Discovery of S1P agonists with a dihydronaphthalene scaffold

Structure-activity relationship of sphingosine-1-phosphate receptor agonists was examined. Cinnamyl derivative 1 was modified to improve S1P₁ agonistic activity as well as selectivity over S1P₃ agonistic activity. Dihydronaphthalene derivative 10d was identified as a potent S1P₁ receptor agonist with high selectivity against S1P₃ and enhanced efficacy in lowering peripheral lymphocyte counts in mice.     

Discovery of a novel series of potent S1P1 agonists

The discovery of a novel series of S1P1 agonists is described. Starting from a micromolar HTS positive, iterative optimization gave rise to several single-digit nanomolar S1P1 agonists. The compounds were able to induce internalization of the S1P1 receptor, and a selected compound was shown to be able to induce lymphopenia in mice after oral dosing.     

Structure-activity relationship studies of flavopiridol analogues

Cyclin dependent kinases (CDKs) along with the complementary cyclins form key regulatory checkpoint controls on the cell cycle. Flavopiridol is a synthetic flavone that shows potent and selective cyclin-dependent kinase inhibitory activity. In this paper, we report modifications of the 3-hydroxy-1-methylpiperidinyl (D ring) of flavopiridol and their effect on CDK inhibitory activity.     

Structure-activity relationship study on small peptidic GPR54 agonists

Metastin (kisspeptin-54) is an endogenous ligand that modulates gonadotropin-releasing hormone (GnRH) secretion through the interaction with a G protein-coupled receptor (GPCR), GPR54. The short-chain C-terminal decapeptide amide, metastin (45-54) (kisspeptin-10), exerts the identical bioactivities to metastin, such as metastasis suppression of cancer cells and inhibition of trophoblast migration and invasion. In order to understand the structural requirement for GPR54 agonistic activity, structure-activity relationship (SAR) study on pentapeptide-based C-terminal metastin analogues was carried out. As a result, H-Amb-Nal(2)-Gly-Leu-Arg-Trp-NH2 34 was identified as a novel GPR54 agonist that possessed the most potent GPR54 agonistic activity reported so far.     

Synthesis and SAR studies of benzyl ether derivatives as potent orally active S1P1 agonists

We report herein the synthesis and structure–activity relationships (SAR) of a series of benzyl ether compounds as an S1P₁ receptor modulator. From our SAR studies, the installation of substituents onto the central benzene ring of 2a was revealed to potently influence the S1P₁ and S1P₃ agonistic activities, in particular, an ethyl group on the 2-position afforded satisfactory S1P₁/S1P₃ selectivity. These changes of the S1P₁ and S1P₃ agonistic activities caused by the alteration of substituents on the 2-position were reasonably explained by a docking study using an S1P₁ X-ray crystal structure and S1P₃ homology modeling. We found that compounds 2b and 2e had a potent in vivo immunosuppressive efficacy along with acceptable S1P₁/S1P₃ selectivity, and confirmed that these compounds had less in vivo bradycardia risk through the evaluation of heart rate change after oral administration of the compounds (30 mg/kg, p.o.) in rats.     

Pyrazole derived from (+)-3-carene; a novel potent,selective scaffold for sphingosine-1-phosphate (S1P1) receptor agonists

High throughput screening and hit to lead optimization led to the identification of ‘carene’ as a promising scaffold showing selective S1P₁ receptor agonism. In parallel to this work we have established a pharmacophore model for the S1P₁ receptor highlighting the minimal structural requirement necessary for potent receptor agonism.     

Structure-activity studies on diphenylpyrazine derivatives: a novel class of prostacyclin receptor agonists

To develop nonprostanoid prostacyclin receptor agonists with a high degree of metabolic resistance and an extended duration of action, a novel series of diphenylpyrazine derivatives was synthesized and evaluated for their inhibition of ADP-induced human platelet aggregation. Structure-activity relationship studies on the side chain containing the carboxylic acid moiety of the lead compound 5c showed that the length of the linker and the presence of the concatenating nitrogen atom adjacent to the pyrazine ring are critical for the antiaggregatory activity. This study led to the discovery of 2-amino-5,6-diphenylpyrazine derivatives 8c, 15a, and 15b, which showed potent inhibition of platelet aggregation with IC(50) values of 0.2 microM. Among these compounds, 15b is an orally available and long-lasting prostacyclin receptor agonist which is promising for the treatment of various vascular diseases.     

Structure-activity relationship study and NMR analysis of fluorobenzoyl pentapeptide GPR54 agonists

GPR54 is a Gq-protein coupled receptor involved in cancer metastasis and regulation of the endocrine system. GPR54 activation by endogenous ligands attenuates the mobility of carcinomas and stimulates the secretion of gonadotropin-releasing hormone. GPR54 agonists are, therefore, potential therapeutic candidates for cancer metastasis and hormonal diseases. Pentapeptide derivatives of kisspeptin C-terminus were identified as potent GPR54 agonists in our previous studies. In the present study, we investigated the structure-activity relationship of a variety of pentapeptides having various fluorine-substituted benzoyl groups at the N-terminus. Among these, a 4-fluorobenzoyl derivative was the most potent agonist. On the other hand, the derivatives having multiple fluoro-substituting groups showed less binding affinity. NMR analysis of these peptides and their N-terminal partial structures suggested that fluorine substituents affect the benzoyl conformation. o-Monofluorobenzoyl is likely to be in a coplanar conformation due to the intramolecular CF--HN hydrogen bonding between o-fluorine and amide hydrogen; the o,o-difluorobenzoyl moiety exists in a distorted conformation probably due to the steric hindrance and/or electrostatic repulsion between two o-fluorine atoms and carbonyl oxygen.     

Identification of benzoxazole analogs as novel, S1P(3) sparing S1P(1) agonists

A novel series of benzoxazole-derived S1P(1) agonists were designed based on scaffold hopping molecular design strategy combined with computational approaches. Extensive SAR studies led to the discovery of compound 17d as a selective S1P(1) agonist (over S1P(3)) with high CNS penetration and favorable DMPK properties. 17d also demonstrated in vivo pharmacological efficacy to reduce blood lymphocyte in mice after oral administration.     

Structure-activity relationship studies of SYA 013, a homopiperazine analog of haloperidol

Structure-activity relationship studies on 4-(4-(4-chlorophenyl)-1,4-diazepan-1-yl)-1-(4-fluorophenyl)butan-1-one (SYA 013), a homopiperazine analog of haloperidol has resulted in an understanding of the effect of structural modifications on binding affinity at dopamine and serotonin receptor subtypes. Further exploration, using bioisosteric replacement strategies has led to the identification of several new agents including compounds 7, 8, 11 and 12 which satisfy the initial criteria for further exploration as new antipsychotic agents. In addition, compound 18, a D(3) selective tropanol, has been identified as having the potential for further optimization into a useful drug which may combat neuropsychiatric diseases.     

Structure-activity relationship of gramicidin S analogues on membrane permeability

The previous study of the action of gramicidin S on bacteria (Katsu, T., Kobayashi, H. and Fujita, Y. (1986) Biochim. Biophys. Acta 860, 608-619) prompted us to investigate further the structure-activity relationship of the gramicidin S analogues on membrane permeability. Two types of the gramicidin S analogues were used in the present study: (1) cyclo(-X-D-Leu-D-Lys-D-Leu-L-Pro-)2, where X = Gly, D-Leu and D-cyclohexylalanine (D-cHxAla); (2) N,N'-diacetyl derivative of gramicidin S (diacetyl-gramicidin S) which lacks a cationic moiety of gramicidin S. All the analogues have a beta-sheet conformation as gramicidin S. The following cellular systems were used: Staphylococcus aureus as Gram-positive bacteria, Escherichia coli as Gram-negative bacteria, human erythrocytes, rat liver mitochondria and artificial liposomal membranes. It was found that gramicidin S and one of the type 1 analogues having X = D-cHxAla induced the efflux of K+ through the cytoplasmic membrane of all types of the cells. In addition, these two peptides had the ability to lower the phase transition temperature of dipalmitoylphosphatidylcholine. Accordingly, it was concluded that, if peptides can expand greatly the membrane structure of neutral lipids which constitute main parts of the biological membrane, they can stimulate the permeability of cells without any selectivity. The action of the type 2 peptide, diacetyl-gramicidin S, was strongly cell dependent. Although this peptide stimulated the efflux of K+ from mitochondria, it did not do so efficiently, if at all, from S. aureus, E. coli and erythrocytes. In experiments using liposomes, diacetyl-gramicidin S increased markedly the permeability of liposomes composed of egg phosphatidylcholine. The presence of egg phosphatidylethanolamine or cholesterol reduced its activity. These results on liposomes explained well the low sensitivity of diacetyl-gramicidin S against E. coli and erythrocytes in terms of lipid constituents of the membranes. The mechanism of action of diacetyl-gramicidin S was discussed from the formation of a boundary lipid induced by this peptide.     

SAR studies of 3-arylpropionic acids as potent and selective agonists of sphingosine-1-phosphate receptor-1 (S1P1) with enhanced pharmacokinetic properties

Structure-activity relationship (SAR) studies of 3-arylpropionic acids-a class of novel S1P(1) selective agonists-by introducing substitution to the propionic acid chain and replacing the adjacent phenyl ring with pyridine led to a series of modified 3-arylpropionic acids with enhanced half-life in rat. These analogs (e.g., cyclopropanecarboxylic acids) exhibited longer half-life in rat than did unmodified 3-arylpropionic acids. This result suggests that metabolic oxidation at the propionic acid chain, particularly at the C3 benzylic position of 3-arylpropionic acids, is probably responsible for their short half-life in rodent.     

Structure-activity relationship studies of permeability modulating peptide AT-1002

AT-1002 a 6-mer synthetic peptide belongs to an emerging novel class of compounds that reversibly increase paracellular transport of molecules across the epithelial barrier. The aim of this project was to elaborate on the structure-activity relationship of this peptide with the specific goal to replace the P2 cysteine amino acid. Herein, we report the discovery of peptides that exhibit reversible permeability enhancement properties with an increased stability profile.     

Structure-activity relationship and docking studies of thiazolidinedione-type compounds with monoamine oxidase B

The neuroprotective activity of pioglitazone and rosiglitazone in the MPTP parkinsonian mouse prompted us to evaluate a set of thiazolidinedione (TZD) type compounds for monoamine oxidase A and B inhibition activity. These compounds were able to inhibit MAO-B over several log units of magnitude (82 nM to 600 μM). Initial structure-activity relationship studies identified key areas to modify the aromatic substituted TZD compounds. Primarily, substitutions on the aromatic group and the TZD nitrogen were key areas where activity was enhanced within this group of compounds.     

Structure-activity relationships of dimeric PPAR agonists

A series of dimeric PPAR agonists were designed and tested for PPAR activity in vitro. The SAR showed that dimeric ligands with a common group or full dimeric ligands had retained or even increased PPARgamma potency. The dimeric agonist concept can be used to fine tune the subtype selectivity of PPAR agonists. The PPARgamma potency could, at least partly, be explained using molecular modeling.     

Highly selective and potent agonists of sphingosine-1-phosphate 1 (S1P1) receptor

Novel series of sphingosine-1-phosphate (S1P) receptor agonists were developed through a systematic SAR aimed to achieve high selectivity for a single member of the S1P family of receptors, S1P1. The optimized structure represents a highly S1P1-selective and efficacious agonist: S1P1/S1P2, S1P1/S1P3, S1P1/S1P4>10,000-fold, S1P1/S1P5>600-fold, while EC50 (S1P1) <0.2 nM. In vivo experiments are consistent with S1P1 receptor agonism alone being sufficient for achieving desired lymphocyte-lowering effect.     

Indole-propionic acid derivatives as potent, S1P3-sparing and EAE efficacious sphingosine-1-phosphate 1 (S1P1) receptor agonists

Novel indole-propionic acid derivatives were developed as sphingosine-1-phosphate (S1P) receptor agonists through a systematic SAR study. The optimized and S1P(3) selective S1P(1) agonist 9f induced peripheral blood lymphocyte reduction in vivo and has an excellent efficacy in mouse experimental autoimmune encephalomyelitis (EAE).     

Structure-activity relationship studies of novel pyrazole and imidazole carboxamides as cannabinoid-1 (CB1) antagonists

The synthesis and biological evaluation of novel pyrazole and imidazole carboxamides as CB1 antagonists are described. As a part of eastern amide SAR, various chemically diverse motifs were introduced on rimonabant template. The central pyrazole core was also replaced with its conformationally constrained motif and imidazole moieties. In general, a range of modifications were well tolerated. Several molecules with low- and sub-nanomolar potencies were identified as potent CB1 receptor antagonists. The in vivo proof of principle for weight loss is demonstrated with a lead compound in DIO mice model.     

Structure-activity relationship studies of carboxamido-biaryl ethers as opioid receptor antagonists (OpRAs). Part 1

A structurally unique and new class of opioid receptor antagonists (OpRAs) that bear no structural resemblance with morphine or endogenous opioid peptides has been discovered. A series of carboxamido-biaryl ethers were identified as potent receptor antagonists against mu, kappa and delta opioid receptors. The structure-activity relationship indicated para-substituted aryloxyaryl primary carboxamide bearing an amine tether on the distal phenyl ring was optimal for potent in vitro functional antagonism against three opioid receptor subtypes.