Optimization of a 5-oxopyrrolopyridine series based upon structure-activity relationships (SARs) developed from our previous efforts on a number of related bicyclic series yielded compound 2s (BMS-767778) with an overall activity, selectivity, efficacy, PK, and developability profile suitable for progression into the clinic. SAR in the series and characterization of 2s are described.
Synthesis and structure-activity relationship of a series of substituted piperidinyl glycine 2-cyano-4,5-methano pyrroline DPP-IV inhibitors are described. Improvement of the inhibitory activity and chemical stability of this series of compounds was respectively achieved by the introduction of bulky groups at the 4-position and 1-position of the piperidinyl glycine, leading to a series of potent and stable DPP-IV inhibitors.
Design, synthesis, and SAR of 7-oxopyrrolopyridine-derived DPP4 inhibitors are described. The preferred stereochemistry of these atropisomeric biaryl analogs has been identified as Sa. Compound (+)-3t, with a K(i) against DPP4, DPP8, and DPP9 of 0.37 nM, 2.2, and 5.7 muM, respectively, showed a significant improvement in insulin response after single doses of 3 and 10 mumol/kg in ob/ob mice.
Several pyrazolo-, triazolo-, and imidazolopyrimidines were synthesized and evaluated as inhibitors of DPP4. Of these three classes of compounds, the imidazolopyrimidines displayed the greatest potency and demonstrated excellent selectivity over the other dipeptidyl peptidases. SAR evaluation for these scaffolds was described as they may represent potential treatments for type 2 diabetes.
Continued structure-activity relationship (SAR) exploration within our previously disclosed azolopyrimidine containing dipeptidyl peptidase-4 (DPP4) inhibitors led us to focus on an imidazolopyrimidine series in particular. Further study revealed that by replacing the aryl substitution on the imidazole ring with a more polar carboxylic ester or amide, these compounds displayed not only increased DPP4 binding activity but also significantly reduced human ether-a-go-go related gene (hERG) and sodium channel inhibitory activities. Additional incremental adjustment of polarity led to permeable molecules which exhibited favorable pharmacokinetic (PK) profiles in preclinical animal species. The active site binding mode of these compounds was determined by X-ray crystallography as exemplified by amide 24c. A subsequent lead molecule from this series, (+)-6-(aminomethyl)-5-(2,4-dichlorophenyl)-N-(1-ethyl-1H-pyrazol-5-yl)-7-methylimidazo[1,2-a]pyrimidine-2-carboxamide (24s), emerged as a potent, selective DPP4 inhibitor that displayed excellent PK profiles and in vivo efficacy in ob/ob mice.
The synthesis and SAR of aminomethyl-substituted imidazolopyrimidine DPP4 inhibitors bearing varied pendant aryl groups is described. Compound 1, which exists as a separable mixture of non-interconvertible atropisomers was used as the starting point for investigation. The effects of substituent pattern and type as well as stereochemical effects on inhibitor potency are discussed.
Saxagliptin is a potent, selective, reversible dipeptidyl peptidase 4 (DPP4) inhibitor specifically designed for extended inhibition of the DPP4 enzyme and is currently under development for the treatment of type-2 diabetes. The pharmacokinetics of saxagliptin were evaluated in rats, dogs, and monkeys and used to predict its human pharmacokinetics. Saxagliptin was rapidly absorbed and had good bioavailability (50-75%) in the species tested. The plasma clearance of saxagliptin was higher in rats (115 ml/min/kg) than in dogs (9.3 ml/min/kg) and monkeys (14.5 ml/min/kg) and was predicted to be low to moderate in humans. The plasma elimination half-life was between 2.1 and 4.4 h in rats, dogs, and monkeys, and both metabolism and renal excretion contributed to the overall elimination. The primary metabolic clearance pathway involved the formation of a significant circulating, pharmacologically active hydroxylated metabolite, M2. The volume of distribution values observed in rats, dogs, and monkeys (1.3-5.2 l/kg) and predicted for humans (2.7 l/kg) were greater than those for total body water, indicating extravascular distribution. The in vitro serum protein binding was low (< or =30%) in rats, dogs, monkeys, and humans. After intra-arterial administration of saxagliptin to Sprague-Dawley and Zucker diabetic fatty rats, higher levels of saxagliptin and M2 were observed in the intestine (a proposed major site of drug action) relative to that in plasma. Saxagliptin has prolonged pharmacodynamic properties relative to its plasma pharmacokinetic profile, presumably due to additional contributions from M2, distribution of saxagliptin and M2 to the intestinal tissue, and prolonged dissociation of both saxagliptin and M2 from DPP4.
The inhibition of DPP-IV by saxagliptin has been proposed to occur through formation of a covalent but reversible complex. To evaluate further the mechanism of inhibition, we determined the X-ray crystal structure of the DPP-IV:saxagliptin complex. This structure reveals covalent attachment between S630 and the inhibitor nitrile carbon (C-O distance <1.3 A). To investigate whether this serine addition is assisted by the catalytic His-Asp dyad, we generated two mutants of DPP-IV, S630A and H740Q, and assayed them for ability to bind inhibitor. DPP-IV H740Q bound saxagliptin with an approximately 1000-fold reduction in affinity relative to DPP-IV WT, while DPP-IV S630A showed no evidence for binding inhibitor. An analog of saxagliptin lacking the nitrile group showed unchanged binding properties to the both mutant proteins, highlighting the essential role S630 and H740 play in covalent bond formation between S630 and saxagliptin. Further supporting mechanism-based inhibition by saxagliptin, NMR spectra of enzyme-saxagliptin complexes revealed the presence of three downfield resonances with low fractionation factors characteristic of short and strong hydrogen bonds (SSHB). Comparison of the NMR spectra of various wild-type and mutant DPP-IV:ligand complexes enabled assignment of a resonance at approximately 14 ppm to H740. Two additional DPP-IV mutants, Y547F and Y547Q, generated to probe potential stabilization of the enzyme-inhibitor complex by this residue, did not show any differences in inhibitor binding either by ITC or NMR. Together with the previously published enzymatic data, the structural and binding data presented here strongly support a histidine-assisted covalent bond formation between S630 hydroxyl oxygen and the nitrile group of saxagliptin.
The synthesis and structure-activity relationships of novel dipeptidyl peptidase IV inhibitors replacing the classical cyanopyrrolidine P1 group with other small nitrogen heterocycles are described. A unique potency enhancement was achieved with beta-branched natural and unnatural amino acids, particularly adamantylglycines, linked to a (2S,3R)-2,3-methanopyrrolidine based scaffold.
A series of seco-prolinenitrile-containing dipeptides were synthesized and assayed as inhibitors of the N-terminal sequence-specific serine protease dipeptidyl peptidase IV, a promising new target for treatment of type 2 diabetes. The inhibitors described herein assess the minimum structural requirements at P1 for this enzyme, resulting in the identification of inhibitors with low nM potency.
Efforts to further elucidate structure-activity relationships (SAR) within our previously disclosed series of beta-quaternary amino acid linked l-cis-4,5-methanoprolinenitrile dipeptidyl peptidase IV (DPP-IV) inhibitors led to the investigation of vinyl substitution at the beta-position of alpha-cycloalkyl-substituted glycines. Despite poor systemic exposure, vinyl-substituted compounds showed extended duration of action in acute rat ex vivo plasma DPP-IV inhibition models. Oxygenated putative metabolites were prepared and were shown to exhibit the potency and extended duration of action of their precursors in efficacy models measuring glucose clearance in Zucker(fa/fa) rats. Extension of this approach to adamantylglycine-derived inhibitors led to the discovery of highly potent inhibitors, including hydroxyadamantyl compound BMS-477118 (saxagliptin), a highly efficacious, stable, and long-acting DPP-IV inhibitor, which is currently undergoing clinical trials for treatment of type 2 diabetes.
Dipeptidyl peptidase IV (DPP4) is a multifunctional type II transmembrane serine peptidase which regulates various physiological processes, most notably plasma glucose homeostasis by cleaving peptide hormones glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide. Inhibition of DPP4 is a potentially valuable therapy for type 2 diabetes. Synthesis and structure-activity relationships of a series of substituted diprolyl nitriles are described, leading to the identification of compound 1 with a measured DPP4 K(i) of 3.6 nM.
A series of methanoprolinenitrile-containing dipeptide mimetics were synthesized and assayed as inhibitors of the N-terminal sequence-specific serine protease dipeptidyl peptidase IV (DPP-IV). The catalytic action of DPP-IV is the principle means of degradation of glucagon-like peptide-1, a key mediator of glucose-stimulated insulin secretion, and DPP-IV inhibition shows clinical benefit as a novel mechanism for treatment of type 2 diabetes. However, many of the reversible inhibitors to date suffer from chemical instability stemming from an amine to nitrile intramolecular cyclization. Installation of a cyclopropyl moiety at either the 3,4- or 4,5-position of traditional 2-cyanopyrrolidide proline mimetics led to compounds with potent inhibitory activity against the enzyme. Additionally, cis-4,5-methanoprolinenitriles with beta-branching in the N-terminal amino acid provided enhanced chemical stability and high inhibitory potency. This class of inhibitors also exhibited the ability to suppress prandial glucose elevations after an oral glucose challenge in male Zucker rats.
