Publications by authors named "Stephen F Rittenhouse"

9 Publications

  • Page 1 of 1

Challenges of antibacterial discovery revisited.

Ann N Y Acad Sci 2010 Dec 8;1213:5-19. Epub 2010 Nov 8.

Antibacterial Discovery Performance Unit, Infectious Diseases Center of Excellence for Drug Discovery, GlaxoSmithKline, Collegeville, Pennsylvania, USA.

The discovery of novel antibiotic classes has not kept pace with the growing threat of bacterial resistance. Antibiotic candidates that act at new targets or via distinct mechanisms have the greatest potential to overcome resistance; however, novel approaches are also associated with higher attrition and longer timelines. This uncertainty has contributed to the withdrawal from antibiotic programs by many pharmaceutical companies. Genomic approaches have not yielded satisfactory results, in part due to nascent knowledge about unprecedented molecular targets, the challenge of achieving antibacterial activity by lead optimization of enzyme inhibitors, and the limitations of compound screening libraries for antibacterial discovery. Enhanced diversity of compound screening banks, entry into new chemical space, and new screening technologies are currently being exploited to improve hit rates for antibacterial discovery. Antibacterial compound lead optimization faces hurdles associated with the high plasma exposures required for efficacy. Lead optimization would be enhanced by the identification of new antibiotic classes with improved tractability and by expanding the predictability of in vitro safety assays. Implementing multiple screening and target identification strategies is recommended for improving the likelihood of discovering new antibacterial compounds that address unmet needs.
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http://dx.doi.org/10.1111/j.1749-6632.2010.05828.xDOI Listing
December 2010

A rapid microtiter plate assay for measuring the effect of compounds on Staphylococcus aureus membrane potential.

J Microbiol Methods 2010 Nov 27;83(2):254-6. Epub 2010 Aug 27.

Antibacterial Discovery Performance Unit, Infectious Diseases Center of Excellence in Drug Discovery, GlaxoSmithKline Pharmaceuticals, Collegeville, PA 19426, United States.

We developed a homogenous microtiter based assay using the cationic dye 3, 3'-Diethyloxacarbocyanine iodide, DiOC2(3), to measure the effect of compounds on membrane potential in Staphylococcus aureus. In a screen of 372 compounds from a synthetic compound collection with anti-Escherichia coli activity due to unknown modes of action at least 17% demonstrated potent membrane activity, enabling rapid discrimination of nuisance compounds.
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http://dx.doi.org/10.1016/j.mimet.2010.08.012DOI Listing
November 2010

Genetic characterization of Vga ABC proteins conferring reduced susceptibility to pleuromutilins in Staphylococcus aureus.

Antimicrob Agents Chemother 2008 Dec 6;52(12):4507-9. Epub 2008 Oct 6.

Department of Microbiology, ID-CEDD, GlaxoSmithKline, Collegeville, Pennsylvania 19426, USA.

Retapamulin MICs of > or =2 microg/ml were noted for 6 of 5,676 S. aureus recent clinical isolates evaluated. The ABC proteins VgaAv and VgaA were found to be responsible for the reduced susceptibility to pleuromutilins exhibited by these six isolates.
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http://dx.doi.org/10.1128/AAC.00915-08DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2592886PMC
December 2008

Stepwise exposure of Staphylococcus aureus to pleuromutilins is associated with stepwise acquisition of mutations in rplC and minimally affects susceptibility to retapamulin.

Antimicrob Agents Chemother 2007 Jun 2;51(6):2048-52. Epub 2007 Apr 2.

UP1345, GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, PA 19426, USA.

To assess their effects on susceptibility to retapamulin in Staphylococcus aureus, first-, second-, and third-step mutants with elevated MICs to tiamulin and other investigational pleuromutilin compounds were isolated and characterized through exposure to high drug concentrations. All first- and second-step mutations were in rplC, encoding ribosomal protein L3. Most third-step mutants acquired a third mutation in rplC. While first- and second-step mutations did cause an elevation in tiamulin and retapamulin MICs, a significant decrease in activity was not seen until a third mutation was acquired. All third-step mutants exhibited severe growth defects, and faster-growing variants arose at a high frequency from most isolates. These faster-growing variants were found to be more susceptible to pleuromutilins. In the case of a mutant with three alterations in rplC, the fast-growing variants acquired an additional mutation in rplC. In the case of fast-growing variants of isolates with two mutations in rplC and at least one mutation at an unmapped locus, one of the two rplC mutations reverted to wild type. These data indicate that mutations in rplC that lead to pleuromutilin resistance have a direct, negative effect on fitness. While reduction in activity of retapamulin against S. aureus can be seen through mutations in rplC, it is likely that target-specific resistance to retapamulin will be slow to emerge due to the need for three mutations for a significant effect on activity and the fitness cost of each mutational step.
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http://dx.doi.org/10.1128/AAC.01066-06DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1891380PMC
June 2007

New benzylidenethiazolidinediones as antibacterial agents.

Bioorg Med Chem Lett 2003 Nov;13(21):3771-3

Medicinal Chemistry Department, Microbial, Musculoskeletal and Proliferative Diseases, GlaxoSmithKline Pharmaceuticals, 1250 S. Collegeville Road, Collegeville, PA 19426, USA.

A novel benzylidenethiazolidinedione has been discovered with antimicrobial activity. Here, we present the results of a structure-activity study on this compound with respect to its antimicrobial activity.
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http://dx.doi.org/10.1016/j.bmcl.2003.07.010DOI Listing
November 2003

Indole naphthyridinones as inhibitors of bacterial enoyl-ACP reductases FabI and FabK.

J Med Chem 2003 Apr;46(9):1627-35

GlaxoSmithKline Pharmaceuticals, 1250 South Collegeville Road, P.O. Box 5089, Collegeville, Pennsylvania 19426, USA.

Bacterial enoyl-ACP reductase (FabI) is responsible for catalyzing the final step of bacterial fatty acid biosynthesis and is an attractive target for the development of novel antibacterial agents. Previously we reported the development of FabI inhibitor 4 with narrow spectrum antimicrobial activity and in vivo efficacy against Staphylococcus aureus via intraperitoneal (ip) administration. Through iterative medicinal chemistry aided by X-ray crystal structure analysis, a new series of inhibitors has been developed with greatly increased potency against FabI-containing organisms. Several of these new inhibitors have potent antibacterial activity against multidrug resistant strains of S. aureus, and compound 30 demonstrates exceptional oral (po) in vivo efficacy in a S. aureus infection model in rats. While optimizing FabI inhibitory activity, compounds 29 and 30 were identified as having low micromolar FabK inhibitory activity, thereby increasing the antimicrobial spectrum of these compounds to include the FabK-containing pathogens Streptococcus pneumoniae and Enterococcus faecalis. The results described herein support the hypothesis that bacterial enoyl-ACP reductases are valid targets for antibacterial agents.
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http://dx.doi.org/10.1021/jm0204035DOI Listing
April 2003

Defining and combating the mechanisms of triclosan resistance in clinical isolates of Staphylococcus aureus.

Antimicrob Agents Chemother 2002 Nov;46(11):3343-7

Microbial, Musculoskeletal and Proliferative Diseases CEDD. Computational and Structural Sciences, GlaxoSmithKline Pharmaceuticals, Collegeville, Pennsylvania 19426, USA.

The MICs of triclosan for 31 clinical isolates of Staphylococcus aureus were 0.016 micro g/ml (24 strains), 1 to 2 micro g/ml (6 strains), and 0.25 micro g/ml (1 strain). All the strains for which triclosan MICs were elevated (>0.016 micro g/ml) showed three- to fivefold increases in their levels of enoyl-acyl carrier protein (ACP) reductase (FabI) production. Furthermore, strains for which triclosan MICs were 1 to 2 micro g/ml overexpressed FabI with an F204C alteration. Binding studies with radiolabeled NAD(+) demonstrated that this change prevents the formation of the stable triclosan-NAD(+)-FabI complex, and both this alteration and its overexpression contributed to achieving MICs of 1 to 2 micro g/ml for these strains. Three novel, potent inhibitors of FabI (50% inhibitory concentrations, < or =64 nM) demonstrated up to 1,000-fold better activity than triclosan against the strains for which triclosan MICs were elevated. None of the compounds tested from this series formed a stable complex with NAD(+)-FabI. Consequently, although the overexpression of wild-type FabI gave rise to an increase in the MICs, as expected, overexpression of FabI with an F204C alteration did not cause an additional increase in resistance. Therefore, this work identifies the mechanisms of triclosan resistance in S. aureus, and we present three compounds from a novel chemical series of FabI inhibitors which have excellent activities against both triclosan-resistant and -sensitive clinical isolates of S. aureus.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC128739PMC
http://dx.doi.org/10.1128/aac.46.11.3343-3347.2002DOI Listing
November 2002

Discovery of a novel and potent class of FabI-directed antibacterial agents.

Antimicrob Agents Chemother 2002 10;46(10):3118-24

Microbial, Musculoskeletal and Proliferative Diseases Center of Excellence in Drug Discovery, GlaxoSmithKline Pharmaceuticals, Collegeville, Pennsylvania 19426, USA.

Bacterial enoyl-acyl carrier protein (ACP) reductase (FabI) catalyzes the final step in each elongation cycle of bacterial fatty acid biosynthesis and is an attractive target for the development of new antibacterial agents. High-throughput screening of the Staphylococcus aureus FabI enzyme identified a novel, weak inhibitor with no detectable antibacterial activity against S. aureus. Iterative medicinal chemistry and X-ray crystal structure-based design led to the identification of compound 4 [(E)-N-methyl-N-(2-methyl-1H-indol-3-ylmethyl)-3-(7-oxo-5,6,7,8-tetrahydro-1,8-naphthyridin-3-yl)acrylamide], which is 350-fold more potent than the original lead compound obtained by high-throughput screening in the FabI inhibition assay. Compound 4 has exquisite antistaphylococci activity, achieving MICs at which 90% of isolates are inhibited more than 500 times lower than those of nine currently available antibiotics against a panel of multidrug-resistant strains of S. aureus and Staphylococcus epidermidis. Furthermore, compound 4 exhibits excellent in vivo efficacy in an S. aureus infection model in rats. Biochemical and genetic approaches have confirmed that the mode of antibacterial action of compound 4 and related compounds is via inhibition of FabI. Compound 4 also exhibits weak FabK inhibitory activity, which may explain its antibacterial activity against Streptococcus pneumoniae and Enterococcus faecalis, which depend on FabK and both FabK and FabI, respectively, for their enoyl-ACP reductase function. These results show that compound 4 is representative of a new, totally synthetic series of antibacterial agents that has the potential to provide novel alternatives for the treatment of S. aureus infections that are resistant to our present armory of antibiotics.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC128775PMC
http://dx.doi.org/10.1128/aac.46.10.3118-3124.2002DOI Listing
October 2002

Discovery of aminopyridine-based inhibitors of bacterial enoyl-ACP reductase (FabI).

J Med Chem 2002 Jul;45(15):3246-56

GlaxoSmithKline Pharmaceuticals, 1250 South Collegeville Road, P.O. Box 5089, Collegeville, PA 19426, USA.

Bacterial enoyl-ACP reductase (FabI) catalyzes the final step in each cycle of bacterial fatty acid biosynthesis and is an attractive target for the development of new antibacterial agents. Our efforts to identify potent, selective FabI inhibitors began with screening of the GlaxoSmithKline proprietary compound collection, which identified several small-molecule inhibitors of Staphylococcus aureus FabI. Through a combination of iterative medicinal chemistry and X-ray crystal structure based design, one of these leads was developed into the novel aminopyridine derivative 9, a low micromolar inhibitor of FabI from S. aureus (IC(50) = 2.4 microM) and Haemophilus influenzae (IC(50) = 4.2 microM). Compound 9 has good in vitro antibacterial activity against several organisms, including S. aureus (MIC = 0.5 microg/mL), and is effective in vivo in a S. aureus groin abscess infection model in rats. Through FabI overexpressor and macromolecular synthesis studies, the mode of action of 9 has been confirmed to be inhibition of fatty acid biosynthesis via inhibition of FabI. Taken together, these results support FabI as a valid antibacterial target and demonstrate the potential of small-molecule FabI inhibitors for the treatment of bacterial infections.
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http://dx.doi.org/10.1021/jm020050+DOI Listing
July 2002