14 research outputs found
Pentacyclic Nitrofurans with <i>In Vivo</i> Efficacy and Activity against Nonreplicating <i>Mycobacterium tuberculosis</i>
<div><p>The reductively activated nitroaromatic class of antimicrobials, which include nitroimidazole and the more metabolically labile nitrofuran antitubercular agents, have demonstrated some potential for development as therapeutics against dormant TB bacilli. In previous studies, the pharmacokinetic properties of nitrofuranyl isoxazolines were improved by incorporation of the outer ring elements of the antitubercular nitroimidazole OPC-67683. This successfully increased stability of the resulting pentacyclic nitrofuran lead compound Lee1106 (referred to herein as <b>9a</b>). In the current study, we report the synthesis and antimicrobial properties of <b>9a</b> and panel of <b>9a</b> analogs, which were developed to increase oral bioavailability. These hybrid nitrofurans remained potent inhibitors of <i>Mycobacterium tuberculosis</i> with favorable selectivity indices (>150) and a narrow spectrum of activity. <i>In vivo</i>, the pentacyclic nitrofuran compounds showed long half-lives and high volumes of distribution. Based on pharmacokinetic testing and lack of toxicity <i>in vivo,</i><b>9a</b> remained the series lead. <b>9a</b> exerted a lengthy post antibiotic effect and was highly active against nonreplicating <i>M. tuberculosis</i> grown under hypoxia. <b>9a</b> showed a low potential for cross resistance to current antitubercular agents, and a mechanism of activation distinct from pre-clinical tuberculosis candidates PA-824 and OPC-67683. Together these studies show that <b>9a</b> is a nanomolar inhibitor of actively growing as well as nonreplicating <i>M. tuberculosis</i>.</p></div
Murine model of acute tuberculosis infection.
<p>Log<sub>10</sub> reduction provided by compound <b>9a</b> in lungs (black bars) and spleen (grey bars) after 9 days of daily oral administration of 300 mg/kg was determined by calculating the difference between bacillary loads in organs from the untreated group and <b>9a</b> dissolved in (<b>1</b>) 0.5% methylcellulose in DI-H<sub>2</sub>O (<b>2</b>) 30% captisol in DI-H<sub>2</sub>O (<b>3</b>) 10% vitamin E TPGS in DI-H<sub>2</sub>O (<b>4</b>) 0.5% Tween 80 in DI-H<sub>2</sub>O (<b>5</b>) 20% cyclodextrin in DI-H<sub>2</sub>O or (<b>6</b>) cold PEG (50βΆ35βΆ15 H<sub>2</sub>O:PEG300:PG). Error bars indicate SEM within treatment groups of 5β7 mice per group.</p
Known nitroaromatic antimicrobial drugs and nitrofurans explored in this study.
<p>Known nitroaromatic antimicrobial drugs and nitrofurans explored in this study.</p
In vitro activity against NRP bacteria grown under hypoxic conditions.
<p>Viability of hypoxic <i>M. tuberculosis</i> cultures was assessed using the rapid anaerobic dormancy model.</p
MIC and MBCs for select nitrofurans and controls.
<p>Treatments were considered cidal when the MBC<sub>99.9</sub> for <i>M. tuberculosis</i> H37Rv was less than 4X the MIC.</p
Nutrient starvation model of nonreplicating persisters.
<p>The viability of mid-log phase (black bars) or nutrient-starved (gray bars) after exposure to DMSO carrier (1% v/v), 1 Β΅g/mL of isoniazid (INH), or 1 Β΅g/mL of <b>9a</b>. Averaged results and SEM from two biologically independent experiments are presented.</p
Cross Resistance Profiles for Compounds 9a Resistant Clones.
<p>Abbreviations: S, susceptible; <b>R</b>, resistant.</p
Synthesis of pentacyclic nitrofurans.
<p>Reagents and conditions: a) MsCl, Et<sub>3</sub>N, CH<sub>2</sub>Cl<sub>2</sub>, RT, 2 h, 94%; b) substituted phenol, <i>n</i>Bu<sub>4</sub>NCl, H<sub>2</sub>O, 100Β°C, 12 h, 86β90%; c) TFA, CH<sub>2</sub>Cl<sub>2</sub>, RT, 1 h, 92β95%; d) aryl bromide, 2-(di-<i>tert</i>-butylphosphino)biphenyl, NaO<i>t</i>Bu, Pd(OAc)<sub>2</sub>, toluene, 100Β°C, 3 h, 50β70%; e) <b>8</b>, Et<sub>3</sub>N, CHCl<sub>3</sub>, RT, 3 h, 50β68%.</p
<i>In vitro</i> Interactions with Antitubercular Drugs.
<p><i>In</i> vitro interactions determined by checkerboard assays.</p>a<p>Ex-vivo synergy assays were performed to determine if <b>9a</b> displayed synergy (FICI β€0.5), indifference (FICI >0.5β4.0) or antagonism (FICI >4.0) with a panel of anti-tuberculosis agents.</p
<i>In vivo</i> pharmacokinetic parameters.
<p>Pharmacokinetic analysis of experimental compounds in rats.</p><p>Values represent means (% coefficient of variation).</p><p>Abbreviations: t<sub>Β½</sub>: half life; CL: clearance; Vd: volume of distribution; fe: fraction excreted unchanged in urine; C<sub>max</sub>: maximum plasma concentration; C<sub>min,24<b> </b>h</sub>: minimum plasma concentration within 24 hours after dosing; AUC<sub>0-β</sub>: systematic exposure; F: oral bioavailability.</p