Aims: Since 2006, DPP-4 inhibitors have become established therapy for the treatment of type 2 diabetes. Despite sharing a common mechanism of action, considerable chemical diversity exists amongst members of the DPP-4 inhibitor class, raising the question as to whether structural differences may result in differentiated enzyme inhibition and antihyperglycaemic activity. Methods: We have compared the binding properties of the most commonly used inhibitors and have investigated the relationship between their inhibitory potency at the level of the enzyme and their acute glucose-lowering efficacy. Results: Firstly, using a combination of published crystal structures and in-house data, we demonstrated that the binding site utilized by all of the DPP-4 inhibitors assessed was the same as that used by neuropeptide Y, supporting the hypothesis that DPP-4 inhibitors are able to competitively inhibit endogenous substrates for the enzyme. Secondly, we ascertained that the enzymatic cleft of DPP-4 is a relatively large cavity which displays conformational flexibility to accommodate structurally diverse inhibitor molecules. Finally, we found that for all inhibitors, irrespective of their chemical structure, the inhibition of plasma DPP-4 enzyme activity correlates directly with acute plasma glucose lowering in mice. Conclusion: The common binding site utilized by different DPP-4 inhibitors enables similar competitive inhibition of the cleavage of the endogenous DPP-4 substrates. Furthermore, despite chemical diversity and a range of binding potencies observed amongst the DPP-4 inhibitors, a direct relationship between enzyme inhibition in the plasma and glucose lowering is evident in mice for each member of the classes studied.
Novel potent and selective 5,6,5- and 5,5,6-tricyclic pyrrolidine dipeptidyl peptidase IV (DPP-4) inhibitors were identified. Structure-activity relationship (SAR) efforts focused on improving the intrinsic DPP-4 inhibition potency, increasing protease selectivity, and demonstrating clean ion channel and cytochrome P450 profiles while trying to achieve a pharmacokinetic profile suitable for once weekly dosing in humans.
A new series of DPP-4 inhibitors derived from piperidine-fused benzimidazoles and imidazopyridines is described. Optimization of this class of DPP-4 inhibitors led to the discovery of imidazopyridine 34. The potency, selectivity, cross-species DMPK profiles, and in vivo efficacy of 34 is reported.
The synthesis, selectivity, rat pharmacokinetic profile, and drug metabolism profiles of a series of potent fluoroolefin-derived DPP-4 inhibitors (4) are reported. A radiolabeled fluoroolefin 33 was shown to possess a high propensity to form reactive metabolites, thus revealing a potential liability for this class of DPP-4 inhibitors.
A series of beta-aminoamides bearing triazolopiperazines have been discovered as potent, selective, and orally active dipeptidyl peptidase IV (DPP-4) inhibitors by extensive structure-activity relationship (SAR) studies around the triazolopiperazine moiety. Among these, compound 34b with excellent in vitro potency (IC50 = 4.3 nM) against DPP-4, high selectivity over other enzymes, and good pharmacokinetic profiles exhibited pronounced in vivo efficacy in an oral glucose tolerance test (OGTT) in lean mice. On the basis of these properties, compound 34b has been profiled in detail. Further refinement of the triazolopiperazines resulted in the discovery of a series of extremely potent compounds with subnanomolar activity against DPP-4 (42b- 49b), that is, 4-fluorobenzyl-substituted compound 46b, which is notable for its superior potency (IC50 = 0.18 nM). X-ray crystal structure determination of compounds 34b and 46b in complex with DPP-4 enzyme revealed that (R)-stereochemistry at the 8-position of triazolopiperazines is strongly preferred over (S) with respect to DPP-4 inhibition.
A series of substituted imidazopiperidine amides has been prepared and evaluated for inhibition of dipeptidyl peptidase IV (DPP-4). Substitution at the 1- and 3-positions produced increased selectivity for DPP-4 relative to DPP-8 and DPP-9. Compounds in this series had IC(50) values as low as 5.8 nM for inhibition of DPP-4.
Substituted 3-aminopiperidines 3 were evaluated as DPP-4 inhibitors. The inhibitors showed good DPP-4 potency with superb selectivity over other peptidases (QPP, DPP8, and DPP9). Selected DPP-4 inhibitors were further evaluated for their hERG potassium channel, calcium channel, Cyp2D6, and pharmacokinetic profiles.
A novel series of 4-aminophenylalanine and 4-aminocyclohexylalanine derivatives were designed and evaluated as inhibitors of dipeptidyl peptidase IV (DPP-4). The phenylalanine series afforded compounds such as 10 that were potent and selective (DPP-4, IC(50)=28nM), but exhibited limited oral bioavailability. The corresponding cyclohexylalanine derivatives such as 25 afforded improved PK exposure and efficacy in a murine OGTT experiment. The X-ray crystal structure of 25 bound to the DPP-4 active site is presented.
Molecular modeling was used to improve potency of the cyclohexylamine series. In addition, a 3-D QSAR method was used to gain insight for reducing off-target DPP-8/9 activities. Compounds 3, 4, and 5 were synthesized and found to be potent DPP-4 inhibitors, in particular 4 and 5 are designed to be highly selective against off-target DASH enzymes while maintaining potency on DPP-4.
A novel series of 4-arylcyclohexylalanine DPP-4 inhibitors was synthesized and tested for inhibitory activity as well as selectivity over the related proline-specific enzymes DPP-8 and DPP-9. Optimization of this series led to 28 (DPP-4 IC(50)=4.8 nM), which showed an excellent pharmacokinetic profile across several preclinical species. Evaluation of 28 in an oral glucose tolerance test demonstrated that this compound effectively reduced glucose excursion in lean mice.
A series of beta-aminoamides bearing triazolopiperazines has been prepared and evaluated as potent, selective, orally active dipeptidyl peptidase IV (DPP-4) inhibitors. Efforts at optimization of the beta-aminoamide series, which ultimately led to the discovery of JANUVIA (sitagliptin phosphate, compound 1), are described.
Various beta-amino amides containing triazolopiperazine heterocycles have been prepared and evaluated as potent, selective, orally active dipeptidyl peptidase IV (DPP-4) inhibitors. These compounds display excellent oral bioavailability and good overall pharmacokinetic profiles in preclinical species. Moreover, in vivo efficacy in an oral glucose tolerance test in lean mice is demonstrated.
A series of beta-substituted biarylphenylalanine amides were synthesized and evaluated as inhibitors of dipeptidyl peptidase IV (DPP-4) for the treatment of type 2 diabetes. Optimization of the metabolic profile of early analogues led to the discovery of (2S,3S)-3-amino-4-(3,3-difluoropyrrolidin-1-yl)-N,N-dimethyl-4-oxo-2-(4-[1,2,4]tr iazolo[1,5-a]pyridin-6-ylphenyl)butanamide (6), a potent, orally active DPP-4 inhibitor (IC(50) = 6.3 nM) with excellent selectivity, oral bioavailability in preclinical species, and in vivo efficacy in animal models. Compound 6 was selected for further characterization as a potential new treatment for type 2 diabetes.
anti-Substituted beta-methylphenylalanine derived amides have been shown to be potent DPP-IV inhibitors exhibiting excellent selectivity over both DPP8 and DPP9. The optimized compound exhibited good pharmacokinetic profiles in three preclinical species.
A novel series of oxadiazole based amides have been shown to be potent DPP-4 inhibitors. The optimized compound 43 exhibited excellent selectivity over a variety of DPP-4 homologs.
A series of beta-aminoacylpiperidines bearing various fused five-membered heterocyclic rings was synthesized as dipeptidyl peptidase IV inhibitors. Potent and relatively selective inhibition could be obtained, depending on choice of heterocycle, regioisomerism, and substitution. In particular, one analog (74, DPP-IV IC50=26 nM) exhibited good oral bioavailability and acceptable half-life in the rat, albeit with rather high clearance.
anti-Substituted biaryl beta-methylphenylalanine derived amides have been shown to be potent DPP-IV inhibitors that suffer from suboptimal selectivity and pharmacokinetics. This letter describes the substitution of the beta-methyl substituent with beta-polar substituents, culminating in the discovery of a beta-dimethylamide substituted phenylalanine derivative with an excellent potency, selectivity, and pharmacokinetic profile.
A novel series of beta-amino amides incorporating fused heterocycles, i.e., triazolopiperazines, were synthesized and evaluated as inhibitors of dipeptidyl peptidase IV (DPP-IV) for the treatment of type 2 diabetes. (2R)-4-Oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)- yl]-1-(2,4,5-trifluorophenyl)butan-2-amine (1) is a potent, orally active DPP-IV inhibitor (IC(50) = 18 nM) with excellent selectivity over other proline-selective peptidases, oral bioavailability in preclinical species, and in vivo efficacy in animal models. MK-0431, the phosphate salt of compound 1, was selected for development as a potential new treatment for type 2 diabetes.
Dipeptidyl peptidase (DPP)-IV inhibitors are a new approach to the treatment of type 2 diabetes. DPP-IV is a member of a family of serine peptidases that includes quiescent cell proline dipeptidase (QPP), DPP8, and DPP9; DPP-IV is a key regulator of incretin hormones, but the functions of other family members are unknown. To determine the importance of selective DPP-IV inhibition for the treatment of diabetes, we tested selective inhibitors of DPP-IV, DPP8/DPP9, or QPP in 2-week rat toxicity studies and in acute dog tolerability studies. In rats, the DPP8/9 inhibitor produced alopecia, thrombocytopenia, reticulocytopenia, enlarged spleen, multiorgan histopathological changes, and mortality. In dogs, the DPP8/9 inhibitor produced gastrointestinal toxicity. The QPP inhibitor produced reticulocytopenia in rats only, and no toxicities were noted in either species for the selective DPP-IV inhibitor. The DPP8/9 inhibitor was also shown to attenuate T-cell activation in human in vitro models; a selective DPP-IV inhibitor was inactive in these assays. Moreover, we found DPP-IV inhibitors that were previously reported to be active in models of immune function to be more potent inhibitors of DPP8/9. These results suggest that assessment of selectivity of potential clinical candidates may be important to an optimal safety profile for this new class of antihyperglycemic agents.
anti-Substituted beta-methylphenylalanine derived amides have been shown to be potent DPP-IV inhibitors exhibiting excellent selectivity over both DPP8 and DPP9. These are among the most potent compounds reported to date lacking an electrophilic trap. The most potent compound among these is 5-oxo-1,2,4-oxadiazole 44, which is a 3 nM DPP-IV inhibitor.
In-house screening of the Merck sample collection identified proline derived homophenylalanine 3 as a DPP-IV inhibitor with modest potency (DPP-IV IC50=1.9 microM). Optimization of 3 led to compound 37, which is among the most potent and selective DPP-IV inhibitors discovered to date.
Substituted 4-amino cyclohexylglycine analogues were evaluated for DP-IV inhibitory properties. Bis-sulfonamide 15e was an extremely potent 2.6 nM inhibitor of the enzyme with excellent selectivity over all counterscreens. 2,4-difluorobenzenesulfonamide 15b and 1-naphthyl amide 16b, however, combined an acceptable in vitro profile with good pharmacokinetic properties in the rat, and 15b was orally efficacious at 3 mpk in an OGTT in lean mice.
