Design, synthesis and biological evaluation of novel 1H-pyrazole-4-carbonyl-4,5,6,7-tetrahydrobenzo [b]thiophene derivatives as gut-selective NaPi2b inhibitors.

Intestinal sodium-dependent phosphate transport protein 2b (SLC34A2, NaPi2b) inhibitors are expected to be potential new candidates for anti-hyperphosphatemia drugs. However, a risk of on-target side effects based on the inhibition of NaPi2b in the lung and testis has been reported. To identify gut-selective (minimally systemic) NaPi2b inhibitors, we prepared and evaluated 1H-pyrazole-4-carbonyl-4,5,6,7-tetrahydrobenzo[b]thiophene derivatives with highly polar functional groups to reduce systemic exposure. As a result, compounds 36a and 36b showed a good activity in vitro and a low bioavailability in Sprague-Dawley (SD) rats. However, these compounds did not suppress phosphate absorption in SD rats. This lack of in vivo efficacy could be due to the high hydrophobicity of these compounds. The results of further investigations of other classes of compounds with appropriate physical properties will be reported in due course.

Design, synthesis and biological evaluation of novel pyridine derivatives as gut-selective NaPi2b inhibitors.

We previously reported thiophene derivatives as gut-selective (minimally systemic) and potent sodium-dependent phosphate transport protein 2b (SLC34A2, NaPi2b) inhibitors. However, these derivatives did not suppress phosphate absorption form the intestinal tract in Sprague-Dawley (SD) rats. The lack of efficacy in vivo could be due to the high hydrophobicity of these compounds. In this report, we identified novel pyridine derivatives as gut-selective NaPi2b inhibitors with good activity in vitro and relatively low hydrophobicity. Especially, gut-selective compound 20b suppressed phosphate absorption in SD rats. These results suggest that physical properties, such as the hydrophobicity of the compounds, might affect the in vivo efficacy.

Design, synthesis and biological evaluation of novel indole derivatives as gut-selective NaPi2b inhibitors.

Intestinal sodium-dependent phosphate transport protein 2b (SLC34A2, NaPi2b) inhibitors are expected to be potential new candidates for anti-hyperphosphatemia drugs. However, a risk of on-target side effects based on the inhibition of NaPi2b in the lung and testis has been reported.In this article, we report on our identification of novel indole derivatives as gut-selective NaPi2b inhibitors with good activity, low systemic exposure and moderate hydrophobicity.In particular, gut-selective compound 27, with even lower bioavailability and lower systemic exposure as compared to previously reported pyridine derivatives, demonstrated excellent phosphate absorption-inhibitory effect in SD rats. Compound 27 has an ideal profile and appears to offer promise as a candidate drug for the treatment of hyperphosphatemia, with minimal risk of side effects due to systemic exposure.

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.

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.

Prostaglandin transporter (OATP2A1/SLCO2A1) contributes to local disposition of eicosapentaenoic acid-derived PGE3.

Eicosapentaenoic acid (EPA)-derived prostaglandin E3 (PGE3) possesses an anti-inflammatory effect; however, information for transporters that regulate its peri-cellular concentration is limited. The present study, therefore, aimed to clarify transporters involved in local disposition of PGE3. PGE3 uptake was assessed in HEK293 cells transfected with OATP2A1/SLCO2A1, OATP1B1/SLCO1B1, OATP2B1/SLCO2B1, OAT1/SLC22A6, OCT1/SLC22A1 or OCT2/SLC22A2 genes, compared with HEK293 cells transfected with plasmid vector alone (Mock). PGE3 uptake by OATP2A1-expressing HEK293 cells (HEK/2A1) was the highest and followed by HEK/1B1, while no significantly higher uptake of PGE3 than Mock cells was detected by other transporters. Saturation kinetics in PGE3 uptake by HEK/2A1 estimated the Km as 7.202 ± 0.595 µM, which was 22 times higher than that of PGE2 (Km=0.331 ± 0.131 µM). Furthermore, tissue disposition of PGE3 was examined in wild-type (WT) and Slco2a1-deficient (Slco2a1(-/-)) mice after oral administration of EPA ethyl ester (EPA-E) when they underwent intraperitoneal injection of endotoxin (e.g., lipopolysaccharide). PGE3 concentration was significantly higher in the lung, and tended to increase in the colon, stomach, and kidney of Slco2a1(-/-), compared to WT mice. Ratio of PGE2 metabolite 15-keto PGE2 over PGE2 concentration was significantly lower in the lung and colon of Slco2a1(-/-) than that of WT mice, suggesting that PGE3 metabolism is downregulated in Slco2a1(-/-) mice. In conclusion, PGE3 was found to be a substrate of OATP2A1, and local disposition of PGE3 could be regulated by OATP2A1 at least in the lung.

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.

Improved intestinal membrane permeability of hexose-quinoline derivatives via the hexose transporter, SGLT1.

Intestinal membrane permeability is an important factor affecting the bioavailability of drugs. As a strategy to improve membrane permeability, membrane transporters are useful targets since essential nutrients are absorbed efficiently via specific transporters. For example, there are reports that intestinal hexose transporters could be used as a tool to improve permeability; however, there has been no direct evidence that the transporter protein, sodium/glucose cotransporter 1 (SGLT1), is involved in the transport of hexose analogs. Accordingly, we examined directly whether the intestinal membrane permeability of hexose analogs can be improved by utilizing SGLT1. Three hexose-quinoline derivatives were synthesized and their interactions with SGLT1 were evaluated. Among the three derivatives, the glucose-quinoline molecule exhibited an inhibitory effect on D-glucose uptake by both rat intestinal brush-border membrane vesicles (BBMVs) and Xenopus oocytes expressing SGLT1. In addition, significant uptake of the glucose-quinoline derivative by Xenopus oocytes expressing SGLT1 was observed by both an electrophysiological assay and direct measurement of the uptake of the compound, while the galactose-quinoline derivative did not show significant uptake via SGLT1. Thus, it was directly demonstrated that SGLT1 could be used as a tool for the improvement of intestinal membrane permeability of drugs by modification to the glucose analogs.