Design and synthesis of 6-methylpyridin-2-one derivatives as novel and potent GluN2A positive allosteric modulators for the treatment of cognitive impairment.

N-Methyl-D-aspartate receptors (NMDARs) are key regulators of synaptic plasticity in the central nervous system. Potentiation of NMDARs containing GluN2A subunit has been recently recognized as a promising therapeutic approach for neurological disorders. We identified a novel series of GluN2A positive allosteric modulator (PAM) with a pyridin-2-one scaffold. Initial lead compound 1 was discovered through in silico-based screening of virtual ligands with various monocyclic scaffolds. GluN2A PAM activity was increased by introduction of a methyl group at the 6-position of the pyridin-2-one ring and a cyano group in the side chain. Modification of the aromatic ring led to the identification of potent and brain-penetrant 6-methylpyridin-2-one 17 with a negligible binding activity for α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). Oral administration of 17 significantly enhanced rat hippocampal long-term potentiation (LTP). Thus, 17 would be a useful in vivo pharmacological tool to investigate complex NMDAR functions for the discovery of therapeutics toward diseases associated with NMDAR dysfunction.

Rationally designed helical peptidomimetics disrupt α-synuclein fibrillation.

Misfolding of the human protein α-synuclein results in toxic fibrils and the aggregation of Lewy bodies, which are a hallmark of Parkinson's disease in brain tissue. Here we disclose a supramolecular approach where peptidomimetics are rationally designed and pre-organised to recognize the surface of native helical α-Syn by forming complementary contacts with key patches of protein surface composed of charged and hydrophobic residues. Under lipid-catalyzed conditions the mimetics slow the rate of aggregation (thioflavin-T assay) and disrupt the misfolding pathway (electron microscopy of aggregates). This hypothesis is supported by comparison with a series of negative control compounds and with circular dichroism spectroscopy. Given the approach relies on selective recognition of both amino acid sequence and conformation (helical secondary structure) there is potential to develop these compounds as tools to unravel the currently intractable structure-function relationships of (i) missense mutation, and (ii) amyloid polymorphism with disease pathogenesis.

Discovery of Pyrazolo[1,5-a]pyrazin-4-ones as Potent and Brain Penetrant GluN2A-Selective Positive Allosteric Modulators Reducing AMPA Receptor Binding Activity.

N-Methyl-d-aspartate receptors (NMDARs) are members of the ionotropic glutamate receptor family and play a crucial role in learning and memory by regulating synaptic plasticity. Activation of NMDARs containing GluN2A, one of the NMDAR subunits, has recently attracted attention as a promising therapeutic approach for neuropsychiatric diseases such as schizophrenia, depression, and epilepsy. In the present study, we developed potent and brain-penetrable GluN2A-selective positive allosteric modulators. Lead compound 2b was generated by scaffold hopping of hit compound 1, identified from the internal alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-focused compound library through a high-throughput screening campaign. Subsequent optimization of the lead compound, including a structure-based drug design approach, resulted in the identification of a potent GluN2A PAM (R)-9, which possessed high selectivity against both subtypes of AMPAR and NMDAR. Furthermore, (R)-9 significantly enhanced long-term potentiation in the rat hippocampus 24 h after oral administration, indicating that this molecule is a potentially useful in vivo pharmacological tool for treating psychiatric diseases.

Design, Synthesis, and Evaluation of [18F]T-914 as a Novel Positron-Emission Tomography Tracer for Lysine-Specific Demethylase 1.

Histone methylation is associated with the pathophysiology of neurodevelopmental disorders. Lysine-specific demethylase 1 (LSD1) catalyzes histone demethylation in a flavin adenine dinucleotide (FAD)-dependent manner. Thus, inhibiting LSD1 enzyme activity could offer a novel way to treat neurodevelopmental disorders. Assessing LSD1 target engagement using positron-emission tomography (PET) imaging could aid in developing therapeutic LSD1 inhibitors. In this study, PET probes based on 4-(2-aminocyclopropyl)benzamide derivatives that bind irreversibly to FAD found in LSD1 were examined. By optimizing the profiles of brain penetrance and brain-penetrant metabolites, T-914 (1g) was identified as a suitable PET tracer candidate. PET studies in nonhuman primates demonstrated that [18F]1g had heterogeneous brain uptake, which corresponded to known LSD1 expression levels. Moreover, brain uptake of [18F]1g was reduced by coadministration of unlabeled 1g, demonstrating blockable binding. These data suggest that [18F]1g warrants further investigation as a potential PET tracer candidate for assessing target engagement of LSD1.

Discovery of novel somatostatin receptor subtype 5 (SSTR5) antagonists: Pharmacological studies and design to improve pharmacokinetic profiles and human Ether-a-go-go-related gene (hERG) inhibition.

Somatostatin (SST) is a peptide hormone comprising 14 or 28 amino acids that inhibits endocrine and exocrine secretion via five distinct G-protein-coupled receptors (SSTR1-5). SSTR5 has an important role in inhibiting the secretion of pancreatic and gastrointestinal hormones (e.g., insulin, GLP-1, PYY) through the binding of SSTs; hence, SSTR5 antagonists are expected to be novel anti-diabetic drugs. In the course of our lead generation program of SSTR5 antagonists, we have discovered a novel spiroazetidine derivative 3a. However, pharmacological evaluation of 3a revealed that it had to be administered at a high dose (100mg/kg) to show a persistent glucose-lowering effect in an oral glucose tolerance test (OGTT). We therefore initiated an optimization study based on 3a aimed at improving the antagonistic activity and mean residence time (MRT), resulting in the identification of 2-cyclopropyl-5-methoxybiphenyl derivative 3k. However, 3k did not show a sufficient persistent glucose-lowering effect in an OGTT; moreover, hERG inhibition was observed. Hence, further optimization study of the biphenyl moiety of compound 3k, focused on improving the pharmacokinetic (PK) profile and hERG inhibition, was conducted. Consequently, the introduction of a chlorine atom at the 6-position on the biphenyl moiety addressed a putative metabolic soft spot and increased the dihedral angle of the biphenyl moiety, leading to the discovery of 3p with an improved PK profile and hERG inhibition. Furthermore, 3p successfully exhibited a persistent glucose-lowering effect in an OGTT at a dose of 3mg/kg.

Design of potent dipeptidyl peptidase IV (DPP-4) inhibitors by employing a strategy to form a salt bridge with Lys554.

We report a design strategy to obtain potent DPP-4 inhibitors by incorporating salt bridge formation with Lys554 in the S1' pocket. By applying the strategy to the previously identified templates, quinoline 4 and pyridines 16a, 16b, and 17 have been identified as subnanomolar or nanomolar inhibitors of human DPP-4. Docking studies suggested that a hydrophobic interaction with Tyr547 as well as the salt bridge interaction is important for the extremely high potency. The design strategy would be useful to explore a novel design for DPP-4 inhibitors having a distinct structure with a unique binding mode.

Non-covalent S···O interactions control conformation in a scaffold that disrupts islet amyloid polypeptide fibrillation.

Conformationally-constrained molecules that selectively recognise the surfaces of proteins have the potential to direct the path of protein folding. Such molecules are of therapeutic interest because the misfolding of proteins, especially that which results in fibrillation and aggregation, is strongly correlated with numerous diseases. Here we report the novel use of S···O interactions as a conformational control element in a new class of non-peptidic scaffold that mimics key elements of protein surfaces. These molecules disrupt the fibrillation of islet amyloid polypeptide (IAPP), a process that is implicated in the pathology of type II diabetes.

A Modular Synthesis of Conformationally Preorganised Extended ß-Strand Peptidomimetics.

A promising strategy for mediating protein-protein interactions is the use of non-peptidic mimics of secondary structural protein elements, such as the α-helix. Recent work has expanded the scope of this approach by providing proof-of-principle scaffolds that are conformationally biased to mimic the projection of side-chains from one face of another common secondary structural element-the ß-strand. Herein, we present a synthetic route that has key advantages over previous work: monomers bearing an amino acid side-chain were pre-formed before rapid assembly to peptidomimetics through a modular, iterative strategy. The resultant oligomers of alternating pyridyl and six-membered cyclic ureas accurately reproduce a recognition domain of several amino acid residues of a ß-strand, demonstrated herein by mimicry of the i, i+2, i+4 and i+6 residues.

A Modular Synthesis of Conformationally Preorganised Extended ß-Strand Peptidomimetics.

Invited for the cover of this issue is the group of Andrew D. Hamilton and Sam Thompson at the University of Oxford (UK). The image depicts a new class of conformationally constrained ß-strand mimetics mediating the interaction between two subunits of a protein that controls transcription. Read the full text of the article at 10.1002/chem.201501366.

Tissue plasminogen activator thrombolytic therapy for acute ischemic stroke in 4 hospital groups in Japan.

In October 2005 in Japan, the recombinant tissue plasminogen activator (tPA) alteplase was approved for patients with acute ischemic stroke within 3 hours of onset at a dose of 0.6 mg/kg. The present study was undertaken to assess the safety and efficacy of alteplase in Japan. Between October 2005 and December 2009, a total of 114 consecutive patients admitted to 4 hospitals received intravenous tPA within 3 hours of stroke onset. Clinical backgrounds and outcomes were investigated. The patients were divided into 2 chronological groups: an early group, comprising 45 patients treated between October 2005 and December 2007, and a later group, comprising 69 patients treated between January 2008 and December 2009. The mean time from arrival at the hospital to the initiation of treatment was significantly reduced in the later group, from 82.6 minutes to 70.9 minutes. Intracerebral hemorrhage (ICH) occurred in 26 patients (22.8%); compared with patients without ICH, these patients had a significantly higher prevalence of cardiogenic embolism (88.5% vs 58.0%); greater warfarin use (26.8% vs 6.8%); higher mean National Institutes of Health Stroke Scale (NIHSS) scores on admission (16 vs 10), at 3 days after admission (14 vs 5), and at 7 days after admission (13.5 vs 3); and a lower Diffusion-Weighted Imaging-Alberta Stroke Program Early CT Score (7.8 vs 9.1). Patients who received edaravone had a higher prevalence of cardiogenic embolism (70.9% vs 36.4%), a higher recanalization rate (77.7% vs 36.4%), and lower NIHSS scores on admission and at 3 and 7 days after admission compared with those who did not receive edaravone. Our data suggest that administration of intravenous alteplase 0.6 mg/kg within 3 hours of stroke onset is safe and effective, that the NIHSS and Diffusion-Weighted Imaging-Alberta Stroke Program Early CT Score are useful predictors of ICH after tPA administration, and that warfarin-treated patients are more likely to develop symptomatic ICH despite an International Normalized Ratio <1.7.

Synthetic studies on chartelline C: stereoselective construction of the core skeleton.

What a core-ker! The title synthesis was achieved using a route featuring an intramolecular Mitsunobu reaction of a nosyl amide, stereoselective construction of the ß-lactam, and formation of an enamide moiety by selenoxide elimination. The stereochemistry of the alkylation for the formation of the ß-lactam was controlled by a secondary hydroxy group on the ten-membered ring. SEM=2-(trimethylsilyl)ethoxymethyl; TBS=tert-butyldimethylsilyl.

Symmetrical approach of spiro-pyrazolidinediones as acetyl-CoA carboxylase inhibitors.

Spiro-pyrazolidinedione derivatives without quaternary chiral center were discovered by structure-based drug design and characterized as potent acetyl-CoA carboxylase (ACC) inhibitors. The high metabolic stability of the spiro-pyrazolo[1,2-a]pyridazine scaffold and enhancement of the activity by incorporation of a 7-methoxy group on the benzothiophene core successfully led to the identification of compound 4c as an orally bioavailable and highly potent ACC inhibitor. Oral administration of 4c significantly decreased the values of the respiratory quotient in rats, indicating the stimulation of fatty acid oxidation.

Design, synthesis, and structure-activity relationships of novel spiro-piperidines as acetyl-CoA carboxylase inhibitors.

Spiro-lactone (S)-1 is a potent acetyl-CoA carboxylase (ACC) inhibitor and was found to be metabolically liable in human hepatic microsomes. To remove one of the risk factors in human study by improving the metabolic stability, we focused on modifying the spiro-lactone ring and the benzothiophene portion of the molecule. Spiro-imide derivative 8c containing a 6-methylthieno[2,3-b]pyridine core exhibited potent ACC inhibitory activity and favorable pharmacokinetic profiles in rats.

Design, synthesis, and structure-activity relationships of spirolactones bearing 2-ureidobenzothiophene as acetyl-CoA carboxylases inhibitors.

The co-crystal structure of the human acetyl-coenzyme A 2 (ACC2) carboxyl transferase domain and the reported compound CP-640186 (1b) suggested that two carbonyl groups are essential for potent ACC2 inhibition. By focusing on enhancing the interactions between the two carbonyl groups and the amino acid residues Gly(2162) and Glu(2230), we used ligand- and structure-based drug design to discover spirolactones bearing a 2-ureidobenzothiophene moiety.

Discovery of a 3-pyridylacetic acid derivative (TAK-100) as a potent, selective and orally active dipeptidyl peptidase IV (DPP-4) inhibitor.

Inhibition of dipeptidyl peptidase IV (DPP-4) is an exciting new approach for the treatment of diabetes. To date there has been no DPP-4 chemotype possessing a carboxy group that has progressed into clinical trials. Originating from the discovery of the structurally novel quinoline derivative 1, we designed novel pyridine derivatives containing a carboxy group. In our design, the carboxy group interacted with the targeted amino acid residues around the catalytic region and thereby increased the inhibitory activity. After further optimization, we identified a hydrate of [5-(aminomethyl)-6-(2,2-dimethylpropyl)-2-ethyl-4-(4-methylphenyl)pyridin-3-yl]acetic acid (30c) as a potent and selective DPP-4 inhibitor. The desired interactions with the critical active-site residues, such as a salt-bridge interaction with Arg125, were confirmed by X-ray cocrystal structure analysis. In addition, compound 30c showed a desired preclinical safety profile, and it was encoded as TAK-100.

Design and synthesis of 3-pyridylacetamide derivatives as dipeptidyl peptidase IV (DPP-4) inhibitors targeting a bidentate interaction with Arg125.

We have previously discovered nicotinic acid derivative 1 as a structurally novel dipeptidyl peptidase IV (DPP-4) inhibitor. In this study, we obtained the X-ray co-crystal structure between nicotinic acid derivative 1 and DPP-4. From these X-ray co-crystallography results, to achieve more potent inhibitory activity, we targeted Arg125 as a potential amino acid residue because it was located near the pyridine core, and some known DPP-4 inhibitors were reported to interact with this residue. We hypothesized that the guanidino group of Arg125 could interact with two hydrogen-bond acceptors in a bidentate manner. Therefore, we designed a series of 3-pyridylacetamide derivatives possessing an additional hydrogen-bond acceptor that could have the desired bidentate interaction with Arg125. We discovered the dihydrochloride of 1-{[5-(aminomethyl)-2-methyl-4-(4-methylphenyl)-6-(2-methylpropyl)pyridin-3-yl]acetyl}-l-prolinamide (13j) to be a potent and selective DPP-4 inhibitor that could interact with the guanidino group of Arg125 in a unique bidentate manner.

Stereocontrolled total synthesis of (-)-eudistomin C.

A stereocontrolled total synthesis of (-)-eudistomin C was accomplished in 18-step sequence with an overall yield of 7.7%. The synthesis features the diastereoselective Pictet-Spengler reaction of a tryptamine derivative and the Garner aldehyde catalyzed by Bronsted acids, and the unprecedented construction of the unusual oxathiazepine ring by intramolecular alkylation.