Pharmacokinetic and Pharmacodynamic Modeling Analysis of Delpazolid (LCB01-0371) in Adult Patients with Pulmonary Tuberculosis.

Delpazolid (LCB01-0371) is a novel oxazolidinone derivative with a good safety profile for treating gram-positive pathogenic infections such as Mycobacterium abscessus, a highly pathogenic drug-resistant Mycobacterium. In this study, we evaluated the pharmacokinetics (PK) and pharmacodynamics (PD) of delpazolid after 14 days of multiple oral administration, using data from adult patients with pulmonary tuberculosis. 800 mg once a day, 400 mg twice a day, 800 mg twice a day, and 1200 mg once a day delpazolid for 14 days were tested in 63 patients with pulmonary tuberculosis. For PK blood collection, inpatient and outpatient scheduling were separately implemented. Plasma concentrations of delpazolid were measured at visits 2, 4, 6, and 8 in outpatients, and four sparse blood samples were measured in inpatients. PD models were sequentially fitted using individual PK parameter estimates obtained from PK compartmental models. For PK modeling, 180 plasma concentrations of delpazolid from 56 patients were included. A two-compartment mixed first- and zero-order absorption model best described the time course of plasma concentration. For the PD model, 448 bacterial titer data from 60 patients were used. The time course of bacterial titers (log10 CFU/mL) was described by a model that consists of the growth and killing rate of bacteria with the sigmoid Emax model. The PK-PD simulation suggested that the bacterial titers are the lowest on the 800 mg bid regimen among the four, consistent with observed data, as all regimens substantially decrease. In the dose-response relationship, the effectiveness of delpazolid was suggested.

Antibacterial Activity of LCB10-0200 against Klebsiella pneumoniae.

Klebsiella pneumoniae is one of the important clinical organisms that causes various infectious diseases, including urinary tract infections, necrotizing pneumonia, and surgical wound infections. The increase in the incidence of multidrug-resistance K. pneumoniae is a major problem in public healthcare. Therefore, a novel antibacterial agent is needed to treat this pathogen. Here, we studied the in vitro and in vivo activities of a novel antibiotic LCB10-0200, a siderophore-conjugated cephalosporin, against clinical isolates of K. pneumoniae. In vitro susceptibility study found that LCB10-0200 showed potent antibacterial activity against K. pneumoniae, including the beta-lactamase producing strains. The in vivo efficacy of LCB10-0200 was examined in three different mouse infection models, including systemic, thigh, and urinary tract infections. LCB10-0200 showed more potent in vivo activity than ceftazidime in the three in vivo models against the drug-susceptible and drug-resistant K. pneumoniae strains. Taken together, these results show that LCB10-0200 is a potential antibacterial agent to treat infection caused by K. pneumoniae.

In Vitro Activity of a Novel Siderophore-Cephalosporin LCB10-0200 (GT-1), and LCB10-0200/Avibactam, against Carbapenem-Resistant Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa Strains at a Tertiary Hospital in Korea.

The siderophore-antibiotic conjugate LCB10-0200 (a.k.a. GT-1) has been developed to combat multidrug-resistant Gram-negative bacteria. In this study, the in vitro activity of LCB10-0200 and LCB10-0200/avibactam (AVI) has been investigated against carbapenem-resistant Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. Minimal inhibitory concentrations (MICs) of LCB10-0200, LCB10-0200/AVI, aztreonam, aztreonam/AVI, ceftazidime, ceftazidime/AVI, and meropenem were measured using the agar dilution method. Whole genome sequencing was performed using Illumina and the resistome was analyzed. LCB10-0200 displayed stronger activity than the comparator drugs in meropenem-resistant E. coli and K. pneumoniae, and the addition of AVI enhanced the LCB10-0200 activity to MIC ≤ 0.12 mg/L for 90.5% of isolates. In contrast, whereas LCB10-0200 alone showed potent activity against meropenem-resistant A. baumannii and P. aeruginosa at MIC ≤ 4 mg/L for 84.3% of isolates, the combination with AVI did not improve its activity. LCB10-0200/AVI was active against CTX-M-, SHV-, CMY-, and KPC- producing E. coli and K. pneumoniae, while LCB10-0200 alone was active against ADC-, OXA-, and VIM- producing A. baumannii and P. aeruginosa. Both LCB10-0200 and LCB10-0200/AVI displayed low activity against IMP- and NDM- producing strains. LCB10-0200 alone exhibited strong activity against selected strains. The addition of AVI significantly increased LCB10-0200 activity against carbapenem-resistant E. coli, K. pneumoniae.

In Vitro Activity of a Novel Siderophore-Cephalosporin, GT-1 and Serine-Type ß-Lactamase Inhibitor, GT-055, against Escherichia coli, Klebsiella pneumoniae and Acinetobacter spp. Panel Strains.

This study investigates GT-1 (also known as LCB10-0200), a novel-siderophore cephalosporin, inhibited multidrug-resistant (MDR) Gram-negative pathogen, via a Trojan horse strategy exploiting iron-uptake systems. We investigated GT-1 activity and the role of siderophore uptake systems, and the combination of GT-1 and a non-ß-lactam ß-lactamase inhibitor (BLI) of diazabicyclooctane, GT-055, (also referred to as LCB18-055) against molecularly characterised resistant Escherichia coli, Klebsiella pneumoniae and Acinetobacter spp. isolates. GT-1 and GT-1/GT-055 were tested in vitro against comparators among three different characterised panel strain sets. Bacterial resistome and siderophore uptake systems were characterised to elucidate the genetic basis for GT-1 minimum inhibitory concentrations (MICs). GT-1 exhibited in vitro activity (≤2 µg/mL MICs) against many MDR isolates, including extended-spectrum ß-lactamase (ESBL)- and carbapenemase-producing E. coli and K. pneumoniae and oxacillinase (OXA)-producing Acinetobacter spp. GT-1 also inhibited strains with mutated siderophore transporters and porins. Although BLI GT-055 exhibited intrinsic activity (MIC 2-8 µg/mL) against most E. coli and K. pneumoniae isolates, GT-055 enhanced the activity of GT-1 against many GT-1-resistant strains. Compared with CAZ-AVI, GT-1/GT-055 exhibited lower MICs against E. coli and K. pneumoniae isolates. GT-1 demonstrated potent in vitro activity against clinical panel strains of E. coli, K. pneumoniae and Acinetobacter spp. GT-055 enhanced the in vitro activity of GT-1 against many GT-1-resistant strains.

Resistome Profiles, Plasmid Typing, and Whole-Genome Phylogenetic Tree Analyses of BlaNDM-9 and Mcr-1 Co-Harboring Escherichia coli ST617 from a Patient without a History of Farm Exposure in Korea.

Recently, a blaNDM-9 and mcr-1 co-harboring E. coli ST 617 isolate was identified from an asymptomatic carrier in Korea. An 81-year-old female was admitted to a university hospital for aortic cardiac valve repair surgery. Following surgery, she was admitted to the intensive care unit (ICU) for three days, and carbapenem-resistant E. coli YMC/2017/02/MS631 was isolated from a surveillance culture (rectal swab). Antimicrobial susceptibility testing (AST) for colistin was not performed at that time. Upon retrospective study, further AST revealed resistance to all tested antibiotics, including meropenem, imipenem, ceftazidime-avibactam, amikacin, gentamicin, ciprofloxacin, trimethoprim-sulfamethoxazole, and colistin, with the exception of tigecycline. Whole genome sequencing analyses showed that this strain belonged to the ST617 serotype O89/162: H10 and harbored three ß-lactamase genes (blaTEM-1B, blaCTX-M-55, blaNDM-9), mcr-1, and 14 other resistance genes. Seven plasmid replicon types (IncB, IncFII, IncI2, IncN, IncY, IncR, IncX1) were identified. Horizontal transfer of blaNDM-9 and mcr-1 from donor cells to the recipient E. coli J53 has been observed. blaNDM-9 and mcr-1 were carried by IncB and IncI2 plasmids, respectively. To speculate on the incidence of this strain, routine rectal swab screening to identify asymptomatic carriers might be warranted, in addition to the screening of ICU patients.

Phenotypic and Genotypic Characterization of Acinetobacter spp. Panel Strains: A Cornerstone to Facilitate Antimicrobial Development.

Acinetobacter spp. have emerged as significant pathogens causing nosocomial infections. Treatment of these pathogens has become a major challenge to clinicians worldwide, due to their increasing tendency to antibiotic resistance. To address this, much revenue and technology are currently being dedicated toward developing novel drugs and antibiotic combinations to combat antimicrobial resistance. To address this issue, we have constructed a panel of Acinetobacter spp. strains expressing different antimicrobial resistance determinants such as narrow spectrum ß-lactamases, extended-spectrum ß-lactamases, OXA-type-carbapenemase, metallo-beta-lactamase, and over-expressed AmpC ß-lactamase. Bacterial strains exhibiting different resistance phenotypes were collected between 2008 and 2013 from Severance Hospital, Seoul. Antimicrobial susceptibility was determined according to the CLSI guidelines using agar dilution method. Selected strains were sequenced using Ion Torrent PGM system, annotated using RAST server and analyzed using Geneious pro 8.0. Genotypic determinants, such as acquired resistance genes, changes in the expression of efflux pumps, mutations, and porin alternations, contributing to the relevant expressed phenotype were characterized. Isolates expressing ESBL phenotype consisted of bla PER-1 gene, the overproduction of intrinsic AmpC beta-lactamase associated with ISAba1 insertion, and carbapenem resistance associated with production of carbapenem-hydrolyzing Ambler class D ß-lactamases, such as OXA-23, OXA-66, OXA-120, OXA-500, and metallo-ß-lactamase, SIM-1. We have analyzed the relative expression of Ade efflux systems, and determined the sequences of their regulators to correlate with phenotypic resistance. Quinolone resistance-determining regions were analyzed to understand fluoroquinolone-resistance. Virulence factors responsible for pathogenesis were also identified. Due to several mutations, acquisition of multiple resistance genes and transposon insertion, phenotypic resistance decision scheme for for evaluating the resistance proved inaccurate, which highlights the urgent need for modification to this scheme. This complete illustration of mechanism contributing to specific resistance phenotypes can be used as a target for novel drug development. It can also be used as a reference strain in the clinical laboratory and for the evaluation of antibiotic efficacy for specific resistance mechanisms.

Single-dose Intravenous Safety, Tolerability, and Pharmacokinetics and Absolute Bioavailability of LCB01-0371.

PURPOSE: LCB01-0371 is a novel broad-spectrum oxazolidinone antibacterial agent under investigation for the treatment of infection by gram-positive pathogens, including methicillin-resistant Staphylococcus aureus. This study evaluated the safety, tolerability, and pharmacokinetics of LCB01-0371 after a single intravenous (IV) infusion and determined its absolute oral bioavailability at a therapeutic dose of 800 mg. METHODS: This study was conducted in 2 parts. The first part was a single-blind, placebo-controlled, escalating single IV dose study (200, 400, 800, and 1200 mg) of LCB01-0371 via 2 different infusion regimens (250 mL over 60 min or 150 mL over 30 min) in 36 healthy male volunteers. The second part was an open-label, 2-way crossover design study in which 8 subjects were randomly assigned to 1 of 2 sequences of a single oral (800 mg) or IV (400 mg) administration of LCB01-0371. Safety assessments were conducted at regular intervals. Blood and urine were serially sampled, and drug concentrations were measured for up to 24 h to calculate pharmacokinetic parameters. FINDINGS: LCB01-0371 after IV administration was generally safe and well tolerated up to 800 mg regardless of the infusion regimen. Adverse events were mild, excluding nausea at the highest dose, and resolved spontaneously. After a single IV administration, LCB01-0371 exhibited linear pharmacokinetic properties over the range of 200-800 mg. The elimination t1/2, volume of distribution, and clearance ranged from 1.48 to 1.68 h, 57.74-76.72 L, and 33.17-43.31 L/h, respectively, and they remained unchanged over the corresponding dose range. Cmax, AUC0-last, and AUC0-∞ increased in a dose-dependent manner. The dose-normalized total exposure after single PO and IV dosing were equivalent, with 90% CIs of the geometric least squares mean ratio of 86.6%-110% for AUC0-last and 86.6%-111% for AUC0-∞. The dose-normalized Cmax was not equivalent between oral and IV dosing, with a 90% CI of the geometric least squares mean ratio of 50.0%-105%. The absolute oral bioavailability of LCB01-0371 after a single 800-mg dose was 99.75%. IMPLICATIONS: After a single IV administration, LCB01-0371 was well tolerated in healthy volunteers at doses up to 800 mg, and it exhibited linear pharmacokinetic properties. The comparable total systemic exposure between IV and oral administration supports the ability to switch administration routes without a need for dose adjustment. ClinicalTrials.gov identifier: NCT02882789.

Multiple-dose Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Oral LCB01-0371 in Healthy Male Volunteers.

PURPOSE: LCB01-0371 is a novel oxazolidinone broad-spectrum antibacterial that is more potent than linezolid against systemic infections in animals. The goal of this investigation was to evaluate the pharmacokinetics, pharmacodynamics, safety, and tolerability of multiple-dose LCB01-0371 as well as the pharmacokinetic characteristics of a new 400-mg tablet formulation. METHODS: Thirty-two healthy male subjects received BID 400-1600 mg multiple oral dosing of LCB01-0371 (200-mg tablet or 400-mg tablet) for 7 days, and 6 subjects received an 800-mg single oral dose of LCB01-0371 (400-mg tablet). Safety assessments were undertaken at regular intervals. Blood and urine were sampled, and drug concentration and inhibitory and bactericidal titers were measured. FINDINGS: LCB01-0371 was generally safe and well tolerated up to 1200 mg BID for 7 days. Adverse events were mild, except for headache, nausea, and dizziness at the dose of 1600 mg, and resolved spontaneously. LCB01-0371 was absorbed rapidly within 2 h after administration, and its accumulation observed on day 7 ranged between 1.10- and 1.46-fold. The elimination t1/2 was 1.64-1.94 h, which remained unchanged across all doses. AUC0-12 and Cmax were not dose proportional across the dose range from 400 to 1200 mg after both single and multiple dosing, indicating a nonlinear pharmacokinetic profile. The percentage of the dose excreted via the urine ranged from 7.84% to 8.95%. The new (400-mg tablet) formulation exhibited less interindividual variability with pharmacokinetic characteristics similar to the original formulation (200-mg tablet). LCB01-0371 exhibited both early serum inhibitory and bactericidal activities against the 4 strains tested in the ex vivo pharmacodynamics study. IMPLICATIONS: BID doses of LCB01-0371 up to 1200 mg for 7 days were well tolerated and exhibited rapid serum inhibitory and bactericidal activities against common gram-positive pathogens. The results warrant further clinical investigation of the antibacterial effect of BID LCB01-0371 administration. ClinicalTrial.gov identifier: NCT01842516.

Effect of food on the pharmacokinetic characteristics of a single oral dose of LCB01-0371, a novel oxazolidinone antibiotic.

BACKGROUND: LCB01-0371 is a novel oxazolidinone antibiotic that blocks protein production by binding to bacterial 23S ribosomes. This antibiotic is active against Gram-positive bacteria. This study aimed to evaluate the effect of food on the pharmacokinetics (PKs) of LCB01-0371 and evaluate its safety profile. SUBJECTS AND METHODS: A randomized, open-label, two-way crossover study was performed in 18 healthy Korean male subjects. All subjects received a single oral 800 mg dose of LCB01-0371 in each period under fed or fasting condition with a 7-day washout in between. The fed condition was defined as consumption of a meal of 800-1,000 kcal containing50% of fat content. Serial blood samples were collected over 24 h after dosing, and the PK parameters were calculated by noncompartment analysis. All available data of the subjects who received LCB01-0371 at least once were included in the safety data summaries. RESULTS: In the fed condition, both the maximum plasma concentration (Cmax) and the total systemic exposure (area under the plasma concentration-time curve from time zero to the last observed time point [AUClast]) decreased by ~33% and 10%, respectively. The time to reach Cmax was delayed by ~1.25 h in the fed condition, whereas the mean elimination half-life remained similar in both conditions. In the fed/fasting condition, the geometric mean ratios and 90% CI of the Cmax and AUClast were 0.666 (0.470-0.945) and 0.897 (0.761-1.057), respectively. There were no drug-related adverse events (AEs) or serious AEs. CONCLUSION: Although the Tmax after a single oral 800 mg dose of LCB01-0371 was slightly delayed under the fed condition compared to the fasting condition, the total systemic exposure was similar under both conditions. Therefore, LCB01-0371 could be administered regardless of food intake.

Pharmacokinetics, Pharmacodynamics, and Tolerability of Single-Dose Oral LCB01-0371, a Novel Oxazolidinone with Broad-Spectrum Activity, in Healthy Volunteers.

LCB01-0371 is a novel oxazolidinone with broad-spectrum activity against Gram-positive pathogens in both in vitro studies and animal infection models. The objectives of this study were to evaluate its safety, tolerability, pharmacokinetics, and pharmacodynamics following single ascending doses. Single oral doses of 600 mg linezolid, a placebo, or LCB01-0371 of between 50 mg and 3,200 mg were tested in 69 healthy male subjects. Blood and urine were sampled, LCB01-0371 concentrations were measured, and the serum inhibitory and bactericidal titers of LCB01-0371 and linezolid were determined. LCB01-0371 was well tolerated up to 2,400 mg. The most common drug-related clinical and laboratory adverse events were nausea with or without vomiting, decreased neutrophil counts, and increased total bilirubin levels. The frequency of adverse events and drug-related adverse events was similar among the treatment groups. The systemic exposure was approximately dose proportional over the range of 50 mg to 800 mg, which includes the anticipated clinical dose. The mean clearance, renal clearance, and volume of distribution were significantly decreased at higher doses (above 800 mg). LCB01-0371 exhibited early bacteriostatic activity against all tested strains except for Streptococcus pneumoniae strains, and the potency of LCB01-0371 at 800 mg was similar to that of linezolid at the therapeutic dose (600 mg). However, LCB01-0371 had less bactericidal activity than linezolid. Taken together, LCB01-0371 was well tolerated, exhibited approximate dose proportionality within the anticipated clinically relevant dose range, and showed bacteriostatic and bactericidal activity comparable to that of linezolid. These results support the further clinical development of LCB01-0371. (This study has been registered at ClinicalTrials.gov under registration no. NCT01554995.).

Safety, tolerability and pharmacokinetics of 21 day multiple oral administration of a new oxazolidinone antibiotic, LCB01-0371, in healthy male subjects.

BACKGROUND: LCB01-0371 is a new oxazolidinone antibiotic, which targets most Gram-positive organisms. High rates of adverse reactions including myelosuppression have been reported for existing oxazolidinones, limiting their long-term use. OBJECTIVES: The safety, tolerability and pharmacokinetics (PK) of 21 day multiple oral administrations of LCB01-0371 in healthy male subjects (clinicaltrials.gov: NCT02540460) were investigated. METHODS: In this randomized, double-blind, placebo-controlled study, subjects received 800 mg of LCB01-0371 once or twice daily or 1200 mg of LCB01-0371 twice-daily for 21 days in a fasting state. Safety and tolerability profiles including laboratory tests were evaluated during the study and on a post-study visit and the results were analysed using repeated-measures analysis of variance (RM-ANOVA). Serial blood samples for PK analysis were collected up to 12 h after dosing on day 21. RESULTS: A total of 40 subjects were enrolled and 34 subjects completed the study. Two subjects dropped out according to stopping rules. In the 1200 mg twice-daily dose group, the absolute value of red blood cell count, haematocrit and haemoglobin decreased by 500 × 106/L (6.5%), 4.5% (6.8%) and 1.6 g/dL (6.9%), respectively, after 21 day administrations of LCB01-0371. However, mean relative changes from baseline of all haematology values were not significantly different among doses, including placebo (all, P < 0.05). PK profiles of LCB01-0371 in the dose range of 800 mg once daily to 1200 mg twice daily were consistent with previous studies. CONCLUSIONS: LCB01-0371 is well tolerated in healthy male subjects with comparable haematology profiles to placebo, after multiple doses of up to 1200 mg twice daily for 21 days.

In Vivo Activity of LCB 01-0699, a Prodrug of LCB 01-0648, against Staphylococcus aureus.

LCB01-0648 is a novel oxazolidinone compound that shows potent antibacterial activities against most Gram-positive cocci, including the multi-drug resistant Staphylococcusaureus. In this study, in vivo activity of LCB01-0699, a LCB01-0648 prodrug, against S.aureus was evaluated in comparison with that of Linezolid. The results of the systemic infection study demonstrated that LCB01-0699 was more potent than Linezolid against methicillin-susceptible and -resistant S. aureus strains. The in vivo efficacy of LCB01-0699 against methicillin-susceptible and -resistant S. aureus strains in a skin infection model showed more potent activity than Linezolid. LCB01-0699 shows potent in vivo activity against methicillin-susceptible and -resistant S. aureus strains, suggesting that LCB01-0699 would be a novel candidate for the treatment of these infectious diseases caused by S. aureus.

Activity of LCB01-0371, a Novel Oxazolidinone, against Mycobacterium abscessus.

Mycobacterium abscessus is a highly pathogenic drug-resistant rapidly growing mycobacterium. In this study, we evaluated the in vitro, intracellular, and in vivo activities of LCB01-0371, a novel and safe oxazolidinone derivative, for the treatment of M. abscessus infection and compared its resistance to that of other oxazolidinone drugs. LCB01-0371 was effective against several M. abscessus strains in vitro and in a macrophage model of infection. In the murine model, a similar efficacy to linezolid was achieved, especially in the lungs. We induced laboratory-generated resistance to LCB01-0371; sequencing analysis revealed mutations in rplC of T424C and G419A and a nucleotide insertion at the 503 position. Furthermore, LCB01-0371 inhibited the growth of amikacin-, cefoxitin-, and clarithromycin-resistant strains. Collectively, our data indicate that LCB01-0371 might represent a promising new class of oxazolidinones with improved safety, which may replace linezolid for the treatment of M. abscessus.

Antimicrobial activities of LCB10-0200, a novel siderophore cephalosporin, against the clinical isolates of Pseudomonas aeruginosa and other pathogens.

Infections caused by multidrug-resistant bacteria, including Pseudomonas aeruginosa, are threatening public health worldwide. Therefore, a novel antibacterial agent is needed to treat these infections. Here, we investigated the in vitro and in vivo activities of a novel siderophore-conjugated cephalosporin, LCB10-0200, against the clinical isolates of Gram-negative bacteria, including multidrug-resistant P. aeruginosa. In vitro susceptibility to LCB10-0200 was assessed by performing a two-fold agar dilution method, as described by the Clinical and Laboratory Standards Institute. LCB10-0200 showed the most potent antibacterial activity against P. aeruginosa clinical isolates, including ß-lactamase-producing strains. Moreover, LCB10-0200 showed better antibacterial activity against recently isolated clinical isolates than its comparators, except colistin. The in vivo activity of LCB10-0200 was examined using four mouse models of systemic, thigh, respiratory tract, and urinary tract infections. LCB10-0200 was more effective than ceftazidime in treating systemic, thigh, respiratory tract, and urinary tract infections caused by drug-susceptible and drug-resistant P. aeruginosa strains in these mouse models. Thus, the potent in vitro and in vivo activities of LCB10-0200 observed in the present study indicate that it has the potential for treating infections caused by Gram-negative bacteria, including P. aeruginosa.

In Vitro Activities of LCB 01-0648, a Novel Oxazolidinone, against Gram-Positive Bacteria.

Oxazolidinones are a novel class of synthetic antibacterial agents that inhibit bacterial protein synthesis. Here, we synthesized and tested a series of oxazolidinone compounds containing cyclic amidrazone. Among these compounds, we further investigated the antibacterial activities of LCB01-0648 against drug-susceptible or resistant Gram-positive cocci in comparison with those of six reference compounds. LCB01-0648 showed the most potent antimicrobial activities against clinically isolated Gram-positive bacteria. Against the methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MRCNS) isolates, LCB01-0648 showed the lowest MIC90s (0.5 mg/L) among the tested compounds. In addition, LCB01-0648 had the lowest minimum inhibitory concentrations (MICs) against the four linezolid-resistant S. aureus (LRSA) strains (range 2-4 mg/L). The results of the time-kill studies demonstrated that LCB01-0648 at a concentration 8× the (MIC) showed bactericidal activity against methicillin-susceptible Staphylococcus aureus MSSA or MRSA, but showed a bacteriostatic effect against LRSA. These results indicate that LCB01-0648 could be a good antibacterial candidate against multidrug-resistant (MDR) Gram-positive cocci.

Efficient single-molecule fluorescence resonance energy transfer analysis by site-specific dual-labeling of protein using an unnatural amino acid.

Single-molecule fluorescence resonance energy transfer (smFRET) measurement provides a unique and powerful approach to understand complex biological processes including conformational and structural dynamics of individual biomolecules. For effective smFRET analysis of protein, site-specific dual-labeling with two fluorophores as an energy donor and an acceptor is crucial. Here we demonstrate that site-specific dual-labeling of protein via incorporation of unnatural amino acid provides a clearer picture for the folded and unfolded states of the protein in smFRET analysis than conventional labeling using double cysteines. As a model study, maltose-binding protein (MBP) was dually labeled via incorporation of ρ-azido-l-phenylalanine and cysteine at specific positions, immobilized on a surface, and subjected to smFRET analysis under native and denaturing conditions. The resulting histograms show that site-specific dual-labeling results in a more homogeneous distribution in protein populations, enabling a precise smFRET analysis of protein.

In vitro and in vivo activities of LCB01-0371, a new oxazolidinone.

LCB01-0371 is a new oxazolidinone with cyclic amidrazone. In vitro activity of LCB01-0371 against 624 clinical isolates was evaluated and compared with those of linezolid, vancomycin, and other antibiotics. LCB01-0371 showed good activity against Gram-positive pathogens. In vivo activity of LCB01-0371 against systemic infections in mice was also evaluated. LCB01-0371 was more active than linezolid against these systemic infections. LCB01-0371 showed bacteriostatic activity against Staphylococcus aureus.

Enhanced thermodynamic and kinetic stability of calix[4]arene dimers locked in the cone conformation.

Wide rim tetraurea derivatives (2a,b) have been prepared from a calix[4]arene rigidified in the cone conformation by two diethyleneglycol ether bridges between adjacent oxygens. In comparison to the analogous tetraurea derivatives (3a,b) of a tetrapentoxy calix[4]arene, 2a,b show an increased thermodynamic stability in mixtures of CDCl(3) and DMSO-d(6). Their kinetic stability as expressed by the rate of guest exchange (benzene or cyclohexane against the solvent benzene-d(6)) is also strongly increased by factors of 30-38. Noticeable differences for the inclusion of selected guests are found.