This invention relates to benzodiazepine derivatives which are useful as drugs exhibiting antagonism at the gastrin and/or CCK-B receptor, and to their production.

Many benzodiazepine derivatives have been described in the course of development of psychotropic drugs which act as agonists at the "benzodiazepine receptor" in the central nervous system. More recently benzodiazepine derivatives have been described which act as antagonists at the CCK-A (cholecystokinin-A) and CCK-B receptors. It was further repoπed that those compounds which were selective antagonists for the CCK-B receptor were able to reduce the secretion of gastric acid in response to the administration of pentagastrin (V J Lotti & R S L Chang, Eur J Pharmacol 1989, 162, 273-280). Examples of benzodiazepine derivatives which act as antagonists at the CCK-B receptor are disclosed in, for example, U.S. Patent No. 4,820,834.

The compounds of the present invention are novel. They differ from the compounds described in U.S. Patent No. 4,820,834, particularly in the nature of the substituent at position 1 of the benzodiazepine nucleus. The present invention includes compounds of superior pharmacological characteristics than those described in U.S. Patent No. 4,820,834; preferred compounds of the invention have a higher affinity for the CCK-B receptor and/or discriminate more selectively between the CCK-B and CCK-A receptors than the previously described compounds.

The present invention provides a benzodiazepine derivative of formula I, or a pharmaceutically acceptable salt thereof:.

wherein:

(a) R ¹ is selected from alkyl and cycloalkyl groups.

(b) R ² is a tertiary cyclic amino substituent of structure II, HI or IV,

π m IV in which a is 1 - 6.

(c) X is either CH or N.

Herein alkyl and cycloalkyl groups are preferably of up to 8 carbon atoms. Examples of alkyl and cycloalkyl groups include rerr-butyl, cyclopentyl and cyclohexylmethyl. Most preferably R ¹ is rerr-butyl. Most preferably R ² is azetidinyl, pyrroiidinyl or piperidinyl.

The compounds of this invention all have at least one stereogenic centre and so can exist as optical isomers. It should be understood that these isomers, either separately or as mixtures, are included within the scope of this invention. In preferred compounds according to the invention, the absolute configuration at the 3-position of the benzodiazepine ring is R (as shown in V).

In addition, the compounds of this invention can form salts with inorganic or organic acids or, in some cases, bases. Examples of such salts would include chlorides, sulphates and acetates, or sodium and potassium salts. These salts should be understood to be included within the scope of this invention.

Compounds according to the invention act as CCK-B and gastrin receptor antagonists. They may be used as drugs for the treatment of diseases induced by the failure of a physiological function controlled by gastrin, such as gastric and duodenal ulcers, gastritis, reflux esophagitis, gastric and colon cancers, and Zollinger-Ellison syndrome; there may be no side effects arising from CCK-A receptor interaction. They may be used as drugs for the treatment of diseases induced by the failure of physiological function controlled by the central CCK-B receptor (e.g. for the reduction of anxiety or for appetite regulation).

Amongst preferred compounds according to the invention are those listed below and salts thereof. Some of the compounds are exemplified hereinafter as indicated against the individual compounds concerned.

1. N-((3R)-l-rerr-Butylcarbonylmethyl-2,3-dihydro-2-oxo-5-(2-py ridyl)-lH-l,4- benzodiazepin-3-yl-N'-(3-(l-pyrτolidinyl)phenyl) urea (Example 1);

2. N-((3R)- l-rerr-Butylcarbonylmethyl-2,3-dihydro-2-oxo-5-phenyl-lH- 1,4- benzodiazepin-3-yl-N'-(3-(l-pyrrolidinyl)phenyl) urea (Example 2);

3. N-((3R)- l-rerr-Butylcaxbonylmethyl-2,3-dihydro-2-oxo-5-(2-pyridyl)-l H-l ,4- benzodiazepin-3-yl-N'-(3-( 1 -azetidinyl)phenyl) urea;

4. N-((3R)- 1 -rerr-Butylcarbonylmethyl-2,3-dihydro-2-oxo-5-(2-pyridyl)- 1H- 1 ,4- benzodiazepin-3-yl-N'-(3-( 1 -piperidinyl)phenyl) urea;

5. N-((3R)-l-rerr-Butylcarbonylmethyl-2,3-dihydro-2-oxo-5-(2-py ridyl)-lH-l,4- benzodiazepin-3-yl-N'-(3-(l-hexamethyleneimino)phenyl) urea.

The compounds of the invention can be prepared according to the route outlined in Scheme 1 below.

Scheme I

The starting material VI is prepared according to procedures described in Intemational Patent Application No. PCT/GB 93/00404.

This general method will now be further illustrated with specific, non-limiting examples.

- -) -

Example 1: N-((3R)-l-rgrr-Butylcarbonylmethyl-2.3-dihvdro-2-oxo-5-(2-Py ridyl')-lH- l,4-benzodiazepin-3-yl-N'-(3-(l-pyrrolidinyl)phenyl ^' ) urea

NHCONH .,

IA 3-(l-pyττolidinvπbenzoic acid m-Amino benzoic acid (13.7 g, 0.1 mol) was taken up in methanol (150 ml) and cooled to O°C. Acetyl chloride (10 ml) was added dropwise, and then the mixture heated under reflux, under nitrogen for 14 h. The mixture was cooled, evaporated and partitioned between EtOAc and 5% KHCO ₃ . The organic portion was washed with brine, filtered (Whatman IPS, phase separator) and evaporated to provide a brown oil which crystallised on standing (13.2 g, 88%).

A portion of the amino ester (5.45 g, 36.1 mmol) was taken up in dry DMF (70 ml) and treated with sodium hydride (3.78 g, 80% disp. in oil, 126 mmol) at O°C under nitrogen for H h. 1,4-dibromobutane (14.05 g, 65 mmol) and potassium iodide (0.6 g, 3.7 mmol) were added and the mixture heated at 80°C for 72 h. The mixture was cooled, evaporated and partitioned between EtOAc and 5% KHCO ₃ . The organic portion was washed with brine, filtered (Whatman IPS, phase separator) and evaporated. The residue was chromatographed on silica (eluant 8% EtOAc hexane) to provide a pale yellow solid (1.70 g, 23%).

The solid was taken up in dioxan/water (40 ml) and treated with LiOH_7H ₂ O (1.75 g, 5 eq) at room temperature for 10 min, then at 40°C for 30 min. Acetic acid (10 ml) was added and the mixture was evaporated, azeotroped with toluene and crystallised from AcOH/water/dioxan to provide a pale brown solid (1.26 g, 80%) which was dried in vacuo over P ₂ O ₅ .

^l Η. NMR (270 MHz, CDC1 ₃ ) δ 7.4 - 7.2 (3H, m); 6.78 (1H, m); 3.35 (4H, m); 2.02 (4H, m) ppm.

IB . (3RS)-Amino-l-rgrr-butylcarbonylmethyl-2.3-dihvdro-5-(2-pyri dylVlH-1.4- benzodiazepin-2-one

The tide compound was prepared as described previously in Intemational Patent Application No. PCT/GB 93/00404.

1C (3R)-Amiho-l-rgrr-butylcarbonylmethyI-2.3-dihvdro-5-(2-pyrid yl)-lH-1.4- benzodiazepin-2-one

The benzodiazepine of example IB (14 g, 40 mmol) was taken up in cold acetonitrile (50 ml) and (R)-mandelic acid added (3.2 g, 21 mmol). The mixture was stirred at -5°C for 1 h and the resultant precipitate collected. Tne precipitate was recrystallised from acetonitrile, then partitioned between 5% KHCO ₃ ^an ^ CHC1 ₃ . The organic portion was washed with brine, dried and evaporated to provide a colourless foam (4.42 g, 32% of amine).

[α] _D = +213° (c = 0.46, CHC1 ₃ ). ^l Η. NMR (270 MHz, CDC1 ₃ ) δ 8.58 (1H, d, J = 7Hz); 8.06 (1H, d, J = 7Hz); 7.75 (1H, t, J = 7Hz); 7.42 (1H, t, J = 7Hz); 7.3 - 7.0 (5H, m); 5.0 (1H, d, J = 17Hz); 4.60 (1H, s); 4.39 (1H, d, J = 17Hz); 2.2 (2H, br.s); 1.22 (9H, s) ppm.

ID (N-((3RVl-rgrr-Butylcarbonylmethyl-2.3-dihvdro-2-oxo-5-(2-Dy ridylVlH-1.4- benzodiazepin-3-yl-N'-(3-pyrrolidinyl ^' .phenyl ^' , urea

3-(l-pyrollidyl)benzoic acid (955 mg, 5 mmol) was taken up in benzene (20 ml) arid triethylamine (1.2 mi) under nitrogen. Diphenyl phosphoryl azide (2.25 g) was added and the mixture heated under reflux 3 h. The mixture was cooled and evaporated and treated with a solution of the benzodiazepine of example 1C (740 mg, 2.114 mmol) in DCM (8 ml). The mixture was stirred at room temperature for 1 h, then evaporated and chromatographed (eluant 65% EtOAc in hexanes — ^» 90% EtOAc in hexanes) to provide a white solid which was recrystallised from acetonitrile (780 g, 69%).

[α] _D = +121.4° (c = 0.331, CHC1 ₃ ). ^l ΕL NMR (270 MHz, CDC1 ₃ ) δ 8.60 (1H, dd, J _t = 4Hz, J ₂ = 1Hz); 8.15 (1H, d, J =

8Hz); 7.78 (1H, dt, Jd = 1Hz, Jt = 8Hz); 7.5 - 7.0 (6H, m); 6.90 (1H, s);

6.72 (1H, m); 6.46 (1H, d, J = 8Hz); 6.26 (1H, d, J = 8Hz); 5.72 (1H, d, J =

8Hz); 4.96 (1H, d, J = 18Hz); 4.50 (1H, d, J = 18Hz); 3.24 (4H, m); 2.0

(4H, m); 1.22 (9H, s) ppm. M.S . (FAB +ve) ion [M+H] ⁺ = 539.

Example 2: N-(3R)-l-rgrr-Butylcarbonylmethyl-2.3-dihvdro-2-oxo-5-phenyl -lH-1.4- benzodiazepin-3-yl-N'-(3-(l-pyrrolidinyl'.phenyl') urea.

2A 3R-Amino-l-rgrr-butylcarbonylmethyl-2.3-dihvdro-5-phenyl-lH- 1.4-benzodiazepin- 2-one

The title compound was prepared as described previously by racemisation-resolution of the RS-amine (Intemational Patent Application No. PCT/GB 93/00404).

2B N-(3R)-l-rgrr-Butylcarbonylmethyl-2.3-dihvdro-2-oxo-5-phenyl -lH-1.4-benzodiazepin- 3-yl-N'-(3-(l-pyrrolidinyl)phenyπ urea.

3-(l-pyrrolidiπyi)phenyl isocyanate was prepared as described in example ID and treated widi the benzodiazepine of example 2A (280 mg, 0.8 mmol). The crude product was evaporated and chromatographed (eluant CHCl ₃ EtOAc, 1/1, v/v) to provide the tide compound as a white solid (276 mg, 64%).

^•• H NMR (270 MHz, CDC1 ₃ ) δ 7.65 - 6.96 (13H, m); 6.46 (1H, d, J = 8Hz); 6.25 (1H, d, J = 8Hz); 5.67 (1H, d, J = 8Hz); 4.88 (1H, d, J = 17Hz); 4.74 (1H, d, J = 17Hz); 3.25 (4H, m); 1.94 (4H, m); 1.16 (9H, s) ppm.

M.S. (FAB +ve ion) [M+H] ⁺ = 538.

Compounds 3 - 5 are obtainable by methods analogous to those described in the above examples.

The compounds of the present invention are potent and selective antagonists at the CCK-B receptor and inhibit gastric acid secretion stimulated by pentagastrin. The methods of measuring these activities are described below:

Measurement of binding affinity for CCK-B receptors

About 100 SD rats were decapitated without anaesthesia, the whole brain was immediately excised from each of the rats and homogenized in 10-fold volume of 0.32 M aqueous solution of sucrose by the use of a Teflon-coated homogenizer, the homogenate thus obtained was centrifuged for ten minutes at 900 g by the use of a cooled centrifuge, and the supernatant was further centrifuged for 15 minutes at 11500 g. The precipitate thus obtained was dispersed in 50 mM Tris-HCl buffer (pH 7.4) containing 0.08% Triton X-100, this suspension was allowed to stand for 30 minutes and again centrifuged for 15 minutes at 11500 g, the precipitate thus obtained was washed twice with 5 mM Tris-HCl buffer and twice with 50 mM Tris-HCl buffer in that order with centrifugal separation, the washed precipitate- was suspended in 50 mM Tris-HCl buffer, and the suspension thus obtained was stored at -80°C until d e membrane preparation was required.

The membrane preparations were warmed to room temperature, diluted witii 10 mM HEPES buffer (containing 130 mM NaCl, 5 mM MgCl ₂ , 1 mM EGTA and 0.25 mg/ml bacitracin; pH 6.5) and incubated at 25°C for 120 minutes in the presence of [ ^{1 5} I]BH-CCK-8 and the test compound, ti en separated by suction filtration. Non-specific binding was determined in d e presence of 1 μM CCK-8. The amount of labelled ligand bound to die receptor was measured by d e use of a γ-counter, IC ₅₀ values were determined, being that concentration of test compound required to inhibit specific binding by 50%.

Measurement of binding affinity for CCK-A receptors

The pancreas of an SD rat was homogenized in a 20- fold volume of 50 mM Tris-HCl buffer (pH 7.7) by the use of a Polytrone-type homogenizer, the homogenate was twice centrifuged for 10 minutes at 50000 g by the use of an ultra-centrifuge, the precipitate thus obtained was suspended in a 40-fold volume of 50 mM Tris-HCl buffer (containing 0.2% BSA, 5 mM MgCl ₂ , 0.1 mg/ml bacitracin and 5 mM DTT; pH 7.7), and d e suspension was stored at -80°C until the membrane preparations were required.

The membrane preparations were d en wanned to room temperature, diluted 1:10 witii die buffer and incubated at 37°C for 30 minutes in the presence of [ ³ H]L-364,718 and die test compound d en separated by suction filtration. Non-specific binding was determined in d e presence of 1 μM L-364,718. The amount of labelled ligand bound to d e receptor was measured by the use of a liquid scintillation counter, IC ₅₀ values were determined, being that concentration of test compound required to inhibit specific binding by 50%.

A high affinity for the CCK-A receptor in a CCK-B/gastrin antagonist is thought to be undesirable as it may lead to side-effects such as cholestasis and gall stone formation during dierapy. Therefore it is preferable for the therapeutic agent to be selective for the CCK-B receptor. This selectivity is expressed by the ratio I _Q (CCK-Ayi o (CCK-B); the higher the value of this ratio die better is the selectivity.

The table below summarises CCK-B and CCK-A binding data for examples of preferred compounds, as well as the A/B ratio. Many compounds display a marked increase in CCK-B receptor binding affinity when compared to the compound of Example 281 of U.S. Patent No. 4,820,834 (also known as L-365,260). Several compounds also show much greater selectivity for the CCK-B receptor over the CCK-A receptor than that reported for die compound of Example 281 of U.S. Patent No. 4,820,834.

Receptor binding affinity IC^n (πM)

Compound CCK-B CCK-A A/B Ratio

Compound of Example 281 of US Patent No. 4,820,834 29 12,000 410

Example 1 0.11 - -

Example 2 0.17 160 940

Measurement of inhibition of pentagastrin-stimulated gastric acid secretion in rat

A cannula was inserted into the trachea of a rat anaesthetised wid urεthane (intraperitoneally administered, 1.25 g/Kg), its abdominal wall was incised to expose the gastric and duodenal portions, and a polyethylene cannula was set in the anterior stomach after ligation of the cardia. The duodenum was men subjected to slight section, a polyediylene cannula was inserted from the incised portion toward the stomach, and d e pylorus was ligated to fix the cannula.

Physiological saline (with pH adjusted to 7.0) was perfused from the anterior stomach toward die pylorus at a rate of 3 ml/min, and the gastric-acid secretion was measured by continuous titration of die perfusate by the use of a pH-stat (AUT-201; product of Toa Electronics, Ltd.). The continuous titration was carried out by using 25 mM NaOH solution until me pH reached 7.0, and die result was expressed as die amount of gastric acid secreted for every 10 minutes (μE _q /10 min.). Pentagastrin was intravenously administered at a rate of 15 μg/Kg/hr.

The secretion of gastric acid increased upon administration of pentagastrin, reaching the maximum level after 60 minutes and stably maintaining tiiis level after diat. A test drug was dien intravenously administered, and the secretion of gastric acid was measured. The effect of each drug was calculated as d e percentage inhibition of stimulated acid ouφut at 0.1 μmol/kg dose of drug. The table below shows the maximum inhibition observed for representative examples. Each result is a mean for 3 - 5 animals.

% Inhibition at 0.1 μmol/kg

Compound of Example 281 of 28 US Patent No. 4,820,834 (at 0.3 μmol/kg)

Compound of Example 1 75.0

Compound of Example 2 79.3

The experiments described above demonstrate that d e compounds of d e present invention are potent and selective CCK-B antagonists and tiiat they inhibit the stimulation of gastric acid release due to pentagastrin. They are therefore useful in the treatment of disease states in which the CCK-B or gastrin receptor is implicated as a mediating factor. Such disease states would include disorders of d e gastro-intestinal system, for example gastric and duodenal ulceration, gastritis, reflux esophagitis, Zollinger-EUison syndrome, gastrin- sensitive pancreas, and gastrin-sensitive tumors. Disorders of d e central nervous system such as anxiety and psychoses would also be amenable to treatment with d e compounds of this invention. The compounds can also be used in the control of appetite and pain.

The compounds of this invention and salts thereof can be administered orally (including sublingual administration) or parenterally in the form of tablets, powders, capsules, pills, liquids, injections, suppositories, ointments and adhesive plasters.

The carrier and excipient for pharmaceutical manufacturing can be a solid or liquid, non-toxic medicinal substance, such as lactose, magnesium stearate, starch, talc, gelatin, agar, pectin, gum arabic, olive oil, sesame oil, cocoa butter, ethylene glycol and odier commonly employed materials.

Examples of formulations using the compounds of this invention are described below.

Examples of tablet preparation

Composition 20 mg-Tablet 40 mg-Tablet

Compound of Example 4 20 mg 40 mg Lactose 73.4 80 Corn Starch 18 20

Hydroxypropylcellulose 4 5 Carboxymethylcellulose Ca 4 4.2 Mg Stearate 0.6 0.8

Total 120 mg 150 mg

Preparation of 20 mg-tablets

Compound of Example 4 (100 g), lactose (367 g) and com starch (90 g) were homogeneously mixed together by die use of a flow granulating coater (product of Ohgawara Seisakusho), 10% aqueous solution of hydroxypropylcellulose (200 g) was sprayed into die mixture, and granulation was dien performed. After drying, the granules were filtered through a 20-mesh sieve, 20 g of carboxymethylcellulose Ca and 3 g of magnesium stearate were then added, and die mixture was treated in a rotary tablet machine equipped with a,pesde of 7 mm x 8.4 R (product of Hata Tekkosho), tiius producing tablets each weighing 120 mg.

Preparation of 40 mg-tablets

Compound of Example 4 (140 g), lactose (280 g) and com starch (70 g) were homogeneously mixed togedier by the use of a flow granulating coater (product of Ohgawara Seisakusho), 10% aqueous solution of hydroxypropylcellulose (175 g) was sprayed into die mixture, and granulation was dien performed. After drying, the granules were filtered dirough a 20-mesh sieve, 14.7 g of carboxymediylcellulose Ca and 2.8 g of magnesium stearate were then added, and die mixture was treated in a rotary tablet machine equipped widi a pestie of 7.5 mm x 9R (product of Hata Tekkosho), thus producing tablets each weighing 150 mg.

The clinical dosage of the compounds of this invention will be determined by die physician taking into account the precise illness, and the body weight, age, sex, medical history and other factors of the patient to be treated. In general the dosage when administered orally will be between 1 and 1000 mg day in either a single dose or sub-divided into smaller multiple doses.