| Cyclic agonists and antagonists of c5a receptors and g protein-coupled receptors -> Monitor Keywords |
|
|
 
Cyclic agonists and antagonists of c5a receptors and g protein-coupled receptorsRelated Patent Categories: Drug, Bio-affecting And Body Treating Compositions, Designated Organic Active Ingredient Containing (doai), Peptide Containing (e.g., Protein, Peptones, Fibrinogen, Etc.) Doai, CyclopeptidesCyclic agonists and antagonists of c5a receptors and g protein-coupled receptors description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060160726, Cyclic agonists and antagonists of c5a receptors and g protein-coupled receptors. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This invention relates to novel cyclic compounds which have the ability to modulate the activity of G protein-coupled receptors. The invention provides both agonists and antagonists. In preferred embodiments, the invention provides cyclic peptidic and cyclic or non-cyclic non-peptidic antagonists or agonists of C5a. The compounds of the invention are both potent and selective, and are useful in the treatment of a variety of inflammatory conditions. BACKGROUND OF THE INVENTION [0002] Activation of human complement, a system of plasma proteins involved in immunological defence against infection and injury, contributes significantly to the pathogenesis of numerous acute and chronic diseases. In particular, the complement protein C5a has been extensively investigated. For general reviews, see Whaley (1987), and Sim (1993). Table 1 provides a summary of known roles of C5a in disease. [0003] During host defence, the complement system of plasma proteins initiates inflammatory and cellular immune responses to stimuli such as infectious organisms (bacteria, viruses, Parasites), chemical or physical injury, radiation or neoplasia. Complement is activated through a complex cascade of interrelated proteolytic events that produce multiple bioactive peptides, some of which (eg. anaphylatoxins C3a and C5a) interact with cellular components to propagate inflammatory processes. Complement activation, either by the classical pathway, after antigen-antibody (Ag/Ab) binding, or by the antibody-independent alternate pathway, ends with a terminal sequence in which protein C5 is proteolytically cleaved by C5 convertase to C5a and C5b. The latter facilitates assembly of a "membrane attack complex" that punches holes in membranes of target cells such as bacteria, leading to leakage, lysis and cell death. Steps in the cascade are tightly regulated to avoid stepwise amplification of proteolysis by sequentially formed proteases. If these regulatory mechanisms become inefficient, protracted activation of complement can result, causing enhanced inflammatory responses as in autoimmune diseases. [0004] Although the broad features of the complement system and its activation are known, mechanistic details remain poorly understood. A principal and very potent mediator of inflammatory responses is the plasma glycoprotein C5a, which interacts with specific surface receptors (C5aR) on mast cells, neutrophils, monocytes, macrophages, non-myeloid cells, and vascular endothelial cells (Gerard and Gerard, 1994). C5aR is a G protein-coupled receptor with seven transmembrane helices (Gerard and Gerard, 1991). This receptor is one of the rhodopsin superfamily of GTP-linked binding proteins, but differs from rhodopsin receptors in that the receptor and G protein are linked prior to activation. [0005] G protein-coupled receptors are prevalent throughout the human body, comprising approximately 80% of known cellular receptor types, and mediate signal transduction across the cell membrane for a very wide range of endogenous ligands. They participate in a diverse array of physiological and pathophysiological processes, including, but not limited to those associated with cardiovascular, central and peripheral nervous system, reproductive, metabolic, digestive, immunoinflammatory, and growth disorders, as well as other cell-regulatory and proliferative disorders. Agents, both agonists and antagonists, which selectively modulate functions of G protein-coupled receptors have important therapeutic applications. [0006] C5a is one of the most potent chemotactic agents known, and recruits neutrophils and macrophages to sites of injury, alters their morphology; induces degranulation; increases calcium mobilisation, vascular permeability (oedema) and neutrophil adhesiveness; contracts smooth muscle; stimulates release of inflammatory mediators (including histamine, TNF-.alpha., IL-1, IL-6, IL-8, prostaglandins, leukotrienes) and lysosomal enzymes; promotes formation of oxygen radicals; and enhances antibody production (Gerard and Gerard, 1994). Overexpression or underregulation of C5a is implicated in the pathogenesis of immunoinflammatory conditions such as rheumatoid arthritis, adult respiratory distress syndrome (ARDS), systemic lupus erythematosus, tissue graft rejection, ischaemic heart disease, reperfusion injury, septic shock, psoriasis, gingivitis, atherosclerosis, Alzheimer's disease, lung injury and extracorporeal post-dialysis syndrome, and in a variety of other conditions, as summarised in Table 1. TABLE-US-00001 TABLE 1 The Role of C5a in Disease C5a C5aR Condition/disease levels expression Details allergy ++ allergen challenge leads to nasal symptoms and increased C5a levels Alzheimer's disease ++ ++ up-regulation of the receptor in reactive astrocytes, microglia and endothelial cells in the CNS, complement system activated by .beta.-amyloid ARDS/respiratory ++ distress Behcet's disease ++ levels highest just prior to ocular attack bronchial asthma ++ capillary leak ++ syndrome chronic lung ++ Increased C5a levels in disease pulmonary effluent fluid from mechanically ventilated infants with chronic lung disease. Churg-Strauss hypersensitivity of granulocytes to C5a cystic fibrosis generation of C5a/effects on PMNs decompression ++ increased C5a levels during stress saturation diving diabetes type I ++ C5a generated during onset; circulating monocytes in newly diagnosed type 1 diabetes patients are activated Familial lack of C5a inactivator Mediterranean fever Guillain-Barre ++ CSF levels elevated ischaemic disease migration of monocytes into states/ myocardial myocardium after reperfusion. infarct Damage prevented with sCR1 Kimura's disease humoral factor up-regulates the response of PMNs to C5a Multiple Sclerosis ++ increased expression of the receptor on foamy macrophages in acute and chronic MS and fibrous astrocytes in chronic MS Meningitis C5a induces experimental meningitis; PMN accumulation seen in the CSF pancreatitis ++ post-dialysis ++ - C5a generated via syndrome complement activation by tubing material, C5aR levels decreased on PMNs & monocytes in chronic state preeclampsia/ HELLP ++ C5a levels elevated at delivery psoriasis ++ C5a levels high in scales reperfusion injury ++ inhibited by C5 antibody retinitis ++ C5a detected in vitreous humor Rheumatoid ++ elevated concentration of C5a arthritis found in synovial fluid (5-fold) and plasma (3-fold) Severe congenital - neutropenia transplant/graft ++ monoclonal antibodies block rejection the damage seen with xenogenic transplant; increased levels of C5a seen in the plasma and urine of patients with renal graft rejection [0007] New agents which limit the pro-inflammatory actions of C5a have potential for inhibiting chronic inflammation, and its accompanying pain and tissue damage. For these reasons, molecules which prevent C5a binding to its receptors are useful for treating chronic inflammatory disorders driven by complement activation. Importantly, such compounds provide valuable new insights to mechanisms of complement-mediate immunity. [0008] In another context, agonists of C5a receptors or other G protein-coupled receptors may also be found to have therapeutic properties in conditions either where the G protein-coupled receptor can be used as a recognition site for drug delivery, or where triggering of such receptors can be used to stimulate some aspect of the human immune system, for example in the treatment of cancers, viral or parasitic infections. [0009] One approach to the development of agonists or antagonists of C5a is through receptor-based design, using knowledge of the three-dimensional structures of C5a, its receptor C5aR, and the interactions between them. The structure of the receptor is unknown. The solution structure of human C5a, a 74 amino acid peptide that is highly cationic and N-glycosylated with a 3 kDa carbohydrate at Asn64, has been determined and is essentially a 4-helix bundle. The C-terminal end (residues 65-74, C5a.sub.65-74) was found to be unstructured (Zuiderweg et al, 1989) and this conformational flexibility in the C-terminus has made structure-function studies extremely difficult to interpret. [0010] C5a has a highly ordered N-terminal core domain (residues 1-64; C5a.sub.1-64), consisting of a compact antiparallel 4-helix bundle (residues 4-12, 18-26, 32-39, 46-63) connected by loops (13-17, 27-31, 40-45), and further stabilised by 3 disulphide bonds (C21-Cys47, Cys22-Cys54, Cys34-Cys55). [0011] Although the structure of the C5a receptor, C5aR, is unknown, the C5a-binding subunit of human monocyte-derived C5aR has been cloned and identified as a G protein-coupled receptor with transmembrane helices (Gerard and Gerard, 1991). Interactions between C5a and C5aR have been the subject of many investigations which, in summary, suggest that C5a binds via a two-site mechanism in which the N-terminal core domain of C5a is involved in receptor-recognition and binding, while the C-terminus is responsible for receptor activation. This mechanism is illustrated schematically in FIG. 1. The C-terminal "effector" region alone possesses all the information necessary for signal transduction, and is thought to bind in the receptor's interhelical region (Siciliano et al, 1994; deMartino et al, 1995). [0012] An N-terminal interhelical positively-charged region of C5a is responsible for receptor recognition and binding, and binds to a negatively-charged extracellular domain of C5aR (site 1), while the C-terminal "effector" region of C5a is thought to bind with the interhelical region of the receptor (site 2), and is responsible for receptor activation leading to signal transduction (Siciliano et al, 1994). [0013] Numerous short peptide derivatives of the C-terminus of C5a have been found to be agonists of C5a (Kawai et al, 1991; Kawai et al, 1992; Kohl et al, 1993; Drapeau et al, 1993; Ember et al, 1992; Sanderson et al, 1994; Sanderson et al, 1995; Finch et al, 1997; Tempero et al, 1997; Konteatis et al, 1994; DeMartino et al, 1995). The structures of some of these agonists are shown in Table 2 below (compounds 1-6). High molecular weight polypeptide inhibitors of the action of C5a at its receptor, such as monoclonal antibodies to the C5a receptor, are also known (Morgan et al, 1992). [0014] A small molecule, N-methylphenylalanine-lysine-proline-D-cyclohexylalanine-tryptophan-D-arg- inine (7, MeF-K-P-dCha-W-R), is a full antagonist of the C5a receptor, with no agonist activity when tested on isolated cellular membranes (Konteatis et al, 1994) or intact whole cells. This hexapeptide was developed by modifications of the agonist NMe-F-K-P-dCha-L-r, in which the molecule was progressively substituted at leucine residues with substituents of increasing size (Cha, F, Nph and W). This had the effect of reducing agonist activity. Receptor-binding assays, performed or isolated human neutrophil membranes, showed that the antagonists had only 0.04% relative affinity of C5a for the receptor (Konteatis et al, 1994). A key feature of these receptors is the definition of the binding of 7 to the C5a receptor. These authors state that the C-terminal arginine is essential for receptor binding and antagonist activity. This is also the case in all the reports of agonist activity by small peptide analogues of the C-terminus of C5a. However, for the antagonist 7, the authors go further and state that [0015] "the C-terminal carboxylate is an essential requirement for antagonist activity and receptor binding." [0016] They proposed that the requirement of the carboxylate is probably the result of its specific interaction with an arginine (Arg 206) in the receptor (De Martino et al, 1995). This idea was supported by a great reduction in receptor-affinity for an analogue of 7 in which the D-arginine (NH.sub.2--CH(CO.sub.2H)--(CH.sub.2).sub.3NHC(:NH)NH.sub.2) was replaced by agmatine (NH.sub.2--CH.sub.2--(CH.sub.2).sub.3NHC(:NH)NH.sub.2). In summary, De Martino et al claim that the D-arginine interacts via its guanidinium side chain with a negatively-charged amino acid side chain in the receptor. A second interaction between the negatively-charged C-terminal carboxylate of 7 and a positively-charged side chain residue in the receptor is also thought to occur. [0017] We have now determined the solution structure of this hexapeptide 7 and several analogues, and have surprisingly found that in fact a terminal carboxylate group is not required for binding to C5aR or for antagonist activity, and that instead an unusual hitherto unrecognised structural feature, a turn conformation, is responsible for C5a antagonist or agonist binding and activity. The hexapeptide and several new structurally related antagonists have been examined for both their receptor-binding affinities and antagonist activity, using intact polymorphonuclear (PMN) cells. Our results show the hitherto unknown specific structural requirement for the binding of C5a antagonists or agonists to the C5a receptor, which we believe to be common to ligands for the G protein-coupled receptor family. Our establishment of this specific structural requirement has enabled us to design and develop improved molecular probes of the complement system and of C5a-based drugs, and to design small molecules that target other G protein-coupled receptors, which are becoming increasingly recognised as important drug targets due to their crucial roles in signal transduction (G protein-coupled Receptors, IBC Biomedical Library Series, 1996). [0018] Thus our results have enabled us to design constrained structural templates which enable hydrophobic groups to be assembled into a hydrophobic array for interaction with a G protein-coupled receptor, for example at Site 2 of the C5a receptor illustrated in FIG. 1. Such templates or scaffolds, which may be cyclic or acyclic, have not heretofore been suggested for modulators of the activity of C5a receptors or other G protein-coupled receptors. SUMMARY OF THE INVENTION [0019] The invention provides cyclic and non-cyclic modulators of the activity of G-protein-coupled receptors. [0020] According to a first aspect, the invention provides a compound which is an antagonist, of a G protein-coupled receptor, which has no agonist activity, and which has a cyclic or constrained acyclic structure adapted to provide a framework of approximate dimensions as follows: where the numerals refer to distances between Ca carbons of amino acids or their analogues or derivatives, and A, B, C and D are not necessarily on adjacent amino acids, or analogues or derivatives thereof; and [0021] where the critical amino acid side chains are designated by A, B, C and D, or are as defined below; [0022] A is any common or uncommon, basic, charged amino acid side chain which serves to position a positively charged group in this position, including, but not limited to the following side chains and other mimetics of arginine side chains: where [0023] X is NCN, NNO.sub.2, CHNO.sub.2 or NSO.sub.2NH.sub.2; Continue reading about Cyclic agonists and antagonists of c5a receptors and g protein-coupled receptors... Full patent description for Cyclic agonists and antagonists of c5a receptors and g protein-coupled receptors Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Cyclic agonists and antagonists of c5a receptors and g protein-coupled receptors patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Cyclic agonists and antagonists of c5a receptors and g protein-coupled receptors or other areas of interest. ### Previous Patent Application: Lipid metabolism improving agent Next Patent Application: 3-ether and 3-thioether substituted cyclosporin derivatives for the treatment and prevention of hepatitis c infection Industry Class: Drug, bio-affecting and body treating compositions ### FreshPatents.com Support Thank you for viewing the Cyclic agonists and antagonists of c5a receptors and g protein-coupled receptors patent info. IP-related news and info Results in 0.12158 seconds Other interesting Feshpatents.com categories: Accenture , Agouron Pharmaceuticals , Amgen , AT&T , Bausch & Lomb , Callaway Golf 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
