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Muscedere J, Maslove DM, Barden CJ, Weaver DF, Boyd JG, Sibley S, Boyd T, Rewa O, Albert M, Roussos M, Norman PA, Day AG. Nebulized Furosemide for Pulmonary Inflammation in Intubated Patients With COVID-19: A Phase 2 Randomized Controlled Double-Blind Study. Crit Care Explor 2024; 6:e1045. [PMID: 38511126 PMCID: PMC10954058 DOI: 10.1097/cce.0000000000001045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2024] Open
Abstract
OBJECTIVES Respiratory failure secondary to COVID-19 is associated with morbidity and mortality. Current anti-inflammatory therapies are effective but are given systemically and have significant side effects. Furosemide has anti-inflammatory properties, can be administered by inhalation, and is inexpensive. We investigated the efficacy of nebulized furosemide as an adjunctive therapy for COVID-19 respiratory failure. DESIGN A double-blind, randomized, placebo-controlled trial. SETTING Multicenter ICU study. PATIENTS Adults requiring invasive mechanical ventilation secondary to COVID-19. INTERVENTION Patients were randomized within 48 hours of intubation to receive inhaled furosemide or placebo until day 28, death, or liberation from mechanical ventilation. MEASUREMENTS AND MAIN RESULTS The study was stopped early due to waning incidence of COVID-19; 39 patients were available for analysis with mean ± sd age of 70.5 (10.8) years, Acute Physiology and Chronic Health Evaluation II 26.1 (7.8) and Fio2 60.0% (21.9). Baseline characteristics were similar between the groups. For the primary outcome of change in Pao2/Fio2 ratio between day 1 and day 6, it was +31.4 (83.5) in the furosemide arm versus +20.1 (92.8) in the control (p = 0.58). For secondary outcomes, furosemide versus control: 60-day mortality was 48% versus 71% (p = 0.20), hospital stay was 25.6 (21.9) versus 27.4 (25.0) days, p = 0.94 and VFD was 6.0 (9.1) versus 3.1 (7.1), p value of equals to 0.28. A post hoc analysis of the hierarchical composite outcome, alive and ventilator-free favored furosemide. There were no adverse events. CONCLUSIONS In this trial of inhaled furosemide for COVID-19 respiratory failure, differences in Pao2/Fio2 ratio to day 6 and other clinical outcomes were not significantly different, although the trial was underpowered due to early termination. Given the favorable profile of inhaled furosemide, further study is warranted in disease states where acute pulmonary inflammation contributes to the underlying pathophysiology.
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Affiliation(s)
- John Muscedere
- Department of Critical Care Medicine, Queen's University, Kingston, ON, Canada
- Kingston Health Sciences Centre, Kingston, ON, Canada
| | - David M Maslove
- Department of Critical Care Medicine, Queen's University, Kingston, ON, Canada
- Kingston Health Sciences Centre, Kingston, ON, Canada
- Department of Medicine, Queen's University, Kingston, ON, Canada
| | | | - Donald F Weaver
- Krembil Research Institute, University Health Network, Toronto, ON, Canada
- Departments of Medicine, Chemistry, and Pharmaceutical Sciences, University of Toronto, Toronto, ON, Canada
| | - J Gordon Boyd
- Department of Critical Care Medicine, Queen's University, Kingston, ON, Canada
- Kingston Health Sciences Centre, Kingston, ON, Canada
- Departments of Medicine, Chemistry, and Pharmaceutical Sciences, University of Toronto, Toronto, ON, Canada
| | - Stephanie Sibley
- Department of Critical Care Medicine, Queen's University, Kingston, ON, Canada
- Kingston Health Sciences Centre, Kingston, ON, Canada
| | - Tracy Boyd
- Department of Critical Care Medicine, Queen's University, Kingston, ON, Canada
| | - Oleksa Rewa
- Department of Critical Care Medicine, University of Alberta, Edmonton, AB, Canada
| | - Martin Albert
- Division of Critical Care, Department of Medicine, Hôpital du Sacré-Coeur Research Center, Université de Montréal, Montreal, QC, Canada
| | - Marios Roussos
- Department of Medicine, Division of Critical Care, Hôpital Cité-de-la-Santé, Laval, QC, Canada
| | - Patrick A Norman
- Kingston Health Sciences Centre, Kingston, ON, Canada
- Kingston General Health Research Institute, Kingston, ON, Canada
| | - Andrew G Day
- Kingston Health Sciences Centre, Kingston, ON, Canada
- Kingston General Health Research Institute, Kingston, ON, Canada
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Stover KR, Stafford PM, Damian AC, Pasangulapati JP, Goodwin-Tindall J, López Vásquez LM, Lee S, Yang SP, Reed MA, Barden CJ, Weaver DF. Development and Optimization of a Target Engagement Model of Brain IDO Inhibition for Alzheimer's Disease. Curr Alzheimer Res 2023; 20:705-714. [PMID: 38288825 DOI: 10.2174/0115672050283199240111111801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 11/26/2023] [Accepted: 11/28/2023] [Indexed: 04/04/2024]
Abstract
BACKGROUND Indoleamine 2,3-dioxygenase (IDO1) inhibition is a promising target as an Alzheimer's disease (AD) Disease-modifying therapy capable of downregulating immunopathic neuroinflammatory processes. METHODS To aid in the development of IDO inhibitors as potential AD therapeutics, we optimized a lipopolysaccharide (LPS) based mouse model of brain IDO1 inhibition by examining the dosedependent and time-course of the brain kynurenine:tryptophan (K:T) ratio to LPS via intraperitoneal dosing. RESULTS We determined the optimal LPS dose to increase IDO1 activity in the brain, and the ideal time point to quantify the brain K:T ratio after LPS administration. We then used a brain penetrant tool compound, EOS200271, to validate the model, determine the optimal dosing profile and found that a complete rescue of the K:T ratio was possible with the tool compound. CONCLUSION This LPS-based model of IDO1 target engagement is a useful tool that can be used in the development of brain penetrant IDO1 inhibitors for AD. A limitation of the present study is the lack of quantification of potential clinically relevant biomarkers in this model, which could be addressed in future studies.
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Affiliation(s)
- Kurt R Stover
- Krembil Research Institute, University Health Network, 399 Bathurst Street, Toronto M5T 2S8, Canada
- Treventis Corporation, 60 Leonard Avenue, Toronto M5T 0S8, Canada
| | - Paul M Stafford
- Krembil Research Institute, University Health Network, 399 Bathurst Street, Toronto M5T 2S8, Canada
| | - Andreea C Damian
- Krembil Research Institute, University Health Network, 399 Bathurst Street, Toronto M5T 2S8, Canada
| | - Jagadeesh P Pasangulapati
- Krembil Research Institute, University Health Network, 399 Bathurst Street, Toronto M5T 2S8, Canada
- Treventis Corporation, 60 Leonard Avenue, Toronto M5T 0S8, Canada
| | - Jake Goodwin-Tindall
- Krembil Research Institute, University Health Network, 399 Bathurst Street, Toronto M5T 2S8, Canada
| | | | - Sanghyun Lee
- Treventis Corporation, 60 Leonard Avenue, Toronto M5T 0S8, Canada
| | - Seung-Pil Yang
- Treventis Corporation, 60 Leonard Avenue, Toronto M5T 0S8, Canada
| | - Mark A Reed
- Krembil Research Institute, University Health Network, 399 Bathurst Street, Toronto M5T 2S8, Canada
- Treventis Corporation, 60 Leonard Avenue, Toronto M5T 0S8, Canada
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, M5S1A8, ON, Canada
| | - Christopher J Barden
- Krembil Research Institute, University Health Network, 399 Bathurst Street, Toronto M5T 2S8, Canada
- Treventis Corporation, 60 Leonard Avenue, Toronto M5T 0S8, Canada
| | - Donald F Weaver
- Krembil Research Institute, University Health Network, 399 Bathurst Street, Toronto M5T 2S8, Canada
- Treventis Corporation, 60 Leonard Avenue, Toronto M5T 0S8, Canada
- Department of Chemistry, University of Toronto, Toronto M55 3H6, Canada
- Department of Medicine (Neurology), University of Toronto, Toronto M5G 2C4, Canada
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3
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Meier-Stephenson FS, Meier-Stephenson VC, Carter MD, Meek AR, Wang Y, Pan L, Chen Q, Jacobo S, Wu F, Lu E, Simms GA, Fisher L, McGrath AJ, Fermo V, Barden CJ, Clair HDS, Galloway TN, Yadav A, Campágna-Slater V, Hadden M, Reed M, Taylor M, Kelly B, Diez-Cecilia E, Kolaj I, Santos C, Liyanage I, Sweeting B, Stafford P, Boudreau R, Reid GA, Noyce RS, Stevens L, Staniszewski A, Zhang H, Murty MRVS, Lemaire P, Chardonnet S, Richardson CD, Gabelica V, DePauw E, Brown R, Darvesh S, Arancio O, Weaver DF. Alzheimer's disease as an autoimmune disorder of innate immunity endogenously modulated by tryptophan metabolites. Alzheimers Dement (N Y) 2022; 8:e12283. [PMID: 35415204 PMCID: PMC8985489 DOI: 10.1002/trc2.12283] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 01/19/2022] [Accepted: 02/11/2022] [Indexed: 12/19/2022]
Abstract
Introduction Alzheimer's disease (AD) is characterized by neurotoxic immuno-inflammation concomitant with cytotoxic oligomerization of amyloid beta (Aβ) and tau, culminating in concurrent, interdependent immunopathic and proteopathic pathogeneses. Methods We performed a comprehensive series of in silico, in vitro, and in vivo studies explicitly evaluating the atomistic-molecular mechanisms of cytokine-mediated and Aβ-mediated neurotoxicities in AD. Next, 471 new chemical entities were designed and synthesized to probe the pathways identified by these molecular mechanism studies and to provide prototypic starting points in the development of small-molecule therapeutics for AD. Results In response to various stimuli (e.g., infection, trauma, ischemia, air pollution, depression), Aβ is released as an early responder immunopeptide triggering an innate immunity cascade in which Aβ exhibits both immunomodulatory and antimicrobial properties (whether bacteria are present, or not), resulting in a misdirected attack upon "self" neurons, arising from analogous electronegative surface topologies between neurons and bacteria, and rendering them similarly susceptible to membrane-penetrating attack by antimicrobial peptides (AMPs) such as Aβ. After this self-attack, the resulting necrotic (but not apoptotic) neuronal breakdown products diffuse to adjacent neurons eliciting further release of Aβ, leading to a chronic self-perpetuating autoimmune cycle. AD thus emerges as a brain-centric autoimmune disorder of innate immunity. Based upon the hypothesis that autoimmune processes are susceptible to endogenous regulatory processes, a subsequent comprehensive screening program of 1137 small molecules normally present in human brain identified tryptophan metabolism as a regulator of brain innate immunity and a source of potential endogenous anti-AD molecules capable of chemical modification into multi-site therapeutic modulators targeting AD's complex immunopathic-proteopathic pathogenesis. Discussion Conceptualizing AD as an autoimmune disease, identifying endogenous regulators of this autoimmunity, and designing small molecule drug-like analogues of these endogenous regulators represents a novel therapeutic approach for AD.
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Affiliation(s)
| | | | - Michael D Carter
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Department of Pathology Dalhousie University Halifax Nova Scotia Canada
| | - Autumn R Meek
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Yanfei Wang
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Luzhe Pan
- Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Qiangwei Chen
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada
| | - Sheila Jacobo
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada
| | - Fan Wu
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Erhu Lu
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Gordon A Simms
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada
| | - Laural Fisher
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada
| | - Alaina J McGrath
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada
| | - Virgil Fermo
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada
| | - Christopher J Barden
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Harman D S Clair
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada
| | - Todd N Galloway
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada
| | - Arun Yadav
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Krembil Research Institute University Health Network Toronto Ontario Canada
| | | | - Mark Hadden
- Department of Chemistry Queen's University Kingston Ontario Canada
| | - Mark Reed
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Marcia Taylor
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Brendan Kelly
- Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Elena Diez-Cecilia
- Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Igri Kolaj
- Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Clarissa Santos
- Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Imindu Liyanage
- Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Braden Sweeting
- Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Paul Stafford
- Krembil Research Institute University Health Network Toronto Ontario Canada
| | - Robert Boudreau
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada
| | - G Andrew Reid
- Department of Medical Neuroscience Dalhousie University Halifax Nova Scotia Canada
| | - Ryan S Noyce
- Department of Microbiology and Immunology Dalhousie University Halifax Nova Scotia Canada
| | - Leanne Stevens
- Department of Psychology Dalhousie University Halifax Nova Scotia Canada
| | - Agnieszka Staniszewski
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain & Department of Pathology and Cell Biology Columbia University New York New York USA
| | - Hong Zhang
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain & Department of Pathology and Cell Biology Columbia University New York New York USA
| | - Mamidanna R V S Murty
- Department of Chemistry University of Liège, Allée de la Chimie, Sart-Tilman Liège Belgium
| | - Pascale Lemaire
- Department of Chemistry University of Liège, Allée de la Chimie, Sart-Tilman Liège Belgium
| | - Solenne Chardonnet
- Department of Chemistry University of Liège, Allée de la Chimie, Sart-Tilman Liège Belgium
| | | | - Valérie Gabelica
- Department of Chemistry University of Liège, Allée de la Chimie, Sart-Tilman Liège Belgium
| | - Edwin DePauw
- Department of Chemistry University of Liège, Allée de la Chimie, Sart-Tilman Liège Belgium
| | - Richard Brown
- Department of Psychology Dalhousie University Halifax Nova Scotia Canada
| | - Sultan Darvesh
- Department of Medical Neuroscience Dalhousie University Halifax Nova Scotia Canada.,Division of Neurology Department of Medicine Dalhousie University Halifax Nova Scotia Canada
| | - Ottavio Arancio
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain & Department of Pathology and Cell Biology Columbia University New York New York USA
| | - Donald F Weaver
- Department of Chemistry Dalhousie University Halifax Nova Scotia Canada.,Krembil Research Institute University Health Network Toronto Ontario Canada.,Division of Neurology Department of Medicine Dalhousie University Halifax Nova Scotia Canada.,Department of Pharmaceutical Sciences University of Toronto Toronto Ontario Canada.,Department of Chemistry University of Toronto Toronto Ontario Canada.,Division of Neurology Department of Medicine University of Toronto Toronto Ontario Canada
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4
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Abstract
Incorporation of heterocycles into drug molecules can enhance physical properties and biological activity. A variety of heterocyclic groups is available to medicinal chemists, many of which have been reviewed in detail elsewhere. Oxadiazoles are a class of heterocycle containing one oxygen and two nitrogen atoms, available in three isomeric forms. While the 1,2,4- and 1,3,4-oxadiazoles have seen widespread application in medicinal chemistry, 1,2,5-oxadiazoles (furazans) are less common. This Review provides a summary of the application of furazan-containing molecules in medicinal chemistry and drug development programs from analysis of both patent and academic literature. Emphasis is placed on programs that reached clinical or preclinical stages of development. The examples provided herein describe the pharmacology and biological activity of furazan derivatives with comparative data provided where possible for other heterocyclic groups and pharmacophores commonly used in medicinal chemistry.
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Affiliation(s)
| | | | - Donald F Weaver
- Department of Fundamental Neurobiology, Krembil Research Institute, Toronto, Ontario M5T 0S8, Canada.,Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.,Department of Medicine, University of Toronto, Toronto, Ontario M5S 3H2, Canada
| | - Mark A Reed
- Treventis Corporation, Toronto, Ontario M5T 0S8, Canada.,Department of Fundamental Neurobiology, Krembil Research Institute, Toronto, Ontario M5T 0S8, Canada
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5
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Abstract
The blood-brain barrier (BBB), composed of microvascular tight junctions and glial cell sheathing, selectively controls drug permeation into the central nervous system (CNS) by either passive diffusion or active transport. Computational techniques capable of predicting molecular brain penetration are important to neurological drug design. A novel prediction algorithm, termed the Brain Exposure Efficiency Score (BEE), is presented. BEE addresses the need to incorporate the role of trans-BBB influx and efflux active transporters by considering key brain penetrance parameters, namely, steady state unbound brain to plasma ratio of drug (Kp,uu) and dose normalized unbound concentration of drug in brain (Cu,b). BEE was devised using quantitative structure-activity relationships (QSARs) and molecular modeling studies on known transporter proteins and their ligands. The developed algorithms are provided as a user-friendly open source calculator to assist in optimizing a brain penetrance strategy during the early phases of small molecule molecular therapeutic design.
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Affiliation(s)
- Mayuri Gupta
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
| | - Thomas Bogdanowicz
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
| | - Mark A. Reed
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
| | - Christopher J. Barden
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
| | - Donald F. Weaver
- Krembil Research Institute, University Health Network, 60 Leonard Avenue, Toronto, Ontario M5T 2S8, Canada
- Department of Medicine, University of Toronto, Toronto, Ontario M5G 2C4, Canada
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario M5S 3M2 Canada
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6
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Abstract
The blood-brain barrier (BBB) protects the brain from the toxic side effects of drugs and exogenous molecules. However, it is crucial that medications developed for neurological disorders cross into the brain in therapeutic concentrations. Understanding the BBB interaction with drug molecules based on physicochemical property space can guide effective and efficient drug design. An algorithm, designated "BBB Score", composed of stepwise and polynomial piecewise functions, is herein proposed for predicting BBB penetration based on five physicochemical descriptors: number of aromatic rings, heavy atoms, MWHBN (a descriptor comprising molecular weight, hydrogen bond donor, and hydrogen bond acceptors), topological polar surface area, and pKa. On the basis of statistical analyses of our results, the BBB Score outperformed (AUC = 0.86) currently employed MPO approaches (MPO, AUC = 0.61; MPO_V2, AUC = 0.67). Initial evaluation of physicochemical property space using the BBB Score is a valuable addition to currently available drug design algorithms.
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Affiliation(s)
- Mayuri Gupta
- Krembil Research Institute , University Health Network , 60 Leonard Avenue , Toronto M5T 2S8 , Canada
| | - Hyeok Jun Lee
- Krembil Research Institute , University Health Network , 60 Leonard Avenue , Toronto M5T 2S8 , Canada
| | - Christopher J Barden
- Krembil Research Institute , University Health Network , 60 Leonard Avenue , Toronto M5T 2S8 , Canada
| | - Donald F Weaver
- Krembil Research Institute , University Health Network , 60 Leonard Avenue , Toronto M5T 2S8 , Canada.,Department of Medicine , University of Toronto , Toronto M5G 2C4 , Canada.,Department of Chemistry , University of Toronto , Toronto M55 3H6 , Canada
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7
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Jha A, Yadav Y, Naidu AB, Rao VK, Kumar A, Parmar VS, MacDonald WJ, Too CK, Balzarini J, Barden CJ, Cameron TS. Design, synthesis and bioevaluation of novel 6-(4-Hydroxypiperidino)naphthalen-2-ol-based potential Selective Estrogen Receptor Modulators for breast cancer. Eur J Med Chem 2015; 92:103-14. [DOI: 10.1016/j.ejmech.2014.12.037] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 11/01/2014] [Accepted: 12/21/2014] [Indexed: 01/07/2023]
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8
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Abstract
The drug discovery pipelines of the major pharmaceutical companies have become shockingly depleted, foreshadowing a potential crisis in the ability of Big Pharma to meet the pharmaceutical demands created by the ever-changing spectrum of human disease. However, from this major crisis is emerging a major opportunity, namely micropharma--academia-originated biotech start-up companies that are efficient, innovative, product-focused and small. In this Feature, we discuss a 'new ecosystem' for drug development, with high-risk innovation in micropharma leading to Big Pharma clinical trials; we also identify the 'five golden goals' that micropharma must strive to achieve to attain success. Although micropharma will encounter numerous hurdles on this road to success, there is room for optimism that micropharma might have the capacity to address society's growing, but unmet, need for effective therapeutics over coming years.
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Affiliation(s)
- Christopher J Barden
- DeNovaMed Inc, Goldbloom Pavilion - IWK Health Centre, 5850/5980 University Avenue, PO Box 9700, Halifax, Nova Scotia, Canada
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9
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Viswanathan B, Barden CJ, Ban F, Boyd * RJ. Calibration of a computational scheme for solvation: Group I and II metal ions bound to water, formaldehyde and ammonia. Mol Phys 2005. [DOI: 10.1080/00268970512331317273] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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10
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Gonzales JM, Barden CJ, Brown ST, Schleyer PVR, Schaefer HF, Li QS. Cyclopentadiene annulated polycyclic aromatic hydrocarbons: investigations of electron affinities. J Am Chem Soc 2003; 125:1064-71. [PMID: 12537506 DOI: 10.1021/ja0210502] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The adiabatic electron affinities of cyclopentadiene and 10 associated benzannelated derivatives have been predicted with both density functional and Hartree-Fock theory. These systems can also be regarded as benzenoid polycyclic aromatic hydrocarbons (PAHs) augmented with five-membered rings. Like the PAHs, the electron affinities of the present systems generally increase with the number of rings. To unequivocally bind an electron, cyclopentadiene must have at least two conventionally fused benzene rings. 1H-Benz[f]indene, a naphthalene-annulated cyclopentadiene, is predicted to have a zero-point energy corrected adiabatic electron affinity of 0.13 eV. Since the experimental E(A) of naphthalene is negative (-0.19 eV), the five-membered ring appendage contributes to the stability of the naphthalene-derived 1H-benz[f]indene radical anion significantly. The key to binding the electron is a contiguous sequence of fused benzenes, since fluorene, the isomer of 1H-benz[f]indene, with separated six-membered rings, has an electron affinity of -0.07 eV. Each additional benzene ring in the sequence fused to cyclopentadiene increases the electron affinity by 0.15-0.65 eV: the most reliable predictions are cyclopentadiene (-0.63 eV), indene (-0.49 eV), fluorene (-0.07 eV), 1H-benz[f]indene (0.13 eV), 1,2-benzofluorene (0.25 eV), 2,3-benzofluorene (0.26 eV), 12H-dibenzo[b,h]fluorene (0.65 eV), 13H-indeno[1,2-b]anthracene (0.82 eV), and 1H-cyclopenta[b]naphthacene (1.10 eV). In contrast, if the six-membered ring-fusion is across the C(2)-C(3) cyclopentadiene single bond, only a single benzene is needed to bind an electron. The theoretical electron affinity of the resulting molecule, isoindene, is 0.49 eV, and this increases to 1.22 eV for 2H-benz[f]indene. The degree of aromaticity is responsible for this behavior. While the radical anions are stabilized by conjugation, which increases with the size of the system, the regular indenes, like PAHs in general, suffer from the loss of aromatic stabilization in forming their radical anions. While indene is 21 kcal mol(-1) more stable than isoindene, the corresponding radical anion isomers have almost the same energy. Nucleus-independent chemical shift calculations show that the highly aromatic molecules lose almost all aromaticity when an extra electron is present. The radical anions of cyclopentadiene and all of its annulated derivatives have remarkably low C-H bond dissociation energies (only 18-34 kcal mol(-1) for the mono-, bi-, and tricyclics considered). Hydrogen atom loss leads to the restoration of aromaticity in the highly stabilized cyclopentadienyl anion congeners.
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Affiliation(s)
- Jason M Gonzales
- Center for Computational Quantum Chemistry, University of Georgia, Athens, GA 30602-2525, USA
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11
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Barden CJ, Charbonneau P, Schaefer HF. Group 13−Group 16 Heterocubanes [RM(μ3-E)]4 (R = H, CH3; M = Al, Ga, In; E = O, S, Se, Te) and Group 13 Cubanes [RM(μ3-M)]4 (R = F, Cl, CH3, NO2; M = Al, Ga, In): A Structural Study. Organometallics 2002. [DOI: 10.1021/om0202672] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Christopher J. Barden
- Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602
| | - Patrick Charbonneau
- Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602
| | - Henry F. Schaefer
- Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602
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12
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Affiliation(s)
| | - Christopher J. Barden
- Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602-2525
| | - Shawn T. Brown
- Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602-2525
| | - Henry F. Schaefer
- Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602-2525
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13
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Barden CJ, Rienstra-Kiracofe JC, Schaefer HF. Homonuclear 3d transition-metal diatomics: A systematic density functional theory study. J Chem Phys 2000. [DOI: 10.1063/1.481916] [Citation(s) in RCA: 235] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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14
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Barden CJ, Schaefer HF. The singlet–triplet separation in dichlorocarbene: A surprising difference between theory and experiment. J Chem Phys 2000. [DOI: 10.1063/1.481601] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Affiliation(s)
| | - Marc K. Boysworth
- Department of Chemistry, James Madison University, Harrisonburg, Virginia 22807
| | - Frank A. Palocsay
- Department of Chemistry, James Madison University, Harrisonburg, Virginia 22807
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