Adult neurogenesis modulates the hippocampus-dependent period of associative fear memory.

Acquired memory initially depends on the hippocampus (HPC) for the process of cortical permanent memory formation. The mechanisms through which memory becomes progressively independent from the HPC remain unknown. In the HPC, adult neurogenesis has been described in many mammalian species, even at old ages. Using two mouse models in which hippocampal neurogenesis is physically or genetically suppressed, we show that decreased neurogenesis is accompanied by a prolonged HPC-dependent period of associative fear memory. Inversely, enhanced neurogenesis by voluntary exercise sped up the decay rate of HPC dependency of memory, without loss of memory. Consistently, decreased neurogenesis facilitated the long-lasting maintenance of rat hippocampal long-term potentiation in vivo. These independent lines of evidence strongly suggest that the level of hippocampal neurogenesis play a role in determination of the HPC-dependent period of memory in adult rodents. These observations provide a framework for understanding the mechanisms of the hippocampal-cortical complementary learning systems.

Pharmacodynamic target assessment and prediction of clinically effective dosing regimen of TP0586532, a novel non-hydroxamate LpxC inhibitor, using a murine lung infection model.

INTRODUCTION: TP0586532 is a novel non-hydroxamate UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) inhibitor. Pharmacokinetic/pharmacodynamic (PK/PD) indices and magnitude of index that correlated with the efficacy of TP0586532 were determined and used to estimate the clinically effective doses of TP0586532. METHODS: Dose-fractionation studies were conducted using a murine neutropenic lung infection model caused by carbapenem-resistant Enterobacteriaceae. The relationships between the efficacy and the PK/PD index (the maximum unbound plasma concentration divided by the MIC [fCmax/MIC], the area under the unbound plasma concentration-time curve from 0 to 24 h divided by the MIC, and the cumulative percentage of a 24-h period that the unbound plasma concentration exceeds the MIC) were determined using an inhibitory sigmoid maximum-effect model. In addition, the magnitudes of fCmax/MIC were evaluated using the dose-response relationships for each of the seven carbapenem-resistant strains of Enterobacteriaceae. Furthermore, the clinically effective doses of TP0586532 were estimated using the predicted human PK parameters, the geometric mean of fCmax/MIC, and the MIC90 for carbapenem-resistant Klebsiella pneumoniae. RESULTS: The PK/PD index that best correlated with the efficacy was the fCmax/MIC. The geometric means of the fCmax/MIC associated with the net stasis and 1-log reduction endpoints were 2.30 and 3.28, respectively. The clinically effective doses of TP0586532 were estimated to be 1.24-2.74 g/day. CONCLUSION: These results indicate the potential for TP0586532 to have clinical efficacy at reasonable doses against infections caused by carbapenem-resistant Enterobacteriaceae. This study provided helpful information for a clinically effective dosing regimen of TP0586532.

In Vitro and In Vivo Activities of TP0480066, a Novel Topoisomerase Inhibitor, against Neisseria gonorrhoeae.

Gonorrhea is a common, sexually transmitted disease caused by Neisseria gonorrhoeae Multidrug-resistant N. gonorrhoeae is an urgent threat, and the development of a new antimicrobial agent that functions via a new mechanism is strongly desired. We evaluated the in vitro and in vivo activities of a DNA gyrase/topoisomerase IV inhibitor, TP0480066, which is a novel 8-(methylamino)-2-oxo-1,2-dihydroquinoline derivative. The MICs of TP0480066 were substantially lower than those of other currently or previously used antimicrobials against gonococcal strains demonstrating resistance to fluoroquinolones, macrolides, ß-lactams, and aminoglycosides (MICs, ≤0.0005 µg/ml). Additionally, no cross-resistance was observed between TP0480066 and ciprofloxacin. The frequencies of spontaneous resistance to TP0480066 for N. gonorrhoeae ATCC 49226 were below the detection limit (<2.4 × 10-10) at concentrations equivalent to 32× MIC. TP0480066 also showed potent in vitro bactericidal activity and in vivo efficacy in a mouse model of N. gonorrhoeae infection. These data suggest that TP0480066 is a candidate antimicrobial agent for gonococcal infections.

Lead optimization of 2-hydroxymethyl imidazoles as non-hydroxamate LpxC inhibitors: Discovery of TP0586532.

Infectious diseases caused by resistant Gram-negative bacteria have become a serious problem, and the development of therapeutic drugs with a novel mechanism of action and that do not exhibit cross-resistance with existing drugs has been earnestly desired. UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) is a drug target that has been studied for a long time. However, no LpxC inhibitors are available on the market at present. In this study, we sought to create a new antibacterial agent without a hydroxamate moiety, which is a common component of the major LpxC inhibitors that have been reported to date and that may cause toxicity. As a result, a development candidate, TP0586532, was created that is effective against carbapenem-resistant Klebsiella pneumoniae and does not pose a cardiovascular risk.

Pharmacological Characterization of TP0591816, a Novel Macrocyclic Respiratory Syncytial Virus Fusion Inhibitor with Antiviral Activity against F Protein Mutants.

Human respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infections in early childhood. However, no vaccines have yet been approved for prevention of RSV infection, and the treatment options are limited. Therefore, development of effective and safe anti-RSV drugs is needed. In this study, we evaluated the antiviral activity and mechanism of action of a novel macrocyclic anti-RSV compound, TP0591816. TP0591816 showed significant antiviral activities against both subgroup A and subgroup B RSV, while exerting no cytotoxicity. Notably, the antiviral activity of TP0591816 was maintained against a known fusion inhibitor-resistant RSV strain with a mutation in the cysteine-rich region or in heptad repeat B. Results of a time-of-addition assay and a temperature shift assay indicated that TP0591816 inhibited fusion of RSV with the cell membrane during viral entry. In addition, TP0591816 added after cell infection also inhibited cell-cell fusion. A TP0591816-resistant virus strain selected by serial passage had an L141F mutation, but no mutation in the cysteine-rich region or in heptad repeat B in the fusion (F) protein. Treatment with TP0591816 reduced lung virus titers in a dose-dependent manner in a mouse model of RSV infection. Furthermore, the estimated effective dose of TP0591816 for use against F protein mutants was thought to be clinically realistic and potentially tolerable. Taken together, these findings suggest that TP0591816 is a promising novel candidate for the treatment of resistant RSV infection.

Vibiro vulnificus hemolysin associates with gangliosides.

BACKGROUND: Vibrio vulnificus hemolysin (VVH) is a pore-forming toxin secreted by Vibrio vulnificus. Cellular cholesterol was believed to be the receptor for VVH, because cholesterol could bind to VVH and preincubation with cholesterol inhibited cytotoxicity. It has been reported that specific glycans such as N-acetyl-D-galactosamine and N-acetyl-D-lactosamine bind to VVH, however, it has not been known whether these glycans could inhibit the cytotoxicity of VVH without oligomer formation. Thus, to date, binding mechanisms of VVH to cellular membrane, including specific receptors have not been elucidated. RESULTS: We show here that VVH associates with ganglioside GM1a, Fucosyl-GM1, GD1a, GT1c, and GD1b by glycan array. Among them, GM1a could pulldown VVH. Moreover, the GD1a inhibited the cytotoxicity of VVH without the formation of oligomers. CONCLUSION: This is the first report of a molecule able to inhibit the binding of VVH to target cells without oligomerization of VVH.

Lead optimization of 8-(methylamino)-2-oxo-1,2-dihydroquinolines as bacterial type II topoisomerase inhibitors.

The global increase in multidrug-resistant pathogens has caused severe problems in the treatment of infections. To overcome these difficulties, the advent of a new chemical class of antibacterial drug is eagerly desired. We aimed at creating novel antibacterial agents against bacterial type II topoisomerases, which are well-validated targets. TP0480066 (compound 32) has been identified by using structure-based optimization originated from lead compound 1, which was obtained as a result of our previous lead identification studies. The MIC90 values of TP0480066 against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci (VRE), and genotype penicillin-resistant Streptococcus pneumoniae (gPRSP) were 0.25, 0.015, and 0.06 µg/mL, respectively. Hence, TP0480066 can be regarded as a promising antibacterial drug candidate of this chemical class.

Discovery of a potent dual inhibitor of wild-type and mutant respiratory syncytial virus fusion proteins through the modulation of atropisomer interconversion properties.

The development of effective respiratory syncytial virus (RSV) fusion glycoprotein (F protein) inhibitors against both wild-type and the D486N-mutant F protein is urgently required. We recently reported a 15-membered macrocyclic pyrazolo[1,5-a]pyrimidine derivative 4 that exhibited potent anti-RSV activities against not only wild-type, but also D486N-mutant F protein. However, NMR studies revealed that the 15-membered derivative 4 existed as a mixture of atropisomers. An optimization study of the linker moiety between the 2-position of the benzoyl moiety and the 7-position of the pyrazolo[1,5-a]pyrimidine scaffold identified a 16-membered derivative 42c with an amide linker that showed a rapid interconversion of atropisomers. Subsequent optimization of the 5-position of the pyrazolo[1,5-a]pyrimidine scaffold and the 5-position of the benzoyl moiety resulted in the discovery of a potent clinical candidate 60b for the treatment of RSV infections.

Design and Synthesis of 2-(1-Alkylaminoalkyl)pyrazolo[1,5-a]pyrimidines as New Respiratory Syncytial Virus Fusion Protein Inhibitors.

Respiratory syncytial virus (RSV) is one of the most common causes of lower respiratory tract infections and a significant pathogen for both adults and children. Although two drugs have been approved for the treatment of RSV infections, the low therapeutic index of these drugs have led pharmaceutical companies to develop safe and effective small-molecule anti-RSV drugs. The pyrazolo[1,5-a]pyrimidine series of compounds containing a piperidine ring at the 2-position of the pyrazolo[1,5-a]pyrimidine scaffold are known as candidate RSV fusion (F) protein inhibitor drugs, such as presatovir and P3. The piperidine ring has been revealed to facilitate the formation of an appropriate dihedral angle between the pyrazolo[1,5-a]pyrimidine scaffold and the plane of the amide bond for exertion of anti-RSV activity. A molecular-dynamic study on newly designed compounds with an acyclic chain instead of the piperidine ring proposed and demonstrated a new series of pyrazolo[1,5-a]pyrimidine derivatives, such as 9c with a 1-methyaminopropyl moiety, showing similar dihedral angle distributions to those in presatovir. Compound 9c exhibited potent anti-RSV activity with an EC50 value of below 1 nM, which was similar to that of presatovir. A subsequent optimization study on the benzene ring of 9c led to the potent RSV F protein inhibitor 14f with an EC50 value of 0.15 nM. The possibility of improving the biological properties of anti-RSV agents by modification at the 7-position of pyrazolo[1,5-a]pyrimidine is also discussed.

Antimicrobial susceptibilities of clinical isolates of the anaerobic bacteria which can cause aspiration pneumonia.

Aspiration pneumonia is an infectious disease of the lungs caused by inhalation of saliva or foods, associated with swallowing dysfunction. Therefore, the major causative organisms are oral or gastric bacteria. In this study, we evaluated the antimicrobial susceptibility patterns of the anaerobic bacteria which can cause aspiration pneumonia, Fusobacterium spp., Finegoldia magna, Bacteroides fragilis, Peptostreptococcus spp., Prevotella spp., and Streptococcus milleri group to ceftriaxone, cefmetazole, flomoxef, ampicillin/sulbactam, and ampicillin. We also tested the ß-lactamase activities of each of the bacterial strains. Fusobacterium spp. and Finegoldia magna were susceptible to all of the tested antimicrobial drugs, except ampicillin, and showed no ß-lactamase activity. The Streptococcus milleri group, Bacteroides fragilis, and Peptostreptococcus spp. showed decreased susceptibility to cefmetazole or flomoxef as compared to the susceptibility levels documented in a previous report. There was one strain of Peptostreptococcus anaerobius which was not susceptible to ampicillin/sulbactam, but also showed no ß-lactamase activity, suggesting that this strain harbored a mechanism of resistance other than the production of ß-lactamase. The susceptibility of Prevotella spp. to ceftriaxone was also decreased as compared to the susceptibility level documented in a previous report. Furthermore, ß-lactamase-positive strains were found even among ceftriaxone-susceptible strains. Elderly persons with swallowing dysfunction carry a risk of recurrent episodes of aspiration pneumonia and repeated use of antibiotics increases the risk of development of antibiotic resistance. In the present study, the antibiotic susceptibilities of some of organisms which can cause aspiration pneumonia were found to be decreased as compared to the susceptibility levels documented in a previous report. Therefore, surveillance of the antimicrobial susceptibility patterns of these bacteria is recommended to prevent the development of resistance.

Abaloparatide Exerts Bone Anabolic Effects with Less Stimulation of Bone Resorption-Related Factors: A Comparison with Teriparatide.

Abaloparatide (ABL) is a novel synthetic peptide analog of parathyroid hormone-related protein. In previous reports, intermittent ABL administration showed robust bone mineral density (BMD) increase and reduced the incidence of fractures in patients with osteoporosis, while its calcemic effect was reduced, as compared with teriparatide (TPTD), a parathyroid hormone N-terminal fragment. The present study aimed to elucidate the effects of ABL on bone anabolism and bone turnover as compared with TPTD. In ovariectomized (OVX) rats, ABL increased the bone strength and BMD of lumbar spine by intermittent administration similar to TPTD. Both ABL and TPTD increased the bone formation marker serum P1NP with little effect on the bone resorption maker urine DPD/Cr, suggesting anabolic effects on bone. In human osteoblastic cells, both peptides increased the expression of bone resorption-related factors such as RANKL/OPG and M-CSF, and the effects of ABL were significantly attenuated as compared with those of TPTD under transient 6-h treatment, although no significant differences were found under continuous treatment. In contrast, ABL and TPTD similarly promoted the expression of bone formation-related factors, IGF-1 and osteocalcin. In addition, there were no significant differences in the effects on WNT signaling inhibitors such as sclerostin and dickkopf-related protein 1 (DKK1) between the two peptides. These results demonstrate that ABL exerts bone anabolic effects in OVX rats. It is also indicated that ABL stimulates the expression of RANKL/OPG and M-CSF less than TPTD, while showing similar effects on bone formation-related factors and WNT signaling inhibitors in vitro. The profile of ABL indicates that it would be a suitable bone anabolic agent for osteoporosis.

High glucose-mediated overexpression of ICAM-1 in human vaginal epithelial cells increases adhesion of Candida albicans.

To investigate the involvement of ICAM-1 in the adhesion of Candida to the genitourinary epithelial cells in high glucose, we examined the adhesion of Candida albicans or Candida glabrata to human vaginal epithelial cells (VK2/E6E7) or human vulvovaginal epidermal cells (A431). These cells were cultured in 100, 500 or 3000 mg/dL glucose for three days and inoculated with Candida for 60 minutes. Followed by, adhering of Candida to the cells, which were counted. While the adhesion of Candida albicans to VK2/E6E7 significantly increased in the high glucose, A431 did not. We next examined the expression of ICAM-1 as a ligand on the epithelial cells. ICAM-1 expression was increased in VK2/E6E7 cultured in the high glucose; however, the expression level in A431 was not high compared with VK2/E6E7. This data suggested that ICAM-1 functions as one of ligands in the adhesion of Candida albicans to the vaginal epithelial cells in a high glucose environment. Impact statement What is already known on the subject: Candida's complement receptor is involved in the adhesion to epithelial cells. The expression of this receptor has been reported to increase as glucose concentration increases. This is considered as a contributing factor to the high risk for vulvovaginal candidiasis (VVC) in diabetes. On the host side, diabetic patients have a factor that facilitates adhesion of Candida to epithelial cells. This factor has been unknown until recently. What the results of this study add: In this study, we used a vaginal epithelial cell line and showed that the adhesion of C. albicans to cells increased at higher glucose concentrations. At the same time, ICAM-1 expression of cells also increased. Thereby, it is suggested that the expression of ICAM-1 in vaginal epithelial cells is increased by glucose such as urinary sugar in diabetic patients and is a condition for facilitating adhesion of Candida. What the implications are of these findings for clinical practice and/or further research: We expect not only host immune dysfunction but also alteration in epithelial cells will be focussed on as a cause of VVC in diabetic patients.

[Myelodysplastic syndrome with rapid disease progression after withdrawal of treatment with azacitidine].

A 73-year-old woman was diagnosed with myelodysplastic syndrome(MDS). After 11 courses of treatment with azacitidine( AZA), her hemoglobin level and platelet count improved significantly, and she became transfusion independent. Therefore, treatment was discontinued and follow-ups were maintained. Three months later, her platelet count reduced again; we therefore treated her again with AZA. However, MDS transformed to acute myeloid leukemia in the 14th course, and she died 19 months after the initial diagnosis. AZA is an important drug for treating MDS, but premature withdrawal of treatment might cause rapid disease progression. In case treatment is discontinued, the patient needs to be carefully observed.

Presynaptic protein synaptotagmin1 regulates the activity-induced remodeling of synaptic structures in cultured hippocampal neurons.

Activity-dependent reorganizations of central neuronal synapses are thought to play important roles in learning and memory. Although the precise mechanisms of how neuronal activities modify synaptic connections in neurons remain to be clarified, the activity-induced neuronal presynaptic proteins such as synaptotagmin1 may contribute to the onset of synaptic remodeling. To understand better the physiological roles of synaptotagmin1, we first examined the prolonged effects of neuronal stimulation capable of inducing synaptotagmin1 on the distribution of a postsynaptic proteins (PSD) protein Homer1c by immunostaining. Previously we found that glutamate stimulation induced other postsynaptic proteins, such as postsynaptic density-95 (PSD95), a biphasic change with an initially diffuse distribution after 30 min to 1 hr, followed by reassembly to more than the original level after 4-8 hr, suggesting that glutamate stimulation induces a global biphasic alteration in synaptic structures. To dissect further the functions of synaptotagmin1 in the activity-induced synaptic remodeling, short hairpin RNA (shRNA) vectors that specifically block the expression of endogenous synaptotagmin1 were constructed. When the shRNA of synaptotagmin1 was introduced to the neurons, the activity-induced changes were almost completely suppressed. We found that synaptotagmin1 contributes to the postsynaptic remodeling in a retrograde manner. Our data indicate that synaptotagmin1 regulates the activity-induced biphasic changes of post- and presynaptic sites.

Synthesis and antibacterial activity of 6-O-(heteroaryl-isoxazolyl)propynyl 2-fluoro ketolides.

Macrolide antibiotics are widely prescribed for the treatment of respiratory tract infections; however, the increasing prevalence of macrolide-resistant pathogens is a public health concern. Therefore, the development of new macrolide derivatives with activities against resistant pathogens is urgently needed. A series of novel 6-O-(heteroaryl-isoxazolyl)propynyl 2-fluoro ketolides has been synthesized from erythromycin A. These compounds have shown very promising in vitro and in vivo antibacterial activities against key respiratory pathogens including erythromycin-susceptible/resistant strains.

Does 20-min arm crank ergometer exercise increase plasma interleukin-6 in individuals with cervical spinal cord injury?

Interleukin-6 (IL-6) is produced by contracting skeletal muscles and then released into the circulation and considered to mediate the health benefits of exercise against chronic diseases. Individuals with spinal cord injury (SCI) are reported to be at higher risk of developing metabolic diseases. We investigated the IL-6 responses to 20-min arm crank ergometer exercise at 60% of maximum oxygen consumption in eight trained individuals with cervical SCI (CSCI) between C6 and C7, and eight able-bodied trained healthy subjects. The plasma concentrations of IL-6, adrenaline, prostaglandin E(2) and cortisol were measured before, immediately after the exercise, 1 and 2 h after exercise. At rest, the plasma adrenaline concentration was significantly lower in individuals with CSCI than in able-bodied subjects (P < 0.01). On the other hand, the concentration of IL-6 was significantly higher at rest in individuals with CSCI (2.18 ± 0.44 pg/ml, mean ± SEM) than the control (1.02 ± 0.22 pg/ml, P < 0.05). In able-bodied subjects, the plasma adrenaline concentration increased significantly immediately after the exercise (P < 0.01) and returned to the baseline level at 1 h after exercise, and the plasma IL-6 level increased significantly at 1 h after exercise (1.91 ± 0.28 pg/ml, P < 0.05) and returned to the baseline level at 2 h after exercise. In contrast, adrenaline and IL-6 levels were steady throughout the study in individuals with CSCI. The lack of exercise-related IL-6 response in individuals with CSCI could be due to muscle atrophy and sympathetic nervous system dysfunction.

[COVID-19 drug candidate pipeline, an overview].

The new coronavirus (SARS-CoV-2) spread throughout the world and caused a pandemic with COVID-19, an infection caused by SARS-CoV-2. Even today, an increase in the number of cases has also been observed in Japan. Since the drugs used in drug repositioning have already been tested for safety and pharmacokinetics in humans, it is possible to skip some development tests, and since the manufacturing method of the drug has already been established, it is possible to shorten the development period and reduce R&D costs. Therefore, the drug repositioning method is one of the methods that should be tried in order to achieve the initial control of a pandemic. In Japan, it has been announced that research and development using drug repositioning has been conducted to date. The following are some of the candidates that have already been identified as COVID-19 therapeutic agents in Japan and are expected to be identified in the future.

TP0586532, a Novel Non-Hydroxamate LpxC Inhibitor: Potentiating Effect on In Vitro Activity of Meropenem against Carbapenem-Resistant Enterobacteriaceae.

Carbapenem-resistant Enterobacteriaceae (CRE) are an urgent threat to public health requiring the development of novel therapies. TP0586532 is a novel non-hydroxamate LpxC inhibitor that inhibits the synthesis of lipopolysaccharides, which are components of the outer membranes of Gram-negative bacteria. Based on the mechanism of action of TP0586532, we hypothesized that it might enhance the antibacterial activity of other antibiotics by increasing the permeability of the outer bacterial membrane. The combination of TP0586532 with meropenem, amikacin, cefepime, piperacillin, and tigecycline showed synergistic and additive effects against carbapenem-susceptible Klebsiella pneumoniae and Escherichia coli. Checkerboard experiments against 21 carbapenem-resistant K. pneumoniae and E. coli strains (13 blaKPC+, 5 blaNDM-1+, 2 blaVIM+, and 1 blaIMP+) showed that the combination of TP0586532 with meropenem yielded synergistic and additive effects against 9 and 12 strains, respectively. In a time-kill assay examining 12 CRE strains, synergistic effects were observed when TP0586532 was combined with meropenem against many of the strains. A membrane permeability assay using ethidium bromide (EtBr) was performed to investigate the mechanism of the potentiating effect. TP0586532 increased the influx of EtBr into a CRE strain, suggesting that TP0586532 increased membrane permeability and facilitated intracellular access for the antibiotics. Our study demonstrates that TP0586532 potentiates the in vitro antibacterial activity of meropenem against CRE. Combination therapy consisting of TP0586532 and meropenem has potential as a treatment for CRE infections. IMPORTANCE Carbapenem-resistant Enterobacteriaceae (CRE) are an urgent public health threat, as therapeutic options are limited. TP0586532 is a novel LpxC inhibitor that inhibits the synthesis of lipopolysaccharides in the outer membranes of Gram-negative bacteria. Here, we demonstrated the potentiating effects of TP0586532 on the antibacterial activity of meropenem against CRE harboring various types of carbapenemase genes (blaKPC+, blaNDM-1+ blaVIM+, and blaIMP+). TP0586532 also augmented the bactericidal effects of meropenem against CRE strains, even against those with a high level of resistance to meropenem. The potentiating effects were suggested to be mediated by an increase in bacterial membrane permeability. Our study revealed that a combination therapy consisting of TP0586532 and meropenem has the potential to be a novel therapeutic option for CRE infections.

TP0586532, a non-hydroxamate LpxC inhibitor, reduces LPS release and IL-6 production both in vitro and in vivo.

UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) is an essential enzyme in the biosynthesis of Lipid A, an active component of lipopolysaccharide (LPS), from UDP-3-O-acyl-N-acetylglicosamine. LPS is a major component of the cell surface of Gram-negative bacteria. LPS is known to be one of causative factors of sepsis and has been associated with high mortality in septic shock. TP0586532 is a novel non-hydroxamate LpxC enzyme inhibitor. In this study, we examined the inhibitory effect of TP0586532 on the LPS release from Klebsiella pneumoniae both in vitro and in vivo. Our results confirmed the inhibitory effect of TP0586532 on LPS release from the pathogenic bacterial species. On the other hand, meropenem and ciprofloxacin increase the level of LPS release. Furthermore, the effects of TP0586532 on LPS release and interleukin (IL)-6 production in the lung were determined using a murine model of pneumonia caused by K. pneumoniae. As observed in the in vitro study, TP0586532 showed the marked inhibitory effect on LPS release in the lungs, whereas meropenem- and ciprofloxacin-treated mice showed higher levels of LPS release and IL-6 production in the lungs as compared to those in the lungs of vehicle-treated mice. Moreover, TP0586532 used in combination with meropenem and ciprofloxacin attenuated the LPS release and IL-6 production induced by meropenem and ciprofloxacin in the lung. These results indicate that the inhibitory effect of TP0586532 on LPS release from pathogenic bacteria might be of benefit in patients with sepsis.

TP0586532, a non-hydroxamate LpxC inhibitor, has in vitro and in vivo antibacterial activities against Enterobacteriaceae.

The emergence of multi-drug resistant pathogenic bacteria, especially Gram-negative bacteria, is a worldwide health problem. New antibiotics directed at previously unexplored targets are urgently needed to overcome resistance to existing antibiotic classes. UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) is an attractive target for a new antibacterial agent. Although a number of LpxC inhibitors have been identified, none have been approved as antibacterial agents. These LpxC inhibitors contain a hydroxamate moiety, which is a robust zinc ion chelator. The nonspecific inhibition of metalloenzymes through zinc ion chelation is one of possibilities leading to unwanted side effects. Herein, we report that TP0586532, a non-hydroxamate LpxC inhibitor, has a broad spectrum of antibacterial activity against carbapenem-resistant Enterobacteriaceae. The MIC90 of TP0586532 against clinical isolates of carbapenem-resistant Klebsiella pneumoniae was 4 µg ml-1. TP0586532 also showed an in vivo efficacy against murine systemic, urinary tract and lung infection models caused by meropenem- or ciprofloxacin-resistant strains. The estimated maximum unbound plasma concentration value at the effective dose of TP0586532 in murine infection models was around 13 µg ml-1. TP0586532 is predicted to exhibit a in vivo efficacy without cardiovascular toxicity and showed the potential of non-hydroxamate LpxC inhibitors as antibacterial agents against carbapenem-resistant Enterobacteriaceae.