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Abstract. The effects of orally administered dipeptidyl peptidase IV (DPP-IV) inhibitor on the glucose-lowering effect of glibenclamide are still unknown. We evaluated the effects of combination treatment with a long-lasting DPP-IV inhibitor, K579 ((S)-1-[4-methyl-1-(2-pyrimidinyl)-4-piperidylamino]acetyl-2-pyrrolidinecarbonitrile), and glibenclamide on the glycemic responses to glucose loading in rats. Treatment with K579 inhibited the plasma DPP-IV activity even 8 h after the administration. K579 significantly suppressed the blood glucose elevation in glibenclamide-pretreated rats without excessive hypoglycemia. These profiles of K579 indicate that it could be useful agent to correct the postprandial glucose excursion in type 2 diabetes patients by combination treatment with glibenclamide.

A novel class of PPARγ ligand 1 (EC 50 = 197 nM) with a dibenzoazepin scaffold was identified through highthroughput screening campaign. To avoid the synthetically troublesome chiral center of 1, its conformational analysis using the MacroModel was conducted, focusing on conformational flip of the tricyclic ring and the conformational restriction by the methyl group at the chiral center. On the basis of this analysis, scaffold hopping of dibenzoazepine into dibenzo[b,e]oxepine by replacing the chiral structures with the corresponding olefinic E/Z isomers was performed. Consequently, dibenzo[b,e]oxepine scaffold 9 was developed showing extremely potent PPARγ reporter activity (EC 50 = 2.4 nM, efficacy = 9.5%) as well as differentiation-inducing activity against a gastric cancer cell line MKN-45 that was more potent than any other well-known PPARγ agonists in vitro (94% at 30 nM). The X-ray crystal structure analysis of 9 complexed with PPARγ showed that it had a unique binding mode to PPARγ ligand-binding domain that differed from that of any other PPARγ agonists identified thus far.

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