In vitro and intracellular activities of LBM415 (NVP PDF-713) against Legionella pneumophila

Legionnaires' disease

Since first identified in early 1977, bacteria of the genus Legionella are recognised as a common cause of community-acquired pneumonia and a rare cause of hospital-acquired pneumonia. Legionella bacteria multisystem manifestations mainly affect susceptible patients as a result of age, underlying debilitating conditions, or immunosuppression. Water is the major natural reservoir for Legionella, and the pathogen is found in many different natural and artificial aquatic environments such as cooling towers or water systems in buildings, including hospitals. The term given to the severe pneumonia and systemic infection caused by Legionella bacteria is Legionnaires' disease. Over time, the prevalence of legionellosis or Legionnaires' disease has risen, which might indicate a greater awareness and reporting of the disease. Advances in microbiology have led to a better understanding of the ecological niches and pathogenesis of the condition. Legionnaires' disease is not always suspected because of its non-specific symptoms, and the diagnostic tests routinely available do not offer the desired sensitivity. However, effective antibiotics are available. Disease notification systems provide the basis for initiating investigations and limiting the scale and recurrence of outbreaks. This report reviews our current understanding of this disease.

Synthesis and in vitro antibacterial activity of oxazolidine LBM-415 analogs as peptide deformylase inhibitors

The drug resistant bacteria pose a severe threat to human health. The increasing resistance of those pathogens to traditional antibacterial therapy renders the identification of new antibacterial agents with novel antibacterial mechanisms an urgent need. In this study, a series of (2S)-N-substituted-1-[(formyhydroxyamino)methyl]-1-oxohexyl]-2-oxazolidinecarboxamides were designed, synthesized and evaluated for in vitro antibacterial activity. Most of these compounds displayed good activities against Gram-positive organisms comparable to reference agent LBM-415.

Drug forecast - the peptide deformylase inhibitors as antibacterial agents

The relatively rapid development of microbial resistance after the entry of every new antimicrobial into the marketplace necessitates a constant supply of new agents to maintain effective pharmacotherapy. Despite extensive efforts to identify novel lead compounds from molecular targets, only the peptide deformylase inhibitors (PDIs) have shown any real promise, with some advancing to phase I human trials. Bacterial peptide deformylase, which catalyzes the removal of the N-formyl group from N-terminal methionine following translation, is essential for bacterial protein synthesis, growth, and survival. The majority of PDIs are pseudopeptide hydroxamic acids and two of these (IV BB-83698 and oral NVP LBM-415) entered phase I human trials. However, agents to the present have suffered from major potential liabilities. Their in vitro activity has been limited to gram-positive aerobes and some anaerobes and has been quite modest against the majority of such species (MIC(90) values ranging from 1-8 mg/L). They have exerted bacteriostatic, not bacteriocidal, activity, thus reducing their potential usefulness in the management of serious infections in the immunocompromised. The relative ease with which microorganisms have been able to develop resistance and the multiple available mechanisms of resistance (mutations in fmt, defB, folD genes; AcrAB/TolC efflux pump; overexpression of peptide deformylase) are worrisome. These could portend a short timespan of efficacy after marketing. Despite these current liabilities, further pursuit of more potent and broader spectrum PDIs which are less susceptible to bacterial mechanisms of resistance is still warranted.

13 – Antibiotic therapy of community-acquired pneumonia (CAP) caused by atypical agents

Macrolides, fluoroquinolones, doxycycline, and ketolides show a good intrinsic activity against intracellular pathogens which are responsible for a variable percentage of community-acquired pneumonia (CAP). These therapeutic agents all seem effective in treating most cases of CAP caused by Mycoplasma pneumoniae, Chlamydia pneumoniae, or Legionella spp. Among quinolones, the more recent fluoroquinolones, such as gemifloxacin or moxifloxacin, generally show a better intrinsic activity than the older ones. Among macrolides, azithromycin, and clarithromycin show a better pharmacokinetic profile. Both of them are available in intravenous form. It is quite common for M. pneumoniae and C. pneumoniae to continue to be shed in respiratory secretions, weeks after an effective therapy. The clinical relevance of this finding is not clear since most of these patients have a good outcome. Azithromycin, due to its advantageous pharmacokinetic profile, seems the best option when antibiotic prophylaxis is considered in some epidemiological settings. It has been proved effective in closed M. pneumoniae outbreaks.

Activity of LBM415 compared to those of 11 other agents against Haemophilus species

When tested against 254 Haemophilus influenzae strains, LBM415, a peptide deformylase inhibitor, gave MIC50 and MIC90 values of 2.0 microg/ml and 8.0 microg/ml, respectively. The MICs were independent of beta-lactam or quinolone susceptibility and the presence or absence of macrolide efflux or ribosomal protein mutations. The MICs of LBM415 against 23 H. parainfluenzae strains were similar to those against H. influenzae. In contrast, erythromycin, azithromycin, and clarithromycin gave unimodal MIC distributions, and apart from beta-lactamase-negative, ampicillin-resistant strains, all strains were susceptible to the beta-lactams tested. Apart from selected quinolone-resistant strains, all strains were susceptible to ciprofloxacin, levofloxacin, gatifloxacin, moxifloxacin, and gemifloxacin. Resistance to trimethoprim-sulfamethoxazole was common. The potencies of all drugs against 23 H. parainfluenzae strains were similar to those against H. influenzae. Time-kill studies with 10 Haemophilus strains showed LBM415 to be bactericidal at 2 x the MIC against 8 of 10 strains after 24 h. For comparison, the macrolides and beta-lactams were bactericidal against 8 to 10 strains each at 2 x the MIC after 24 h. Quinolones were bactericidal against all 10 strains tested at 2 x the MIC after 24 h. Against six H. influenzae strains, postantibiotic effects for LBM415 lasted between 0.8 and 2.2 h. In multistep resistance selection studies, LBM415 produced resistant clones in 7 of the 10 strains tested, with MICs ranging from 4 to 64 microg/ml. No mutations in deformylase (def) and formyltransferase (fmt) genes were detected in any of the LBM415-resistant mutants.