An ex vivo screening using mouse brain mitochondria identified seco-cycline D as an inhibitor of mitochondrial permeability transition pore.

Mitochondrial dysfunction is implicated in neuropsychiatric disorders. Inhibition of mitochondrial permeability transition pore (mPTP) and thereby enhancement of mitochondrial Ca2+ retention capacity (CRC) is a promising treatment strategy. Here, we screened 1718 compounds to search for drug candidates inhibiting mPTP by measuring their effects on CRC in mitochondria isolated from mouse brains. We identified seco-cycline D (SCD) as an active compound. SCD and its derivative were more potent than a known mPTP inhibitor, cyclosporine A (CsA). The mechanism of action of SCD was suggested likely to be different from CsA that acts on cyclophilin D. Repeated administration of SCD decreased ischemic area in a middle cerebral artery occlusion model in mice. These results suggest that SCD is a useful probe to explore mPTP function.

Discovery of Novel Substrate-Competitive Lysine Methyltransferase G9a Inhibitors as Anticancer Agents.

Identification of structurally novel inhibitors of lysine methyltransferase G9a has been a subject of intense research in cancer epigenetics. Starting with the high-throughput screening (HTS) hit rac-10a obtained from the chemical library of the University of Tokyo Drug Discovery Initiative, the structure-activity relationship of the unique substrate-competitive inhibitors was established with the help of X-ray crystallography and fragment molecular orbital (FMO) calculations for the ligand-protein interaction. Further optimization of the in vitro characteristics and drug metabolism and pharmacokinetics (DMPK) properties led to the identification of 26j (RK-701), which is a structurally distinct potent inhibitor of G9a/GLP (IC50 = 27/53 nM). Compound 26j exhibited remarkable selectivity against other related methyltransferases, dose-dependent attenuation of cellular H3K9me2 levels, and tumor growth inhibition in MOLT-4 cells in vitro. Moreover, compound 26j showed inhibition of tumor initiation and growth in a carcinogen-induced hepatocellular carcinoma (HCC) in vivo mouse model without overt acute toxicity.

New antimalarials identified by a cell-based phenotypic approach: Structure-activity relationships of 2,3,4,9-tetrahydro-1H-ß-carboline derivatives possessing a 2-((coumarin-5-yl)oxy)alkanoyl moiety.

The identification, structure-activity relationships (SARs), and biological effects of new antimalarials consisting of a 2,3,4,9-tetrahydro-1H-ß-carboline core, a coumarin ring, and an oxyalkanoyl linker are described. A cell-based phenotypic approach was employed in this search for novel antimalarial drugs with unique modes of action. Our screening campaign of the RIKEN compound library succeeded in the identification of the known tetrahydro-ß-carboline derivative (4e) as a hit compound showing significant in vitro activity. SAR studies on this chemical series led to the discovery of compound 4h having a (R)-methyl group on the oxyacetyl linker with potent inhibition of parasite growth (IC50 = 2.0 nM). Compound 4h was also found to exhibit significant in vivo antimalarial effects in mouse models. Furthermore, molecular modeling studies on 4e, 4h, and its diastereomer (4j) suggested that the (R)-methyl group of 4h forces the preferential adoption of a specific conformer which is considered to be an active conformer.

Chemical Synthesis of Triazole-Derived Suppressors of Strigolactone Functions.

Triazole is a five-membered heteroring consists of two carbon atoms and three nitrogen atoms and exhibits a wide range of biological activities. The basic heterocyclic rings are 1,2,3-triazole and 1,2,4-triazole. Here we describe the chemical synthetic methods for triazole derivatives that can suppress the function of SL by inhibiting SL biosynthesis pathway or SL perception sites such as D14.

Triazole Ureas Covalently Bind to Strigolactone Receptor and Antagonize Strigolactone Responses.

Strigolactones, a class of plant hormones with multiple functions, mediate plant-plant and plant-microorganism communications in the rhizosphere. In this study, we developed potent strigolactone antagonists, which covalently bind to the strigolactone receptor D14, by preparing an array of triazole urea compounds. Using yeast two-hybrid and rice-tillering assays, we identified a triazole urea compound KK094 as a potent inhibitor of strigolactone receptors. Liquid chromatography-tandem mass spectrometry analysis and X-ray crystallography revealed that KK094 was hydrolyzed by D14, and that a reaction product of this degradation covalently binds to the Ser residue of the catalytic triad of D14. Furthermore, we identified two triazole urea compounds KK052 and KK073, whose effects on D14-D53/D14-SLR1 complex formation were opposite due to the absence (KK052) or presence (KK073) of a trifluoromethyl group on their phenyl ring. These results demonstrate that triazole urea compounds are potentially powerful tools for agricultural application and may be useful for the elucidation of the complicated mechanism underlying strigolactone perception.

Identification of pyrrolo[2,3-d]pyrimidines as potent HCK and FLT3-ITD dual inhibitors.

A series of novel pyrrolo[2,3-d]pyrimidines were synthesized by introducing 15 different amino acids to 7-cyclohexyl-5-(4-phenoxyphenyl)-7H-pyrrolo[2,3-d]pyrimidine-4-amine. Compounds with potent activities against HCK and FLT3-ITD were evaluated in viability studies with acute myeloid leukemia cell line MV4-11. Our structure activity relationship analyses lead to the identification of compound 31, which exhibited potent HCK and FLT3-ITD inhibition and activity against the MV4-11 cell line.

Activity cliff for 7-substituted pyrrolo-pyrimidine inhibitors of HCK explained in terms of predicted basicity of the amine nitrogen.

We previously reported the structure-based design of a highly potent hematopoietic cell kinase (HCK) inhibitor, a pyrrolo-pyrimidine compound designated RK-20449, for treatment of recurrent leukemia. Herein we report the synthesis and structure-activity relationships of some amino acid derivatives of 7-substituted pyrrolo-pyrimidine. Although these derivatives had the same predicted binding conformation as RK-20449, their IC50 values were 100-1000 times larger than that of the parent compound. We assumed that the basicity of the amine nitrogen, which formed an ionic bond with Asp348 of HCK, markedly affected inhibitory activity against HCK. The pKa values of the nitrogen were predicted by means of an ab initio quantum mechanical method, and complexes of the derivatives with HCK were analyzed by X-ray crystallography. We observed a significant correlation between the predicted pKa and IC50 values, and the crystal structures of the less potent derivatives showed various types of defects around the ionic bond.

Aminooxy-naphthylpropionic acid and its derivatives are inhibitors of auxin biosynthesis targeting l-tryptophan aminotransferase: structure-activity relationships.

We previously reported l-α-aminooxy-phenylpropionic acid (AOPP) to be an inhibitor of auxin biosynthesis, but its precise molecular target was not identified. In this study we found that AOPP targets TRYPTOPHAN AMINOTRANSFERASE of ARABIDOPSIS 1 (TAA1). We then synthesized 14 novel compounds derived from AOPP to study the structure-activity relationships of TAA1 inhibitors in vitro. The aminooxy and carboxy groups of the compounds were essential for inhibition of TAA1 in vitro. Docking simulation analysis revealed that the inhibitory activity of the compounds was correlated with their binding energy with TAA1. These active compounds reduced the endogenous indole-3-acetic acid (IAA) content upon application to Arabidopsis seedlings. Among the compounds, we selected 2-(aminooxy)-3-(naphthalen-2-yl)propanoic acid (KOK1169/AONP) and analyzed its activities in vitro and in vivo. Arabidopsis seedlings treated with KOK1169 showed typical auxin-deficient phenotypes, which were reversed by exogenous IAA. In vitro and in vivo experiments indicated that KOK1169 is more specific for TAA1 than other enzymes, such as phenylalanine ammonia-lyase. We further tested 41 novel compounds with aminooxy and carboxy groups to which we added protection groups to increase their calculated hydrophobicity. Most of these compounds decreased the endogenous auxin level to a greater degree than the original compounds, and resulted in a maximum reduction of about 90% in the endogenous IAA level in Arabidopsis seedlings. We conclude that the newly developed compounds constitute a class of inhibitors of TAA1. We designated them 'pyruvamine'.