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Novel effectors of dipeptidyl peptidase iv

Novel effectors of dipeptidyl peptidase iv description/claims

The present invention relates to dipeptide compounds and compounds analogous to dipeptide compounds that are formed from an amino acid and a thiazolidine or pyrrolidine group, and salts thereof, referred to hereinafter as dipeptide compounds, and to the use of the compounds in the treatment of impaired glucose tolerance, glycosuria, hyperlipidaemia, metabolic acidoses, diabetes mellitus, diabetic neuropathy and nephropathy and also of sequelae of diabetes mellitus in mammals.

The invention therefore relates also to a simple method of lowering the blood sugar concentration in mammals with the aid of dipeptide compounds as activity-reducing effectors (substrates, pseudosubstrates, inhibitors, binding proteins, antibodies etc.) for enzymes having activity comparable to or identical to the enzymatic activity of the enzyme dipeptidyl peptidase IV.

DP IV or DP IV-analogous activity (for example the cytosolic DP II has a substrate specificity almost identical to DP IV) occurs in the blood circulation where it splits off dipeptides highly specifically from the N-terminus of biologically active peptides when proline or alanine are the adjacent residues of the N-terminal amino acid in their sequence.

The glucose-dependent insulinotropic polypeptides:

gastric inhibitory polypeptide 1-2 (GIP1-42) and glucagon-like peptide amide-1 7-36 (GLP-17-36), that is to say hormones that stimulate glucose-induced secretion of insulin by the pancreas (also called incretins), are substrates of DP IV, since the latter is able to split off the dipeptides tyrosinyl-alanine and histidylalanine, respectively, from the N-terminal sequences of those peptides in vitro and in vivo.

The reduction of such DP IV and DP IV-analogous enzyme activity of the cleavage of those substrates in vivo can be used to bring about effective suppression of undesired enzyme activity under laboratory conditions and also in the case of pathological conditions in mammalian organisms. For example, diabetes mellitus Type II (including adult-onset diabetes) is based on a reduced secretion of insulin or disorders in the receptor function resulting inter alia from anomalous incretin concentrations arising from proteolysis.

According to the current state of the art, hyperglycaemia and associated causes and sequelae (including diabetes mellitus) are treated by the administration of insulin (e.g. material isolated from bovine pancreas or obtained by genetic engineering techniques) to the diseased organisms in various forms of administration. All the methods known hitherto, including more modern procedures, are distinguished by the requirement of a large amount of material, by high costs and often by a distinct impairment of the quality of life of the patients. The conventional method (daily i.v. insulin injection, customary since the 1930s) treats the acute symptoms of the disease, but after prolonged use leads inter alia to serious vascular changes (arteriosclerosis) and nerve damage.

More recently the installation of subcutaneous depot implants (the insulin is released in metered amounts, and daily injections are unnecessary) and implantation (transplantation) of intact Langerhan's cells into the functionally impaired pancreatic gland or into other organs and tissues have been proposed. Such transplants require a high level of technical resources. Furthermore, they involve a surgical intervention into the recipient organism, which is associated with risks, and even in the case of cell transplants require methods of suppressing or circumventing the immune system.

The use of alanyl pyrrolidide and isoleucyl thiazolidide as inhibitors of DP IV or of DP IV-analogous enzyme activity is already known from PCT/DE 97/00820 and the use of isoleucyl pyrrolidide and isoleucyl thiazolidide hydrochloride is already known from DD 296 075. Isoleucyl thiazolidide, which is used in the latter prior art, is a natural, that is to say L-threo-isoleucyl thiazolidide: on the priority date and also on the application date of the two specifications, only that form, the natural form, of isoleucyl thiazolidide was available.

It has been established that those compounds, especially L-threo-isoleucyl thiazolidide, are good effectors for DP IV and DP IV-analogous enzyme activities, but the use of that compound may give rise to certain problems in the case of some patients or some forms of the disease:

Depending upon the symptoms and the severity e.g. of diabetes mellitus it would be desirable, for example, to have available effectors that have an action different from that of the known compounds: for example, it is known that diabetes mellitus patients must be “stabilised” individually in order that their illness can be treated in an optimum manner. In some cases, for example, a reduction in the activity by DP IV effectors ought to be sufficient. It is also possible that too high a level of inhibitor activity and the permanent administration of the same medicament, especially in view of the life-long duration of treatment, may result in undesirable side-effects. Furthermore, it could also be desirable to improve certain transport properties in order to increase the rate of absorption of the effectors in vivo.

The aim of the invention is therefore to provide new (especially activity-reducing) effectors for the treatment of e.g. impaired glucose tolerance, glycosuria, hyperlipidaemia, metabolic acidoses, diabetes mellitus, diabetic neuropathy and nephropathy and also of sequelae of diabetes mellitus in mammals, and a simple method of treating such diseases.

This aim is achieved according to the invention by the provision of dipeptide compounds or analogues of dipeptides that are formed from an amino acid and a thiazolidine or pyrrolidine group, and salts thereof.

On administration, preferably oral administration, of these effectors to a mammalian organism, the endogenous (or additionally exogenously administered) insulinotropic peptides GIP1-42 and GLP-17-36 (or alternatively GLP-17-37 or analogues thereof) are broken down to a reduced extent by DP IV or DP IV-like enzymes and therefore the decrease in the concentration of those peptide hormones or their analogues is reduced or delayed. The invention is therefore based on the finding that a reduction, in the DP IV or DP IV-like enzymatic activity acting in the blood circulation has an effect on the blood sugar level. It has been found that

1. the reduction in DP IV or DP IV-analogous activity leads to an increase in the relative stability of the glucose-stimulated or externally introduced incretins (or analogues thereof), that is to say by administration of effectors of DP IV or DP IV-analogous proteins it is possible to control the breakdown of incretin in the blood;

2. the increase in the biological breakdown stability of the incretins (or their analogues) results in a change in the action of endogenous insulin;

3. the increase in the stability of the incretins brought about by the reduction in DP IV or DP IV-analogous enzymatic activity in the blood results in a subsequent change in the glucose-induced insulin action and therefore in a modulation of the blood glucose level that is controllable by means of DP IV-effectors.

Especially suitable for that purpose according to the invention are dipeptide compounds in which the amino acid is selected from a natural amino acid, such as, for example, leucine, valine, glutamine, proline, isoleucine, asparagine and aspartic acid.

The administration, where possible oral administration, of the high-affinity, low molecular weight enzyme inhibitors according to the invention is a more economical alternative e.g. to invasive surgical techniques in the treatment of pathological symptoms. Through a chemical design of stability, transport and clearance properties, their mode of action can be modified and matched to individual characteristics.

As mentioned above, it may be necessary, for example in the case of the long-term treatment of diabetes mellitus, to provide effectors having a defined activity with which it is possible to meet the individual needs of patients and to treat their symptoms. The dipeptide compounds according to the invention therefore exhibit at a concentration (of dipeptide compounds) of 10 μM, especially under the conditions indicated in Table 1, a reduction in the activity of dipeptidyl peptidase IV or DP IV-analogous enzyme activities of at least 10%, especially of at least 40%. Frequently a reduction in activity of at least 60% or at least 70% is also required. Preferred effectors may also exhibit a reduction in activity of a maximum of 20% or 30%. Furthermore, the transport properties of the present compounds, especially by the peptide transporter Pep T1, are significantly improved.

Especially preferred dipeptide compounds are L-allo-isoleucyl thiazolidide and salts thereof. Those compounds surprisingly exhibit an approximately five-fold improvement in transport by the peptide transporter Pep T1 in comparison with L-threo-isoleucyl thiazolidide, while having approximately the same degree of action with respect to glucose modulation.

Further preferred compounds are given in Table 1.

The salts of the dipeptide compounds according to the invention may be, for example, organic salts such as acetates, succinates, tartrates or fumarates, or inorganic acid radicals such as phosphates or sulphates. Special preference is given to the fumarates, which have an excellent action combined with a surprisingly high degree of stability towards hydrolysis and are considerably less soluble than the hydrochlorides. Those properties are also advantageous from the galenical standpoint.

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• Utility Patent

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