In vitro activity of sitafloxacin against atypical bacteria (2009-2014) and comparison between susceptibility of clinical isolates in 2009 and 2012.

In vitro activities of sitafloxacin (STFX) along with fluoroquinolones (levofloxacin (LVFX), moxifloxacin (MFLX), garenoxacin (GRNX)) and macrolides (azithromycin, clarithromycin) against atypical bacteria (Mycoplasma pneumoniae, Legionella pneumophila, Chlamydia trachomatis, Chlamydophila pneumoniae) recovered from clinical specimens from 2009 to 2014 at different healthcare facilities in Japan were investigated. The minimum inhibitory concentration of STFX at which 90% of isolates (MIC90) against M pneumoniae (n= 14) was 0.03µg/mL which was comparable to GRNX, 4- and 16-fold more active than MFLX and LVFX, respectively. Reduced susceptibilities of M pneumoniae (9/14 isolates) to macrolides were observed. MIC90 of STFX against L. pneumophila (n =15) was 0.004µg/mL which was 2- and 4-fold more active than GRNX/LVFX and MFLX, respectively. The minimum inhibitory concentration range of STFX against C. trachomatis (n=5) and C. pneumoniae (n=5) were from 0.015 to 0.03 and from 0.03 to 0.06µg/mL, respectively. Furthermore, differences between the activities of STFX against various clinical isolates in 2009 and those in 2012, which were already published in two articles (Jpn. J. Antibiotics 63:411- 430, 2010, 66:311-330, 2013), were also evaluated. The MIC90s of STFX against methicillin- susceptible Staphylococcus aureus (MSSA), Streptococcus spp. and Enterococcus faecalis isolated in 2012 were 4 or 8 times higher than those in 2009, however there was no difference between STFX activities against other species in 2009 and those in 2012. In conclusion, STFX showed potent activity against atypical bacteria (M pneumoniae, L. pneumophila, C. trachomatis, C. pneumoniae) and no tendency for emergence resistance to Gram- positive cocci, Gram-negative bacteria and anaerobes except MSSA, Streptococcus spp. andt. faecalis.

Discovery of a new 2-aminobenzhydrol template for highly potent squalene synthase inhibitors.

To obtain small and efficient squalene synthase inhibitors, a flexible 2-aminobenzhydrol open form structure was designed and showed potent inhibitory activity comparable to 4,1-benzoxazepin compounds. Further chemical modification led to the discovery of a novel template with a strong squalene synthase inhibitory activity, and its basic structure-activity relationship was revealed. The X-ray crystallographic data of compound 12 bound to the active site of squalene synthase provided an important insight into the binding mode of this alternative template that formed 11-membered ring conformations with an intramolecular hydrogen bond.

Discovery of atrop fixed alkoxy-aminobenzhydrol derivatives: novel, highly potent and orally efficacious squalene synthase inhibitors.

We have recently reported the discovery of the new benzhydrol template, which has a highly potent inhibitory activity for squalene synthase, as typified by compound 1 (SSI IC(50)=0.85 nM). However, it was composed of a pair of easy rotatable atropisomers. In the effort to fix the isomerization, a highly potent alkoxy-aminobenzhydrol scaffold was developed. Some of these acquired compounds demonstrating strong cholesterol synthesis inhibitory activities in a rat hepatic cell. Moreover, two of the series compounds exhibited specific plasma lipid-lowering effects in in vivo animal models.

Discovery of N-[(1R,2S,5S)-2-{[(5-chloroindol-2-yl)carbonyl]amino}-5-(dimethylcarbamoyl)cyclohexyl]-5-methyl-4,5,6,7-tetrahydrothiazolo[5,4-c]pyridine-2-carboxamide hydrochloride: a novel, potent and orally active direct inhibitor of factor Xa.

In the early 1990's, we reported on the low-molecular selective fXa inhibitor DX-9065a having two amidino groups. However, it had poor oral bioavailability due to its strong basic amidino groups. To obtain fXa inhibitors with improved oral bioavailability, we investigated various non-amidino fXa inhibitors and finally discovered cis-1,2-diaminocyclohexane derivative 4c to have potent fXa inhibition, promising anticoagulant activity, and good oral bioavailability, compared with amidino compound DX-9065a. In addition, we will discuss the influence of the third substituent on the cyclohexane ring on anti-fXa activity, anticoagulant activity, PK profile, and lipophilicity.

Design, synthesis, and SAR of cis-1,2-diaminocyclohexane derivatives as potent factor Xa inhibitors. Part I: exploration of 5-6 fused rings as alternative S1 moieties.

A series of cis-1,2-diaminocyclohexane derivatives were synthesized with the aim of optimizing previously disclosed factor Xa (fXa) inhibitors. The exploration of 5-6 fused rings as alternative S1 moieties resulted in two compounds which demonstrated improved solubility and reduced food effect compared to the clinical candidate, compound A. Herein, we describe the synthesis and structure-activity relationship (SAR), together with the physicochemical properties and pharmacokinetic (PK) profiles of some prospective compounds.