Discovery and structure-activity relationships of a novel oxazolidinone class of bacterial type II topoisomerase inhibitors.

There is an increasingly urgent and unmet medical need for novel antibiotic drugs that tackle infections caused by multidrug-resistant (MDR) pathogens. Novel bacterial type II topoisomerase inhibitors (NBTIs) are of high interest due to limited cross-resistance with fluoroquinolones, however analogues with Gram-negative activity often suffer from hERG channel inhibition. A novel series of bicyclic-oxazolidinone inhibitors of bacterial type II topoisomerase were identified which display potent broad-spectrum anti-bacterial activity, including against MDR strains, along with an encouraging in vitro safety profile. In vivo proof of concept was achieved in a A. baumannii mouse thigh infection model.

Impact of Mitochondrial Targeting Antibiotics on Mitochondrial Function and Proliferation of Cancer Cells.

Some marketed antibiotics can cause mitochondria dysfunction via inhibition of the mitochondrial translation process. There is great interest in exploiting such effects within a cancer setting. To enhance accumulation of antibiotics within the mitochondria of cancer cells, and therefore delivery of a greater potency payload, a mitochondrial targeting group in the form of a triphenylphosphonium (TPP) cation was appended via an alkyl chain length consisting of 7 to 11 carbons to the ribosomal antibiotics azithromycin and doxycycline. Using MDA-MB-231 cells, the effects of each subseries on mitochondrial translation, mitochondrial bioenergetics, and cell viability are described.

Design, synthesis and antibacterial properties of pyrimido[4,5-b]indol-8-amine inhibitors of DNA gyrase.

According to the World Health Organization (WHO), approximately 1.7 million deaths per year are caused by tuberculosis infections. Furthermore, it has been predicted that, by 2050, antibacterial resistance will be the cause of approximately 10 million deaths annually if the issue is not tackled. As a result, novel approaches to treating broad-spectrum bacterial infections are of vital importance. During the course of our wider efforts to discover unique methods of targeting multidrug-resistant (MDR) pathogens, we identified a novel series of amide-linked pyrimido[4,5-b]indol-8-amine inhibitors of bacterial type II topoisomerases. Compounds from the series were highly potent against gram-positive bacteria and mycobacteria, with excellent potency being retained against a panel of relevant Mycobacterium tuberculosis drug-resistant clinical isolates.

Novel Bacterial Topoisomerase Inhibitors with Potent Broad-Spectrum Activity against Drug-Resistant Bacteria.

The novel bacterial topoisomerase inhibitor class is an investigational type of antibacterial inhibitor of DNA gyrase and topoisomerase IV that does not have cross-resistance with the quinolones. Here, we report the evaluation of the in vitro properties of a new series of this type of small molecule. Exemplar compounds selectively and potently inhibited the catalytic activities of Escherichia coli DNA gyrase and topoisomerase IV but did not block the DNA breakage-reunion step. Compounds showed broad-spectrum inhibitory activity against a wide range of Gram-positive and Gram-negative pathogens, including biodefence microorganisms and Mycobacterium tuberculosis No cross-resistance with fluoroquinolone-resistant Staphylococcus aureus and E. coli isolates was observed. Measured MIC90 values were 4 and 8 µg/ml against a panel of contemporary multidrug-resistant isolates of Acinetobacter baumannii and E. coli, respectively. In addition, representative compounds exhibited greater antibacterial potency than the quinolones against obligate anaerobic species. Spontaneous mutation rates were low, with frequencies of resistance typically <10-8 against E. coli and A. baumannii at concentrations equivalent to 4-fold the MIC. Compound-resistant E. coli mutants that were isolated following serial passage were characterized by whole-genome sequencing and carried a single Arg38Leu amino acid substitution in the GyrA subunit of DNA gyrase. Preliminary in vitro safety data indicate that the series shows a promising therapeutic index and potential for low human ether-a-go-go-related gene (hERG) inhibition (50% inhibitory concentration [IC50], >100 µM). In summary, the compounds' distinct mechanism of action relative to the fluoroquinolones, whole-cell potency, low potential for resistance development, and favorable in vitro safety profile warrant their continued investigation as potential broad-spectrum antibacterial agents.

Discovery and structure-activity relationships of a novel isothiazolone class of bacterial type II topoisomerase inhibitors.

There is an urgent and unmet medical need for new antibacterial drugs that tackle infections caused by multidrug-resistant (MDR) pathogens. During the course of our wider efforts to discover and exploit novel mechanism of action antibacterials, we have identified a novel series of isothiazolone based inhibitors of bacterial type II topoisomerase. Compounds from the class displayed excellent activity against both Gram-positive and Gram-negative bacteria with encouraging activity against a panel of MDR clinical Escherichia coli isolates when compared to ciprofloxacin. Representative compounds also displayed a promising in vitro safety profile.

In vitro biological evaluation of novel broad-spectrum isothiazolone inhibitors of bacterial type II topoisomerases.

OBJECTIVES: To evaluate the in vitro biological properties of a novel class of isothiazolone inhibitors of the bacterial type II topoisomerases. METHODS: Inhibition of DNA gyrase and topoisomerase IV activity was assessed using DNA supercoiling and decatenation assays. MIC and MBC were determined according to CLSI guidelines. Antibacterial combinations were assessed using a two-dimensional chequerboard MIC method. Spontaneous frequency of resistance was measured at various multiples of the MIC. Resistant mutants were generated by serial passage at subinhibitory concentrations of antibacterials and genetic mutations were determined through whole genome sequencing. Mammalian cytotoxicity was evaluated using the HepG2 cell line. RESULTS: Representative isothiazolone compound REDX04957 and its enantiomers (REDX05967 and REDX05990) showed broad-spectrum bactericidal activity against the ESKAPE organisms, with the exception of Enterococcus spp., as well as against a variety of other human bacterial pathogens. Compounds retained activity against quinolone-resistant strains harbouring GyrA S83L and D87G mutations (MIC ≤4 mg/L). Compounds inhibited the supercoiling activity of wild-type DNA gyrase and the decatenation function of topoisomerase IV. Frequency of resistance of REDX04957 at 4× MIC was <9.1 × 10(-9). Against a panel of recent MDR isolates, REDX05967 demonstrated activity against Acinetobacter baumannii with MIC50 and MIC90 of 16 and 64 mg/L, respectively. Compounds showed a lack of cytotoxicity against HepG2 cells at 128 mg/L. CONCLUSIONS: Isothiazolone compounds show potent activity against Gram-positive and -negative pathogens with a dual targeting mechanism-of-action and a low potential for resistance development, meriting their continued investigation as broad-spectrum antibacterial agents.

Efficacy of a Novel Tricyclic Topoisomerase Inhibitor in a Murine Model of Neisseria gonorrhoeae Infection.

There is an urgent need for new antibiotics to treat multidrug-resistant Neisseria gonorrhoeae In this report, the microbiology, in vivo pharmacokinetics, and efficacy of REDX05931, a representative novel tricyclic topoisomerase inhibitor, were evaluated. REDX05931 demonstrated high oral bioavailability in mice and reduced N. gonorrhoeae infection after a single dose in a mouse model of gonorrhea. These data support the potential of this series of small molecules as a new treatment for drug-resistant gonorrheal infections.

Biological profiling of novel tricyclic inhibitors of bacterial DNA gyrase and topoisomerase IV.

OBJECTIVES: The objective of this study was to characterize the in vitro and in vivo biological properties of a novel series of small-molecule bacterial type IIA topoisomerase inhibitors. METHODS: Bacterial susceptibility testing was performed by broth microdilution. Resistance frequencies were determined by plating bacteria onto agar containing test compound and enumerating mutants. Bacteria were passaged using subinhibitory concentrations of antibacterials to generate resistance. Target enzyme inhibition was determined by exposure to antibacterials and DNA; topoisomers were visualized by gel electrophoresis. Oral and intravenous pharmacokinetic profiles were determined in mice. In vivo efficacy was determined using a mouse model of septicaemia and thigh infection with MSSA and MRSA, respectively. RESULTS: Representative compounds REDX04139, REDX05604 and REDX05931 demonstrated in vitro potency against a range of Gram-positive and fastidious Gram-negative pathogens. Clinical isolate testing revealed REDX04139 and REDX05931 had MIC90 values of 0.25 and 0.5 mg/L, respectively, for MRSA and MIC90 values of 2 mg/L for streptococci. REDX04139 was bactericidal in vitro against Staphylococcus aureus at 8× MIC over 6 h. Pharmacokinetic profiling of REDX04139 and REDX05604 in mice revealed low clearance and excellent bioavailability (≥71%). REDX04139 provided 100% survival against S. aureus in a mouse septicaemia model, while REDX05604 reduced bacterial load by up to 3.7 log units in the MRSA mouse thigh infection model. CONCLUSIONS: Redx Pharma has discovered a novel series of topoisomerase inhibitors that are being further developed for drug-resistant bacteria.

Medicinal chemistry strategies to minimize phospholipidosis.

Drug-induced phospholipidosis is characterised by an excessive accumulation of polar phospholipids in cells or tissues. However, from a toxicological perspective the functional consequences of phospholipidosis remain uncertain and a regulatory position unclear. As a consequence, to minimize compound development risk pharmaceutical companies are beginning to proactively address phospholipidosis within drug discovery programs, and implement strategies to identify compounds predicted to show no phospholipidosis. Examples of optimization of compounds to minimize phospholipidosis, and the status of current in silico prediction models, are presented and discussed.

Imidazopyridines as VLA-4 integrin antagonists.

We describe a novel series of imidazopyridine substituted phenylalanines which are potent VLA-4 antagonists. A wide variety of substituents are tolerated as replacements for the pendant 3-pyridyl ring. A clear structure-activity relationship was identified around the substitution of the 3-amino-cyclobut-2-enone portion of the molecule.

Synthesis and SAR of aminopyrimidines as novel c-Jun N-terminal kinase (JNK) inhibitors.

The development of a series of novel aminopyrimidines as inhibitors of c-Jun N-terminal kinases is described. The synthesis, in vitro inhibitory values for JNK1, JNK2 and CDK2, and the in vitro inhibitory value for a c-Jun cellular assay are discussed.

Inosine 5'-monophosphate dehydrogenase inhibitors for the treatment of autoimmune diseases.

Inosine 5'-monophosphate dehydrogenase (IMPDH) is a key enzyme in the de novo biosynthesis of guanine nucleotides. Proliferation of T- and B-lymphocytes, a hallmark of many autoimnunne diseases, is heavily dependent on access to a large pool of guanine nucleotides. To support this activity IMPDH is upregulated. The clinical benefit observed with mnycophenolic acid, a potent IMPDH inhibitor, in a number of autoimmune diseases, including those associated with organ transplantation, rheumatoid arthritis, psoriasis, systemic lupus erythenmatosus and inflammatory bowel disease, has validated IMPDH as an immunosuppressive target, and triggered the search from the pharmaceutical industry for IMPDH inhibitors with best-in-class status. This review will highlight recent advances in the IMPDH field, with a focus on the discovery and development of non-nucleoside IMPDH inhibitors.

Low molecular weight indole fragments as IMPDH inhibitors.

The study of non-oxazole containing indole fragments as inhibitors of inosine monophosphate dehydrogenase (IMPDH) is described. The synthesis and in vitro inhibitory values for IMPDH II are discussed.

Novel indole inhibitors of IMPDH from fragments: synthesis and initial structure-activity relationships.

The elaboration of previously reported indole fragments as inhibitors of inosine monophosphate dehydrogenase (IMPDH) is described. The synthesis, in vitro inhibitory values for IMPDH II, PBMC proliferation and physicochemical properties are discussed.

Novel 7-methoxy-6-oxazol-5-yl-2,3-dihydro-1H-quinazolin-4-ones as IMPDH inhibitors.

The synthesis and biological activity of a novel series of 7-methoxy-6-oxazol-5-yl-2,3-dihydro-1H-quinazolin-4-ones are described. Some of these compounds were found to be potent inhibitors of inosine 5'-monophosphate dehydrogenase type II (IMPDH II).