Dipeptidyl peptidase IV (DPP-IV) is a post-proline/alanine cleaving serine protease found in various tissues of the body including kidney, liver, and intestine. DPP-IV is thought to regulate the activity of multiple physiogically important peptides, including, but not limited to, GLP1, GIP, GLP2, GRP, vasoactive intestinal peptide, peptide histidine methionine, PYY, substance P, beta-casomorphine, NPY, PACAP38, prolactin, chorionic gonadotropin, aprotinin, corticotropin-like intermediate lobe peptide, pituitary adenylyl cyclase-activating peptide, (Tyr)melanostatin, LD78beta(3-70), RANTES, eotaxin procolipase, enterostatin, vasostatin 1, endomorphin, morphiceptin, stromal cell derived factor, macrophage-derived chemokine, granulocyte chemotactic protein-2, and GHRH/GRF. As examples of the therapeutic value of DPP-IV, DPP-IV is believed to be involved in a variety of metabolic, gastrointestinal, viral, and inflammatory diseases, including, but not limited to, diabetes, obesity, hyperlipidemia, dermatological or mucous membrane disorders, psoriasis, intestinal distress, constipation, autoimmune disorders such as encephalomyelitis, complement mediated disorders such as glomerulonepritis, lipodystrophy, and tissue damage, psychosomatic, depressive, and neuropsychiatric disease such as anxiety, depression, insomnia, schizophrenia, epilepsy, spasm, and chronic pain, HIV infection, allergies, inflammation, arthritis, transplant rejection, high blood pressure, congestive heart failure, tumors, and stress-induced abortions, for example cytokine-mediated murine abortions. For example, DPP-IV, also known as CD26, mediates T-cell activation and HIV infection (Ohtsuki et al., 2000). T-cells expressing DPP-IV/CD26 are preferentially infected and depleted in HIV-infected individuals (Ohtsuki et al., 2000). DPP-IV inhibitors have demonstrated anti-inflammatory effects in animal models of arthritis (Tanaka et al, 1997). Additionally, DPP-IV inhibition has been shown to prolong cardiac transplant survival (Korom et al., 1997). In vitro studies suggest that DPP-IV/CD26 expression correlate with tumor progression of malignant melanomas of the skin (Van den Oord, 1998). Furthermore, DPP-IV is thought to regulate metabolism by cleaving the penultimate proline/alanine at the amino-terminus of polypeptides (Mentlein, 1999), such as glucagon-like peptides (GLP) and neuropeptide Y (NPY).
More specifically, GLPs help metabolize glucose and, thus, regulation of GLPs likely should be beneficial in the treatment of metabolic disorders such as diabetes. Diabetes, for example type 2 (also called noninsulin-dependent diabetes mellitus (NIDDM) or maturity-onset) diabetes, results in elevated blood sugar levels due to absolute or relative insufficiencies of insulin. Type 2 diabetes is the more common form of diabetes, accounting for 90% of cases, or about 16 million Americans. Most type 2 diabetics produce variable, sometimes normal, amounts of insulin, but they have abnormalities in liver and muscle cells that resist its actions. Insulin attaches to the receptors of cells, but glucose does not get inside, a condition known as insulin resistance. Many type 2 diabetics seem to be incapable of secreting enough insulin to overcome insulin resistance. GLP-1 enhances insulin secretion. Thus, regulation of GLP-1 correlates to a regulation of insulin secretion. Moreover, GLP-1 decreases hepatic glucose production, gastric emptying, and food intake (Deacon et al., 1995). Further, GLP-2 maintains the integrity of the intestinal mucosal epithelium via effects on gastric motility, nutrient absorption, crypt cell proliferation and apoptosis, and intestinal permeability (Drucker, 2001).
DPP-IV inhibitors preserve GLP-1 function for a longer time (Balka, 1999). Thus, DPP-IV inhibitors may promote satiety, weight loss, and the antidiabetic effects of GLP-1 (Deacon et al., 1995; Holst and Deacon, 1998). For example, inhibition of DPP-IV with the known compound NVP-DPP728 increases plasma GLP-1 (2-36 amide) concentrations and improves oral glucose tolerance in obese Zucker rats. See, Diabetologia 42: 1324–1331. Both subcutaneously and intravenously administered GLP-1 is rapidly degraded from the NH2-terminus in type II diabetic patients and in healthy subjects. See, Diabetes 44:1126, 1995.
Moreover, DPP-IV inhibitors preserve GLP-2 for longer periods of time and, thus, may be useful for treating intestinal insufficiencies and mucous membrane disorders (Hartmann B et al., 2000).
While DPP-IV is the predominate protease regulating GLP turnover, similar substrate or inhibitor specificity may be observed for related proteases. Related serine proteases include, but are not limited to, dipeptidyl peptidase-II (DPP-II), dipeptidyl peptidase IV beta, dipeptidyl peptidase 8, dipeptidyl peptidase 9, aminopeptidase P, fibroblast activating protein alpha (seprase), prolyl tripeptidyl peptidase, prolyl oligopeptidase (endoproteinase Pro-C), attractin (soluble dipeptidyl-aminopeptidase), acylaminoacyl-peptidase (N-acylpeptide hydrolase; fMet aminopeptidase) and lysosomal Pro-X carboxypeptidase (angiotensinase C, prolyl carboxypeptidase). Proline-cleaving metallopeptidases that may share similar substrate or inhibitor specificity to DPP-IV include membrane Pro-X carboxypeptidase (carboxypeptidase P), angiotensin-converting enzyme [Peptidyl-dipeptidase A multipeptidase], collagenase 1 (interstitial collagenase; matrix metalloproteinase 1; MMP-1; Mcol-A), ADAM 10 (alpha-secretase, myelin-associated disintegrin metalloproteinase), neprilysin (atriopeptidase; CALLA; CD10; endopeptidase 24.11; enkephalinase), Macrophage elastase [metalloelastase; matrix metalloproteinase 12; MMP-12], Matrilysin (matrix metalloproteinase 7; MMP-7), and neurolysin (endopeptidase 24.16; microsomal endopeptidase; mitochondrial oligopeptidase).
Furthermore, beyond mammalian serine peptidases and proline-cleaving metallopeptidases, other non-mammalian proteases may share similar substrate or inhibitor specificity to DPP-IV. Non-limiting examples of such non-mammalian serine proteases include prolyl aminopeptidase (prolyl iminopeptidase), IgA1-specific serine type prolyl endopeptidase (IgA protease, Neisseria, Haemophilus), dipeptidyl aminopeptidase A (STE13) (Saccharomyces cerevisiae), dipeptidyl aminopeptidase B (fungus), prolyl oligopeptidase homologue (Pyrococcus sp.), oligopeptidase B (Escherichia coli alkaline proteinase II; protease II), dipeptidyl aminopeptidase B1 (Pseudomonas sp.), dipeptidyl-peptidase IV (bacteria), dipeptidyl aminopeptidase (Aureobacterium), dipeptidyl-peptidase IV (insect), dipeptidyl-peptidase V, allergen Tri t4 (Trichophyton tonsurans), secreted alanyl DPP (Aspergillus oryzae), peptidase II-mes (Prosopis velutina), and bamboo serine proteinase (Pleloblastus hindsii). Non-limiting examples of such non-mammalian proline-cleaving metallopeptidases include penicillolysin (fungal acid metalloendopeptidase), proline-specific peptidyl-dipeptidase (Streptomyces), coccolysin (gelatinase, Enterococcus faecalis), aminopeptidase Ey, (hen egg yolk) (apdE g.p.; Gallus gallus domesticus), gametolysin (Chlamydomonas cell wall degrading protease), and snake venom proline-cleaving metalloproteases as well. for further reference.
Dipeptidyl peptidase II (DPP II) is a serine protease localized to lysosomes in cells and believed to be involved in lysosomal degradation and protein turnover. The order of expression of DPP-II is kidney>>testis>or=heart>brain>or=lung>spleen>skeletal muscle>or=liver (Araki H et al., J Biochem (Tokyo) 2001, 129:279–88). This expression suggests possible utility in kidney or lysosomal-related disorders. Substrate specificity studies indicated that purified DPP-II hydrolyzes specifically alanine or proline residues at acidic pH (4.5–5.5). DPP-II has significant sequence homology and substrate specificity to quiescent cell proline dipeptidase and prolyl carboxypeptidase, suggesting possible overlapping functions between these proteases (Araki H et al., J Biochem (Tokyo) 2001, 129:279–88).
The present invention includes novel DPP-II and/or DPP-IV inhibitors, as well as methods of their therapeutic use and methods of their production. While not being limited thereby, the compounds of the present invention are believed useful for the treatment of a variety of metabolic, gastrointestinal, viral, and inflammatory diseases, including, but not limited to, diabetes, obesity, hyperlipidemia, dermatological or mucous membrane disorders, psoriasis, intestinal distress, constipation, autoimmune disorders such as encephalomyelitis, complement mediated disorders such as glomerulonepritis, lipodystrophy, and tissue damage, psychosomatic, depressive, and neuropsychiatric disease such as anxiety, depression, insomnia, schizophrenia, epilepsy, spasm, and chronic pain, HIV infection, allergies, inflammation, arthritis, transplant rejection, high blood pressure, congestive heart failure, tumors, and stress-induced abortions, for example cytokine-mediated murine abortions.