POLYPEPTIDE COMPOUNDS CONTAINING D-2-ALKYLTRYPTOPHAN CAPABLE OF PROMOTING THE RELEASE OF GROWTH HORMONE

Abstract: A peptide of the formula: A-D-Mrp-(Ala)n-B-C wherein A is any natural L-amino acid or its D-isomer with the proviso that A is not His if B is Trp and C is D-Phe-Lys-NH2; or A is imidazoleacetyl, isonipecotyl, 4-aminobutyryl, 4-(aminomethyl)cyclohexanecarbonyl, Glu-Tyr-Ala-His, Tyr-Ala-His, Tyr-His, D-Thr-His; D relates to the dextro isomer, Mrp is 2-alkyltryptophan; n is 0 or 1; B is L- or D-Trp, Phe or D- beta -naphthylalanine, C is NH2, D-Phe-LysNH2, D-Trp-LysNH2, D-Phe-Lys-NH2, Phe-Lys-NH2, D-Phe-Lys-ThrNH2, D-Phe-Lys-D-ThrNH2, OR, wherein R is a C1-C3 alkyl group, and the addition salts with pharmaceutically acceptable organic or inorganic acids of anyone of said polypeptides, these compounds are capable of promoting the release of growth hormone, and are active by the oral route.

Description: POLYPEPTIDE COMPOUNDS CONTAINING D-2-ALKYLTRYPTOPHAN CAPABLE OF PROMOTING THE RELEASE OF GROWTH HORMONE The present invention relates to oligopeptide compounds containing a D-2-alkyltryptophan ammo acid and which are capable of releasing growth hormone (GH) from somatotropes, and are active by oral route. Background of the invention The increase of growth hormone (GH) levels in mammals after the administration of compounds inducing GH release can yield to growth acceleration and muscular mass increase and enhanced production of milk, if sufficiently high GH levels are obtained after the administration. Moreover, it is known that the increase of growth hormone levels in mammals can be achieved by administering known growth hormone release agents, such as growth hormone release hormones (GHRH). The increase of growth hormone levels in mammals can also be obtained by administering growth hormone release peptides, some of them having previously been described, for example in US 4,223,019, US 4,223,020, US 4,223,021, US 4,224,316, US 4,226,857, US 4,228,155, US 4,228,156, US 4,228,157, US 4,223,158, US 4,410,512, US 4,410.513, US 4,411,890 and US 4,839,344. Therefore, rather simple short chain-polypeptides , capable of promoting growth hormone release on condition that they are easily and conveniently preparable, as well as of easy purification and formulation and active when administered by oral route, are presently desired. One of the more studied growth hormone release peptides (GHRP) has been known since many years as GHRP- 6 (C.Y. Bowers et al. , Endocrinology 114:1537 (1984) and has the formula Hιs-D-Trp-Ala-Trp-D-Phe-Lys-NH 2 . GHRP-6 releases growth hormone in vitro and m vivo and is orally active in animals and n humans. Its molecular mechanism has been studied, as well as the one of its analogue heptapeptide GHRP-1 (Cheng et al . , Endocrinology 124:2791 (1989); M.S. Akman et al. , Endocrinology 132:1286 (1993)). It was found that, contrarily to natural GHRH, these peptides act through different receptors for the release of GH and through a different mechanism, which is independent from cAMP and which operates through other mtracellular pathways, such as the mobilization of calcium supplies and a proteinkinase C (PKC )-dependent process (L. Bresson- Bepoldm and L. Dufy-Barbe, Cell. Calcium 15, 247, (1994) . Summary of the invention In a completely surprising manner it has now been found that the introduction of a D-2-alkyltryptophan (2- Mrp) in the oligopeptide of the GHRP series, modifies the known mtracellular mechanism of GH release. In some cases, it has been evidenced a substantial increase of the activity of the adenylcyclase in the anterior pituitary glands, both of munne origin, and of human origin, but the specific mechanism remains still to be completely clarified. Thus, the modification given by a single alkyl group in the 2-posιtιon of tryptophan (in its D- confor ation) , besides favourably increasing the stability of the Trp residue (R. Deghenghi WO 91/18016 published on 28.11.1991 and R. Deghenghi et. al, Life Sciences 54, 1321, (1994)), is responsible for a completely unexpected change of the mtracellular mechanisms which now are independent from calcium, sometimes dependent on adenylcyclase and more similar to those of GHRH, as well as other peptide hormones. (James D. Watson et al. , Molecular Biology of the Gene, 4 t ^ 1 ed. , The Benjamin /Cummings Publishing Company, Inc. , Menlo Park, California, 1987, pag . 60). Another unexpected characteristic feature of the present invention is the very high potency of some penta- , hexa- , and heptapeptides and the favourable oral activity/potency ratio also of the smaller tetrapeptides of the series. The oligopeptides of the present invention have the following formula: A-D-Mrp-(Ala) n ~B-C, wherein A is any natural L-ammo acid or its D-isomer, with the proviso that A is not His if B is Trp and C is D-Phe-Lys-NH , or A is lmidazoleacetyl , isonipecotyl , 4- a mobutyryl , 4-( am omethyl )cyclohexanecarbonyl , Glu- Tyr-Ala-His, Tyr-Ala-His, Tyr-His, D-Thr-His, and more preferably A is D-Ala, D-Thr , Tyr; D relates to dextro isomer, Mrp is 2-alkyltryptophan preferably 2-methyl- tryptophan; n is 0 or 1; B is L- or D-Trp , Phe or D-β- Nal; C is NH 2 , D-Phe-LyεNH 2 , Phe-LysNH 2 , D-Trp-LysNH 2 , D-Phe-Lys-ThrNH 2 , D-Phe-Lys-D-ThrNH 2 , OR, wherein R is a c l~ c 3 a lkγl group, more preferably, when B is Trp, then C is Phe-LysNH 2 or D-Phe-LysNH 2 and when B is Phe, then C is D-Trp-LysNH 2 . Detailed Disclosure of the Invention The present invention lies on the discovery that different short-chain polypeptides which promote the release and increase of growth hormone levels blood of animals are characterized in that all of them comprise in the peptide chain a D-isomer of 2- alkyltryptophan (D-2-Me-Trp or D-Mrp). The polypeptides comprised in the scope of the present invention are defined by the following formula A-D-Mrp-(Ala) n -B-C , wherein A is any natural L-amino acid or its D-isomer, with the proviso that is not His if B is Trp and C is D- Phe-Lys-NH 2 , or A is lmidazoleacetyl , isonipecotyl , 4- aminobutyryl, 4-( aminomethyl )cyclohexanecarbonyl , Glu- Tyr-Ala-His, Tyr-Ala-His , Tyr-His, D-Thr-His , and more preferably A is D-Ala, D-Thr, Tyr; D relates to dextro isomer, Mrp is 2-alkyltryptophan, preferably 2- methyltryptophan; n is 0 or 1; B is L- or D-Trp, or D-β- Nal; C is NH 2 , D-Phe-LysNH 2 , Phe-LysNH 2 , D-Trp-LysNH 2 , D-Phe-Lys-ThrNH 2 , D-Phe-Lys-D-ThrNH 2 , OR, wherein R is a c l _c 3 ^^ --- group, more preferably, when B is Trp, then C is Phe-LysNH 2 or D-Phe-LysNH 2 and when B is Phe, then C is D-Trp-LysNH 2 and the addition salts with pharmaceutically acceptable organic or inorganic acids of anyone of said polypeptides. The abbreviations for the residues of ammo acids therein used are in agreement with the standard nomenclature for the peptides: Gly = Glycine Tyr = L-Tyrosme lie = L-Isoleucme Glu = L-Glutamic Acid Thr = L-Threonme Phe = L-Phenylalanine Ala = L-Alanine Lys = L-Lysine Asp = L-Aspartic Acid Cys = L-Cysteine Arg = L-Arginine Gin = L-Glutamine Pro = L-Proline Leu = L-Leucine Met = L-Methionine Ser = L-Serine Asn = L-Asparagine His = L-Histidine Trp = L-Tryptophan Val = L-Valine. Moreover , D-β-Nal = D-β-Naphthylalanine; INIP = Isonipecotyl; IMA = Imidazolylacetyl; GAB = 4-aminobutyryl; Mrp = 2-alkyltryptophan. According to the present invention, for alkyl it is intended lower alkyl, comprising from 1 to 3 carbon atoms. Examples of lower alkyl are methyl, ethyl, propyl, isopropyl . Among these methyl group is mostly preferre . All the three letter-abbreviations of the amino acids preceded by a "D" indicate the D-configuration of the a inoacidic residue. The preferred growth hormone release compounds in the embodiment of the present invention are: INIP-D-Mrp-D-Trp-Phe-Lys-NH 2 ; INIP-D-Mrp-D-β-Nal-Phe-Lys-NH 2 ; IMA-D-Mrp-D-Trp-Phe-Lys-NH 9 ; IMA-D-Mrp-D-β-Nal-Phe-Lys-NH 2 ; GAB-D-Mrp-D-Trp-Phe-Lys-NH 2 ; GAB-D-Mrp-D-β-Nal-Phe-Lys-NH 2 ; GAB-D-Mrp-D-β-Nal-NH 2 ; GAB-D-Mrp-D-β-Nal-OC 2 H 5 ; 4-(am omethyl )eyelohexanecarbony1-D-Mrp-D-Trp-Phe-Lys- NH 2 ; 4-( ammomethyl )cιclohexanecarbonyl-D-Mrp-D-β-Nal-Phe- Lys-NH 2 ; D-Ala-D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; D-Thr-D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; Hιs-D-Mrp-Ala-Phe-D-Trp-LysNH 2 ; Tyr-Hιs-D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; Hιs-D-Mrp-Ala-TrpNH 2 ; D-Thr-D-Mrp-Ala-TrpNH 2 ; wherein Mrp is 2-methyltryptophan, INIP, IMA and GAB are as defined above, and the addition salts with pharmaceutically acceptable organic or inorganic acids of anyone of said polypeptides . These compounds can be administered parenterally, but more conveniently intranasally and orally, or can be formulated in controlled release systems, such as biodegradable microcapsules, microspheres, subcutaneous implants and the like. The polypeptide compounds according to the present invention can be synthesized according to the usual methods of peptide chemistry, both solid-phase and solution, or by means of the classical methods known in the art. The solid-phase synthesis starts from C- termmal end of peptide. A suitable starting material can be prepared, for example attaching the required protected alpha-ammo acid to a chloromethylated resin, a hydroxymethylated resin, a benzhydrylamme resin (BHA), or to a para- ethylbenzhydryla me resin (p-Me- BHA) . As example, a chloromethylated resin is sold with the Trade Mark BIOBEADS ( R ) SX 1 by BioRad Laboratories, Richmond, California. The preparation of the hydroxymethyl resin is described by Bodansky et al . , Chem. Ind. (London) 38, 15997, (1966). The BHA resin is described by Pietta and Marshall, Chem. Comm. , 650 (1970) and is commercially available by Peninsula Laboratories Inc. , Bel ont, California. After the starting attachment, the protecting group of the alpha-amino acid can be removed by means of different acid reagents, comprising tπfluoroacetic acid (TFA) or hydrochloric acid (HC1) dissolved in organic solvents at room temperature. After the removal of the protecting group of the alpha-ammo acid, the remaining protected ammo acids can be coupled step by step in the desired order. Each protected ammo acid can generally be reacted in excess of about three times using a suitable carboxyl activating group, such as dicyclohexylcarbodiimiide (DCC) or dusopropylcarbodi- lmide (DIC) dissolved, for example, m methylene chloride (CH 2 C1 2 ) or dimethylformamide (DMF) and their mixtures. After the desired am oacidic sequence has been completed, the desired peptide can be cleaved from the supporting resin by treatment with a reagent such as hydrogen fluoride (HF), which not only cleaves the peptide from the resin, but also the more common protecting groups of the lateral chains. When a chloromethylated resm or a hydroxymethylated resin is used, the treatment with HF leads to the formation of the acid peptide in free form. When a BHA or p-Me-BHA resm is used, the treatment with HF directly leads to the formation of the amide peptide in free form. The above discussed solid-phase procedure is known in the art and was described by Atherton and Sheppard, Solid Phase Peptide Synthesis (IRL Press, Oxford, 1989). Some methods in solution, which can be used to synthesize the peptide moieties of the present invention are detailed in Bodansky et al. , Peptide Synthesis, 2 n(* * edition, John Wiley & Sons, New York, N.Y. 1976 and from Jones, The Chemical Synthesis of Peptides, (Clarendon Press, Oxford, 1994). These compounds can be administered to animals and humans at an effective dose which can be easily determined by the expert in the field and which can vary according to the specie, age, sex and weight of the treated subject. For example, m humans, v/hen intravenously administered, the preferred dose falls in the range from about 0.1 μg to 10 μg of total peptide per kg of body weight. When orally administered, typically higher amounts are necessary. For example, in humans for the oral administration, the dosage level is typically from about 30 μg to about 1000 μg of polypeptide per kg of body weight. The exact level can be easily determined empirically based on the above disclosure . Compositions, which comprise as active ingredient the organic and inorganic addition salts of the above described polypeptides and their combinations, optionally, m admixture with a vehicle, diluent, matrix or delayed release coating, are also comprised in the scope of the present invention. The delayed release pharmaceutical forms, comprising bioerodible matrixes, suitable for subcutaneous implant are particularly interesting. Examples of these matrices are described in WO9222600 and W09512629. Biological activity In vivo activity of these compounds was determined m ten day-rats, which were subcutaneously injected (s.c. ) with a dose of 300 μg/kg or with different doses in dose-response studies, according to what described in detail by R. Deghenghi et. al, Life Sciences 54, 1321, (1994). The results are resumed in the Table below, the released GH was measured after 15 minutes from the treatment . The GHRP-2 (reference standard) has the structure D-Ala-D-β-Nal-Ala-Trp-D-Phe-Lys-NH 2 (Chen and Clarke, J. Neuroend. 7, 179 (1995). TABLE Peptide Dose yg/kg s.c GH control GH released (ng/ml) (ng/ml) His-D-Mrp-Ala-Trp-DPhe- 300 31±8 176120 Lys-Thr-NH 2 His-D-Mrp-Ala-Trp-DPhe- 300 31+8 169±27 Lys-D-Thr-NH 2 D-Thr-D-Mrp-Ala-Trp-D- 300 31+8 266120 Phe-Lys-D-Thr-NH 2 D-Thr-His-D-Mrp-Ala-Trp-D- 300 31+8 86119 Phe-Lγs-NH 2 D-Ala-D-Mrp-Ala-Trp-D- 40 34+1 200120 Phe-Lys-NH 2 D-Ala-D-Mrp-Ala-Trp-D- 320 34+1 251132 Phe-Lys-NH 2 - continued - continued - TABLE Peptide Dose μg/kg s.c. GH control GH released (ng/ml) (ng/ml) His-D-Mrp-Ala-Trp-NH 2 5000 69114 124137 imidazolacetyl-D-Mrp- 300 2013 159127 Ala-Trp-D-Phe-Lys-NH 2 INIP-D-Mrp-D-Trp-Phe- 300 15 155 Lys-NH 2 INIP-D-Mrp-D-β-Nal- 300 15 150 Phe-Lys-NH 2 GAB-D-Mrp-D-Trp-Phe-Lys-NH 2 300 10 110 (GHRP-2) 300 10 98.6 In vitro activity on adenylcyclase activity was measured in anterior pituitary gland cells from rats weighing 150 g and showed a 30% increase compared with the baseline with n for the peptide D-Ala-D- Mrp-Ala-Trp-D-Phe-LysNH 2 , whereas GHRP-6 (His-D-Trp-Ala- Trp-D-Phe-LysNH 2 ) resulted inactive. The following examples further illustrate the invention. EXAMPLE 1 Synthesis of GAB-D-Mrp-D-Trp-Phe-Lvs-NH 2 (Mrp= 2- methylthryptophan) . The synthesis was carried out by solid-phase with 9-fluorenylmethyloxycarbonyl (Fmoc )-ammoacιds involving resm preparation, assembly in a reactor column according to one of several methods available to the skilled m the art, as exemplified in "Solid phase peptide synthesis" by E.Atherton and R.C. Sheppard, IRL press at Oxford University press, 1989. The protected ammo acids are Fmoc-Lys(Fmoc )-Opfp (Opfp=pentafluorophenyl ester), Fmoc-Phe-Opfp, Fmoc-D- Trp-Opfp, Fmoc-2-MeTrp-Opfp and F oc-GAB-Opfp (GAB=gamma-ammobutyrιc ) . Alternatively, the use of Castro's reagents, BOP and PyBOP (cfr. Le Nguyen and Castro (1988) in Peptide Chemistry 1987, p.231-238. Protein Research Foundation Osaka; and Tetrahedron Letters 31,205 (1990) can also be used advantageously as direct coupling reagents. After cleavage and isolation, the title peptide was purified as acetate salt. Purity (HPLC): 98%, MW (M+H + )=764.3 (theoretιcal=763.9 ) . EXAMPLE 2 According to the procedures described in Example 1, the following peptides were prepared and obtained as acetate salts: INIP-D-Mrp-D-Trp-Phe-Lys-NH 2 ; purity (HPLC)=99.0% , MW (M+H + =790.4; theoretιcal=790.0 ) INIP-D-Mrp-D-β-Nal-Phe-Lys-NH 2 ; purity (HPLC)=96.5% , MW (M+H + =801.4; theoretιcal=801.0 ) IMA-D-Mrp-D-Trp-Phe-Lys-NH 2 ; purity (HPLC)=99.2% , MW (M+H + =786.5; theoretιcal=786.8 ) IMA-D-Mrp-D-β-Nal-Phe-Lys-NH 2 ; purity ( HPLC )=97.3% , MW (M+H + =798.3; theoretιcal=797.9 ) GAB-D-Mrp-D-β-Nal-Phe-Lys-NH 2 ; 4 - ( ami nome thy 1 eye lohexanecar bony 1-D-Mrp-D-Tr p-Phe-Lys - NH 2 ; 4- ( ammomethyl ) c ιclohexanecarbonyl-D-Mrp-D-β-Nal-Phe- Lys-NH 2 ; D-Ala-D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; D-Thr -D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; Hιs-D-Mrp-Ala-Phe-D-Trp-LysNH 2 ; Tyr-Hιs-D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; Hιs-D-Mrp-Ala-TrpNH 2 ; D-Thr-D-Mrp-Ala-TrpNH 2 ; wherein Mrp is 2-methyltryptopha , INIP, IMA and GAB are as defined above.

Claims: CLAIMS 1. A peptide of formula: A-D-Mrp-(Ala) n -B-C wherein A is any natural L-ammo acid or its D-isomer, with the proviso that A is not His if B is Trp and C is D-Lys-NH 2 ; or A is lmidazoleacetyl , isonipecotyl , 4- ammobutyryl, 4-( ammomethyl )cyclohexanecarbonyl , Glu- Tyr-Ala-His, Tyr-Ala-His, Tyr-His, D-Thr-His; D relates to the dextro isomer, Mrp is 2-alkyltryptophan; n is 0 or 1; B is L- or D-Trp, Phe or D-β-Nal; C is NH 9 , D-Trp- LysNH 2 , D-Phe-LysNH 2 , Phe-LysNH 2 , D-Phe-Lys-ThrNH 2 , D- Phe-Lys-D-ThrNH 2 , OR, wherein R is a C.-C-^ alkyl group, and the addition salts with pharmaceutically acceptable organic or inorganic acids of anyone of said polypeptides . 2. A peptide according to claim 1, wherein Mrp is selected from 2-methyltryptophan, 2-ethyltryptophan, 2- propyltryptophan, 2-ιsopropyltryptophan. 3 A peptide according to claim 1, wherein Mrp is 2- methyltryptophan. 4. A peptide according to claim 1, wherein A is lmidazoleacetyl, isonipecotyl, 4-amιnobutyryl , D-Ala, D- Thr , Tyr . 5. A peptide according to claim 1, wherein C is Phe- LysNH 2 , D-Trp-LysNH 2 , NH 2 , or, wherein R is a C-*_-C 3 alkyl group, . 6. A peptide according to claim 1, selected from in the group consisting of: IMA-D-Mrp-D-Trp-Phe-LysNH 2 ; IMA-D-Mrp-D-β-Nal-Phe-LysNH 2 ; INIP-D-Mrp-D-Trp-Phe-LysNH 2 ; INIP-D-Mrp-D-β-Nal-Phe-LysNH 2 ; GAB-D-Mrp-D-Trp-Phe-LysNH 2 ; GAB-D-Mrp-D-β-Nal-Phe-LysNH 2 ; GAB-D-Mrp-D-β-Nal-NH 2 ; GAB-D-Mrp-D-β-Nal-OC 2 H 5 ; 4-(ammomethyl )cyclohexanecarbony1-D-Mrp-D-Trp-Phe-Lys- NH 2 ; 4-( ammomethyl )cyclohexanecarbonγl-D-Mrp-D-β-Nal-Phe- Lys-NH 2 . 7. A peptide according to claim 1, selected from the group consisting of: Imιdazolacetyl-D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; D-Ala-D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; D-Thr-D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; Hιs-D-Mrp-Ala-TrpNH 2 ; D-Thr-D-Mrp-Ala-TrpNH 2 ; Hιs-D-Mrp-Ala-Phe-D-Trp-LysNH 2 ; D-Thr-D-Mrp-Ala-Trp-D-Phe-Lys-D-ThrNH 2 ; D-Thr-Hιs-D-Mrp-Ala-Trp-D-Phe-LysNH 2 ; Hιs-D-Mrp-Ala-Trp-D-Phe-Lys-ThrNH 2 ; Hιs-D-Mrp-Ala-Trp-D-Phe-Lys-D-ThrNH 9 . 8. A peptide according to claim 6 or 7 , wherein Mrp is 2-methyltryptophan. 9. The use of the peptides of claims 1-8 for the manufacturing of a medicament useful for promoting the release of growth hormone in an animal. 10. The use according to claim 9, wherein the medicament is useful in human medicine. 11. The use of the peptides of claim 7 for the manufacturing of a medicament useful to promote the increase of the mtracellular activity of adenylcyclase. 12. Pharmaceutical compositions comprising an effective amount of at least a peptide of claims 1-8 as active ingredient, optionally in admixture with carriers and excipients . 13. Compositions according to claim 12 in the form of compositions for parenteral , mtranasal, oral, controlled release administration, subcutaneous implants .

Inventors: DEGHENGHI ROMANO, DEGHENGHI, ROMANO
Applicants: DEGHENGHI ROMANO, DEGHENGHI, ROMANO
Application year: 1995
Main classification: C07K14
IPC codes: A61K38, A61P5, C07K5, C07K7, C07K14