Discovery of TAK-925 as a Potent, Selective, and Brain-Penetrant Orexin 2 Receptor Agonist.

TAK-925, a potent, selective, and brain-penetrant orexin 2 receptor (OX2R) agonist, [methyl (2R,3S)-3-((methylsulfonyl)amino)-2-(((cis-4-phenylcyclohexyl)oxy)methyl)piperidine-1-carboxylate, 16], was identified through the optimization of compound 2, which was discovered by a high throughput screening (HTS) campaign. Subcutaneous administration of compound 16 produced wake-promoting effects in mice during the sleep phase. Compound 16 (TAK-925) is being developed for the treatment of narcolepsy and other related disorders.

TAK-925, an orexin 2 receptor-selective agonist, shows robust wake-promoting effects in mice.

Orexin-producing neurons in the lateral hypothalamus are a critical regulator of sleep/wake states, and their loss is associated with narcolepsy type 1 (NT1). Orexin peptides act on two G protein-coupled receptors: orexin 1 receptor (OX1R) and orexin 2 receptor (OX2R). OX2R knockout (KO) mice, but not OX1R KO mice, showed clear narcolepsy-like phenotypes, including fragmented sleep-wake cycles. Moreover, OX2R-selective antagonists have been shown to induce sleepiness in mice, and activation of OX2R has been reported to increase wakefulness. In this study, we characterized in vitro and in vivo profiles of a novel, highly selective OX2R agonist, TAK-925 [methyl (2R,3S)-3-[(methylsulfonyl)amino]-2-{[(cis-4-phenylcyclohexyl)oxy]methyl}piperidine-1-carboxylate]. TAK-925 activated human recombinant OX2R with 50% effective concentration value of 5.5 nM, and showed >5,000-fold selectivity over OX1R in calcium mobilization assays. TAK-925 induced OX2R-downstream signals similar to those displayed by orexin peptides in Chinese hamster ovary cells stably expressing human OX2R. In an electrophysiological study, TAK-925 activated physiological OX2R on histaminergic neurons in the mouse tuberomammillary nucleus (TMN). Subcutaneous (SC) administration of TAK-925 also modulated neuronal activity in various brain regions, including TMN, as measured by an immunohistochemical analysis using an anti-c-fos antibody. TAK-925 (SC) increased wakefulness in wild-type mice, but not in OX2R KO mice, during their sleep phase, demonstrating that a highly selective OX2R agonist can increase wakefulness in mice via OX2R activation. TAK-925 may have therapeutic potential to reduce hypersomnia in multiple disorders including NT1.

Discovery of spiropiperidine-based potent and selective Orexin-2 receptor antagonists.

To generate novel human Orexin-2 Receptor (OX2R) antagonists, a spiropiperidine based scaffold was designed and a SAR study was carried out. Compound 4f possessed the highest OX2R antagonistic activity with an IC(50) value of 3nM with 450-fold selectivity against Orexin-1 Receptor (OX1R).

Discovery of potent, selective, orally active benzoxazepine-based Orexin-2 receptor antagonists.

During our efforts to identify a series of potent, selective, orally active human Orexin-2 Receptor (OX2R) antagonists, we elucidated structure-activity relationship (SAR) on the 7-position of a benzoxazepine scaffold by utilizing Hammett σ(p) and Hansch-Fujita π value as aromatic substituent constants. The attempts led to the discovery of compound 1m, possessing good in vitro potency with over 100-fold selectivity against OX1R, good metabolic stability in human and rat liver microsome, good oral bioavailability in rats, and in vivo antagonistic activity in rats by oral administration.

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.

Identification of face-to-face inclusion complex formation of cyclodextrin bearing an azobenzene group by electrospray ionization mass spectrometry.

The solution-based self-assembly of native and permethylated cyclodextrins (CD) bearing an azobenzene substituent has been studied by electrospray ionization mass spectrometry (ESI-MS). The results revealed that the CD molecules form either a contact or a face-to-face inclusion complex depending on the interaction of their substituents. The mass spectrometric study further demonstrated that the inclusion complex is formed through the interaction between the host CD cavity and the guest-substituent and that a contact complex is formed by hydrogen-bonding of the hydroxyl functions at the rims of the CD molecule. We also found that in order to detect the face-to-face inclusion complex by ESI-MS, the following conditions have to be met: (1) The CD moieties must be permethylated to avoid formation of the contact complex, (2) they must possess a guest-substituent of suitable length, such as an azobenzene moiety, and (3) they must possess an NH(2) or OH group at the substituent terminals for protonation and for detection as cations by ESI-MS. Formation of the inclusion complexes was further confirmed by the synthesis of a capped inclusion dimer and a capped monomer. Collision-induced dissociation (CID) experiments have been carried out for the contact, the host-guest inclusion, and the capped inclusion dimers, and the contact complexes are found to be the most stable among them.