Design and synthesis of a novel series of orally active, selective somatostatin receptor 2 agonists for the treatment of type 2 diabetes.

The discovery of a novel series of ß-methyltryptophan (ß MeTrp) derivatives as selective and orally active non-peptide somatostatin receptor 2 (SSTR2) agonists for the treatment of Type 2 diabetes is described. In our previous research, Compound A, ß-MeTrp derivative with highly potent and selective SSTR2 agonistic activity IC50 (SSTR2/SSTR5)=0.3/>100 (nM), was identified asa drug candidate for treatment of Type 2 diabetes which lowers significantly plasma glucose level in Wistar fatty rats in its oral administrations. However, as serious increase in AUC and phospholipidosis (PLsis) were observed in its toxicological studies in rats, follow-up compounds were searched to avoid risk of PLsis with reference to their in vitro PLsis potentials evaluated on the basis of accumulation of phospholipids in HepG2 cells exposed to the compounds. It has been found that introduction of a carbonyl group onto the piperidine and piperazine or aniline moiety of compounds A and B reduced markedly the in vitro PLsis potentials. And further modification of the compounds and their evaluation led to a discovery of compounds 3k with lower in vitro PLsis potentials exhibiting lowering effect of hypoglycemia-induced glucagon secretion in SD rats (ED50=1.1mg/kg) and glucose excursion in meal tolerance test in Wistar fatty diabetic rats (MED=3.0mg/kg) in oral administrations. Compound 3k was selected asa new drug candidate of selective and orally active non-peptide SSTR2 agonists for treatment of Type 2 diabetes with low in vivo PLsis potential.

Design of potent dipeptidyl peptidase IV (DPP-4) inhibitors by employing a strategy to form a salt bridge with Lys554.

We report a design strategy to obtain potent DPP-4 inhibitors by incorporating salt bridge formation with Lys554 in the S1' pocket. By applying the strategy to the previously identified templates, quinoline 4 and pyridines 16a, 16b, and 17 have been identified as subnanomolar or nanomolar inhibitors of human DPP-4. Docking studies suggested that a hydrophobic interaction with Tyr547 as well as the salt bridge interaction is important for the extremely high potency. The design strategy would be useful to explore a novel design for DPP-4 inhibitors having a distinct structure with a unique binding mode.

Discovery of potent, selective, and orally bioavailable quinoline-based dipeptidyl peptidase IV inhibitors targeting Lys554.

Dipeptidyl peptidase IV (DPP-4) inhibition is a validated therapeutic option for type 2 diabetes, exhibiting multiple antidiabetic effects with little or no risk of hypoglycemia. In our studies involving non-covalent DPP-4 inhibitors, a novel series of quinoline-based inhibitors were designed based on the co-crystal structure of isoquinolone 2 in complex with DPP-4 to target the side chain of Lys554. Synthesis and evaluation of designed compounds revealed 1-[3-(aminomethyl)-4-(4-methylphenyl)-2-(2-methylpropyl)quinolin-6-yl]piperazine-2,5-dione (1) as a potent, selective, and orally active DPP-4 inhibitor (IC50=1.3 nM) with long-lasting ex vivo activity in dogs and excellent antihyperglycemic effects in rats. A docking study of compound 1 revealed a hydrogen-bonding interaction with the side chain of Lys554, suggesting this residue as a potential target site useful for enhancing DPP-4 inhibition.

Identification of 3-aminomethyl-1,2-dihydro-4-phenyl-1-isoquinolones: a new class of potent, selective, and orally active non-peptide dipeptidyl peptidase IV inhibitors that form a unique interaction with Lys554.

The design, synthesis, and structure-activity relationships of a new class of potent and orally active non-peptide dipeptidyl peptidase IV (DPP-4) inhibitors, 3-aminomethyl-1,2-dihydro-4-phenyl-1-isoquinolones, are described. We hypothesized that the 4-phenyl group of the isoquinolone occupies the S1 pocket of the enzyme, the 3-aminomethyl group forms an electrostatic interaction with the S2 pocket, and the introduction of a hydrogen bond donor onto the 6- or 7-substituent provides interaction with the hydrophilic region of the enzyme. Based on this hypothesis, intensive research focused on developing new non-peptide DPP-4 inhibitors has been carried out. Among the compounds designed in this study, we identified 2-[(3-aminomethyl-2-(2-methylpropyl)-1-oxo-4-phenyl-1,2-dihydro-6-isoquinolinyl)oxy]acetamide (35a) as a potent, selective, and orally bioavailable DPP-4 inhibitor, which exhibited in vivo efficacy in diabetic model rats. Finally, X-ray crystallography of 35a in a complex with the enzyme validated our hypothesized binding mode and identified Lys554 as a new target-binding site available for DPP-4 inhibitors.

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.