of treatment). GS-9688 treatment reduced intrahepatic WHV RNA and DNA levels by >95% in animals in which the antiviral response was sustained after treatment cessation, and these woodchucks also developed detectable anti-WHsAg antibodies. The antiviral efficacy of weekly oral dosing with 3 mg/kg GS-9688 was confirmed in a second woodchuck study. The antiviral response to GS-9688 did not correlate with systemic GS-9688 or cytokine levels but was associated with transient elevation of liver injury biomarkers and enhanced proliferative response of peripheral blood mononuclear cells to WHV peptides. Transcriptomic analysis of liver biopsies taken prior to treatment suggested that T follicular helper cells and various other immune cell subsets may play a role in the antiviral response to GS-9688. CONCLUSIONS Finite, short-duration treatment with a clinically relevant dose of GS-9688 is well tolerated and can induce a sustained antiviral response in WHV-infected woodchucks; the identification of a baseline intrahepatic transcriptional signature associated with response to GS-9688 treatment provides insights into the immune mechanisms that mediate this antiviral effect.
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Structure-guided discovery of a novel, potent, and orally bioavailable 3,5-dimethylisoxazole aryl-benzimidazole BET bromodomain inhibitor. Bioorg Med Chem 2018; 27:457-469. [PMID: 30606676 DOI: 10.1016/j.bmc.2018.11.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 11/05/2018] [Accepted: 11/13/2018] [Indexed: 12/12/2022]
Abstract
The bromodomain and extra-terminal (BET) family of proteins, consisting of the bromodomains containing protein 2 (BRD2), BRD3, BRD4, and the testis-specific BRDT, are key epigenetic regulators of gene transcription and has emerged as an attractive target for anticancer therapy. Herein, we describe the discovery of a novel potent BET bromodomain inhibitor, using a systematic structure-based approach focused on improving potency, metabolic stability, and permeability. The optimized dimethylisoxazole aryl-benzimidazole inhibitor exhibited high potency towards BRD4 and related BET proteins in biochemical and cell-based assays and inhibited tumor growth in two proof-of-concept preclinical animal models.
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Lithium Chloride Catalyzed Asymmetric Domino Aza-Michael Addition/[3 + 2] Cycloaddition Reactions for the Synthesis of Spiro- and Bicyclic α,β,γ-Triamino Acid Derivatives. European J Org Chem 2018. [DOI: 10.1002/ejoc.201800585] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Phase 1 First-in-Human, Single- and Multiple-Ascending Dose, and Food Effect Studies to Assess the Safety, Tolerability, and Pharmacokinetics of Presatovir for the Treatment of Respiratory Syncytial Virus Infection. J Clin Pharmacol 2018; 58:1025-1034. [PMID: 29663420 DOI: 10.1002/jcph.1112] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 01/31/2018] [Indexed: 12/12/2022]
Abstract
Respiratory syncytial virus (RSV)-associated respiratory tract infection is a leading cause of hospitalizations in infants for which no effective treatment exists. RSV infection is also an important cause of respiratory disease in adults and immunocompromised patients. Presatovir (GS-5806) is an orally bioavailable antiviral agent that inhibits fusion of RSV with host cell membranes. Here, results from 2 phase 1 studies that evaluated safety, tolerability, and pharmacokinetics of presatovir in healthy adults following administration of single and multiple (7 days) once- or twice-daily ascending doses (first-in-human study) and in the presence or absence of food (food effect study) are described. Presatovir exhibited favorable safety and pharmacokinetic profiles that supported once-daily dosing. Presatovir exposure increased in an approximately dose-proportional manner across the evaluated dose range (single doses 25-300 mg; multiple doses 10-75 mg once daily for 7 days). Administration of presatovir with a high-fat meal did not alter exposure, supporting administration without regard to a meal in further clinical studies. These data were subsequently used to inform presatovir dosing regimens in a phase 2a challenge study of adults experimentally infected with RSV. Collectively, results from phase 1 evaluations and a phase 2a challenge study support further clinical investigation of presatovir for the treatment of RSV infection.
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Control of α/β Anomer Formation by a 2',5' Bridge: Toward Nucleoside Derivatives Locked in the South Conformation. J Org Chem 2017; 82:11337-11347. [PMID: 28972760 DOI: 10.1021/acs.joc.7b01000] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We describe a novel stereoselective synthesis of nucleoside derivatives with the ribose ring locked in the South conformation by a bridge between C2' and C5'. Despite the intrinsic constraints of the bicyclic structure, we demonstrate that their synthesis can be achieved by ring closing metathesis of readily accessible precursors. The obtained ribose derivatives are, however, very poor substrates for further installation of the nucleobases, and even simple nucleophiles, such as azido or cyano anions, react with unexpected stereo- or regioselectivity under standard glycosylation conditions. Here we explain this behavior by employing density functional theory (DFT) computations and devise an alternative approach resulting in isomers with the desired orientation of the nucleobase.
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Broad-spectrum Investigational Agent GS-5734 for the Treatment of Ebola, MERS Coronavirus and Other Pathogenic Viral Infections with High Outbreak Potential. Open Forum Infect Dis 2017. [PMCID: PMC5630887 DOI: 10.1093/ofid/ofx180.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Background Recent viral outbreaks with significant mortality such as Ebola virus (EBOV), SARS-coronavirus (CoV), and MERS-CoV reinforced the need for effective antiviral therapeutics to control future epidemics. GS-5734 is a novel nucleotide analog prodrug in the development for treatment of EBOV. Method Antiviral activity of GS-5734 has been established in vitro against a wide range of pathogenic RNA virus families, including filoviruses, coronaviruses, and paramyxoviruses (EC50 = 37 to 200 nM) (Warren et al., Nature 2016; Sheahan et al., Sci Transl Med 2017; Lo et al., Sci Rep 2017). Herein, we describe the in vivo translation of the broad-spectrum activity of GS-5734 in relevant animal disease models for Ebola, Marburg, MERS-CoV, and Nipah. Result Therapeutic efficacy against multiple filoviruses with 80–100% survival was observed in rhesus monkeys infected with lethal doses of EBOV (Kikwit/1995 or Makona/2014) or Marburg virus and treated with once daily intravenous (IV) administration of 5 to 10 mg/kg GS-5734 beginning 3 to 5 days post-infection (p.i.). In all rhesus monkey filovirus infection models, GS-5734 significantly reduced systemic viremia and ameliorated severe clinical disease signs and anatomic pathology. In mice infected with MERS-CoV, twice daily subcutaneous administration of 25 mg/kg GS-5734 beginning 1 day p.i. significantly reduced lung viral load and improved respiratory function. In rhesus monkeys, once-daily IV administration of 5 mg/kg GS-5734 initiated 1 day prior to MERS-CoV infection reduced lung viral load, improved clinical disease signs, and ameliorated severe lung pathology. Finally, in African green monkeys infected with a lethal dose of Nipah virus therapeutic once-daily IV administration of 10 mg/kg GS-5734, starting 1 day p.i. resulted in 100% survival to at least day 35 without any major respiratory or CNS symptoms. Conclusion GS-5734 is currently being tested in a phase 2 study in male Ebola survivors with persistent viral RNA in semen. Lyophilized drug formulation has been developed that can be administered to humans via a 30-minutes IV infusion and does not require cold chain storage. Together, these results support further development of GS-5734 as a broad-spectrum antiviral to treat viral infections with high mortality and significant outbreak potential. Disclosures R. Jordan, Gilead: Employee, Salary. J. Feng, Gilead: Employee, Salary I. Trantcheva, Gilead: Employee, Salary. D. Babusis, Gilead: Employee, Salary. D. Porter-Poulin, Gilead: Employee, Salary. R. Bannister, Gilead: Employee, Salary R. Mackman, Gilead: Employee, Salary. D. Siegel, Gilead: Employee, Salary A. Ray, Gilead: Employee, Salary, T. Cihlar, Gilead: Employee, Salary.
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N,2,3,4-Tetrasubstituted Pyrrolidines through Tandem Lithium Amide Conjugate Addition/Radical Cyclization/Oxygenation Reactions. European J Org Chem 2016. [DOI: 10.1002/ejoc.201600621] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Analysis of GS-5806 Resistance Emergence in Human Healthy Adult Subjects Experimentally Infected With Respiratory Syncytial Virus (RSV). Open Forum Infect Dis 2015. [DOI: 10.1093/ofid/ofv133.901] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Nucleotide Prodrug GS-5734 Is a Broad-Spectrum Filovirus Inhibitor That Provides Complete Therapeutic Protection Against the Development of Ebola Virus Disease (EVD) in Infected Non-human Primates. Open Forum Infect Dis 2015. [DOI: 10.1093/ofid/ofv130.02] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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GS-5806, A Novel Fusion Inhibitor of Respiratory Syncytial Virus Delivers High Respiratory Tract Levels in Preclinical Species. Open Forum Infect Dis 2015. [DOI: 10.1093/ofid/ofv133.523] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Synthesis and biological evaluation of conformationally restricted adenine bicycloribonucleosides. Org Biomol Chem 2015; 13:9300-13. [PMID: 26239898 DOI: 10.1039/c5ob00987a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We prepared a novel series of conformationally restricted bicyclonucleosides and nucleotides. The synthetic approach employed a ring closing metathesis to provide access to both 6 and 7 membered saturated and unsaturated rings linking the 3' to 5' methylene groups of the sugar. The bicyclonucleosides were also transformed to the corresponding phosphoramidate prodrugs by an innovative one-pot protocol of boronate ester protection, coupling of the phosphoryl chloridate and deprotection of the boronate. A similar strategy was also employed for the synthesis of the corresponding monophosphates as crucial intermediates for the synthesis of selected triphosphates. The biological properties of the nucleosides and monophosphate prodrugs were assessed for antiviral and cytostatic activities in cell based assays whilst the triphosphates were evaluated in enzymatic assays. The lack of significant effects suggests that the linkage of the 3' to 5'via a ring system and the subsequent conformational restriction of the ribose ring to the South conformation are incompatible with the kinases and polymerases that recognize nucleosides and their metabolites.
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Discovery of β-D-2'-deoxy-2'-α-fluoro-4'-α-cyano-5-aza-7,9-dideaza adenosine as a potent nucleoside inhibitor of respiratory syncytial virus with excellent selectivity over mitochondrial RNA and DNA polymerases. Bioorg Med Chem Lett 2015; 25:2484-7. [PMID: 25978965 DOI: 10.1016/j.bmcl.2015.04.073] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 04/16/2015] [Accepted: 04/20/2015] [Indexed: 11/16/2022]
Abstract
Novel 4'-substituted β-d-2'-deoxy-2'-α-fluoro (2'd2'F) nucleoside inhibitors of respiratory syncytial virus (RSV) are reported. The introduction of 4'-substitution onto 2'd2'F nucleoside analogs resulted in compounds demonstrating potent cell based RSV inhibition, improved inhibition of the RSV polymerase by the nucleoside triphosphate metabolites, and enhanced selectivity over incorporation by mitochondrial RNA and DNA polymerases. Selectivity over the mitochondrial polymerases was found to be extremely sensitive to the specific 4'-substitution and not readily predictable. Combining the most potent and selective 4'-groups from N-nucleoside analogs onto a 2'd2'F C-nucleoside analog resulted in the identification of β-D-2'-deoxy-2'-α-fluoro-4'-α-cyano-5-aza-7,9-dideaza adenosine as a promising nucleoside lead for RSV.
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Highly functionalized and potent antiviral cyclopentane derivatives formed by a tandem process consisting of organometallic, transition-metal-catalyzed, and radical reaction steps. Chemistry 2014; 20:10298-304. [PMID: 25043655 DOI: 10.1002/chem.201402595] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Indexed: 11/11/2022]
Abstract
A simple modular tandem approach to multiply substituted cyclopentane derivatives is reported, which succeeds by joining organometallic addition, conjugate addition, radical cyclization, and oxygenation steps. The key steps enabling this tandem process are the thus far rarely used isomerization of allylic alkoxides to enolates and single-electron transfer to merge the organometallic step with the radical and oxygenation chemistry. This controlled lineup of multiple electronically contrasting reactive intermediates provides versatile access to highly functionalized cyclopentane derivatives from very simple and readily available commodity precursors. The antiviral activity of the synthesized compounds was screened and a number of compounds showed potent activity against hepatitis C and dengue viruses.
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Respiratory Syncytial Virus Fusion Inhibitors. SUCCESSFUL STRATEGIES FOR THE DISCOVERY OF ANTIVIRAL DRUGS 2013. [DOI: 10.1039/9781849737814-00029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Infections with the respiratory syncytical virus (RSV) are the leading cause of lower respiratory tract infections and a serious health concern in infants less than 2 years of age, the immunocompromised and the geriatric population. Numerous research programs directed at small‐molecule inhibitors of RSV have been initiated over the last 50 years. RSV inhibitors that target the fusion event have shown a lot of promise and are reviewed in this chapter. However, none of these programs have yet reached the market or late‐stage clinical development. Therefore, focus in this review is given to the challenges in the preclinical development phase and the ideal target product profile. The challenges in clinical development are also discussed, including the use of a new RSV challenge strain (Memphis 37), clinical trial design in immunosupressed patients, patients with chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) and clinical trials in infants.
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A novel and efficient one-pot synthesis of symmetrical diamide (bis-amidate) prodrugs of acyclic nucleoside phosphonates and evaluation of their biological activities. Eur J Med Chem 2011; 46:3748-54. [DOI: 10.1016/j.ejmech.2011.05.040] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Revised: 05/12/2011] [Accepted: 05/14/2011] [Indexed: 10/18/2022]
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Abstract
A series of novel 7-deazapurine ribonucleosides bearing an alkyl, aryl, or hetaryl group in position 6 and H, F, or Cl atom in position 7 has been prepared either by Pd-catalyzed cross-coupling reactions of the corresponding protected 6-chloro-(7-halogenated-)7-deazapurine ribonucleosides with alkyl- or (het)arylorganometallics followed by deprotection, or by single-step aqueous phase cross-coupling reactions of unprotected 6-chloro-(7-halogenated-)7-deazapurine ribonucleosides with (het)arylboronic acids. Significant cytostatic effect was detected with a substantial proportion of the prepared compounds. The most potent were 7-H or 7-F derivatives of 6-furyl- or 6-thienyl-7-deazapurines displaying cytostatic activity in multiple cancer cell lines with a geometric mean of 50% growth inhibition concentration ranging from 16 to 96 nM, a potency comparable to or better than that of the nucleoside analogue clofarabine. Intracellular phosphorylation to mono- and triphosphates and the inhibition of total RNA synthesis was demonstrated in preliminary study of metabolism and mechanism of action studies.
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Low In Vitro Potential for Class-specific Toxicity of GS-9148, A Novel Nucleotide Reverse Transcriptase Inhibitor. Antiviral Res 2008. [DOI: 10.1016/j.antiviral.2008.01.043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Synthesis, cytostatic and anti-HCV activity of 6-(N-substituted aminomethyl)-, 6-(O-substituted hydroxymethyl)- and 6-(S-substituted sulfanylmethyl)purine nucleosides. Bioorg Med Chem 2008; 16:2329-66. [DOI: 10.1016/j.bmc.2007.11.067] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Revised: 11/21/2007] [Accepted: 11/23/2007] [Indexed: 10/22/2022]
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Synthesis, cytostatic, and antiviral activity of novel 6-[2-(dialkylamino)ethyl]-, 6-(2-alkoxyethyl)-, 6-[2-(alkylsulfanyl)ethyl]-, and 6-[2-(dialkylamino)vinyl]purine nucleosides. Bioorg Med Chem 2008; 16:1400-24. [DOI: 10.1016/j.bmc.2007.10.063] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Revised: 10/17/2007] [Accepted: 10/18/2007] [Indexed: 11/29/2022]
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Purines Bearing Phenanthroline or Bipyridine Ligands and Their RuII Complexes in Position 8 as Model Compounds for Electrochemical DNA Labeling – Synthesis, Crystal Structure, Electrochemistry, Quantum Chemical Calculations, Cytostatic and Antiviral Activity. Eur J Inorg Chem 2007. [DOI: 10.1002/ejic.200700030] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Cytostatic and antiviral 6-arylpurine ribonucleosides. Part 7: Synthesis and evaluation of 6-substituted purine l-ribonucleosides. Bioorg Med Chem Lett 2006; 16:5290-3. [PMID: 16905315 DOI: 10.1016/j.bmcl.2006.07.092] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2006] [Revised: 07/28/2006] [Accepted: 07/31/2006] [Indexed: 10/24/2022]
Abstract
A series of purine l-ribonucleosides 2a-2i bearing diverse C-substituents (alkyl, aryl, hetaryl or hydroxymethyl) in the position 6 were prepared by Pd-catalyzed cross-coupling reactions of 6-chloro-9-(2,3,5-tri-O-acetyl-beta-l-ribofuranosyl)purine with the corresponding organometallics followed by deprotection. Unlike their d-ribonucleoside enantiomers that possess strong cytostatic and anti-HCV activity, the l-ribonucleosides were inactive except for 6-benzylpurine nucleoside 2h showing moderate anti-HCV effect in replicon assay. A triphosphate of 2h did not inhibit HCV RNA polymerase.
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Structural basis for selectivity of a small molecule, S1-binding, submicromolar inhibitor of urokinase-type plasminogen activator. CHEMISTRY & BIOLOGY 2000; 7:299-312. [PMID: 10779411 DOI: 10.1016/s1074-5521(00)00104-6] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Urokinase-type plasminogen activator (uPA) is a protease associated with tumor metastasis and invasion. Inhibitors of uPA may have potential as drugs for prostate, breast and other cancers. Therapeutically useful inhibitors must be selective for uPA and not appreciably inhibit the related, and structurally and functionally similar enzyme, tissue-type plasminogen activator (tPA), involved in the vital blood-clotting cascade. RESULTS We produced mutagenically deglycosylated low molecular weight uPA and determined the crystal structure of its complex with 4-iodobenzo[b]thiophene 2-carboxamidine (K(i) = 0.21 +/- 0.02 microM). To probe the structural determinants of the affinity and selectivity of this inhibitor for uPA we also determined the structures of its trypsin and thrombin complexes, of apo-trypsin, apo-thrombin and apo-factor Xa, and of uPA, trypsin and thrombin bound by compounds that are less effective uPA inhibitors, benzo[b]thiophene-2-carboxamidine, thieno[2,3-b]-pyridine-2-carboxamidine and benzamidine. The K(i) values of each inhibitor toward uPA, tPA, trypsin, tryptase, thrombin and factor Xa were determined and compared. One selectivity determinant of the benzo[b]thiophene-2-carboxamidines for uPA involves a hydrogen bond at the S1 site to Ogamma(Ser190) that is absent in the Ala190 proteases, tPA, thrombin and factor Xa. Other subtle differences in the architecture of the S1 site also influence inhibitor affinity and enzyme-bound structure. CONCLUSIONS Subtle structural differences in the S1 site of uPA compared with that of related proteases, which result in part from the presence of a serine residue at position 190, account for the selectivity of small thiophene-2-carboxamidines for uPA, and afford a framework for structure-based design of small, potent, selective uPA inhibitors.
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Active-site topologies of human CYP2D6 and its aspartate-301 --> glutamate, asparagine, and glycine mutants. Arch Biochem Biophys 1996; 331:134-40. [PMID: 8660692 DOI: 10.1006/abbi.1996.0291] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Cytochrome P450 2D6 (CYP2D6) catalyzes the oxidation of substrates with a positively charged nitrogen atom 5-7 angstroms from the site of the oxidation. The active-site topology of CYP2D6 is examined here with phenyl-, 2-naphthyl-, and p-biphenyldiazene, which react with P450 enzymes to form sigma-bonded aryl-iron (Fe-Ar) complexes. Ferricyanide-mediated migration of the aryl group from the iron to the porphyrin nitrogens produces the N-arylprotoporphyrin IX regioisomers (NB:NA:NC:ND, in which the aryl group is bound to the nitrogen of pyrrole rings B, A, C, and D, respectively) in the following ratios (zero means <5%): phenyl, 10:90:00:00; 2-naphthyl, 09:91:00:00; and p-biphenyl, 16:84:00:00. These results suggest that the CYP2D6 active site is open above pyrrole ring A and to a small extent above pyrrole ring B but is closed above pyrrole rings C and D. This geometry differs from those determined by the same method for P450s for which crystal structures are available. Replacement of Asp-301 by a Glu, which preserves the carboxylate side chain, causes no detectable change in the N-aryl porphyrin regioisomer patterns and only minor changes in the catalytic activity. Replacement of Asp-301 by an Asn or Gly, which eliminates the negatively charged side chain, suppresses migration of the aryl groups to pyrrole ring B without impairing migration to pyrrole ring A and virtually abolishes catalytic activity. These results provide a refined model of the active site of CYP2D6. They confirm, furthermore, that the loss of activity observed when Asp-301 is replaced by a neutral residue is due to loss of the charge-pairing interaction with the substrate positive charge and/or subtle structural effects in the vicinity of pyrrole ring B, but not to major structural reorganization of the active site.
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Abstract
Cytochrome P450 2E1 (CYP2E1), an enzyme that is induced by ethanol, plays an important role in the metabolism of various toxic and carcinogenic substances, including dialkylnitrosamines and small halocarbons. Little information is available on the active site of the enzyme. We report here the formation of aryl-iron complexes (Fe-Ar) in the reactions of human CYP2E1 with phenyldiazene, (2-naphthyl)hydrazine, and p-biphenylhydrazine. Migration of the aryl group from the iron to the porphyrin nitrogens within the intact active site produces the four possible N-arylprotoporphyrin IX regioisomers in the following ratios (NB:NA:NC:ND, where the subscript indicates the pyrrole ring): phenyl, 03:34:02:61; 2-naphthyl, 02:18:03:77; p-biphenyl, 02:52:04:42. The results indicate that the active site of human CYP2E1 is sterically unhindered directly above the iron for a distance of 10 A. It appears, furthermore, that the active site cavity is relatively open above pyrrole rings A and D but is closed above pyrrole rings B and C, a topology similar to that deduced for the rat enzyme.
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