A compound having the formula (I) ##STR1## and solvates thereof, wherein: R.sup.0 represents hydrogen, halogen or C.sub.1-6 alkyl; PA1 R.sup.1 represents hydrogen or C.sub.1-6 alkyl; PA1 R.sup.2 represents the bicyclic ring ##STR2## which may be optionally substituted by one or more groups selected from halogen and C.sub.1-3 alkyl; and PA1 R.sup.3 represents hydrogen or C.sub.1-3 alkyl is disclosed. The compounds are potent and selective inhibitors of cGMP-specific PDE, and are useful in a variety of therapeutic areas where such inhibition is beneficial.

This invention relates to a series of tetracyclic derivatives, to processes 
for their preparation, pharmaceutical compositions containing them, and 
their use as therapeutic agents. In particular, the invention relates to 
tetracyclic derivatives which are potent and selective inhibitors of 
cyclic guanosine 3',5'-monophosphate specific phosphodiesterase (cGMP 
specific PDE) having utility in a variety of therapeutic areas where such 
inhibition is thought to be beneficial, including the treatment of 
cardiovascular disorders. 
Thus, according to a first aspect, the present invention provides compounds 
of formula (I) 
##STR3## 
and solvates (e.g. hydrates) thereof, in which: R.sup.0 represents 
hydrogen, halogen or C.sub.1-6 alkyl; 
R.sup.1 represents hydrogen or C.sub.1-6 alkyl; 
R.sup.2 represents the bicyclic ring 
##STR4## 
which may be optionally substituted by one or more groups selected from 
halogen and C.sub.1-3 alkyl; and 
R.sup.3 represents hydrogen or C.sub.1-3 alkyl. 
The term "halogen" as used herein denotes bromine, chlorine, fluorine and 
iodine. 
The terms "C.sub.1-3 alkyl" and "C.sub.1-6 alkyl" as used herein denote a 
straight or branched alkyl chain such as methyl, ethyl, i-propyl, n-butyl, 
pentyl,hexyl or the like. 
A particularly preferred subgroup of compounds according to the present 
invention are.compounds wherein R.sup.0 represents hydrogen. 
A further preferred subgroup includes compounds wherein R.sup.1 is selected 
from hydrogen, methyl and iso-propyl. 
Preferably, R.sup.2 represents the unsubstituted bicyclic ring 
##STR5## 
A still further subgroup of compounds of formula (I), are compounds wherein 
R.sup.3 represents hydrogen or methyl. 
It is to be understood that the present invention covers all appropriate 
combinations of particular and preferred groupings hereinabove. 
The compounds of formula (I) may contain one or more asymmetric centres and 
thus can exist as enantiomers or diastereoisomers. It is to be understood 
that the invention includes both mixtures and separate individual isomers 
of the compounds of formula (I). Particularly preferred are 6R and 12aR 
isomers. 
Particular individual compounds of the invention include: 
(6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-2-methyl-pyrazino[2', 
1':6,1]pyrido[3,4-b]indole-1,4-dione; 
(6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-pyrazino[2',1':6,1]py 
rido[3,4-b]indole-1,4-dione; 
(3S,6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-3-methyl-pyrazino[ 
2',1':6,1]pyrido[3,4-b]indole-1,4-dione; 
(3S,6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-2,3-dimethyl-pyraz 
ino[2',1':6,1]pyrido[3,4-b]indole-1,4-dione; 
(6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-2-isopropyl-pyrazino[ 
2',1':6,1]pyrido[3,4-b]indole-1,4-dione; 
and physiologically acceptable solvates (e.g. hydrates) thereof. 
A most particular compound of the invention is 
(6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-2-methyl-pyrazino[2', 
1':6,1]pyrido[3,4-b]indole-1,4-dione; 
and physiologically acceptable solvates (e.g. hydrates) thereof. 
It has been shown that compounds of the present invention are potent and 
selective inhibitors of cGMP specific PDE. Thus, compounds of formula (I) 
are of interest for use in therapy, specifically for the treatment of a 
variety of conditions where inhibition of cGMP specific PDE is thought to 
be beneficial. 
As a consequence of the selective PDE 5 inhibition exhibited by compounds 
of the present invention, cGMP levels are elevated, which in turn can give 
rise to beneficial anti-platelet, anti-neutrophil, anti-vasospastic, 
vasodilatory, natriuretic and diuretic activities as well as potentiation 
of the effects of endothelium-derived relaxing factor (EDRF), 
nitrovasodilators, atrial natriuretic factor (ANF), brain natriuretic 
peptide (BNP), C-type natriuretic peptide (CNP) and endothelium-dependent 
relaxing agents such as bradykinin, acetylcholine and 5-HT.sub.1. The 
compounds of formula (I) therefore have utility in the treatment of a 
number of disorders, including stable, unstable and variant (Prinzmetal) 
angina, hypertension, pulmonary hypertension, congestive heart failure, 
renal failure, atherosclerosis, conditions of reduced blood vessel patency 
(e.g. post-percutaneous transluminal coronary angioplasty), peripheral 
vascular disease, vascular disorders such as Raynaud's disease, 
inflammatory diseases, stroke, bronchitis, chronic asthma, allergic 
asthma, allergic rhinitis, glaucoma, erectile dysfunction and diseases 
characterised by disorders of gut motility (e.g. irritable bowel 
syndrome). 
It will be appreciated that references herein to treatment extend to 
prophylaxis as well as treatment of established conditions. 
It will also be appreciated that `a compound of formula (I),` or a 
physiologically acceptable salt or solvate thereof can be administered as 
the raw compound, or as a pharmaceutical composition containing either 
entity. 
There is thus provided as a further aspect of the invention a compound of 
formula (I) for use in the treatment of stable, unstable and variant 
(Prinzmetal) angina, hypertension, pulmonary hypertension, chronic 
obstructive pulmonary disease, congestive heart failure, renal failure, 
atherosclerosis, conditions of reduced blood vessel patency, (e.g. 
post-PTCA), peripheral vascular disease, vascular disorders such as 
Raynaud's disease, inflammatory diseases, stroke, bronchitis, chronic 
asthma, allergic asthma, allergic rhinitis, glaucoma, erectile dysfunction 
or diseases characterised by disorders of gut motility (e.g. IBS). 
According to another aspect of the invention, there is provided the use of 
a compound of formula (I) for the manufacture of a medicament for the 
treatment of stable, unstable and variant (Prinzmetal) angina, 
hypertension, pulmonary hypertension, chronic obstructive pulmonary 
disease, congestive heart failure, renal failure, atherosclerosis, 
conditions of reduced blood vessel patency, (e.g. post-PTCA), peripheral 
vascular disease, vascular disorders such as Raynaud's disease, 
inflammatory diseases, stroke, bronchitis, chronic asthma, allergic 
asthma, allergic rhinitis, glaucoma, erectile dysfunction or diseases 
characterised by disorders of gut motility (e.g. IBS). 
In a further aspect, the invention provides a method of treating stable, 
unstable and variant (Prinzmetal) angina, hypertension, pulmonary 
hypertension, chronic obstructive pulmonary disease, congestive heart 
failure, renal failure, atherosclerosis, conditions of reduced blood 
vessel patency, (e.g. post-PTCA), peripheral vascular disease, vascular 
disorders such as Raynaud's disease, inflammatory diseases, stroke, 
bronchitis, chronic asthma, allergic asthma, allergic rhinitis, glaucoma, 
erectile dysfunction or diseases characterised by disorders of gut 
motility (e.g. IBS) in a human or non-human animal body which comprises 
administering to said body a therapeutically effective amount of a 
compound with formula (I). 
Compounds of the invention may be administered by any suitable route, for 
example by oral, buccal, sub-lingual, rectal, vaginal, nasal, topical or 
parenteral (including intravenous, intramuscular, subcutaneous and 
intracoronary) administration. Oral administration is generally preferred. 
For administration to man in the curative or prophylactic treatment of the 
disorders identified above, oral dosages of a compound of formula (I) will 
generally be in the range of from 0.5-800 mg daily for an average adult 
patient (70 kg). Thus for a typical adult patient, individual tablets or 
capsules contain from 0.2-400 mg of active compound, in a suitable 
pharmaceutically acceptable vehicle or carrier, for administration in 
single or multiple doses, once or several times per day. Dosages for 
intravenous, buccal or sublingual administration will typically be within 
the range of from 0.1-400 mg per single dose as required. In practice the 
physician will determine the actual dosing regimen which will be most 
suitable for an individual patient and it will vary with the age, weight 
and response of the particular patient. The above dosages are exemplary of 
the average case but there can be individual instances in which higher or 
lower dosage ranges may be merited, and such are within the scope of this 
invention. 
For human use, a compound of the formula (I) can be administered alone, but 
will generally be administered in admixture with a pharmaceutical carrier 
selected with regard to the intended route of administration and standard 
pharmaceutical practice. For example, the compound may be administered 
orally, buccally or sublingually, in the form of tablets containing 
excipients such as starch or lactose, or in capsules or ovules either 
alone or in admixture with excipients, or in the form of elixirs or 
suspensions containing flavouring or colouring agents. Such liquid 
preparations may be prepared with pharmaceutically acceptable additives 
such as suspending agents (e.g. methylcellulose, a semi-synthetic 
glyceride such as witepsol or mixtures of glycerides such as a mixture of 
apricot kernel oil and PEG-6 esters or mixtures of PEG-8 and 
caprylic/capric glycerides). A compound may also be injected parenterally, 
for example intravenously, intramuscularly, subcutaneously or 
intracoronarily. For parenteral administration, the compound is best used 
in the form of a sterile aqueous solution which may contain other 
substances, for example salts, or monosaccharides such as mannitol or 
glucose, to make the solution isotonic with blood. 
Thus, the invention provides in a further aspect a pharmaceutical 
composition comprising a compound of the formula (I) together with a 
pharmaceutically acceptable diluent or carrier therefor. 
There is further provided by the present invention a process of preparing a 
pharmaceutical composition comprising a compound of formula (I), which 
process comprises mixing a compound of formula (I) together with a 
pharmaceutically acceptable diluent or carrier therefor. 
A compound of formula (I) may also be used in combination with other 
therapeutic agents which may be useful in the treatment of the 
above-mentioned disease states. The invention thus provides, in another 
aspect, a combination of a compound of formula (I) together with another 
therapeutically active agent. 
The combination referred to above may conveniently be presented for use in 
the form of a pharmaceutical formulation and thus pharmaceutical 
compositions comprising a combination as defined above together with a 
pharmaceutically acceptable diluent or carrier comprise a further aspect 
of the invention. 
The individual components of such a combination may also be administered 
either sequentially or simultaneously in separate pharmaceutical 
formulations. 
Appropriate doses of known therapeutic agents for use in combination with a 
compound of formula (I) will be readily appreciated by those skilled in 
the art. 
Compounds of formula (I) may be prepared by any suitable method known in 
the art or by the following processes which form part of the present 
invention. In the methods below R.sup.0, R.sup.1, R.sup.2 and R.sup.3 are 
as defined in formula (I) above unless otherwise indicated. 
Thus, a first process (A) for preparing a compound of formula (I) comprises 
treating a compound of formula (II) 
##STR6## 
(in which Alk represents C.sub.1-6 alkyl, e.g. methyl or ethyl, and Hal is 
a halogen atom, e.g. chlorine) with a primary amine R.sup.1 NH.sub.2 in a 
suitable solvent such as an alcohol (e.g. methanol or ethanol) or a 
mixture of solvents, conveniently at a temperature of from 20.degree. C. 
to reflux (e.g. at about 50.degree. C.). 
According to a second process (B) for preparing a compound of formula (I) 
comprises hydrogenating a compound of formula (III) 
##STR7## 
in which Alk is defined as above and Cbz represents a carbobenzyloxy 
group, in the presence of a catalyst e.g. palladium on activated carbon in 
a suitable solvent such as an alcohol, e.g. methanol or ethanol, at 
elevated temperature. 
A compound of formula (II) may conveniently be prepared by treating a 
compound of formula (IV) 
##STR8## 
with a haloacetyl halide (e.g. chloroacetyl chloride) in a suitable 
solvent such as a halogenated hydrocarbon (e.g. trichloromethane or 
dichloromethane), or an ether (e.g. tetrahydrofuran), preferably in the 
presence of a base such as an organic amine (e.g. a trialkylamine such as 
triethylamine) or an alkali metal carbonate or bicarbonate (e.g. 
NaHCO.sub.3). The reaction may conveniently be effected at a temperature 
of from -20.degree. C. to +20.degree. C. (e.g. at about 0.degree. C.). 
A compound of formula (IV) may conveniently be prepared from a tryptophan 
alkyl ester of formula (V) 
##STR9## 
This step comprises a Pictet-Spengler cyclisation between a compound of 
formula (V) and an aldehyde R.sup.2 CHO. The reaction may conveniently be 
effected in a suitable solvent such as a halogenated hydrocarbon (e.g. 
dichloromethane) or an aromatic hydrocarbon (e.g. toluene) in the presence 
of an acid such as trifluoroacetic acid. The reaction may conveniently be 
carried out at a temperature of from -20.degree. C. to reflux to provide a 
compound of formula (III) in one step. The reaction may also be carried 
out in a solvent such as an aromatic hydrocarbon (e.g. benzene or toluene) 
under reflux, optionally using a Dean-Stark apparatus to trap the water 
produced. The reaction provides a mixture of cis and trans isomers which 
may be either individual enantiomers or racemates of pairs of cis or trans 
isomers depending upon whether racemic or enantiomerically pure tryptophan 
alkyl ester was used as the starting material. Individual cis or trans 
enantiomers may conveniently be separated from mixtures thereof by 
fractional crystallisation or by chromatography (e.g. flash column 
chromatography) using appropriate solvents and eluents. Similarly, pairs 
of cis and trans isomers may be separated by chromatography (e.g. flash 
column chromatography) using appropriate eluents. An optically pure trans 
isomer may also be converted to an optically pure cis isomer using 
suitable epimerisation procedures. One such procedure comprises treating 
the trans isomer or a mixture (e.g. 1:1 mixture) of cis and trans isomers 
with methanolic or aqueous hydrogen chloride at a temperature of from 
0.degree. C. to the refluxing temperature of the solution. The mixture is 
then subjected to chromatography (e.g. flash column chromatography) to 
separate the resulting diastereoisomers. 
A compound of formula (III) may be prepared by reaction of a compound of 
formula (IV) as hereinbefore described, with a compound of formula (VI) 
##STR10## 
wherein Cbz is defined above. Suitably, the reaction is carried out in the 
presence of 1,3-dicyclohexyl carbodiimide (DCC), in a solvent such as 
halogenated hydrocarbon (e.g. dichloromethane) from 0.degree. C. to room 
temperature. 
Compounds of formula (V) and (VI) are known compounds or may be prepared by 
standard methods hereinafter described. 
Compounds of the invention may be isolated in association with solvent 
molecules by crystallisation from or evaporation of an appropriate 
solvent. 
Thus, according to a further aspect of the invention, we provide a process 
(C) for preparing a compound of formula (I) or a solvate (e.g. hydrate) 
thereof which comprises process (A) or (B) as hereinbefore described 
followed by 
i) an interconversion step; and/or either 
ii) solvate (e.g. hydrate) formation.

The synthesis of the compounds of the invention and of the intermediates 
for use therein are illustrated by the following, non-limiting Examples. 
Intermediates 1 and 2 
(1R,3R)-Methyl 
1,2,3,4-tetrahydro-1-(5-benzofuranyl)-9H-pyrido[3,4-b]indole-3-carboxylate 
, cis isomer and (1S,3R)-methyl 
1,2,3,4-tetrahydro-1-(5-benzofuranyl)-9H-pyrido[3,4-b]indole-3-carboxylate 
trans isomer 
To a stirred solution of D-tryptophan methyl ester (3.73 g) and 
5-formyl-benzofuran.sup.1 (2.5 g) in anhydrous dichloromethane (1 00 mL) 
cooled at 0.degree. C. was added dropwise trifluoroacetic acid (2.63 mL) 
and the solution was allowed to react at ambient temperature. After 72 
hours, the solution was washed with a saturated aqueous solution of 
NaHCO.sub.3, then with water and dried over Na.sub.2 SO.sub.4.The organic 
layer was evaporated under reduced pressure and the residue was purified 
by flash chromatography eluting with dichloromethane/ethyl acetate (90/10) 
to give first the cis isomer (Intermediate 1) (3 g) as an amorphous 
compound, followed by the trans isomer (Intermediate 2) (2.5 g) as white 
crystals, m.p.: 194-195.degree. C. 
FNT .sup.1 The synthesis of 5-formyl-benzofuran is described in Chimie 
Therapeutique 4, pp 221-227 (1966). 
Intermediate 3 
(1R,3R)-Methyl 
1,2,3,4-tetrahydro-1-(5-benzofuranyl)-2-chloroacetyl-9H-pyrido[3,4-b]indol 
e-3-carboxylate 
To a stirred solution of Intermediate 1 (2 g) and triethylamine (0.88 mL) 
in anhydrous dichloromethane (40 mL) cooled at 0.degree. C. was added 
dropwise chloroacetylchloride (0.5 mL) and the solution was stirred at the 
same temperature for 1 hour. The solution was washed with water, dried 
over Na.sub.2 SO.sub.4 and evaporated to dryness and the residue was 
crystallised from methanol to give the title compound (1.8 g) as pale 
yellow crystals. 
m.p.: 227-228.degree. C. 
Intermediate 4 
(1R,3R)-Methyl 
1,2,3,4-tetrahydro-1-(5-benzofuranyl)-2-(2-(S)-benzyloxycarbonylaminopropi 
onyl)-9H-pyrido[3,4-b]indole-3-carboxylate 
To a stirred solution of (S)-2-benzyloxycarbonylaminopropionic acid (1.3 g) 
and 1,3-dicyclohexyl carbodiimide (DCC) (1.2 g) in anhydrous 
dichloromethane (50 ml) at 0.degree. C. was added Intermediate 1 (1.0 g). 
The resulting mixture was stirred for 72 hours then the resulting 
precipitate filtered off. The filtrate was evaporated to dryness and the 
residue purified by flash chromatography, eluting with cyclohexane/ethyl 
acetate (60/40) to give the title compound as white crystals (1.4 g) 
m.p.: 91-92.degree. C. 
Intermediate 5 
(1R,3R)-Methyl 
1,2,3,4-tetrahydro-1-(5-benzofuranyl)-2-[2-(S)-benzyloxycarbonylmethylamin 
o)propionyl]-9H-pyrido[3,4-b]indole-3-carboxylate 
The same procedure as employed in the preparation of Intermediate 4 but 
starting from 2-(S)-benzyloxycarbonylmethylamino)propionic acid (0.82 g) 
and using Intermediate 1 (0.6 g), DCC (0.72 g) and dichloromethane (25 ml) 
gave after chromatography, eluting with cyclohexane/ethyl acetate (70/30), 
the title compound as a white foam. 
.sup.1 H NMR (240 MHz, CDCl3) .delta. 7.7(s,1H), 7.6(d,2H), 
7.4-7.05(m,11H), 6.6(d,1H), 5.4-5.0(m,4H), 3.5(d,1H), 3.0(m,1H), 
2.9-2.7(m,6H), 2.6(dd,1H), 1.3(s,3H). 
EXAMPLE 1 
(6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-2-methyl-pyrazino[2', 
1':6,1]pyrido[3,4-b]indole-1,4-dione 
To a stirred suspension of Intermediate 3 (0.42 g) in methanol (30 mL) was 
added at ambient temperature a solution of methylamine (33% in EtOH) (0.47 
mL) and the resulting mixture was heated at 50.degree. C. under N.sub.2 
for 72 hours. The solvent was removed under reduced pressure and dissolved 
in dichloromethane. After washing with water, drying over Na.sub.2 
SO.sub.4 and evaporating to dryness, the crude product was purified by 
crystallisation from methanol to give the title compound as white crystals 
(0.21 g). 
m.p.: 291-293.degree. C. 
Analysis for C.sub.23 H.sub.19 N.sub.3 O.sub.3 : Calculated: C, 71.68; H, 
4.97; N, 10.90; Found: C, 71.5; H, 4.91; N, 10.74%. 
[.alpha.].sup.20.sub.D =+55.7.degree. (C=1; CHCl.sub.3). 
The Following Compounds were Obtained in a Similar Manner 
EXAMPLE 2 
(6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-pyrazino[2',1':6,1]py 
rido[3,4-]indole-1,4-dione 
The same procedure as employed in the preparation of Example 1 but starting 
from ammonia and Intermediate 3 gave, after recrystallisation from 
methanol, the title compound as white crystals. 
m.p.: 310-311.degree. C. 
Analysis for C.sub.22 H.sub.17 N.sub.3 O.sub.3 (0.4 MeOH): Calculated: C, 
70.03; H, 4.88; N, 10.94; Found: C, 70.01; H, 4.8; N, 10.61%; 
[.alpha.].sup.20.sub.D =+60.4.degree. (C=0.5; pyridine). 
EXAMPLE 3 
(6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-2-isopropyl-pyrazino[ 
2',1':6,1]pyrido[3,4-b]indole-1,4-dione 
The same procedure as employed in the preparation of Example 1 but starting 
from isopropylamine and Intermediate 3 gave, after recrystallisation from 
methanol, the title compound as white crystals. 
m.p.: 291-292.degree. C. 
Analysis for C.sub.25 H.sub.23 N.sub.3 O.sub.3 (0.6 MeOH): Calculated: C, 
71.06; H, 5.92; N, 9.71; Found: C, 70.94; H, 5.62; N, 9.77%. 
[.alpha.].sup.20.sub.D =+37.9.degree. (C=1; CHCl.sub.3). 
EXAMPLE 4 
(3S,6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-3-methyl-pyrazino[ 
2',1':6,1]pyrido[3,4-b]indole-1,4-dione 
A solution of Intermediate 4 (0.3 g) in the presence of 10% Pd/C (30 mg) in 
methanol (10 ml) was stirred under an atmosphere of hydrogen at 50.degree. 
C. for two hours. The reaction mixture was cooled, filtered through 
Celite, the filter cake washed with methanol and the filtrate evaporated 
in vacuo. The residue was purified by flash chromatography, eluting with 
dichloromethane/methanol (98/2) to give the title compound as white 
crystals after recrystallisation from methanol (0.15 g) 
m.p.: 150-151.degree. C. 
Analysis for C.sub.23 H.sub.19 N.sub.3 O.sub.3 (0.1 MeOH) Calculated: C, 
71.39; H, 5.03; N, 10.81; Found: C, 71.08; H, 5.16; N, 10.50%; 
[.alpha.].sup.20.sub.D =+50.degree. (C=0.25; CHCl.sub.3). 
EXAMPLE 5 
(3S,6R,12aR)-2,3,6,7,12,12a-Hexahydro-6-(5-benzofuranyl)-2,3-dimethyl-pyraz 
ino[2',1':6,1]pyrido[3,4-b]indole-1,4-dione 
The same procedure as employed in in the preparation of Example 4 but 
starting from Intermediate 5 (0.52 g) and using 10% Pd/C (50 mg) in 
methanol (20 ml) gave, after recrystallisation from methanol, the title 
compound as white crystals (40 mg). 
m.p.: 323-324.degree. C. 
Analysis for C.sub.24 H.sub.21 N.sub.3 O.sub.3. (0.1 Methanol) Calculated: 
C, 71.52; H, 5.35; N, 10.43; Found: C, 71.71; H, 5.44; N, 10.39%; 
[.alpha.].sup.20.sub.D =+53.degree. (C=0.35; CHCl.sub.3). 
Tablets for Oral Administration 
A. Direct Compression 
______________________________________ 
1. mg/tablet 
______________________________________ 
Active ingredient 50.0 
Crospovidone USNF 8.0 
Magnesium Stearate Ph Eur 1.0 
Anhydrous Lactose 141.0 
______________________________________ 
The active ingredient was sieved and blended with the excipients. The 
resultant mix was compressed into tablets. 
______________________________________ 
2. mg/tablet 
______________________________________ 
Active ingredient 50.0 
Colloidal Silicon Dioxide 0.5 
Crospovidone 8.0 
Sodium Lauryl Sulphate 1.0 
Magnesium Stearate Ph Eur 1.0 
Microcrystalline Cellulose USNF 139.5 
______________________________________ 
The active ingredient was sieved and blended with the excipients. The 
resultant mix was compressed into tablets. 
B. Wet Granulation 
______________________________________ 
1. mg/tablet 
______________________________________ 
Active ingredient 50.0 
Polyvinyl pyrollidone 150.0 
Polyethylene glycol 50.0 
Polysorbate 80 10.0 
Magnesium Stearate Ph Eur 2.5 
Croscarmellose Sodium 25.0 
Colloidal Silicon Dioxide 2.5 
Microcrystalline Cellulose USNF 210.0 
______________________________________ 
The polyvinyl pyrollidone, polyethylene glycol and polysorbate 80 were 
dissolved in water. The resultant solution was used to granulate the 
active ingredient. After drying the granules were screened, then extruded 
at elevated temperatures and pressures. The extrudate was milled and/or 
screened then was blended with the microcrystalline cellulose, 
croscarmellose sodium, colloidal silicon dioxide and magnesium stearate. 
The resultant mix was compressed into tablets. 
______________________________________ 
2. mg/tablet 
______________________________________ 
Active ingredient 50.0 
Polysorbate 80 3.0 
Lactose Ph Eur 178.0 
Starch BP 45.0 
Pregelatinised Maize Starch BP 22.5 
Magnesium Stearate BP 1.5 
______________________________________ 
The active ingredient was sieved and blended with the lactose, starch and 
pregelatinised maize starch. The polysorbate 80 was dissolved in purified 
water. Suitable volumes of the polysorbate 80 solution were added and the 
powders were granulated. After drying, the granules were screened and 
blended with the magnesium stearate. The granules were then compressed 
into tablets. 
Tablets of other strengths may be prepared by altering the ratio of active 
ingredient to the other excipients. 
Film Coated Tablets 
The aforementioned tablet formulations were film coated. 
______________________________________ 
Coating Suspension 
% w/w 
______________________________________ 
Opadry white.dagger. 
13.2 
Purified water Ph Eur to 100.0* 
______________________________________ 
*The water did not appear in the final product. The maximum theoretical 
weight of solids applied during coating was 20 mg/tablet. 
.dagger.Opadry white is a proprietary material obtainable from Colorcon 
Limited, UK which contains hydroxypropyl methylcellulose, titanium dioxid 
and triacetin. 
The tablets were film coated using the coating suspension in conventional 
film coating equipment. 
Capsules 
______________________________________ 
1. mg/capsule 
______________________________________ 
Active ingredient 
50.0 
Lactose 148.5 
Polyvinyl pyrollidone 100.0 
Magnesium Stearate 1.5 
______________________________________ 
The active ingredient was sieved and blended with the excipients. The mix 
was filled into size No. 1 hard gelatin capsules using suitable equipment. 
______________________________________ 
2. mg/capsule 
______________________________________ 
Active ingredient 50.0 
Microcrystalline Cellulose 233.5 
Sodium Lauryl Sulphate 3.0 
Crospovidone 12.0 
Magnesium Stearate 1.5 
______________________________________ 
The active ingredient was sieved and blended with the excipients. The mix 
was filled into size No. 1 hard gelatin capsules using suitable equipment. 
Other doses may be prepared by altering the ratio of active ingredient to 
excipient, the fill weight and if necessary changing the capsule size. 
______________________________________ 
3. mg/capsule 
______________________________________ 
Active ingredient 
50.0 
Labrafil M1944CS to 1.0 ml 
______________________________________ 
The active ingredient was sieved and blended with the Labrafil. The 
suspension was filled into soft gelatin capsules using appropriate 
equipment. 
Inhibitory Effect on cGMP-PDE 
cGMP-PDE activity of compounds of the present invention was measured using 
a one-step assay adapted from Wells at al. (Wells, J. N., Baird, C. E., 
Wu, Y. J. and Hardman, J. G., Biochim. Biophys. Acta 384, 430 (1975)). The 
reaction medium contained 50 mM Tris-HCl,pH 7.5, 5 mM Mg-acetate, 250 
.mu.g/ml 5'-Nucleotidase, 1 mM EGTA and 0.15 .mu.M 8-[H.sup.3 ]-cGMP. The 
enzyme used was a human recombinant PDE V (ICOS, Seattle U.S.A.). 
Compounds of the invention were dissolved in DMSO finally present at 2% in 
the assay. The incubation time was 30 minutes during which the total 
substrate conversion did not exceed 30%. 
The IC.sub.50 values for the compounds examined were determined from 
concentration-response curves using typically concentrations ranging from 
10 nM to 10 .mu.M. Tests against other PDE enzymes using standard 
methodology also showed that compounds of the invention are highly 
selective for the cGMP specific PDE enzyme. 
cGMP Level Measurements 
Rat aortic smooth muscle cells (RSMC) prepared according to Chamley et al. 
in Cell Tissue Res. 177, 503-522 (1977) were used between the 10th and 
25th passage at confluence in 24-well culture dishes. Culture media was 
aspirated and replaced with PBS (0.5 ml) containing the compound tested at 
the appropriate concentration. After 30 minutes at 37.degree. C., 
particulates guanylate cyclase was stimulated by addition of ANF (100 nM) 
for 10 minutes. At the end of incubation, the medium was withdrawn and two 
extractions were performed by addition of 65% ethanol (0.25 ml). The two 
ethanolic extracts were pooled and evaporated until dryness, using a 
Speed-vat system. c-GMP was measured after acetylation by scintillation 
proximity immunoassay (AMERSHAM). The EC.sub.50 values are expressed as 
the dose giving half of the stimulation at saturating concentrations. 
Biological Data 
The compounds according to the present invention were typically found to 
exhibit an IC.sub.50 value of less than 500 nM and an EC.sub.50 value of 
less than 5 .mu.M. In vitro test data for representative compounds of the 
invention is given in the following table: 
TABLE 1 
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In vitro results 
Example No. IC.sub.50 nM 
EC.sub.50 .mu.M 
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1 15 0.6 
2 20 &lt;1 
3 30 &lt;1 
4 8 &lt;1 
5 8 &lt;1 
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The hypotensive effects of compounds according to the invention as 
identified in Table 2 were studied in conscious spontaneously hypertensive 
rats (SHRs). The compounds were administered orally at a dose of 5 mg/kg 
in a mixture of 5% DMF and 95% olive oil. Blood pressure was measured from 
a catheter inserted in the carotid artery and recorded for 5 hours after 
administration. The results are expressed as Area Under the Curve (AUC 
from 0 to 5 hours, mmHg.hour) of the fall in blood pressure over time. 
TABLE 2 
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In vivo results 
Example No. 
AUC PO (mmHg .multidot. h) 
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1 137 
2 93 
3 108 
4 101 
5 89 
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