Publications by authors named "Masahiro Sakaitani"

A new compound, a derivative of 3,4,5-trimethoxy--phenyl benzamide bearing an 8''-methylimidazopyridine moiety, is found to demonstrate neuroprotective effects by preventing cell death caused by oxidative stress. The compound possesses high solubility and metabolic stability, and inhibits MPTP-induced effects , indicating high potential as a therapeutic drug for Parkinson's disease.

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Ebolaviruses and marburgviruses, members of the family Filoviridae, are known to cause fatal diseases often associated with hemorrhagic fever. Recent outbreaks of Ebola virus disease in West African countries and the Democratic Republic of the Congo have made clear the urgent need for the development of therapeutics and vaccines against filoviruses. Using replication-incompetent vesicular stomatitis virus (VSV) pseudotyped with the Ebola virus (EBOV) envelope glycoprotein (GP), we screened a chemical compound library to obtain new drug candidates that inhibit filoviral entry into target cells.

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The Notch receptor serves a fundamental role in the regulation of cell fate determination through intracellular signal transmission. Mutation of the Notch receptor results in abnormal active signaling, leading to the development of diseases involving abnormal cell growth, including malignant tumors. Therefore, the Notch signaling pathway is a useful pharmacological target for the treatment of cancer.

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Article Synopsis
  • AU-rich elements (ARE) in mRNA are key for cell growth-related gene expression, and the protein HuR stabilizes these mRNAs; high HuR levels are found in cancer cells.
  • A study identified suramin, a drug with potential anticancer properties, which binds to HuR and disrupts its function by destabilizing specific mRNAs, leading to reduced expression of important proteins involved in cancer progression.
  • Results showed that suramin significantly decreased the invasive behavior of tongue carcinoma cells and may serve as a promising treatment for oral cancer, especially in cases resistant to current therapies.
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We accomplished divergent synthesis of potent kinase inhibitor BAY 61-3606 (1) and 27 derivatives via conjugation of imidazo[1,2-c]pyrimidine and indole ring compounds with aromatic (including pyridine) derivatives by means of palladium-catalyzed cross-coupling reaction. Spleen tyrosine kinase (Syk) and germinal center kinase (Gck, MAP4K2) inhibition assays showed that some of the synthesized compounds were selective Gck inhibitors.

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Glioblastoma (GBM), one of the most malignant human cancers, frequently recurs despite multimodal treatment with surgery and chemo/radiotherapies. GBM-initiating cells (GICs) are the likely cell-of-origin in recurrences, as they proliferate indefinitely, form tumors in vivo, and are resistant to chemo/radiotherapies. It is therefore crucial to find chemicals that specifically kill GICs.

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Substituting a carbon atom with a nitrogen atom (nitrogen substitution) on an aromatic ring in our leads 11a and 13g by applying nitrogen scanning afforded a set of compounds that improved not only the solubility but also the metabolic stability. The impact after nitrogen substitution on interactions between a derivative and its on- and off-target proteins (Raf/MEK, CYPs, and hERG channel) was also detected, most of them contributing to weaker interactions. After identifying the positions that kept inhibitory activity on HCT116 cell growth and Raf/MEK, compound 1 (CH5126766/RO5126766) was selected as a clinical compound.

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A facile methodology effective in obtaining a set of compounds monofluorinated at various positions (fluorine scan) by chemical synthesis is reported. Direct and nonselective fluorination reactions of our lead compound 1a and key intermediate 2a worked efficiently to afford a total of six monofluorinated derivatives. All of the derivatives kept their physicochemical properties compared with the lead 1a and one of them had enhanced Raf/MEK inhibitory activity.

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Introducing a sulfamide moiety to our coumarin derivatives afforded enhanced Raf/MEK inhibitory activity concomitantly with an acceptable PK profile. Novel sulfamide 17 showed potent HCT116 cell growth inhibition (IC50=8 nM) and good PK profile (bioavailability of 51% in mouse), resulting in high in vivo antitumor efficacy in the HCT116 xenograft (ED50=4.8 mg/kg).

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A series of benzofuran-based farnesyltransferase inhibitors have been designed and synthesized as antitumor agents. Among them, 11f showed the most potent enzyme inhibitory activity (IC(50)=1.1nM) and antitumor activity in human cancer xenografts in mice.

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1,3-beta-D-Glucan synthase, which synthesizes a main component of fungal cell wall, is one of the promising targets for antifungal agents. In order to identify novel chemical classes of 1,3-beta-D-glucan synthase inhibitors, we screened a chemical library monitoring inhibition of the Candida albicans 1,3-beta-D-glucan synthase activity. The piperazine propanol derivative GSI578 [(2,6-difluoro-phenyl)-carbamic acid 3-(4-benzothiazol-2-yl-piperazine-1-yl)-propyl ester] was identified as a potent inhibitor against 1,3-beta-D-glucan synthase with an IC50 value of 0.

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A highly potent water soluble triazole antifungal prodrug, RO0098557 (1), has been identified from its parent, the novel antifungal agent RO0094815 (2). The prodrug includes a triazolium salt linked to an aminocarboxyl moiety, which undergoes enzymatic activation followed by spontaneous chemical degradation to release 2. Prodrug 1 showed high chemical stability and water solubility and exhibited strong antifungal activity against systemic candidiasis and aspergillosis as well as pulmonary aspergillosis in rats.

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