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We have developed a new class of PDE10A inhibitor, a pyrazolo[1,5-a]pyrimidine derivative MT-3014 (1). A previous compound introduced was deprioritized due to concerns for E/Z-isomerization and glutathione-adduct formation at the core stilbene structure. We discovered pyrazolo [1,5-a] pyrimidine as a new lead scaffold by structure-based drug design utilizing a co-crystal structure with PDE10A. The lead compound was optimized for in vitro activity, solubility, and selectivity against human ether-á-go-go related gene cardiac channel binding. We observed that MT-3014 shows excellent efficacy in rat conditioned avoidance response test and suitable pharmacokinetic properties in rats, especially high brain penetration., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Phosphodiesterase (PDE) 10A is a dual hydrolase of cAMP and cGMP and highly expressed in striatal medium spiny neurons. Inhibition of PDE10A modulates the activity of medium spiny neurons (MSN) via the regulation of cAMP and cGMP. Signal control of MSN is considered associated with psychotic symptoms. Therefore PDE10A inhibitor is expected as a therapeutic method for psychosis disease such as schizophrenia. Avanafil (1) is a PDE5 inhibitor (treatment for erectile dysfunction) discovered by our company. We paid attention to the homology of PDE10A and PDE5 and took advantage of PDE5 inhibitor library to discover PDE10A inhibitors, and found a series of compounds that exhibit higher potency for PDE10A than PDE5. We transformed the afforded derivatives, which had weak inhibitory activity against PDE10A, and discovered stilbene as a PDE10A inhibitor. Brain penetration of this compound was improved by further conversion of N-containing heterocycles and their substituents. The afforded dimethylaminopyrimidine was effective for rat conditioned avoidance response (CAR) test; however, it did not exhibit good brain penetration. We performed in-depth optimization focusing on substituents of the quinoxaline ring, and produced 3-methyl-7-fluoro quinoxaline. This compound was the most effective in rat CAR test due to its strong PDE10A inhibitory activity and good pharmacokinetics.

Canagliflozin (1), a novel inhibitor for sodium-dependent glucose cotransporter 2 (SGLT2), has been developed for the treatment of type 2 diabetes. To investigate the effect of replacement of the phenyl ring in 1 with heteroaromatics, C-glucosides 2 were designed, synthesized, and evaluated for their inhibitory activities against SGLT2. Of these, 3-pyridyl, 2-pyrimidyl or 5-membered heteroaryl substituted derivatives showed highly potent inhibitory activity against SGLT2, while 5-pyrimidyl substitution was associated with slightly reduced activity. In particular, 2g (TA-3404) had remarkable anti-hyperglycemic effects in high-fat diet fed KK (HF-KK) mice., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

We discovered that C-glucosides 4 bearing a heteroaromatic ring formed metabolically more stable inhibitors for sodium-dependent glucose cotransporter 2 (SGLT2) than the O-glucoside, 2 (T-1095). A novel thiophene derivative 4b-3 (canagliflozin) was a highly potent and selective SGLT2 inhibitor and showed pronounced anti-hyperglycemic effects in high-fat diet fed KK (HF-KK) mice.

To overcome hydrolysis by beta-glucosidase present in the digestive tract, the OH groups on the glucose moiety of the 4'-dehydroxyphlorizin derivatives (1, 2, 3) were modified with various kinds of patterns, and then the effects of the modified compounds on urinary glucose excretion were evaluated in rats. Among them, triacetyl (9), 2,3-O-diacetyl (17), 6-O-methoxycarbonyl (34), 4-O-methoxycarbonyl (38), and 2-O-acetyl (41) derivatives showed more potent effect than the parent compound 2 by oral administration (p.o.). The stabilities of the compounds 34, 38, and 41 against beta-glucosidase were higher than that of 2. The increase in oral activity was found to correlate with the enhancement of the stability against beta-glucosidase.

A novel series of 4'-dehydroxyphlorizin derivatives was synthesized and the effects of these compounds on urinary glucose excretion were evaluated in rats. There was a strict structural requirement for activity. Introduction of a small substituent or a flat ring at the 3- and/or the 4-position on the A ring was permissible, but any change at the bridge part between the A and B rings or in the sugar moiety resulted in complete loss of activity. The 6'-OH group on the B ring was also necessary, and even small structural modifications of the 6'-OH group reduced the activity considerably. Among the compounds synthesized, the 5-benzofuryl derivative 25 was the most potent and was selected as a new lead for further structure-activity relationship investigations.

In an attempt to improve the effectiveness of action of 5-fluoro-2'-deoxyuridine (FUdR), various kinds of O-alkylated water-soluble analogues were synthesized. Antitumor activities against sarcoma 180 (solid) were also evaluated. Some compounds exhibited potent activities. In particular, 3'-O-p-chlorobenzyl-3-N-aminoacyloxy-methylester derivatives were effective over a very wide range of dose and gave extremely large therapeutic ratios compared with known 5-fluorouracil (5-FU) derivations.

Based on our new concept that inhibitors of the Na(+)-glucose cotransporter (SGLT) would be useful as antidiabetics, 4'-dehydroxyphlorizin derivatives 1a--f were designed, synthesized, and examined for various pharmacological properties related to antidiabetic activity. In normal rats, 1a, e and phlorizin showed a strong SGLT-inhibitory effect and significantly increased urinary glucose on intraperitoneal administration at 10 mg/kg, though only 1a resulted in excretion of large quantities of urinary glucose on oral administration at 100 mg/kg. Compounds 1a, e, and phlorizin markedly inhibited glucose uptake in the small intestine during enteric perfusion in normal rats. Compound 1a had a significant reducing effect on blood glucose in the glucose tolerance test in mice when administered orally and also lowered blood glucose in streptozotocin-induced diabetic rats. The aglycons 2a, e of 1a, e, and 1a showed weak inhibitory effects on the facilitated glucose transporter-1 (GLUT-1) in human erythrocytes, while phloretin had a strong inhibitory effect on GLUT-1. Compound 1a caused no apparent renal damage in rats when administered orally at 1 g/kg for 4 successive weeks. Thus, 1a was considered to be a promising candidate as a lead compound for antidiabetics of a new type, and was selected for further pharmacological evaluation.

In an attempt to improve the effectiveness and bioavailability of 6-mercaptopurine, various kinds of water-soluble analogues, such as 6-S-aminoacyloxymethyl mercaptopurine derivatives (3a--m) and 6-S,9-disubstituted derivates (7a,b and 9a,b), were synthesized. These compounds were evaluated for activity to augment antitumor immunity by using a double grated tumor system. Antitumor activities against solid tumors (sarcoma 180 and colon 26) were also evaluated. Many compounds exhibited potent activities in both test systems. In particular, the aminopropionate derivative (3a) and the L-glutamate derivative (3f) showed significant enhancement of antitumor immunity together with potent antitumor activities.