A comparative study of the binding modes of recently launched dipeptidyl peptidase IV inhibitors in the active site.

In recent years, various dipeptidyl peptidase IV (DPP-4) inhibitors have been released as therapeutic drugs for type 2 diabetes in many countries. In spite of their diverse chemical structures, no comparative studies of their binding modes in the active site of DPP-4 have been disclosed. We determined the co-crystal structure of vildagliptin with DPP-4 by X-ray crystallography and compared the binding modes of six launched inhibitors in DPP-4. The inhibitors were categorized into three classes on the basis of their binding subsites: (i) vildagliptin and saxagliptin (Class 1) form interactions with the core S1 and S2 subsites and a covalent bond with Ser630 in the catalytic triad; (ii) alogliptin and linagliptin (Class 2) form interactions with the S1' and/or S2' subsites in addition to the S1 and S2 subsites; and (iii) sitagliptin and teneligliptin (Class 3) form interactions with the S1, S2 and S2 extensive subsites. The present study revealed that the additional interactions with the S1', S2' or S2 extensive subsite may increase DPP-4 inhibition beyond the level afforded by the fundamental interactions with the S1 and S2 subsites and are more effective than forming a covalent bond with Ser630.

Discovery and preclinical profile of teneligliptin (3-[(2S,4S)-4-[4-(3-methyl-1-phenyl-1H-pyrazol-5-yl)piperazin-1-yl]pyrrolidin-2-ylcarbonyl]thiazolidine): a highly potent, selective, long-lasting and orally active dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes.

Dipeptidyl peptidase IV (DPP-4) inhibition is suitable mechanism for once daily oral dosing regimen because of its low risk of hypoglycemia. We explored linked bicyclic heteroarylpiperazines substituted at the γ-position of the proline structure in the course of the investigation of l-prolylthiazolidines. The efforts led to the discovery of a highly potent, selective, long-lasting and orally active DPP-4 inhibitor, 3-[(2S,4S)-4-[4-(3-methyl-1-phenyl-1H-pyrazol-5-yl)piperazin-1-yl]pyrrolidin-2-ylcarbonyl]thiazolidine (8 g), which has a unique structure characterized by five consecutive rings. An X-ray co-crystal structure of 8 g in DPP-4 demonstrated that the key interaction between the phenyl ring on the pyrazole and the S(2) extensive subsite of DPP-4 not only boosted potency, but also increased selectivity. Compound 8 g, at 0.03 mg/kg or higher doses, significantly inhibited the increase of plasma glucose levels after an oral glucose load in Zucker fatty rats. Compound 8 g (teneligliptin) has been approved for the treatment of type 2 diabetes in Japan.

Fused bicyclic heteroarylpiperazine-substituted L-prolylthiazolidines as highly potent DPP-4 inhibitors lacking the electrophilic nitrile group.

Hypoglycemic agents with a mechanism of depeptidyl peptidase IV (DPP-4) inhibition are suitable for once daily oral dosing. It is difficult to strike a balance between inhibitory activity and duration of action in plasma for inhibitors bearing an electrophilic nitrile group. We explored fused bicyclic heteroarylpiperazine substituted at the γ-position of the proline structure in the investigation of L-prolylthiazolidines lacking the electrophilic nitrile. Among them, 2-trifluoroquinolyl compound 8g is the most potent, long-lasting DPP-4 inhibitor (IC(50) = 0.37 nmol/L) with high selectivity against other related peptidases. X-ray crystal structure determination of 8g indicates that CH-π interactions generated between the quinolyl ring and the guanidinyl group of Arg358 enhances the DPP-4 inhibitory activity and selectivity.

Heterogeneous environment of the S-H group of Cys966 near the flavin chromophore in the LOV2 domain of Adiantum neochrome1.

The primary photochemistry of the blue-light sensor protein, phototropin, is adduct formation between the C4a atom of the flavin mononucleotide (FMN) chromophore and a nearby, reactive cysteine (Cys966), following decay of the triplet excited state of FMN. The distance between the C4a position of FMN and the sulfur atom of Cys966 is 4.2 A in the LOV2 domain of Adiantum neochrome 1 (neo1-LOV2), a fusion protein of phototropin containing the phytochrome chromophoric domain. We previously reported the presence of an unreactive fraction in neo1-LOV2 at low temperatures, which presumably originated from the heterogeneous environment of Cys966 [Iwata, T., Nozaki, D., Tokutomi, S., Kagawa, T., Wada, M., and Kandori, H. (2003) Biochemistry 42, 8183-8191]. The present study showed that (i) 28% forms an adduct at 77 K (state I), (ii) 50% forms an adduct at 150 K but not at 77 K (state II), and (iii) 22% does not form an adduct at 150 K (state III). By Fourier transform infrared (FTIR) spectroscopy, we observed the S-H stretching frequencies at 2570 and 2562 cm-1 for state I and at 2563 cm-1 for state II, suggesting that the microenvironment of the S-H group of Cys966 determines the reactivity at low temperatures. Adduct formation is more efficient for state I than for states II and III. Molecular dynamics simulation strongly suggests that the observed multiple structures originate from the isomeric forms of Cys966. We thus concluded that there are multiple local structures of FMN and cysteine in neo1-LOV2, each of which is thermally converted by protein fluctuation at physiological temperatures.