Osamu Uchikawa

Bio: Osamu Uchikawa is an academic researcher from Takeda Pharmaceutical Company. The author has contributed to research in topics: Aminothiazole & Melatonin. The author has an hindex of 20, co-authored 49 publications receiving 1322 citations.

Synthesis of a Novel Series of Tricyclic Indan Derivatives as Melatonin Receptor Agonists

Abstract: To develop a new therapeutic agent for sleep disorders, we synthesized a novel series of tricyclic indan derivatives and evaluated them for their binding affinity to melatonin receptors. In our previous paper, we proposed a conformation of the methoxy group favorable for the binding of the MT(1) receptor. To fix the methoxy group in an active conformation, we decided to synthesize conformationally restricted tricyclic indan analogues with the oxygen atom in the 6-position incorporated into a furan, 1,3-dioxane, oxazole, pyran, morpholine, or 1,4-dioxane ring system. Among these compounds, indeno[5,4-b]furan analogues were found to be the most potent and selective MT(1) receptor ligands and to have superior metabolic stability. The optimization of substituents led to (S)-(-)-22b, which showed very strong affinity for human MT(1) (K(i) = 0.014 nM), but no significant affinity for hamster MT(3)() (K(i) = 2600 nM) or other neurotransmitter receptors. The pharmacological effects of (S)-(-)-22b were studied in experimental animals, and it was found that a dose of 0.1 mg/kg, po promoted a sleep in freely moving cats, as demonstrated by a decrease in wakefulness and increases in slow wave sleep and rapid eye movement sleep, which lasted for 6 h after administration. Melatonin (1 mg/kg, po) also had a sleep-promoting effect, though it lasted only 2 h. A new chiral method for the synthesis of (S)-(-)-22b starting from 60, which was prepared from 59 employing asymmetric hydrogenation with the (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl-Ru complex, was developed. (S)-(-)-22b (TAK-375) is currently under clinical trial for the treatment of insomnia and circadian rhythm disorders.

Tricyclic compounds, their production and use

Abstract: A compound of formula (I) wherein R1 is an optionally substituted hydrocarbon, amino or heterocyclic group; R2 is H or an optionally substituted hydrocarbon group; R3 is H or an optionally substituted hydrocarbon or heterocyclic group; X is CHR4, NR4, O or S in which R4 is H or an optionally substituted hydrocarbon group; Y is C, CH or N; ring A is an optionally substituted 5- to 7-membered ring; ring B is an optionally substituted benzene ring; and m is 1 to 4, or a salt thereof, a process for producing it, an intermediate for the production and a pharmaceutical composition comprising it are provided.

The sleep-promoting action of ramelteon (TAK-375) in freely moving cats.

Abstract: Introduction: Ramelteon (TAK-375) is an MT 1 /MT 2 receptor agonist being studied for the treatment of insomnia and circadian rhythm sleep disorders. We compared the behavioral effects of ramelteon and exogenous melatonin in freely moving cats. Methods: Ramelteon and melatonin were each suspended in a 0.5% (weight per volume) methylcellulose solution and administered orally to freely moving cats. In the control trial, each cat was given vehicle. Each dose of ramelteon or melatonin was compared with the vehicle control in a crossover design. Electroencephalogram, electromyogram, and electrooculogram recordings were assessed. Results: Ramelteon significantly decreased wakefulness at doses of 0.001, 0.01, and 0.1 mg/kg, increased slow-wave sleep at doses of 0.001, 0.01, and 0.1 mg/kg, and increased rapid eye movement sleep at a dose of 0.1 mg/kg, compared with the vehicle controls, as assessed by analysis of variance. The effects of ramelteon lasted for up to 6 hours when evaluated by reduction of wakefulness. Exogenous melatonin (0.01-1 mg/kg) significantly increased slow-wave sleep, but the effect was weaker than that of ramelteon and lasted for only 2 hours. The lowest doses of ramelteon (0.0001 mg/kg) and melatonin (0.001 mg/kg) had no significant effect on sleep-wakefulness stage. Conclusions: Ramelteon was more effective than exogenous melatonin in promoting and maintaining sleep in freely moving cats. Based on its unique mechanism of action, ramelteon should be studied further to evaluate its potential for the treatment of sleep disorders.

Fused heterocyclic compound

Abstract: Disclosed are a compound represented by the formula (I) below or a salt thereof, and a pharmaceutical product containing such a compound or a salt thereof. The compound has ASK1 inhibitory activity, and is thus useful as a pharmaceutical product for prevention and treatment of diabetes, inflammatory diseases or the like. (I) (In the formula, ring A represents an optionally further substituted ring; R1-R6 independently represent a hydrogen atom or a substituent; and X represents =N- or =C(Z)- (wherein Z represents a hydrogen atom or a substituent). When X is =C(Z)-, Z and R6 may combine together to form an optionally substituted ring together with the carbon atom to which they are bonded.)

Cell death and endoplasmic reticulum stress: disease relevance and therapeutic opportunities

Abstract: The accumulation of unfolded proteins in the endoplasmic reticulum (ER) represents a cellular stress induced by multiple stimuli and pathological conditions. These include hypoxia, oxidative injury, high-fat diet, hypoglycaemia, protein inclusion bodies and viral infection. ER stress triggers an evolutionarily conserved series of signal-transduction events, which constitutes the unfolded protein response. These signalling events aim to ameliorate the accumulation of unfolded proteins in the ER; however, when these events are severe or protracted they can induce cell death. With the increasing recognition of an association between ER stress and human diseases, and with the improved understanding of the diverse underlying molecular mechanisms, novel targets for drug discovery and new strategies for therapeutic intervention are beginning to emerge.

How were new medicines discovered

Abstract: Preclinical strategies that are used to identify potential drug candidates include target-based screening, phenotypic screening, modification of natural substances and biologic-based approaches. To investigate whether some strategies have been more successful than others in the discovery of new drugs, we analysed the discovery strategies and the molecular mechanism of action (MMOA) for new molecular entities and new biologics that were approved by the US Food and Drug Administration between 1999 and 2008. Out of the 259 agents that were approved, 75 were first-in-class drugs with new MMOAs, and out of these, 50 (67%) were small molecules and 25 (33%) were biologics. The results also show that the contribution of phenotypic screening to the discovery of first-in-class small-molecule drugs exceeded that of target-based approaches — with 28 and 17 of these drugs coming from the two approaches, respectively — in an era in which the major focus was on target-based approaches. We postulate that a target-centric approach for first-in-class drugs, without consideration of an optimal MMOA, may contribute to the current high attrition rates and low productivity in pharmaceutical research and development.

Melatonin: a multitasking molecule.

Abstract: Melatonin (N-acetyl-5-methoxytryptamine) has revealed itself as an ubiquitously distributed and functionally diverse molecule. The mechanisms that control its synthesis within the pineal gland have been well characterized and the retinal and biological clock processes that modulate the circadian production of melatonin in the pineal gland are rapidly being unravelled. A feature that characterizes melatonin is the variety of mechanisms it employs to modulate the physiology and molecular biology of cells. While many of these actions are mediated by well-characterized, G-protein coupled melatonin receptors in cellular membranes, other actions of the indole seem to involve its interaction with orphan nuclear receptors and with molecules, for example calmodulin, in the cytosol. Additionally, by virtue of its ability to detoxify free radicals and related oxygen derivatives, melatonin influences the molecular physiology of cells via receptor-independent means. These uncommonly complex processes often make it difficult to determine specifically how melatonin functions to exert its obvious actions. What is apparent, however, is that the actions of melatonin contribute to improved cellular and organismal physiology. In view of this and its virtual absence of toxicity, melatonin may well find applications in both human and veterinary medicine.

International Union of Basic and Clinical Pharmacology. LXXV. Nomenclature, Classification, and Pharmacology of G Protein-Coupled Melatonin Receptors

Abstract: The hormone melatonin (5-methoxy- N -acetyltryptamine) is synthesized primarily in the pineal gland and retina, and in several peripheral tissues and organs. In the circulation, the concentration of melatonin follows a circadian rhythm, with high levels at night providing timing cues to target tissues endowed with melatonin receptors. Melatonin receptors receive and translate melatonin's message to influence daily and seasonal rhythms of physiology and behavior. The melatonin message is translated through activation of two G protein-coupled receptors, MT1 and MT2, that are potential therapeutic targets in disorders ranging from insomnia and circadian sleep disorders to depression, cardiovascular diseases, and cancer. This review summarizes the steps taken since melatonin's discovery by Aaron Lerner in 1958 to functionally characterize, clone, and localize receptors in mammalian tissues. The pharmacological and molecular properties of the receptors are described as well as current efforts to discover and develop ligands for treatment of a number of illnesses, including sleep disorders, depression, and cancer.