Discovery of a Novel Fluoroquinolone Antibiotic Candidate WFQ-228 with Potent Antimicrobial Activity and the Potential to Overcome Major Drug Resistance.

WFQ-101 with a unique N-1 substituent, 5-amino-4-fluoro-2-(hydroxymethyl)phenyl group, was selected as a lead compound through combination screening based on antimicrobial activity and the efflux index against quinolone-resistant (QR) Pseudomonas aeruginosa (P. aeruginosa). Through structural optimization, we identified WFQ-228 as a novel fluoroquinolone antibiotic candidate. WFQ-228 had potent and superior activity in comparison to levofloxacin (LVX) and ciprofloxacin (CIP) against clinical isolates of P. aeruginosa, Escherichia coli and Acinetobacter baumannii, including QR strains. Furthermore, WFQ-228 demonstrated the potential to overcome major mechanisms of drug resistance; its antimicrobial activity was less affected by both pump-mediated efflux and mutations of the quinolone resistance-determining region in P. aeruginosa compared with LVX and CIP. These results suggest that WFQ-228 is a promising candidate for further evaluation in the treatment of infections caused by QR Gram-negative pathogens.

Discovery of WQ-3810: Design, synthesis, and evaluation of 7-(3-alkylaminoazetidin-1-yl)fluoro-quinolones as orally active antibacterial agents.

Novel 7-(3-alkylaminoazetidin-1-yl)fluoroquinolones were designed, synthesized, and evaluated for their antibacterial activities and oral absorption rates. Against Gram-negative bacteria, 10a-e, which have various alkyl groups containing different numbers of carbon atoms (C0-C3) at the C-7 alkylaminoazetidine position, showed potent and similar antibacterial activities, whereas the activity of 10f (C4, t-Bu) was significantly lower than those of 10a-e. Conversely, the oral absorption rates of 10a-e in rats increased depending on the number of carbon atoms in the alkyl groups; 10d (C3, n-Pr) and 10e (C3, i-Pr) had high oral absorption rates (>90% at 10 mg/kg). These results demonstrated that the introduction of alkyl groups onto C-7 aminoazetidine is useful for the improvement of the oral absorption rates of these drugs while maintaining their antibacterial activities. As a conclusion, from this series of fluoroquinolones, WQ-3810 (10e), having 3-isopropylaminoazetidine as the C-7 substituent, was identified as an orally active antibacterial agent with a potent in vitro activity.

In vitro activity of WQ-3810, a novel fluoroquinolone, against multidrug-resistant and fluoroquinolone-resistant pathogens.

The aim of this study was to examine the in vitro antibacterial activity of WQ-3810, a new fluoroquinolone, against clinically relevant pathogens such as Acinetobacter baumannii, Escherichia coli and Streptococcus pneumoniae, including multidrug-resistant (MDR) and fluoroquinolone-resistant (FQR) isolates, compared with those of ciprofloxacin, levofloxacin, moxifloxacin and gemifloxacin. WQ-3810 demonstrated the most potent activity against the antimicrobial-resistant pathogens tested. Against A. baumannii, including MDR isolates, the potency of WQ-3810 [minimum inhibitory concentration for 90% of the organisms (MIC(90))=1 mg/L] was more than eight-fold higher than that of ciprofloxacin (64 mg/L) and levofloxacin (8 mg/L). Against E. coli and S. pneumoniae, including FQR isolates, WQ-3810 (MIC(90)=4 mg/L and 0.06 mg/L, respectively) was also more active than ciprofloxacin (64 mg/L and 2 mg/L) and levofloxacin (32 mg/L and 2 mg/L). Furthermore, WQ-3810 was the most potent among the fluoroquinolones tested against meticillin-resistant Staphylococcus aureus (MRSA) and Neisseria gonorrhoeae, including FQR isolates. In particular, WQ-3810 demonstrated highly potent activity against FQR isolates of A. baumannii, E. coli and S. pneumoniae with amino acid mutation(s) in the quinolone resistance-determining region of DNA gyrase and/or topoisomerase IV, which are the target enzymes of fluoroquinolones. An enzyme inhibition study performed using FQR E. coli DNA gyrase suggested that the potent antibacterial activity of WQ-3810 against drug-resistant isolates partly results from the strong inhibition of the target enzymes. In conclusion, this study demonstrated that WQ-3810 exhibits extremely potent antibacterial activity over the existing fluoroquinolones, particularly against MDR and FQR pathogens.

Deletion of chromosome arm 15q in a case of minimally differentiated hypoplastic AML-M0.

Deletion of the long arm of chromosome 15 is known as a rare but recurrent chromosomal abnormality in myeloid malignancies. We report a novel case of minimally differentiated hypoplastic acute myeloid leukemia (AML M0) in a patient who initially had a normal karyotype, but clonal interstitial deletion of chromosome 15, del(15)(q11.2q22), coincided with increment of leukemic cells a year later. We also summarize 18 published cases with myeloid malignancies and this chromosomal abnormality.

Calyculin A retraction of mature megakaryocytes proplatelets from embryonic stem cells.

Platelets are produced by megakaryocytes (MKs) through proplatelet formation (PPF), or cytoplasmic extensions, in vitro. Through the use of video-enhanced light microscopy, as well as localization of cytoskeletal proteins by confocal microscopy, the reaction of fully mature MK proplatelets, derived from murine embryonic stem cells, to various agents was studied. Calyculin A (protein phosphatase 1/2A inhibitor) treatment induced proplatelet retraction. In MKs with PPF, the expression of actin, myosin IIA, monophosphorylated myosin light chain (MLC-P1), and diphosphorylated myosin light chain (MLC-P2) was diffusely located. Following calyculin A treatment, actin was diffusely localized in retracted MKs and was expressed particularly in the periphery. MLC-P1 was also localized primarily in the periphery; however, MLC-P2 was expressed mostly in the inner area of proplatelets. Protein phosphatase inhibitors may result in increased hyperphosphorylation of localized MLC, which could alter the balance of actomyosin force in a cell, and therefore induce proplatelets retraction.

Inhibition by Rho-kinase and protein kinase C of myosin phosphatase is involved in thrombin-induced shape change of megakaryocytic leukemia cell line UT-7/TPO.

Thrombin induced a shape change of UT-7/TPO, a thrombopoietin-dependent human megakaryocytic cell line. Expression of myosin light chain (MLC) kinase was negligible in UT-7/TPO cells, while Rho-kinase and protein kinase C (PKC) were detected. Thrombin stimulated both monophosphorylation at Ser19 and diphosphorylation at Thr18 and Ser19 of 20 kDa MLC, as well as phosphorylation of myosin-binding subunit (MBS) and PKC-potentiated inhibitory phosphoprotein of myosin phosphatase (CPI). The Rho-kinase inhibitor Y-27632 [(+)-(R)-trans-(1-aminoethyl)-N-(4-phynidyl) cyclohexane-carboxamide dihydrochloride, monohydrade] strongly inhibited thrombin-induced shape change, MBS phosphorylation, and mono- and diphosphorylation of MLC. The PKC inhibitor GF109203X (2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)-maleimide) partially inhibited thrombin-induced shape change and MLC diphosphorylation even at the concentration that completely inhibited thrombin-induced CPI phosphorylation. In shape-changed UT-7/TPO cells induced by thrombin, phosphorylated MBS and CPI were colocalized with diphosphorylated MLC at pseudopods, whereas monophosphorylated MLC was mainly located in the cortical region. The accumulation of diphosphorylated MLC was blocked by preincubation with either Y-27632 or GF109203X. These results suggest that Rho-kinase is responsible for the induction of MLC phosphorylation in thrombin-induced shape change of UT-7/TPO cells and that myosin phosphatase inactivation through Rho-kinase-MBS and PKC-CPI pathways could be necessary for enhancement of MLC diphosphorylation which promote the pseudopod formation.

New findings on the structure-phototoxicity relationship and photostability of fluoroquinolones with various substituents at position 1.

The present study examined the phototoxicities of a series of 7-(3-aminopyrrolidinyl) quinolones containing various substituents at position 1 (in which the substituent at R8 is a hydrogen or a halogen) by use of a mouse model. For the 7-(3-aminopyrrolidinyl) quinolones with a halogen atom at position 8, well-known substituent groups such as a cyclopropyl, an ethyl, or a difluorophenyl at position 1 were found to be responsible for severe phototoxicity. However, when an aminodifluorophenyl or an isoxazolyl group was placed at position 1, even 8-halogeno quinolones were found to be mildly phototoxic. This is the first report of 8-halogeno quinolones that are not severely phototoxic. Two structurally similar 8-chloro quinolones (the 1-aminodifluorophenyl 8-chloro quinolone and the 1-difluorophenyl 8-chloro quinolone) were investigated further. The former was mildly phototoxic; the latter was severely phototoxic. We demonstrate that these two 8-chloro quinolones have practically the same areas under the concentration-time curves from 0 to 4 h in auricular tissue, suggesting that the mild phototoxicity is not due to pharmacokinetic instability. The rates of UV photodegradation of these compounds were also measured. We found that these two quinolones photodegrade at similar rates, suggesting that the mild phototoxicity is not attained through increased photostability. In conclusion, the phototoxic potentials of fluoroquinolones are influenced not only by the substituent at position 8 but also by that at position 1 (a new finding from this study). We also discovered a mildly phototoxic 8-chloro quinolone which did not have increased photostability.

Pharmacologic platelet anesthesia by glycoprotein IIb/IIIa complex antagonist and argatroban during in vitro extracorporeal circulation.

OBJECTIVE: Contact between blood and the synthetic surfaces of a cardiopulmonary bypass circuit leads to platelet activation, and resultant platelet dysfunction contributes to postoperative bleeding. We compared the effects of various platelet inhibitors on preservation of platelet function during simulated cardiopulmonary bypass circulation. METHODS: Fresh human blood was recirculated in an in vitro cardiopulmonary bypass model circuit. We measured various platelet activation markers including expressions of PAC-1 and P-selectin, annexin V binding, and microparticle formations by means of whole-blood flow cytometry. RESULTS: Two types of glycoprotein IIb/IIIa complex antagonists, peptide-mimetic FK633 and abciximab and prostaglandin E(1), significantly prevented platelet loss and the increase in binding of PAC-1, an antibody specific for fibrinogen receptor on activated platelets, during extracorporeal circulation of heparinized blood. These antagonists significantly suppressed but did not abolish P-selectin expression, annexin V binding, and microparticle formation. Anti-von Willebrand factor monoclonal antibody and aurin tricarboxylic acid (an inhibitor of glycoprotein Ib) had no effect on platelet activation during simulated cardiopulmonary bypass circulation. These data suggest that inhibition of fibrinogen binding glycoprotein IIb/IIIa complex is partly effective in attenuating platelet activation in a heparinized cardiopulmonary bypass model circuit. The direct thrombin inhibitor argatroban prevented platelet loss and expression of P-selectin significantly more than did heparin. A combination of FK633 with argatroban as a substitute for heparin further prevented platelet loss and platelet secretion during simulated cardiopulmonary bypass circulation, although the inhibition of microparticle formation was less. CONCLUSION: The inhibition of both platelet adhesion and thrombin may be effective to preserve platelet number and function during cardiopulmonary bypass circulation.

A novel antibacterial 8-chloroquinolone with a distorted orientation of the N1-(5-amino-2,4-difluorophenyl) group.

Fluoroquinolones represent a major class of antibacterial agents with great therapeutic potential. In this study, we designed m-aminophenyl groups as novel N-1 substituents of naphthyridones and quinolones. Among newly synthesized compounds, 7-(3-aminoazetidin-1-yl)-1-(5-amino-2,4-difluorophenyl)-8-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (4) has extremely potent antibacterial activities against Gram (+) as well as Gram (-) bacteria. This compound is significantly more potent than trovafloxacin against clinical isolates: 30 times against Streptococcus pneumoniae and 128 times against methicillin resistant Staphylococcus aureus. The structure-activity relationship (SAR) study revealed that a limited combination of 1-(5-amino-2,4-difluorophenyl) group, 7-(azetidin-1-yl) group, and 8-Cl atom (or Br atom or Me group) gave potent antibacterial activity. An X-ray crystallographic study of a 7-(3-ethylaminoazetidin-1-yl)-8-chloro derivative demonstrated that the N-1 aromatic group was remarkably distorted out of the core quinolone plane by steric repulsion between the C-8 Cl atom and the N-1 substituent. Furthermore, a molecular modeling study of 4 and its analogues demonstrated that a highly distorted orientation was induced by a steric hindrance of the C-8 substituent, such as Cl, Br, or a methyl group. Thus, their highly strained conformation should be a key factor for the potent antibacterial activity.

Effect of direct infusion of antifungal agent on invasive pulmonary aspergillosis in a patient with acute leukemia.

Invasive pulmonary aspergillosis is a serious problem in the treatment of patients with acute leukemia. A 52-year-old woman with acute myeloid leukemia developed invasive pulmonary aspergillosis during remission induction chemotherapy. Initially, we treated her with a continuous intravenous drip infusion of amphotericin B, together with itraconazole, given orally. A peripheral crescentic cavity formed in the fungal lesion after the number of neutrophils recovered, and we therefore performed a direct infusion of miconazole into the cavity transbronchially. The lung lesion resolved dramatically shortly after this treatment. In this patient, the transbronchial infusion of an antifungal agent seemed to have been very useful for bringing about prompt resolution of the fungal lesion.