The present invention relates to new vasotocin derivatives, more specifically such vasotocin deriva¬ tives as differ from the native hormone in that the vasotocin (VT) structure has been modified at posi- tions 1, 2 and 8.

The new VT derivatives are vasoactive, more par¬ ticularly by specifically raising the blood pressure, and in some cases have a considerably prolonged effect. Background The peptide hormone vasopressin, produced by the posterior lobe of the pituitary, mainly has two functions, that is the hormone has both an antidiuretic effect (reduced excretion of urine) and a contracting effect on smooth muscles in the vascular wall, the latter effect causing a blood pressure increase and a reduced tendency to bleeding. In clinical use, vasopres¬ sin thus has a non-specific effect of short duration.

Today, there is on the market a vasopressin analog having a prolonged effect, namely lysine-vasopressin extended in the N-terminal by three amino acid residues. This vasopressin analog acts as a so-called prohormone or hormonogen, i.e it increases the duration of the vasopressin effect. The extended vasopressin analog has in itself a very small pharmacological effect which does not occur until the extra N-terminal amino acid residues are cleaved by enzymatic hydrolysis and free lysine-vasopressin is formed. Besides the prolonged effect, such a prohormone is advantageous in that the risk of overdosage is minimised by the limited enzyme capacity of the organism determining the plasma levels of the liberated vasopressin. In this manner, it is possible to avoid excessively high plasma levels of vasopressin leading to increased blood pressure which

may harm the patient. The above-mentioned vasopressin analog however suffers from major drawbacks by having low potency and, like vasopressin, being non-specific. There is a need for vasoconstrictive substances for use as bleeding inhibitors and in so-called ortho- static hypotension, i.e. conditions of blood pressure drop following changes of body position. These agents should specifically increase blood pressure, thus having a low antidiuretic effect in order to avoid water intoxication in patients subjected to long-term treatment. Also, it is advantageous if they exhibit an effect of long duration. Description of the invention

The present new vasoactive peptides specifically increase blood pressure, i.e. they are pressor-specific, meaning a high ratio of blood pressure- to antidiuretic activity. Furthermore they have a considerably pro¬ longed effect in some cases. The compounds according to the invention are intended to be used in a pharma- ceutical composition for inhibiting bleeding and in conditions of blood pressure drop following changes of body position, so-called orthostatic hypotension, and also as general blood pressure increasing agents. The VT derivatives according to the invention are of the formula

1 2 3 4 5 6 7 8 9 Q, -Hmp-Phe-Ile-Gln-Asn-Cys-Pro-X-Gly-NH_,

¹ I 1 ²

where

Hmp = a 2-hydroxy-3-mercaptopropionic acid residue

(-0-CH-C0-) CH~ s-

X = -HN-CH-CO-

^Q ₂

Q, and Q„ are the same or different and are H or from 1 to 3 peptide residues of the same or different natural or unnatural L- or D-amino acids, and n is i, 2 or 3.

The VT derivatives according to the invention can be presented in the form of pharmaceutical compositions in which at least one VT derivative according to the invention is included as active constituent in combi- nation with pharmaceutically acceptable additives and/or diluents. The pharmaceutical compositions according to the invention preferably are in the form of preparations suitable for parenteral administration. They are suit ^¬ ably administered by injection, infusion or intranasal application. The diluent may be e.g. a physiological saline solution.

A pharmaceutical composition according to the invention may contain a specifically blood pressure increasing derivative having a relatively short dura- tion for providing an instant effect, in combination with a specifically blood pressure incresaing derivative having a long duration for providing a prolongation of the effect. Preparation of the VT derivatives according to the in- vention

The VT derivatives according to the invention can be prepared by methods analogous with those which are known in the peptide field.

For instance, the compounds according to the inven- tion can be prepared in conventional manner by coupling amino acids stepwise to one another in liquid phase, e.g. as disclosed by Law, H.B. & Du Vigneaud, V. in Journal

of the American Chemical Society 8_2, (1960) 4579-4581, Zhuze, A.L. , Jδst, K. , Kasafi'rek, E. & Rudinger, J. in Collection of Czechoslovak Chemical Communications 29, (1964), 2648-2662, and modified by Larsson, L.-E. , Lindeberg, G. _f Melin, P. / Pliska, V. in Journal of Medicinal Chemistry 21, (1978), 352-356. The coupling of the amino acids to one another, yielding so-called peptide bonds, can also be effected with a solid phase (generally a resin) as starting material to which the C-terminal of the first amino acid is coupled, whereupon the C-terminal of the next amino acid is coupled to the N-terminal of the first amino acid and so on. Finally, the finished peptide is liberated from the solid phase. In the Examples hereinbelow, this so-called solid phase technique has been used in accordance with the disclosure of Merrifield, R.B., J. Am. Chem. Soc. (1963) 85, 2149, Merrifield, R.B. Biochemistry (1964), 3_, 1385 and Kδnig, . , Geiger, R. , Chem. Ber. (1970), 103, 788. General_ des_criptiqn_ of .synthesis All the VT derivatives prepared in the Examples given below were synthesised on an Applied Biosystems 430A Peptide Synthesizer using a double coupling pro¬ gram with a termination step after the second coupling. The resin used was of 4-methylbenzhydrylamine type with a theoretical loading of 0.66 meq/g (Peptides

International, Louisville, KY, USA). The final product of the synthesis was dried in vacuo overnight. The peptide was then cleaved from the resin by treatment with liquid hydrogen fluoride in the presence of anisole and ethyl-methyl-sulphide as scavengers (HF:anisole:EMS - 10:05:05). After removal of hydrogen fluoride by evapora¬ tion, the resin was suspended in ethyl acetate (100 ml) and filtered. The solid was washed on filter with addi¬ tional ethyl acetate (3x100 ml), and the cleaved peptide was extracted with acetic acid (100 ml). The extract was promptly diluted to a volume of 2 1 with 20% acetic acid in methanol and treated with 0.1 M solution of

iodine in ethanol until a faint brown colour remained. Then a Dowex 1x8 ion exchanger in acetate form (3 g) (Bio-Rad, Richmond, CA) was added and the mixture filtered. The filtrate was evaporated and the residue freeze-dried from 1% acetic acid in water. The product was then purified by reversed phase liquid chromatogra- phy on a column filled with Vydac 20-25 μ (Separation Group, CA) in a suitable system containing acetonitrile in 0.1% trifluoroacetic acid water solution. The samples collected from the column were analysed by analytical high performance liquid chromatography (HPLC) (Varian 5500, Sunnyvale, CA) equipped with a Bondapak C18 column (Millipore, Milford, Mass.). Fractions containing pure substance were pooled, the solvent was evaporated and the product freeze-dried from 1% acetic acid in water. The final HPLC analysis was performed on ready product, and the structure of the peptide was confirmed by amino acid analysis and fast atom bombardment mass spectrometry (FAB MS). All amino acids used during the synthesis were L- amino acids, and they were protected with a tert-butoxy- carbonyl group at the α-amino function. The side chains were protected as follows:

Ser(BZL), Thr(BZL), Tyr(2-BrCbz) , Lys(2-ClCbz) ,

Orn(Cbz), Asp(BZL), Glu(BZL), Arg(Tos), Cys(Mob), Hmp(Acm) , Cys(Ac ) , Orm(Boc) .

The abbreviations within brackets are: BZL = benzyl;

2-BrCbz = 2-bromocarbobenzoxy;

2-ClCbz = 2-chlorocarbobenzoxy;

Cbz = carbobenzoxy;

Tos = tosyl ; Mob = 4-methoxybenzyl ;

Acm = acetamidomethyl ; and

Boc = t-butyloxycarbonyl

The amino acid derivatives were supplied by Bachem

AG, Switzerland.

EXAMPLE 1 l-Hmp-2-Phe-8-Orn-VT [Q _χ = H, n = 3 and Q_ ₂ = H]

The peptide was synthesised according to the gene¬ ral description. 2-hydroxy-mercaptopropionic acid

[S-(p-methoxy)benzyl ] was used for position 1.

Purity (HPLC): 99.5% (27% acetonitrile in 0.1% TFA, retention time 8.13 min at 2 ml/min, detection at 223 nm) .

Amino_acid _analysiε_:

Asp 1.05; Glu 1.02; Pro 1.00; Gly 0.94; He 1.00;

Phe 0.95; Orn 0.91. EXAMPLE 2 l-Hmp-2-Phe-8-Dab-VT

[Q ₁ = H, n = 2, Q ₂ = H]

This analog was synthesised according to the ge¬ neral description and Example 1. Boc Dab(Cbz) was used for coupling at position 8 (Dab = 2,4-diaminobutyric acid) .

Purity (HPLC): 99.5% (24% acetonitrile/0.1% TFA, retention time 6.0 min at 2 ml/min, detection at 223 nm) . Amino_acid _anal sis_:

Asp 1.00; Glu 1.03; Pro 0.97; Gly 1.08;

He 0.98; Phe 0.99.

Example 3 l-Hmp-2-Phe-8-Orn( la)-VT [ Q _τ = H, n = 3, Q ₂ = alanyl]

The synthesis of this compound was performed as in Example 1 with the exception of the amino acid at position 8. Boc-0rn(Ala)-0H was used instead of

Boc-Orn(Cbz)OH. Purity (HPLC): 97.8% (27% acetonitrile/0.1% TFA; retention time 10.09 min at 2 ml/min, detection at 223 nm).

Amino_a_cid _anal_ysis_:

Asp 1.05; Glu 0.95; Pro 1.03; Gly 1.0; Ala 0.98; Cyε 0.87; He 0.73; Phe 0.90; Orn 0.96. EXAMPLE 4 Gly°-l-Hmp-2-Phe-8-Orn-VT l Q ₁ Gly, n = 3 and Q ₂ = H]

The protected nonapeptide Hmp(Acm)-Phe-Ile-Gln- -Asn-Cys(Acm)-Pro-Orn(Boc)-Gly-NH ₂ (500 g; prepared by solid phase method according to the general descrip- tion) was dissolved in DMF (25 ml). Pyridine ( 5 ml ) and previously formed Boc Gly anhydride (10 equivalents! were added at 0°C under vigorous stirring. The reaction mixture was left overnight at room temperature. The pro¬ duct was isolated by precipitation with ethanol and diethyl ether, filtration and drying in vacuo.

The protected decapeptide (Boc-Gly-Hmp(Acm)-Phe- -Ile-Glu-Asn-Cys(Acm)-Pro-Orn(Boc)-Gly-NH ₂ (342 mg, 0.25 mmole) was dissolved in 70% methanol (1500 ml) and a solution of iodine (160 mg) in methanol (375 ml) was added dropwise under stirring. Dowex 1x8 (50 g acetate form) was added and the mixture filtered. The filtrate was evaporated and the residue dried by eva¬ poration with toluene followed by drying in dessicator in vacuo. The product was then treated with TFA (10 ml) containing anisole (1 ml), stirred for 15 min and then treated with diethyl ether (100 ml). The preci¬ pitation was separated by filtration and dried in vacuo. The product was purified by reversed phase liquid chromatography.

Purity (HPLC): 95% (24% acetonitrole/0.1% TFA, retention time 5.8 min at 1 ml/min, detection at 223 nm) . The structure was confirmed by amino acid analysis and FAB MS analysis.

Amino_acid _analy_sis_:

Asp 1.29; Glu 1.00; Pro 0.96; Gly 2.35; Cys 0.44; He 0.82; Phe 0.97; Orn 1.12. Pharmacological tests Vasotocin derivatives according to the invention have been tested for potency of both blood pressure and antidiuretic activity in a so-called 4-point test, i.e. the activity of the test substances has been related to a standard preparation (AVP = arginine- vasopressin) , and the effects of two dose levels for each substance have been analysed. In addition, two known pressor-specific analogs (VT derivatives) have been tested for a comparison, namely l-mpa-2-Phe-8- -Orn-VT (mpa = 3-mercaptopropionyl ) (Huguenin, R.L. , Boissonnas, R.A. , 1966. Helv. Chim. Acta, 49, 711), and 2-Phe-8-Orn-VT (SE-332993, Sandoz).

Blood pressure tests were carried out on anaesthe¬ tised Sprague Dawley rats (about 250 g) , previously treated with dibenamine (Dekanski, J., 1952. Br. J. Phar- macol. 7, 567). Maximal blood pressure increase after intravenous injections of peptide was used as a mea¬ sure of the effect, expressed as intensity.

In addition to potency determination based on ef¬ fect intensity, a measure of the length of the effect has been stated (index of persistence (I.P.), Pliska, V., 1966. Arzheim. Forsch. 16, 886). This dimensionless fac¬ tor is a measure of the effect duration of the respec¬ tive analog in relation to the standard AVP.

Antidiuretic potency was determined with the aid of anaesthetised water-loaded Sprague Dawley rats

(200 g) (Larsson, L.E. , Lindeberg, G. , Melin, P. and Pliska, V., 1978, J. Med. Chem. 21, 353). Maximal in ^¬ crease of urine conductivity after intravenous injec¬ tions was used as effect parameter. In these two tests, a comparison was made between the effects of the respective derivative and the effect of a standard preparation, AVP, and potency was deter-

mined with the aid of a 4-point test and is indicated in international units per milligram (IU/mg) (Stϋrmer, E., i: Handbook of Experimental Pharmacology, 1966, Vol 23, pp 130-189) . The specificity in respect of blood pressure is indicated by the ratio of potency blood pressure/potency antidiuresis (BP/AD).

The pharmacological results are given in Table 1. From Table 1 appears that compounds 4 and 5 accord- ing to the invention exhibit a very high potency in respect of blood pressure increase in relation to the known derivatives 2 and 3 , and an equivalent or higher specificity than the known compounds 1 , 2 and 3. The very high potency in respect of blood pressure increase makes it possible to administer compounds 4 and 5 in considerably lower doses than the known pressor- specific substances 2 and 3. It further appears from Table 1 that compounds 6 and 7, which can be regarded as prodrugs, have surprisingly high blood pressure potency and adequate specificity. Furthermore, they exhibit a considerably prolonged effect as compared with the known substances 1 , 2 and 3.

Example of the preparation of a pharmaceutical compo¬ sition The VT derivative is dissolved in distilled water together with mannitol. The solution is poured into an ampoule, subjected to freeze-drying and is sealed. The contents in the ampoule can then, when desired, be di¬ luted with an isotonic saline solution to a concentra- tion suitable for administration.

TABLE 1