Molecular Periphery Design Allows Control of the New Nitrofurans Antimicrobial Selectivity.

A series of 13 new 3-substituted 5-(5-nitro-2-furyl)-1,2,4-oxadiazoles was synthesized from different aminonitriles. All compounds were screened in the disc diffusion test at a 100 µg/mL concentration to determine the bacterial growth inhibition zone presence and diameter, and then the minimum inhibitory concentrations (MICs) were determined for the most active compounds by serial dilution. The compounds showed antibacterial activity against ESKAPE bacteria, predominantly suppressing the growth of 5 species out of the panel. Some compounds had similar or lower MICs against ESKAPE pathogens compared to ciprofloxacin, nitrofurantoin, and furazidin. In particular, 3-azetidin-3-yl-5-(5-nitro-2-furyl)-1,2,4-oxadiazole (2h) inhibited S. aureus at a concentration lower than all comparators. Compound 2e (5-(5-nitro-2-furyl)-3-[4-(pyrrolidin-3-yloxy)phenyl]-1,2,4-oxadiazole) was active against Gram-positive ESKAPE pathogens as well as M. tuberculosis. Differences in the molecular periphery led to high selectivity for the compounds. The induced-fit docking (IFD) modeling technique was applied to in silico research. Molecular docking results indicated the targeting of compounds against various nitrofuran-associated biological targets.

The Nitrofuran-Warhead-Equipped Spirocyclic Azetidines Show Excellent Activity against Mycobacterium tuberculosis.

A series of 21 new 7'H-spiro[azetidine-3,5'-furo [3,4-d]pyrimidine]s substituted at the pyrimidine ring second position were synthesized. The compounds showed high antibacterial in vitro activity against M. tuberculosis. Two compounds had lower minimum inhibitory concentrations against Mtb (H37Rv strain) compared with isoniazid. The novel spirocyclic scaffold shows excellent properties for anti-tuberculosis drug development.

5-Nitrofuran-Tagged Oxazolyl Pyrazolopiperidines: Synthesis and Activity against ESKAPE Pathogens.

A series of eight 5-nitrofuran-tagged oxazolyl tetrahydropyrazolopyridines (THPPs) has been prepared in six stages with excellent regioselectivity. The testing of these compounds against pathogens of the ESKAPE panel showed a good activity of lead compound 1-(2-methoxyethyl)-5-(5-nitro-2-furoyl)-3-(1,3-oxazol-5-yl)-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c] pyridine (13g), which is superior to nitrofurantoin. These results confirmed the benefit of combining a THPP scaffold with a nitrofuran warhead. Certain structure-activity relationships were established in the course of this study which were rationalized by the induced-fit docking experiments in silico.

Discovery and In Vivo Efficacy of Trace Amine-Associated Receptor 1 (TAAR1) Agonist 4-(2-Aminoethyl)-N-(3,5-dimethylphenyl)piperidine-1-carboxamide Hydrochloride (AP163) for the Treatment of Psychotic Disorders.

Starting from a screening hit, a set of analogs was synthesized based on a 4-(2-aminoethyl)piperidine core not associated previously with trace amine-associated receptor 1 (TAAR1) modulation in the literature. Several structure-activity relationship generalizations have been drawn from the observed data, some of which were corroborated by molecular modeling against the crystal structure of TAAR1. The four most active compounds (EC50 for TAAR1 agonistic activity ranging from 0.033 to 0.112 µM) were nominated for evaluation in vivo. The dopamine transporter knockout (DAT-KO) rat model of dopamine-dependent hyperlocomotion was used to evaluate compounds' efficacy in vivo. Out of four compounds, only one compound (AP163) displayed a statistically significant and dose-dependent reduction in hyperlocomotion in DAT-KO rats. As such, compound AP163 represents a viable lead for further preclinical characterization as a potential novel treatment option for disorders associated with increased dopaminergic function, such as schizophrenia.

Strained contacts with the cell membrane may influence ligand affinity to G protein coupled receptors: a case of free fatty acid receptor 1 agonists.

A set of 1,3,4-thiadiazole-2-carboxamides bearing a substituted biphenyl in the amide portion was synthesised and tested for agonistic activity towards free fatty acid receptor 1 (FFA1). The observed activity trends were impossible to rationalised based solely on the docking energy scores of Glide SP. On the contrary, when the phospholipid cell membrane bilayer was reconstructed around FFA1, it became apparent that inactive compounds displayed significant strained contacts with the membrane while for active compounds the strain was noticeably lower. These findings justify using the improved docking protocol for modelling GPCR-ligand interactions which uses the crystal structure of the receptor and a reconstructed portion of a cell membrane.

Exploration of the nitrogen heterocyclic periphery around the core of the advanced FFA1 agonist fasiglifam (TAK-875).

Three types of heterocyclic moieties-piperidines fused to a heteroaromatic moiety-were explored as potential periphery motifs for the pharmacophoric core of fasiglifam (TAK-875), with fasiglifam being the most advanced agonist of free fatty acid receptor 1, a promising target for therapeutic intervention in type 2 diabetes. Several observed structure-activity relationship trends were corroborated by in silico docking results. Balanced selection based on potency and Caco-2 permeability advanced six compounds to cellular efficacy tests (glucose-stimulated insulin secretion in rat insulinoma INS1E cells). This led to the nomination of compound 16a (LK1408, 3-[4-({4-[(3-{[(2-fluorobenzyl)oxy]methyl}-1-methyl-1,4,6,7-tetrahydro-5H-pyrazolo[4,3-c]pyridin-5-yl)methyl]benzyl}oxy)phenyl]propanoic acid hydrochloride) as the lead for further development.

Discovery of polar spirocyclic orally bioavailable urea inhibitors of soluble epoxide hydrolase.

Spirocyclic 1-oxa-9-azaspiro[5.5]undecan-4-amine scaffold was explored as a basis for the design of potential inhibitors of soluble epoxide hydrolase (sEH). Synthesis and testing of the initial SAR-probing library followed by biochemical testing against sEH allowed nominating a racemic lead compound (±)-22. The latter showed remarkable (> 0.5 mM) solubility in aqueous phosphate buffer solution, unusually low (for sEH inhibitors) lipophilicity as confirmed by experimentally determined logD7.4 of 0.99, and an excellent oral bioavailability in mice (as well as other pharmacokinetic characteristics). Individual enantiomer profiling revealed that the inhibitory potency primarily resided with the dextrorotatory eutomer (+)-22 (IC50 4.99 ±â€¯0.18 nM). For the latter, a crystal structure of its complex with a C-terminal domain of sEH was obtained and resolved. These data fully validate (+)-22 as a new non-racemic advanced lead compound for further development as a potential therapeutic agent for use in such areas as cardiovascular disease, inflammation and pain.

Novel FFA1 (GPR40) agonists containing spirocyclic periphery: polar azine periphery as a driver of potency.

A series of nine compounds based on 3-[4-(benzyloxy)phenyl]propanoic acid core containing a 1-oxa-9-azaspiro[5.5]undecane periphery was designed, synthesized and evaluated as free fatty acid 1 (FFA1 or GPR40) agonists. The spirocyclic appendages included in these compounds were inspired by LY2881835, Eli Lilly's advanced drug candidate for type II diabetes mellitus that was in phase I clinical trials. These polar spirocyclic, fully saturated appendages (that are themselves uncharacteristic of the known FFA1 ligand space) were further decorated with diverse polar groups (such as basic heterocycles or secondary amides). To our surprise, while seven of nine compounds were found to be inactive (likely due to the decrease in lipophilicity, which is known to be detrimental to FFA1 ligand affinity), two compounds containing 2-pyridyloxy and 2-pyrimidinyloxy groups were found to have EC50 of 1.621 and 0.904 µM, respectively. This result is significant in the context of the worldwide quest for more polar FFA1 agonists, which would be devoid of liver toxicity effects earlier observed for a FFA1 agonist fasiglifam (TAk-875) in clinical studies.

Novel free fatty acid receptor 1 (GPR40) agonists based on 1,3,4-thiadiazole-2-carboxamide scaffold.

Free fatty acid receptor 1 (FFA1), previously known as GPR40 is a G protein-coupled receptor and a new target for treatment of type 2 diabetes. Two series of FFA1 agonists utilizing a 1,3,4-thiadiazole-2-caboxamide scaffold were synthetized. Both series offered significant improvement of the potency compared to the previously described 1,3,4-thiadiazole-based FFA1 agonists and high selectivity for FFA1. Molecular docking predicts new aromatic interactions with the receptor that improve agonist potency. The most potent compounds from both series were profiled for in vitro ADME properties (plasma and metabolic stability, LogD, plasma protein binding, hERG binding and CYP inhibition). One series suffered very rapid degradation in plasma and in presence of mouse liver microsomes. However, the other series delivered a lead compound that displayed a reasonable ADME profile together with the improved FFA1 potency.

Free fatty acid receptor 1 (GPR40) agonists containing spirocyclic periphery inspired by LY2881835.

The free fatty acid receptor 1 (FFA1), a G protein-coupled receptor (GPCR) naturally activated by long-chain fatty acids is a novel target for the treatment of metabolic diseases. The basic amine spirocyclic periphery of Eli Lilly's drug candidate LY2881835 for treatment of type 2 diabetes mellitus (which reached phase I clinical trials) inspired a series of novel FFA1 agonists. These were designed to incorporate the 3-[4-(benzyloxy)phenyl]propanoic acid pharmacophore core decorated with a range of spirocyclic motifs. The latter were prepared via the Prins cyclization and subsequent modification of the 4-hydroxytetrahydropyran moiety in the Prins product. Here, we synthesize 19 compounds and test for FFA1 activity. Within this pilot set, a nanomolar potency (EC50=55nM) was reached. Four lead compounds (EC50 range 55-410nM) were characterized for aqueous solubility, metabolic stability, plasma protein binding and Caco-2 permeability. While some instability in the presence of mouse liver microsomes was noted, mouse pharmacokinetic profile of the compound having the best overall ADME properties was evaluated to reveal acceptable bioavailability (F=10.3%) and plasma levels achieved on oral administration.

Novel agonists of free fatty acid receptor 1 (GPR40) based on 3-(1,3,4-thiadiazol-2-yl)propanoic acid scaffold.

1,3,4-Thiadiazole was explored as a more polar, heterocyclic replacement for the phenyl ring in the 3-arylpropionic acid pharmacophore present in the majority of GPR40 agonists. Out of 13 compounds synthesized using a flexible, three-step protocol (involving no chromatographic purification), four compounds were confirmed to activate the target in micromolar concentration range. While the potency of the series should be subject of further optimization, the remarkable aqueous solubility and microsomal stability observed for the lead compound (8g) apparently attests to this new scaffold's high promise in the GPR40 agonist field.

Discovery of Trace Amine Associated Receptor 1 (TAAR1) Agonist 2-(5-(4'-Chloro-[1,1'-biphenyl]-4-yl)-4H-1,2,4-triazol-3-yl)ethan-1-amine (LK00764) for the Treatment of Psychotic Disorders.

A focused in-house library of about 1000 compounds comprising various heterocyclic motifs in combination with structural fragments similar to ß-phenethylamine (PEA) or tyramine was screened for the agonistic activity towards trace amine-associated receptor 1 (TAAR1). The screening yielded two closely related hits displaying EC50 values in the upper submicromolar range. Extensive analog synthesis and testing for TAAR1 agonism in a BRET-based cellular assay identified compound 62 (LK00764) with EC50 = 4.0 nM. The compound demonstrated notable efficacy in such schizophrenia-related in vivo tests as MK-801-induced hyperactivity and spontaneous activity in rats, locomotor hyperactivity of dopamine transporter knockout (DAT-KO) rats, and stress-induced hyperthermia (i.p. administration). Further preclinical studies are necessary to evaluate efficacy, safety and tolerability of this potent TAAR1 agonist for the potential development of this compound as a new pharmacotherapy option for schizophrenia and other psychiatric disorders.

Polar aromatic periphery increases agonist potency of spirocyclic free fatty acid receptor (GPR40) agonists inspired by LY2881835.

A series of spirocyclic compounds inspired by Eli Lilly's phase 1 antidiabetic FFA1 receptor agonist LY2881835 was designed to include polar aromatic periphery groups and explore a possibility of building additional contacts with the target near the agonist binding site. The frontrunner compound in the series (9i) was shown to be a potent (EC50 = 260 nM) FFA1 agonist with excellent aqueous (PBS) solubility and good Caco-2 permeability. The observed structure-activity relationships were rationalized by a docking study. The new series significantly expands the ligand landscape for the ongoing quest for new potent and more polar FFA1 agonists as fundamentally new class of therapeutic agents against type 2 diabetes mellitus.