DPP-4 Inhibitory Activity Research Articles

Abstract P635: Effect of Patient Characteristics and DPP4 genotype on Dipeptidyl Peptidase IV Activity and Inhibition by Sitagliptin

Dipeptidyl peptidase IV (DPP4) inhibitors are a class of oral antihyperglycemic agents commonly used to treat type 2 diabetes mellitus (T2DM). Evidence suggests that these medications also have cardiovascular effects. We tested the hypothesis that subject characteristics and genetic variability in DPP4 , the gene encoding DPP4, affect response to DPP4 inhibition with sitagliptin. We studied 56 subjects undergoing trials of sitagliptin therapy. DPP4 activity was measured during placebo and after sitagliptin and percent inhibition calculated. Subject characteristics were: 41.1% men (n=23), 19.6% African American (n=11), 30.4% with both T2DM and hypertension (HTN) (n=17), mean age 39.16±15.70 years, and mean BMI 26.71±6.24 kg/m 2 . Sitagliptin doses were 100mg daily for 4-7 days (n=31) or a single dose of 200mg (n=25). Baseline DPP4 activity decreased significantly with age (r=-0.36, p<0.01) and was lower in T2DM HTN (22.54±5.20 vs 26.08±5.88U in non-diabetics, p=0.02). There was no effect of gender, race, weight, or BMI on baseline or inhibited DPP4 activity in T2DM or non-T2DM. Baseline DPP4 activity was significantly lower in rs4664446 (p=0.03; lower activity GG). These characteristics were not significant in a multivariable model. During sitagliptin, DPP4 activity was significantly higher (13.06±5.56 vs 6.85±3.34U, p<0.01) and percent inhibition lower (43±13% vs 74 ±11.2%, p<0.01) in T2DM HTN. Inhibited DPP4 activity declined with age in non-diabetics but not in T2DM. The variant rs2909451 was significantly associated with DPP4 activity during sitagliptin (p<0.01; higher activity TT). In multivariable analysis, inhibited DPP4 activity was associated with T2DM (p=0.02), rs2909451 genotype (p<0.01), but not age (p=0.08) or sitagliptin dose regimen (p=0.24). Inhibition of DPP4 by sitagliptin is decreased in T2DM HTN. Future studies are needed to determine if DPP4 inhibitor dose should be increased in T2DM HTN.

Cardiac DPP-4 inhibition by saxagliptin ameliorates isoproterenol-induced myocardial remodeling and cardiac diastolic dysfunction in rats

Saxagliptin, a potent and selective DPP-4 inhibitor, is characterized by its slow dissociation from DPP-4 and its long half-life and is expected to have a potent tissue membrane-bound DPP-4-inhibitory effect in various tissues. In the present study, we examined the effects of saxagliptin on in situ cardiac DPP-4 activity. We also examined the effects of saxagliptin on isoproterenol-induced the changes in the early stage such as, myocardial remodeling and cardiac diastolic dysfunction. Male SD rats treated with isoproterenol (1 mg/kg/day via osmotic pump) received vehicle or saxagliptin (17.5 mg/kg via drinking water) for 2 weeks. In situ cardiac DPP-4 activity was measured by a colorimetric assay. Cardiac gene expressions were examined and an echocardiographic analysis was performed. Saxagliptin treatment significantly inhibited in situ cardiac DPP-4 activity and suppressed isoproterenol-induced myocardial remodeling and the expression of related genes without altering the blood glucose levels. Saxagliptin also significantly ameliorated cardiac diastolic dysfunction in isoproterenol-treated rats. In conclusion, the inhibition of DPP-4 activity in cardiac tissue by saxagliptin was associated with suppression of myocardial remodeling and cardiac diastolic dysfunction independently of its glucose-lowering action in isoproterenol-treated rats. Cardiac DPP-4 activity may contribute to myocardial remodeling in the development of heart failure.

Pharmacological profiles of gemigliptin (LC15-0444), a novel dipeptidyl peptidase-4 inhibitor, in vitro and in vivo

Gemigliptin, a novel dipeptidyl peptidase (DPP)-4 inhibitor, is approved for use as a monotherapy or in combination therapy to treat hyperglycemia in patients with type 2 diabetes mellitus. In this study, we investigated the pharmacological profiles of gemigliptin in vitro and in vivo and compared them to those of the other DPP-4 inhibitors. Gemigliptin was a reversible and competitive inhibitor with a Ki value of 7.25±0.67nM. Similar potency was shown in plasma from humans, rats, dogs, and monkeys. The kinetics of DPP-4 inhibition by gemigliptin was characterized by a fast association and a slow dissociation rate compared to sitagliptin (fast on and fast off rate) or vildagliptin (slow on and slow off rate). In addition, gemigliptin showed at least >23,000-fold selectivity for DPP-4 over various proteases and peptidases, including DPP-8, DPP-9, and fibroblast activation protein (FAP)-α. In the rat, dog, and monkey, gemigliptin showed more potent DPP-4 inhibitory activity in vivo compared with sitagliptin.In mice and dogs, gemigliptin prevented the degradation of active glucagon-like peptide-1 by DPP-4 inhibition, which improved glucose tolerance by increasing insulin secretion and reducing glucagon secretion during an oral glucose tolerance test. The long-term anti-hyperglycemic effect of gemigliptin was evaluated in diet-induced obese mice and high-fat diet/streptozotocin-induced diabetic mice. Gemigliptin dose-dependently decreased hemoglobin A1c (HbA1c) levels and ameliorated β-cell damage. In conclusion, gemigliptin is a potent, long-acting, and highly selective DPP-4 inhibitor and can be a safe and effective drug for the long-term treatment of type 2 diabetes.

Dipeptidyl Peptidase IV Inhibitory Peptides Derived from Oat (Avena sativa L.), Buckwheat (Fagopyrum esculentum), and Highland Barley (Hordeum vulgare trifurcatum (L.) Trofim) Proteins

Peptides released from oat, buckwheat, and highland barley proteins were examined for their in vitro inhibitory effects on dipeptidyl peptidase IV (DPP4), an enzyme that deactivates incretin hormones involved in insulin secretion. All of the hydrolysates exhibited DPP4 inhibitory activities, with IC50 values ranging from 0.13 mg/mL (oat glutelin alcalase digestion) to 8.15 mg/mL (highland barley albumin tryptic digestion). The lowest IC50 values in gastrointestinal, alcalase, and tryptic digestions were 0.99 mg/mL (oat flour), 0.13 mg/mL (oat glutelin), and 1.83 mg/mL (highland barley glutelin). In all, 35 peptides of more than seven residues were identified in the tryptic hydrolysates of oat globulin using liquid chromatography-mass spectroscopy. Peptides LQAFEPLR and EFLLAGNNK were synthesized and their DPP4 inhibitory activities determined. LQAFEPLR showed high in vitro DPP4 inhibitory activity with an IC50 value of 103.5 μM.

Design, synthesis and biological evaluation of 4-fluoropyrrolidine-2-carbonitrile and octahydrocyclopenta[b]pyrrole-2-carbonitrile derivatives as dipeptidyl peptidase IV inhibitors

Based on the previous work in our group and the principle of computer-aided drug design, a series of novel β-amino pyrrole-2-carbonitrile derivatives was designed and synthesized. Compounds 8l and 9l were efficacious and selective DPP4 inhibitors resulting in decreased blood glucose in vivo. Compound 8l had moderate DPP4 inhibitory activity (IC50 = 0.05 μM) and good oral bioavailability (F = 53.2%). Compound 9l showed excellent DPP4 inhibitory activity (IC50 = 0.01 μM), good selectivity (selective ratio: DPP8/DPP4 = 898.00; DPP9/DPP4 = 566.00) against related peptidases, and good efficacy in an oral glucose tolerance tests in ICR mice and moderate PK profiles (F = 22.8%, t1/2 = 2.74 h). Moreover, compound 9l did not block hERG channel and exhibited no inhibition of liver metabolic enzymes such as CYP2C9.

Discovery of highly potent DPP-4 inhibitors by hybrid compound design based on linagliptin and alogliptin

Highly potent DPP-4 inhibitors have been identified by hybrid compound design based on linagliptin and alogliptin. The most promising compound 2h (IC50 = 0.31 nM) exhibited 8.5-fold and 2.5-fold more potent activity than that of alogliptin (IC50 = 2.63 nM) and linagliptin (IC50 = 0.77 nM), respectively. Compound 2h had a good inhibition selectivity for DPP-4 over DPP-8/9 and thus was selected for further biological evaluation, including oral glucose tolerance, plasma DPP-4 inhibitory activity, pharmacokinetic profile, acute toxicity and hERG inhibition. The assay results showed that 2h displayed significant in vivo glucose-lowering effect and low risk of toxicity. Further studies are expected to confirm 2h as a potential drug candidate for the treatment of type 2 diabetes.

Design, Synthesis and Biological Evaluation of Novel Imidazolone Derivatives as Dipeptidyl Peptidase 4 Inhibitors

A series of novel imidazolone derivatives were designed and synthesized via a rational drug design strategy. These compounds were obtained from 3-substituted imidazolidine-2,4-dione through alkylation, formylation, dehydration, and amination. The structures were characterized by (1)H NMR, (13)C NMR, and MS. All target compounds were screened for their DPP-4 inhibitory activity in vitro. The results revealed that some imidazolone derivatives showed potent DPP-4 inhibition. Compound 5b had an IC50 value of 2.21 µM inhibitory activity against DPP-4. As a promising lead compound, compound 5b with DPP-4 binding mode was further studied by docking analysis. The expected interaction mode was obtained.

발아기간에 따른 벼(Oryza sativa L.)의 부위별 효소저해활성

This study investigated the enzyme inhibitory effects of ethanol extracts from the different parts of rough rice (Oryza sativar L.) from its germination period. Rough rice was germinated at for 6 days, then separated into hull+sprout and brown rice. -Glucosidase inhibitory activity had the highest value (39.38%) in hull+sprout extracts after 5 days of germination. -Amylase and DPP-4 inhibitory activity had the highest values (75.32% and 47.77%, respectively) in hull+sprout extracts after germination for 5 days. ACE inhibitory activity of hull+ sprout extracts increased from 43.16% at the beginning to 58.60% at 5 days, while brown rice extracts increased this activity from 0.88% at the beginning to 14.50% at 4 days. The xanthine oxidase inhibitory activity of hull+ sprout extracts increased from 62.02% at the beginning to 64.49% at one day, and then decreased. Lipase inhibitory activity had its highest value (55.17%) in hull+sprout extracts after germination for 5 days. These results indicate that the optimal germination period for increasing enzyme inhibitory activities may be 5 days, and that hull+sprout extracts have a higher enzyme inhibition activity than brown rice.

Bioassay-guided isolation of DPP-4 inhibitory fractions from extracts of submerged cultured of Inonotus obliquus.

Inonotus obliquus is a medicinal mushroom used in Russian and Eastern European folk medicine for the treatment of gastrointestinal cancer, cardiovascular disease and diabetes. Previous studies in our laboratory have demonstrated that the mycelium powders of I. obliquus possess significant antihyperglycemic effects in a mouse model of diabetic disease induced by alloxan. However, the active ingredients of mycelium powders responsible for the diabetes activity have not been identified. This study aims to identify the active ingredients of I. obliquus mycelium powders by a bioassay-guided fractionation approach and explore the mechanism of action of these active ingredients by using a well-established DPP-4 (an important enzyme as a new therapeutic target for diabetes) inhibitory assay model. The results showed the chloroform extract of mycelium was potential inhibitory against DPP-4. Bioactivity guided fractionation led to the identification of 19 compounds using UPLC-Q-TOF-MS. Molecular docking between the compounds and DPP-4 revealed that compounds 5, 8, 9, 14, 15 may be the active components responsible for the DPP-4 inhibitory activity.

2型糖尿病治療薬テネリグリプチンの創製：新規DPP-4阻害剤の創薬研究と結合様式

Dipeptidyl peptidase IV (DPP-4) inhibitors have built trust through both efficacy and safety in the treatment of type 2 diabetes and have increased the prescription both in Japan and overseas. Among them, teneligliptin has potent and selective DPP-4 inhibitory activity, has an elimination half-life of 24.2 h in human plasma, and is eliminated via excretion from the kidney and metabolism involving some metabolizing enzymes. Therefore, teneligliptin provides postprandial blood glucose-lowering effects that are sustained throughout the day by once-daily treatment and has unnecessary dosage regulation in patients with renal impairment. In this article, discovery and preferable profiles of a novel DPP-4 inhibitor, teneligliptin, discovered first in Japan, are described. By comparative studies of the binding modes of launched DPP-4 inhibitors in the active site, the unique binding mode of teneligliptin in DPP-4 has been revealed.

Attenuation of Renovascular Damage in Zucker Diabetic Fatty Rat by NWT-03, an Egg Protein Hydrolysate with ACE- and DPP4-Inhibitory Activity

BackgroundDipeptidyl peptidase 4 (DPP4) and angiotensin-converting enzyme (ACE) are important target enzymes in glycemic control and renovascular protection. Here, we studied the effect of NWT-03, an egg protein hydrolysate with DPP4- and ACE-inhibitory activity, on renovascular damage in Zucker diabetic fatty (ZDF) rats. Comparisons were made to rats treated with vildagliptin (VIL), included as a positive control for the effect of DPP4 inhibition.MethodsZDF rats received NWT-03 (1 g/kg/day) or VIL (3 mg/kg/day) from 10 to 25 weeks of age. Metabolic and renal functions were assessed; the kidney was removed for histological analysis of glomerulosclerosis and expression of pro-inflammatory/fibrotic markers (RT-PCR and Western blotting); and the aorta was removed for studies of endothelium-dependent relaxation (EDR).FindingsHyperinsulinemic ZDF rats typically developed signs of type-2 diabetes and renovascular damage, as evidenced by albuminuria, glomerulosclerosis, and impaired EDR. Neither NWT-03 nor VIL improved metabolic parameters; for VIL, this was despite a 5-fold increase in glucagon-like peptide (GLP)-1 levels. NWT-03 and VIL both reduced renal interleukin (Il)-1β/Il-13 mRNA expression and glomerulosclerosis. However, only NWT-03 additionally decreased renal tumor necrosis factor (TNF)-α mRNA and P22phox protein expression, reduced albuminuria, and restored aortic EDR. Indomethacin added to the organ bath instantly improved aortic EDR, indicating a role for cyclooxygenase (COX)-derived contractile prostanoids in opposing relaxation in ZDF rats. This indomethacin effect was reduced by NWT-03, but not by VIL, and coincided with decreased renal COX-1/2 protein expression.Conclusion and InterpretationLong-term supplementation with the egg protein hydrolysate NWT-03 attenuated renovascular damage in this preclinical rat model of type 2 diabetes. A comparison to the DPP4-inhibitor VIL suggests that the effects of NWT-03 were related to both ACE- and DPP4-inhibitory properties. The development of protein hydrolysates with a multiple-targeting strategy may be of benefit to functional food formulations.

Novel series of 3-amino-N-(4-aryl-1,1-dioxothian-4-yl)butanamides as potent and selective dipeptidyl peptidase IV inhibitors

A series of novel 3-amino-N-(4-aryl-1,1-dioxothian-4-yl)butanamides were investigated as dipeptidyl peptidase IV (DPP-4) inhibitors. Introduction of a 4-phenylthiazol-2-yl group showed highly potent DPP-4 inhibitory activity. Among various derivatives, (3R)-3-amino-N-(4-(4-phenylthiazol-2-yl)-tetrahydro-2H-thiopyran-4-yl)-4-(2,4,5-trifluorophenyl)butanamide 1,1-dioxide (30) reduced blood glucose excursion in an oral glucose tolerance test by oral administration.

Discovery of 3H-imidazo[4,5-c]quinolin-4(5H)-ones as potent and selective dipeptidyl peptidase IV (DPP-4) inhibitors

In recent years, dipeptidyl peptidase IV inhibitors have been noted as valuable agents for treatment of type 2 diabetes. Herein, we report the discovery of a novel potent DPP-4 inhibitor with 3H-imidazo[4,5-c]quinolin-4(5H)-one as skeleton. After efficient optimization of the lead compound 2a at the 7- and 8-positions using a docking study, we found 28 as a novel DPP-4 inhibitor with excellent selectivity against various DPP-4 homologues. Compound 28 showed strong DPP-4 inhibitory activity compared to marketed DPP-4 inhibitors. We also found that a carboxyl group at the 7-position could interact with the residue of Lys554 to form a salt bridge. Additionally, introduction of a carboxyl group to 7-position led to both activity enhancement and reduced risk for hERG channel inhibition and induced phospholipidosis. In our synthesis of compounds with 7-carboxyl group, we achieved efficient regioselective synthesis using bulky ester in the intramolecular palladium coupling reaction.

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 (IC50=0.37nmol/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.

Identification of diverse dipeptidyl peptidase IV inhibitors via structure-based virtual screening

Dipeptidyl peptidase IV (DPP4) is an important target for the treatment of type II diabetes mellitus. Inhibition of DPP4 will improve glycemic control in such patients by preventing the rapid breakdown and thereby prolonging the physiological actions of incretin hormones. Known DPP4 inhibitors (including marketed drugs and those drug candidates) appear to share similar structural features: the cyanopyrrolidine moieties, the xanthenes/pyrimidine parts and amino-like linkages. In this study, a multi-step virtual screening strategy including both rigid and flexible docking was employed to search for novel structures with DPP4 inhibition. From SPECS database, consisting of over 190,000 commercially available compounds, 99 virtual hits were picked up and 15 of them were eventually identified to have DPP4 inhibitory activities at 5 ~ 50μM. Diverse structures of our compounds were out of usual structural categories. Hence a pharmacophore model was built to further explore their common binding features on the enzyme. The results provided a new pathway for the discovery of DPP4 inhibitors and would be helpful for further optimization of DPP4 inhibitors.

Anti-diabetic effect of a traditional Chinese medicine formula

An anti-diabetic TCM formula consisting of Schizandra chinensis Baill. (SC), Coptis chinensis (CC), Psidium guajava L. leaves (PG) and Morus alba L. leaves (MA) was developed based on its α-glucosidase, DPP-4 and AGE inhibitory activities in vitro using response surface methodology (RSM). Then, the in vivo study was carried out to confirm the anti-diabetic function of the formula. RSM results showed that the optimum anti-diabetic TCM formula is the combination SC (3000 μg mL(-1)), CC (80 μg mL(-1)), PG (374.56 μg mL(-1)) and MA (480 μg mL(-1)). For the in vivo study, insulin resistant mice were induced by high-fat/high-sucrose (HF/HS) feeding for 6 weeks. Administration of the developed formula significantly decreased non-fasting blood glucose in the HF/HS diet mice. Moreover, the formula decreased blood glucose levels in the insulin tolerance test. These results indicated that the anti-diabetic mechanism of the formula might be due to decreased insulin resistance. The serum fructosamine level in the high dose group was significantly lower than the HF/HS and normal control groups, indicating that the formula could improve middle term glucose levels and reduce the risk of complications. The contents of berberine and 1-deoxynojirimycin in the formula were 4.7 ± 0.4 and 77.1 ± 1.1 μg mL(-1), respectively. These two compounds can be used as indicators for quality control during production.

Sitagliptin Improves Engraftment and Platelet Recovery After Single Unit, Very Low Cell Dose Cord Blood Transplantation

Abstract 2963Cord blood transplantation (CBT) is an emerging treatment for many hematologic diseases. However, the low cell dose of most banked cord blood units precludes the safe use of single unit CBT for many adults. We developed a dog model of unrelated CBT to evaluate approaches to overcome the poor engraftment associated with low cell dose cord blood. The results of initial studies with double unit CBT in the dog model were previously reported.Nine dogs were conditioned with 9.2 Gy total body irradiation. A single unit of low cell dose (median, 0.7×107total nucleated cells/kg), major histocompatibility complex (MHC)-matched unrelated dog umbilical cord blood was infused on day 0. Post-grafting immunosuppression was cyclosporine from day -3 to +98 and mycophenolate mofetil from day 0 to +84. Among the 5 control recipients, there was poor neutrophil and platelet engraftment, 2 dogs had secondary graft rejection and only 1 dog had platelet engraftment (day +68). All 5 control recipients were euthanized due to severe infectious complications on days 11, 54, 70, 74 and 105, despite intensive supportive care including transfusions and prompt intervention with broad-spectrum antibiotics.Next, based on studies showing inhibition of CD26/dipeptidyl-peptidase-IV (DPP4) blocks inactivation of the chemokine CXCL-12 (SDF-1a), improving homing of hematopoietic stem/progenitor cells, we asked if pharmacologic inhibition of DPP4 with sitagliptin at the time of CBT improved the engraftment of a single low cell dose MHC-matched unit. Sitagliptin is clinically approved to lower post-prandial hyperglycemia in patients with Type II diabetes mellitus since DPP4 inhibition reduces proteolysis of glucagon like peptide-1.In 4 dogs sitagliptin was administered orally 10 mg/kg twice daily from day -3 to day +6. These dogs were otherwise treated identically to the control group. There were no adverse effects from sitagliptin treatment. Serum from treated dogs showed >90% inhibition of DPP4 activity. All 4 sitagliptin treated dogs engrafted with donor neutrophils (median, day +21) and platelets (median, day +48). There was no late graft rejection or secondary thrombocytopenia. None of the dogs developed GVHD. One dog was euthanized on day +66 due to seizures; necropsy showed viral encephalitis. The remaining 3 dogs remain alive and well with stable engraftment and prompt immune reconstitution. Even though a very limited number of dogs were studied, the survival benefit of sitagliptin treatment was significant, p =0.047 (log-rank test). Donor chimerism was increased and platelet recovery was significantly improved in sitagliptin recipients compared to single unit controls. The median number of blood/platelet transfusions given to sitagliptin vs. control recipients for supportive care was 9 vs. 17, respectively, p = 0.03.The results suggest that DPP4 inhibition with sitagliptin is effective in improving engraftment and survival after low cell dose CBT. Our findings are novel and can be readily translated to clinical trials. If a simple treatment with a well tolerated oral drug could make a significant difference in neutrophil and platelet recovery after human CBT, this would be a substantial therapeutic advance. Our data support further clinical trials of sitagliptin with CBT to improve engraftment. Disclosures:Off Label Use: Sitagliptin is a DPP4 inhibitor approved for reducing post-prandial hyperglycemia in patients with Type II diabetes mellitus.

Comparison of goat and sheep β-lactoglobulin to bovine β-lactoglobulin as potential source of dipeptidyl peptidase IV (DPP-4) inhibitors

We recently reported on the presence of DPP-4 inhibitors among bioactive peptides generated by proteolysis of β-lactoglobulin (β-LG), proving that the bioactive peptide Ile-Pro-Ala (IPA) can be regarded as a moderate DPP-4 inhibitor and could be a molecular determinant of the previously observed inhibitory effect of whey protein ingestion on DPP-4 activity in the proximal bowel of mice. The aim of the present study was to predict differences in potential DPP-4 inhibitory activity between goat/sheep and bovine β-LG hydrolysates by means of in silico analysis and in vitro DPP-4 activity assay. Combined results proved that caprine/ovine whey is richer in the content of short amino acid sequences carrying weak DPP-4 inhibitory activity than bovine whey. Based on in vitro analysis, no significant differences should be expected in activity between species due to the leading role of the conserved IPA peptide.

2-({6-[(3R)-3-amino-3-methylpiperidine-1-yl]-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-5H-pyrrolo[3,2-d]pyrimidine-5-yl}methyl)-4-fluorobenzonitrile (DSR-12727): A potent, orally active dipeptidyl peptidase IV inhibitor without mechanism-based inactivation of CYP3A

We report on the identification of 2-({6-[(3R)-3-amino-3-methylpiperidine-1-yl]-1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-5H-pyrrolo[3,2-d]pyrimidine-5-yl}methyl)-4-fluorobenzonitrile (DSR-12727) (7a) as a potent and orally active DPP-4 inhibitor without mechanism-based inactivation of CYP3A. Compound 7a showed good DPP-4 inhibitory activity (IC50=1.1nM), excellent selectivity against related peptidases and other off-targets, good pharmacokinetic and pharmacodynamic profile, great in vivo efficacy in Zucker-fatty rat, and no safety concerns both in vitro and in vivo.

Novel Dipeptidyl Peptidase-4–Inhibiting Peptide Derived From β-Lactoglobulin

Trypsin-treated β-lactoglobulin significantly decreased the glucose level after an oral glucose tolerance test using mice. We performed the present study to identify the active peptide inhibiting dipeptidyl peptidase-4 from trypsin-treated β-lactoglobulin. Trypsin-treated β-lactoglobulin showed a concentration-dependent inhibition for dipeptidyl peptidase-4, with an IC(50) value of 210 µM, although non-treated β-lactoglobulin showed no significant effect in the in vitro assay. The active peptide was isolated from trypsin-treated β-lactoglobulin and identified as the hexapeptide Val-Ala-Gly-Thr-Trp-Tyr (β-lactoglobulin f15-20). This hexapeptide also exhibited a concentration-dependent inhibitory effect and IC(50) value was 174 µM, suggesting that this hexapeptide is almost totally responsible for the DPP-4 inhibitory activity of trypsin-treated β-lactoglobulin.