Bicycle compounds, processes for their preparation and pharmaceutical formulations containing compounds

Compounds of formula (I'), and compositions containing them: ##STR1## wherein n is 1, 2 or 3, each R.sub.1 independently represents a halogen atom; a hydroxy, carboxyl or C.sub.1-4 alkyl group, a C.sub.2-4 alkenyloxy, phenyl or phenyl-C.sub.1-4 alkoxy group which may be optionally substituted by one or more halogen atoms; an amino, mono- or dialkyl-amino, morpholino or piperazino group; a group of formula --S(O).sub.x R.sub.a where x is 0, 1 or 2 and R.sub.a is a C.sub.1-4 alkyl group; or a C.sub.1-4 alkoxy group which may be optionally substituted by one or more radicals selected from hydroxy, C.sub.1-4 alkoxy, amino, mono- or di-C.sub.1-4 alkylamino, (phenyl-C.sub.1-4 alkyl)amino, N,N-C.sub.1-4 alkyl(phenyl-C.sub.1-4 alkyl)amino and N,N-(C.sub.1-4 alkoxyphenyl-C.sub.1-4 alkyl)C.sub.1-4 alkyl-amino; n is 1, 2 or 3; m is 0 or 1; R.sub.2 represents a C.sub.1-4 alkyl group in the 1- or 3-position of the imidazo ring; R.sub.3 represents a hydrogen or halogen (fluorine, chlorine, bromine or iodine) atom, or a hydroxy, amino or C.sub.1-4 alkyl or alkoxy group; and physiologically acceptable acid addition salts thereof and N-oxides of such compounds and salts. Formula (I') includes the alternative tautomeric form. The compounds and compositions are useful for treatment of the human or animal body by therapy, particularly for use in the treatment or prophylaxis of heart failure and myocardial insufficiency.

The present invention relates to novel imidazo[4,5-c]pyridine derivatives 
having positive inotropic activity. 
Cardiac glycosides such as digoxin and sympathomimetics have been widely 
used for many years for the treatment of heart failure. It is, however, 
well known that these compounds suffer from a number of disadvantages 
which limit their use in practice as described, for example, by Opie L. 
H., Drugs and the Heart V and VII, Lancet 1980, i, 912 and 1011; 
Editorial, Treatments for heart failure: Stimulation or unloading, Lancet 
1979, ii, 777; and Braunwald E, Pharmacological treatment of 
cardiovascular disorders in Harrison's Principles of Internal Medicine, p 
1064, ed. Isselbacher et al McGraw-Hill, New York. Another compound which 
has more recently been proposed for use in the treatment of congestive 
heart failure is amrinone. Furthermore, U.K. Patent Specification No. 
1,445,824 describes certain imidazo[4,5-b]pyridine derivatives which are 
said in the specification to have positive inotropic activity. Of these 
compounds, 
2-[(2-methoxy-4-methylsulphinyl)phenyl]-1H-imidazo[4,5-b]pyridine, 
specifically described in the specification, and otherwise known as AR-L 
115 BS or Vardax, has been the subject of reports in the literature. 
We have now discovered that imidazo[4,5-c]pyridine derivatives of formula 
(I) below possess advantageous inotropic properties which render the 
compounds useful for the treatment of heart failure while avoiding or 
obviating problems associated with the use of previously proposed 
inotropic agents. 
The present invention thus provides compounds of the general formula (I): 
##STR2## 
wherein n is 1, 2 or 3, each R.sub.1 independently represents a halogen 
atom; a hydroxy, carboxyl or C.sub.1-4 alkyl group; a C.sub.2-4 
alkenyloxy, phenyl or phenyl-C.sub.1-4 alkoxy group which may be 
optionally substituted by one or more halogen atoms; an amino, mono- or 
di-C.sub.1-4 alkyl-amino, morpholino or piperazino group; a group of 
formula --S(O).sub.x R.sub.a wherein x is 0, 1 or 2 and R.sub.a is a 
C.sub.1-4 alkyl group; or a C.sub.1-4 alkoxy group which may be optionally 
substituted by one or more radicals selected from hydroxy, C.sub.1-4 
alkoxy, amino, mono or di-C.sub.1-4 alkylamino, (phenyl-C.sub.1-4 
alkyl)amino, N,N-C.sub.1-4 alkyl(phenyl-C.sub.1-4 alkyl)amino and 
N,N-(C.sub.1-4 alkoxyphenyl-C.sub.1-4 alkyl)C.sub.1-4 alkylamino; m is 0 
or 1; R.sub.2 represents a C.sub.1-4 alkyl group in the 1- or 3-position 
of the imidazo ring; R.sub.3 represents a hydrogen or halogen (fluorine, 
chlorine, bromine or iodine) atom, or a hydroxy, amino or C.sub.1-4 alkyl 
or alkoxy group; providing that when n is 1, m is 0 and R.sub.3 represents 
a hydrogen atom, R.sub.1 does not represent a 4-methoxy, 4-dimethylamino, 
2- or 4-amino, 2-hydroxy or 3 or 4-chloro group. 
It will be appreciated that formula (I) may be depicted in the alternative 
tautomeric form: 
##STR3## 
(wherein R.sub.1 R.sub.2, R.sub.3, n and m are as defined above). Thus, 
references herein to formula (I) should be taken to include, where 
appropriate, references to the above-mentioned alternative tautomeric 
form. 
Those compounds of formula (I) wherein R.sub.1 is a 4-methoxy or 
4-dimethylamino group, n is 1, m is 0 and R.sub.3 is hydrogen are 
disclosed in USSR Patent Specification No. 566842. Compounds of formula 
(I) wherein R.sub.1 represents a 3- or 4-chlorine atom or a 2-hydroxy or 
4-amino group, n is 1, m is 0 and R.sub.3 is hydrogen are described by R. 
W. Middleton and D. G. Wibberly, J. Heterocyclic Chem. 17, 1957 (1980). A 
compound of formula (I) wherein R.sub.1 is a 2-amino group, n is 1, m is 0 
and R.sub.3 is hydrogen are disclosed by Maskell et al in J. Med. Chem., 
1970, 13(4), 697. These references do not, however, disclose or suggest 
the use of the compounds for the therapeutic treatment of the human or 
animal body. 
The present invention also includes the acid addition salts of the 
compounds of formula (I). These salts may be formed by protonation of one 
or more of the basic nitrogen atoms in formula (I). It will be appreciated 
that for therapeutic use a physiologically acceptable acid addition salt 
will be required, for example, a salt derived from hydrochloric, 
hydrobromic, phosphoric, malic, maleic, fumaric, citric, sulphuric, lactic 
or tartaric acid. However, the present invention also includes other acid 
addition salts which may be used for isolating, purifying or 
characterising the parent compounds of formula (I). The present invention 
further includes the N-oxides of the compounds of formula (I) and the acid 
addition salts of such N-oxides. 
In general formula (I), R.sub.1 may for example represent a methyl, ethyl, 
allyloxy, benzyloxy, methylthio, methylsulphinyl, methylsulphonyl, 
methoxy, ethoxy, or propoxy group. R.sub.2 may for example represent a 
methyl or ethyl group while R.sub.3 may for example represent a hydrogen 
or halogen (e.g. chlorine) atom or a methyl, ethyl, methoxy or ethoxy 
group. In the definitions of R.sub.1 and R.sub.3, the references to 
halogen atoms include fluorine, chlorine, bromine, and iodine atoms. 
In general, preferred compounds of formula (I) having particularly 
advantageous inotropic activity include those wherein R.sub.3 represents a 
hydrogen atom, m is 0 and/or those wherein n is 1, 2 or 3. 
Preferred R.sub.1 groups in formula (I) include halogen atoms (especially 
chlorine), C.sub.2-4 alkenyloxy groups, especially allyloxy, C.sub.1-4 
alkoxy groups, especially methoxy and ethoxy, methoxy being particularly 
preferred, and groups of formula --S(O).sub.x R.sub.a (wherein x is 0, 1 
or 2, preferably 1, and R.sub.a represents a methyl or ethyl group), 
especially methylsulphinyl. 
Particularly preferred classes of compounds of formula (I) include those 
wherein m is 0, R.sub.3 preferably represents a hydrogen atom and: 
(a) in the case where n is 1, the group R.sub.1 represents a C.sub.1-4 
alkoxy group in the 2- or 4-position or a group of formula --S(O).sub.x 
R.sub.a in the 2-position. 
(b) in the case where n is 2: 
(i) both R.sub.1 groups represent C.sub.1-4 alkoxy groups in the 2,4-, 2,5- 
or 3,4-positions; 
(ii) one R.sub.1 group represents a C.sub.1-4 alkoxy group in the 
2-position and the other represents a halogen atom or a group of formula 
--S(O).sub.x R.sub.a in the 4-position; or 
(iii) one R.sub.1 groups represents a C.sub.2-4 alkenyloxy group in the 
2-position and the other represents a C.sub.1-4 alkoxy or --S(O).sub.x 
R.sub.a group in the 4-position. 
(c) in the case where n is 3, the R.sub.1 groups all represent C.sub.1-4 
alkoxy groups in the 2,3,4- or 2,4,5- positions. 
The compounds according to the invention are useful as cardiotonic agents 
since they have been found in both in vitro and in vivo experiments to 
produce a positive inotropic effect at low concentrations, as demonstrated 
in the tests described hereinafter. Experiments in vivo have also 
indicated that these effects are long-lasting, and accompanied by a 
vasodilatory effect. The latter may be of additional benefit in the 
treatment of heart failure to counteract the marked vasoconstriction which 
is frequently associated with this condition. 
From in vitro and in vivo experiments it is evident that the positive 
inotropic stimulation caused by these compounds is independent of the 
myocardial .beta.-adrenoceptors whereas, it has been suggested that at 
least part of the positive inotropic stimulation caused by the 
above-mentioned compound Vardax is attributable to stimulation of 
myocardial .beta.-adrenoceptors (Brutsaert et al, 1982 J. Cardiovasc. 
Pharmacol. 4, 333-43; Pouleur et al, 1982 J. Cardiovasc. Pharmacol. 4, 
409-18). 
A further advantage of the compounds according to the invention is that 
they do not demonstrate any significant myocardial phosphodiesterase 
inhibitory activity. This contrasts with reports for Vardax which find 
this compound to be an effective inhibitor of myocardial phosphodiesterase 
(Diederan and Wiesenberger, 1981, Drug Res. 31(1), 177-82). 
Phosphodiesterase enzymes are widely distributed throughout the tissues of 
the body and the administration of an inhibitor, which is inherently 
non-specific, may result in phosphodiesterase inhibition at sites other 
than the myocardium, which may be undesirable from the clinical point of 
view. 
The stimulation of myocardial .beta.-adrenoceptors results in an increase 
in the level of intracellular cAMP, as does the inhibition of myocardial 
phosphodiesterase. The resultant positive inotropic effects of these 
interventions are directly linked to the increased levels of cAMP and thus 
an inotropic stimulation based on either mechanism may be criticised for 
the same reasons. Both mechanisms are likely to promote myocardial 
ischaemia through increasing myocardial oxygen demand by their positive 
chronotropic effects, and in addition evoke arrythmias. In experimental 
studies it has been found that 
2-(2-methoxy-4-methylsulphinylphenyl)-1H-imidazo[4,5-c]pyridine does not 
exacerbate myocardial injury following selective ligation of the coronary 
artery in vivo. Furthermore, the last-mentioned compound does not increase 
ventricular vulnerability to arrythmias in the ischaemic heart. 
The compounds according to the invention also possess an inhibitory effect 
on blood platelet aggregation which could facilitate the treatment of 
heart failure by providing some protection against the effects of platelet 
interaction in the myocardium, particularly after infarctions. 
A particularly preferred compound by virtue of its advantageous 
pharmacological properties is 
2-(2-methoxy-4-methylsulphinylphenyl)-1H-imidazo[4,5-c]pyridine and its 
N-oxides and physiologically acceptable acid addition salts. 
Other examples of compounds of formula (I) and their acid addition salts 
include the following bases and their N-oxides and acid addition salts: 
2-(2,4-dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(4-methoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(3,4,5-trimethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(2,3,4-trimethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(2-methoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(3,4-dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(3,4-diethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(2-methoxy-4-chlorophenyl)-1H-imidazo[4,5-c]pyridine 
2-(2,5-dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(2-methylthiophenyl)-1H-imidazo[4,5-c]pyridine 
2-(2-methoxy-4-methylsulphonylphenyl)-1H-imidazo[4,5-c]pyridine 
2-(2-propyloxy-4-methoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(2-methoxy-4-methylsulphinylphenyl)-1H-imidazo[4,5-c]pyridine 
3-methyl-2-(2,4-dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
1-methyl-2-(2,4-dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(2,4,5-trimethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
2-(3-methylthio-4-methoxy)-1H-imidazo[4,5-c]pyridine 
The present invention also provides compounds of formula 
##STR4## 
(wherein n is 1, 2 or 3, each R.sub.1 independently represents a halogen 
atom; a hydroxy, carboxyl or C.sub.1-4 alkyl group, a C.sub.2-4 
alkenyloxy, phenyl or phenyl-C.sub.1-4 alkoxy group which may be 
optionally substituted by one or more halogen atoms; an amino, mono- or 
dialkyl-amino, morpholino or piperazino group; a group of formula 
--S(O).sub.x R.sub.a where x is 0, 1 or 2 and R.sub.a is a C.sub.1-4 alkyl 
group; or a C.sub.1-4 alkoxy group which may be optionally substituted by 
one or more radicals selected from hydroxy, C.sub.1-4 alkoxy, amino, mono- 
or di-C.sub.1-4 alkylamino, (phenyl-C.sub.1-4 alkyl)amino, N,N-C.sub.1-4 
alkyl(phenyl-C.sub.1-4 alkyl)amino and N,N-(C.sub.1-4 
alkoxyphenyl-C.sub.1-4 alkyl)C.sub.1-4 alkyl-amino; n is 1, 2 or 3; m is 0 
or 1; R.sub.2 represents a C.sub.1-4 alkyl group in the 1- or 3-position 
of the imidazo ring; R.sub.3 represents a hydrogen or halogen (fluorine, 
chlorine, bromine or iodine) atom, or a hydroxy, amino or C.sub.1-4 alkyl 
or alkoxy group; and physiologically acceptable acid addition salts 
thereof and N-oxides of such compounds and salts, for use in a method of 
treatment of the human or animal body by therapy, particularly for use in 
the treatment or prophylaxis of heart failure and myocardial 
insufficiency. 
It will be appreciated that formula (I') may be written in a similar 
alternative tautomeric form to formula (I), as indicated above, and 
references herein to formula (I') should also be taken to include, where 
appropriate, the alternative tautomeric form. 
The compounds of formula (I') and their salts and N-oxides may be 
administered by the oral, rectal or parenteral route. In general, these 
compounds may be administered at a dosage in the range of 1 to 1200 mg per 
day although the precise dosage will naturally depend on a number of 
clinical factors, for example, the type (i.e. human or animal), age and 
weight of the subject, the condition under treatment and its severity, and 
the particular compound employed. For administration of the compounds by 
the oral route, a dosage regime of 100 to 400 mg, e.g. about 200 mg per 
day may be used, while for administration by the parenteral route, 
especially intravenously, a dosage regime of 20 to 300 mg, advantageously 
35 to 70 mg, e.g. about 50 mg per day is generally preferred. The 
compounds may be administered intravenously by infusion, if desired, in 
which case, a dosage rate of, for example, 1-4 mg/min may be employed. 
The compounds of formula (I') and their physiologically acceptable acid 
addition salts and N-oxides of such compounds and salts are preferably 
administered in the form of pharmaceutical formulations. 
The present invention thus further provides pharmaceutically acceptable 
formulations comprising at least one compound of formula (I') (as defined 
above) or a physiologically acceptable acid addition salt or an N-oxide of 
the said compound or salt, in association with at least one pharmaceutical 
carrier or excipient. The pharmaceutical formulations may be adapted for 
oral, parenteral (particularly intravenous) or rectal administration. The 
formulations may conveniently be presented in unit dosage form and may be 
prepared by any of the methods well known in the art of pharmacy. Such 
methods include the step of bringing into association the active 
ingredient with the carrier which may comprise one or more accessory 
ingredients. In general the formulations are prepared by uniformly and 
intimately bringing into association the active ingredient with liquid 
carriers or finely divided solid carriers or both, and then, if necessary, 
shaping the product. 
Formulations of the present invention suitable for oral administration may 
be presented as discrete units such as capsules, cachets or tablets each 
containing a predetermined amount of the active ingredient; as a powder or 
granules; as a solution or a suspension in an aqueous liquid or a 
non-aqueous liquid; or as an oil-in-water liquid emulsion or a 
water-in-oil liquid emulsion. 
A tablet may be made by compression or moulding, optionally with one or 
more accessory ingredients. Compressed tablets may be prepared by 
compressing in a suitable machine the active ingredient in a free-flowing 
form such as a powder or granules, optionally mixed with a binder, 
lubricant, inert diluent, lubricating, surface active or dispersing agent. 
Moulded tablets may be made by moulding in a suitable machine a mixture of 
the powdered compound moistened with an inert liquid diluent. The tablets 
may optionally be coated or scored and may be formulated so as to provide 
slow or controlled release of the active ingredient therein. 
Formulations for rectal administration may be presented as a suppository 
with the usual carriers such as cocoa butter. 
Formulations suitable for parenteral administration include aqueous sterile 
injection solutions which may contain anti-oxidants, buffers, 
bacteriostats and solutes which render the formulation isotonic with the 
blood of the intended recipient; and aqueous and non-aqueous sterile 
suspensions which may include suspending agents and thickening agents. The 
formulations may be presented in unit-dose or multi-dose containers, for 
example sealed ampoules and vials, and may be stored in a freeze-dried 
(lyophilized) condition requiring only the addition of the sterile liquid 
carrier, for example water for injections, immediately prior to use. 
Extemporaneous injection solutions and suspensions may be prepared from 
sterile powder, granules and tablets of the kind previously described. 
Preferred unit dosage formulations are those containing a daily dose or 
unit daily sub-dose, as hereinabove recited, or an appropriate fraction 
thereof, of an active ingredient. 
It should be understood that in addition to the ingredients particularly 
mentioned above the formulations of this invention may include other 
agents conventional in the art having regard to the type of formulation in 
question, for example those suitable for oral administration may include 
flavouring agents. 
The compounds of formula (I) and their acid addition salts and N-oxides may 
be prepared by any convenient process, e.g. using procedures described in 
the above-mentioned references. 
Thus, for example, according to a further feature of the present invention, 
we provide a process for the preparation of compounds of formula (I) and 
their N-oxides and acid addition salts which comprises 
(a) reacting a compound of formula 
##STR5## 
(wherein R.sub.3 is as defined above, X and Y which may be the same or 
different, each represents an amino group, a group of formula --NHR.sub.2 
(wherein R.sub.2 is as defined above) or a displaceable radical, e.g. 
hydrogen or a halogen atom such as chlorine,providing that X and Y do not 
both represent displaceable radicals or groups of formula --NHR.sub.2) 
with a compound of formula 
##STR6## 
(wherein R.sub.1 and n are as defined above and Z represents a group 
capable of reacting with groups X and Y (sequentially or simultaneously) 
to form an imidazo ring system with consequential formation of a compound 
of formula (I) or an acid addition salt thereof; or 
(b) reacting a compound of formula 
##STR7## 
(wherein R.sub.2, n and m and are as defined above, each R.sub.1.sup.a 
independently represents a group as defined for R.sub.1 above or a 
precursor group therefor and R.sub.3.sup.a represents a group as defined 
for R.sub.3 above or a precursor group therefor, providing at least one of 
R.sub.1.sup.a and R.sub.3.sup.a represent such a precursor group) or an 
acid addition salt thereof with an agent serving to effect conversion of 
the precursor group(s) for R.sub.1.sup.a and/or R.sub.3.sup.a into the 
desired group(s); or 
(c) radical arylation of a compound of formula 
##STR8## 
(wherein R.sub.2, R.sub.3 and m are as hereinbefore defined) by reaction 
with a compound of formula 
##STR9## 
(wherein R.sub.1 and n are as hereinbefore defined and A represents a 
displaceable radical, e.g. a diazonium halide, for example the chloride) 
and where a compound of formula (I) is formed, optionally converting the 
said compound into an N-oxide or acid addition salt thereof. 
The reaction in process (a) may optionally be carried out in a solvent, 
e.g. an organic solvent for example, ethylene glycol, conveniently at a 
elevated temperature, e.g. up to the reflux temperature of the reaction 
mixture. 
According to a preferred embodiment of process (a) above according to the 
invention, a compound of formula (II) (wherein R.sub.3 is as hereinbefore 
defined and either X and Y both represent amino groups or one of X and Y 
represents an amino group and the other represents a group of formula 
--NHR.sub.2) is reacted with a compound of formula (III) (wherein R.sub.1 
and n are as hereinbefore defined and Z is a carboxyl, thiocarboxyl or 
dithiocarboxyl group) or a functional equivalent thereof (e.g. an acid 
halide, acid anhydride, amide, thioamide, imidate, thioimidate or ester 
thereof) or an aldehyde or nitrile thereof. 
When a compound of formula (III) is employed, wherein Z represents a free 
carboxylic acid group, the reaction is advantageously effected in the 
presence of a dehydrating agent such as phosphorus oxychloride. 
Alternatively, the reaction may be effected in the presence of 
polyphosphoric acid. When a compound of formula (III) is employed, wherein 
Z represents an acid halide, the reaction is advantageously effected in 
the presence of an acid binding agent e.g. a tertiary base such as 
triethylamine. Where a nitrile of a compound of formula (III) is employed, 
the reaction is advantageously effected in the presence of an acid, e.g. 
p-toluenesulphonic acid or polyphosphoric acid. 
Alternatively, a compound of formula (III) (wherein Z represents an 
aldehyde group) may be employed, in which case the reaction may be 
effected for example, as described by R. Weidenhagen et al, Chem, Ber. 
1942, 75, 1936 or in USSR Patent Specification No. 566842. Thus, for 
example following the procedure described in the last-mentioned Patent 
Specification, a compound of formula (II) (wherein X and Y both represent 
amino groups) may be reacted with an aldehyde compound of formula (III) in 
the presence of sulphur. 
In one example of the preferred embodiment above, the compound of formula 
(II) may be reacted with a thioamide of a compound of formula (III), e.g. 
a thiomorpholide which is advantageously employed in the form of a 
quaternised product thereof, e.g. the appropriate S-methyl-thiobenzyl 
morpholide iodide. Alternatively, the compound of formula (III) may be 
employed in the form of a morpholide. 
A further preferred embodiment of process (a) according to the present 
invention comprises reacting a compound of formula (II) (wherein R.sub.3 
is as hereinbefore defined, one of X and Y represents a halogen atom and 
the other represents an amino group or a group of formula --NHR.sub.2 
(wherein R.sub.2 is as hereinbefore defined)) with a compound of formula 
(III) (wherein R.sub.1 and n are as hereinbefore defined and Z represents 
an amino-or NHR.sub.2 -containing group derived from a carboxyl group, 
e.g. a H.sub.2 NCO-group. 
In process (a), the Z group in the compound of formula (III) may react 
sequentially with groups X and Y in the compound of formula (II), e.g. 
with the initial formation of a compound of formula 
##STR10## 
(wherein R.sub.1 and n are as hereinbefore defined) which may subsequently 
be cyclised, eg. by treatment with lead tetra-acetate to form a compound 
of formula (I). 
With regard to process (b) above, those compounds of formula (I) wherein 
R.sub.3 represents an amino group may be prepared for example by treatment 
of a corresponding compound wherein R.sub.3 represents chlorine atom with 
aqueous ammonia while compounds wherein R.sub.3 represents hydroxy may be 
prepared by treatment of a corresponding compound wherein R.sub.3 
represents an amino group by treatment with nitrous acid. Compounds of 
formula (I) wherein R.sub.3 represents C.sub.1-4 alkoxy group may for 
example be prepared by alkoxylation of a corresponding compound wherein 
R.sub.3 represents a chlorine atom. 
Compounds of formula (I) wherein R.sub.1 represents a C.sub.1-4 
alkyl-sulphinyl or -sulphonyl group may be prepared for example by 
oxidation, e.g. using hydrogen peroxide, organic peracids, or bromine or 
one of its addition compounds, eg. an alkali metal hypobromite, as 
described in German Offenlegungsschrift DE No. 3044 497 of the 
corresponding C.sub.1-4 alkylthio compound. 
Compounds wherein R.sub.1 represents a hydroxy group may be prepared for 
example by treatment with boron tribromide of the corresponding methoxy 
compounds. 
Compounds wherein R.sub.1 represents a methoxy group may be prepared by 
treatment of a corresponding compound wherein R.sub.1 represents a hydroxy 
group, with a methylating agent, e.g. methyl sulphate. 
Compounds wherein R.sub.1 represents a C.sub.1-4 alkylthio group may be 
prepared by diazotisation of a corresponding compound wherein R.sub.1 
represents an amino group (e.g. by treatment with nitrous acid), followed 
by reaction of the product with an appropriate C.sub.1-4 alkyl mercaptan. 
The radical arylation in process (c) above may be conveniently effected by 
the general method of M-H Hung and L. M. Stock, J. Org. Chem., 1982, 47, 
448-453. When the compound of formula (VI) is employed in the form of 
diazonium salt, this salt may be prepared in conventional manner e.g. from 
the corresponding amino compound. 
The acid addition salts of the compounds of formula (I) may be prepared in 
conventional manner, e.g. by treatment of the free base with an 
appropriate acid. The N-oxides of the compounds of formula (I) may also be 
prepared in conventional manner e.g. by oxidation of the parent compound 
with an appropriate oxidising agent, eg. m-chloroperbenzoic acid.

The following examples illustrate the present invention. 
EXAMPLE 1 
2-(2,4-Dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine 
A mixture of 2,4 dimethoxybenzoic acid (2.5 g) and 3,4-diaminopyridine (1.5 
g) was ground to a fine powder and added portionwise to phosphorus 
oxychloride (50 ml) with stirring. The mixture was stirred and heated 
under reflux for 2.5 hours before excess phosphorus oxychloride was 
removed in vacuo. The residue was cooled, water (20 ml) added and the pH 
adjusted to 7 with ammonium hydroxide to yield a pale yellow solid which 
was collected, washed with water and dried. The solid was recrystallised 
twice from aqueous ethanol to yield a cream coloured crystalline solid 
m.p. 195.degree.-198.degree.. 
Analysis: Calc. C, 65.88; H, 5.09; N, 16.47. Found: C, 65.70, H, 5.15; N, 
16.05. 
The structure was confirmed by N.M.R. and M.S. data 
EXAMPLE 2 
2-(4-Methoxyphenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride 
A mixture of 3,4-diaminopyridine (1.5 g) and 4-methoxybenzoic acid (2.1 g) 
were ground up to a powder and added portionwise to phosphorus oxychloride 
(50 ml) with stirring. 
The mixture was heated under reflux for 2.5 hr before the excess 
oxychloride was removed in vacuo. The residue was cooled, water (20 ml) 
added and pH adjusted to 7 with 1N NaOH to yield a pale yellow solid which 
was collected, washed with water, and dried. Recrystallisation from 
aqueous ethanol gave a pale yellow crystalline solid 1.06 g. 
The solid was taken up in hot acetone (30 ml) and the insoluble material 
removed by filtration; the filtrate was treated with ethereal HCl to 
precipitate the dihydrochloride salt which was collected, washed with dry 
ether and dried m.p. 263.degree.-266.degree.. 
EXAMPLES 3-22 
In an analogous manner to that described in Example 1, the following 
compounds were prepared: 
(3) 2-(3,4,5-trimethoxyphenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride, 
m.p. 250.degree.-254.degree. C. 
(4) 2-(2-methoxy-4-methylthiophenyl)-1H-imidazo[4,5-c]pyridine 
dihydrochloride, m.p. 205.degree.-206.degree. C. 
(5) 2-(2,3,4-trimethoxyphenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride, 
m.p. 250.degree.-252.degree. C. (dec) 
(6) 2-(2-methylaminophenyl)-1H-imidazo[4,5-c]pyridine hydrochloride, m.p. 
218.degree.-221.degree. C. 
(7) 2-(2-methoxyphenyl)-1H-imidazo[4,5-c]pyridine hydrochloride, m.p. 
190.degree.-194.degree. C. 
(8) 2-(3,4-dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride, m.p. 
262.degree. C. (decomp) 
(9) 2-(3,4-diethoxyphenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride, m.p. 
259.degree.-260.degree. C. 
(10) 2-(2-methoxy-4-chlorophenyl)-1H-imidazo[4,5-c]pyridine hydrochloride, 
m.p. 185.degree.-191.degree. C. 
(11) 2-(2-propyloxy-4-methoxyphenyl)-1H-imidazo[4,5-c]pyridine 
hydrochloride, m.p. 228.degree.-231.degree. C. 
(12) 2-(2,4-dimethylphenyl)-1H-imidazo[4,5-c]pyridine, m.p. 
108.degree.-12.degree. C. and its hydrochloride, m.p. 
288.degree.-292.degree. C. 
(13) 2-[2-(2-methoxyethoxy)-4-methoxyphenyl]-1H-imidazo[4,5-c]pyridine, 
m.p. 130.degree.-132.degree. C. and its hydrochloride, m.p. 
211.degree.-214.degree. C. 
The following compounds and their salts are also prepared in an analogous 
manner: 
(14) 2-(2-methoxy-5-methylthiophenyl)-1H-imidazo[4,5-c]pyridine 
(15) 2-(2-methoxy-5-methylsulphinylphenyl)-1H-imidazo[4,5-c]pyridine 
(16) 2-(2-methoxy-4-carboxyphenyl)-1H-imidazo[4,5-c]pyridine 
(17) 2-(2-methoxy-4-fluorophenyl)-1H-imidazo[4,5-c]pyridine 
(18) 2-(2-methoxy-4-aminophenyl)-1H-imidazo[4,5-c]pyridine 
(19) 2-(2,4-dimethoxyphenyl)-4-methyl-1H-imidazo[4,5-c]pyridine 
(20) 2-(2,4-dimethoxyphenyl)-7-methyl-1H-imidazo[4,5-c]pyridine 
EXAMPLE 21 
2-(2-Methoxy-4-methylsulphinylphenyl)-1H-imidazo[4,5-c]pyridine 
To a mixture of acetic acid (20 ml), water (6 ml) and hydrogen peroxide 
(30% solution) (2.5 eq), while stirring at room temperature, was added, in 
portions, the compound of Example 4 (1.5 g). The reaction mixture was 
stirred at room temperature for 2 hours and allowed to stand overnight at 
4.degree. C. Tlc indicated that the reaction was complete. The resulting 
mixture was poured into water (25 ml), basified with 0.88 ammonia and 
extracted with chloroform. The organic extract was dried, decolourised and 
evaporated in vacuo to a foam which was crystallised from ethyl 
acetate/acetone to give the title compound, m.p. 202.degree.-204.degree. 
C. 
In an alternative preparation, the title compound was prepared as follows: 
To a stirred and cooled suspension of the compound of Example 4 (18 g) and 
sodium acetate (1 eq) in glacial acetic acid was added bromine (3.2 ml) in 
glacial acetic acid at such a rate that the temperature was held below 
about 5.degree. C. The mixture was poured into 100 g crushed ice and the 
pH adjusted to 9 with 0.88 ammonia. The resulting solution (containing 
some brown solid) was saturated with sodium chloride and extracted with 
chloroform (4.times.300 ml). The combined chloroform extracts were dried, 
decolourised with animal charcoal and evaporated in vacuo to a froth which 
on trituration with ether gave the title product. 
EXAMPLE 22 
2-(2-Methylsulphinyl-4-methoxyphenyl)-1H-imidazo[4,5-c]pyridine 
hydrochloride 
Using the method of Example 21, and starting from 
2-(2-methylthio-4-methoxyphenyl)-1H-imidazo[4,5-c]pyridine, the title 
compound was prepared in analogous manner. 
EXAMPLE 23 
2-(2-Methoxy-4-methylsulphinylphenyl)-1H-imidazo[4,5-c]pyridine 
hydrochloride 
The compound of Example 21 was suspended in ether and dry hydrogen chloride 
gas was bubbled through the suspension for about 2 minutes. The insoluble 
solid was filtered off and dried to give the title compound as a white 
solid, m.p. 153.degree.-155.degree. C. 
EXAMPLE 24 
2-(2,5-Dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride 
2,5-Dimethoxybenzaldehyde, morpholine and sulphur were heated for 3 hours 
at 120.degree. C. The solid mixture melted to give a liquid. The reaction 
mixture was cooled and dissolved in hot methanol. On cooling the methanol 
solution, solid (thiomorpholide) resulted which was filtered and dried. 
The thiomorpholide was refluxed for about 2 hours in acetone with methyl 
iodide (1.2 equivalents). Acetone was then removed in vacuo to give a 
brown viscous oil (thiomorpholide methiodide) which was mixed with 
3,4-diaminopyridine in ethylene glycol and the mixture heated at 
120.degree. C. for 2 hours. The reaction mixture was diluted with water 
and the solid obtained was filtered off, suspended in water and basified 
with 0.88 ammonia. The solid was filtered off, dried and converted to the 
title dihydrochloride salt, m.p. 188.degree.-190.degree. C. (decomp). 
EXAMPLE 25 
2-(2,4-Dimethoxy-3-methylthiophenyl)-1H-imidazo[4,5-c]pyridine 
hydrochloride 
The title compound was made in an analogous manner to that of Example 24, 
m.p. 205.degree.-207.degree. C. 
EXAMPLE 26 
2-(2,4-Dimethoxy-3-methylsulphinylphenyl)-1H-imidazo[4,5-c]pyridine 
The title compound is made from the compound of Example 25, by a method 
analogous to that described in Example 21. 
EXAMPLES 27-30 
The following compounds, namely: 
(27) 2-(4-biphenyl-4-yl)-1H-imidazo[4,5-c]pyridine 1.5 hydrochloride, m.p. 
352.degree.-355.degree. C., 
(28) 2-(2,4-dichlorophenyl)-1H-imidazo[4,5-c]pyridine hydrochloride, m.p. 
230.degree.-232.degree. C., 
(29) 2-(2-methylthiophenyl)-1H-imidazo[4,5-c]pyridine hydrochloride, m.p. 
158.degree.-160.degree. C. 
(30) 2-(3-methylthiophenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride, m.p. 
123.5.degree.-125.degree. C. 
(31) 2-(4-methylthiophenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride, m.p. 
301.degree.-303.degree. C. 
were prepared according to the following general procedure: 
The appropriate diaminopyridine was pulverised with the appropriate 
substituted benzoic acid and the mixture was added portionwise to 
polyphosphoric acid. The resulting reaction mixture was heated at 
180.degree. for about 3 hours. The cooled reaction mixture was poured onto 
ice, and the precipitated solid was filtered off, suspended in water and 
neutralised with 0.88 ammonia. The solid so obtained was filtered, dried 
and converted to the hydrochloride salt. 
EXAMPLE 32 
2-(2-Methoxy-4-methylsulphonylphenyl)-1H-imidazo[4,5-c]pyridine and its 
hydrochloride 
2-(2-Methoxy-4-methylthiophenyl)-1H-imidazo[4,5-c]pyridine was added 
portionwise to a stirred solution of 30% hydrogen peroxide in glacial 
acetic acid and water. The clear brown solution was stirred at 70.degree. 
C. for 3 hours. T.l.c. indicated the reaction to be complete. The reaction 
mixture was evaporated in vacuo to remove solvents and the residue was 
purified by column chromatography to the title free base, m.p. 
225.degree.-227.degree. C. The free base obtained above was suspended in 
methanol and dry hydrogen chloride gas was bubbled through the solution. 
The solid was filtered off and dried to yield the title hydrochloride, 
m.p. 221.degree.-223.degree. C. (decomp). 
EXAMPLE 33 
2-(2-Hydroxy-4-methylthiophenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride 
2-(2-Methoxy-4-methylthiophenyl-1H-imidazo[4,5-c]pyridine was suspended in 
dry dichloromethane and a solution of boron tribromide (3 eq) in dry 
dichloromethane was added slowly at room temperature. The mixture was 
refluxed for 5 hours and was then poured into water and basified with 0.88 
ammonia. The resulting solution was extracted with chloroform. T.l.c. 
indicated the product to be in the aqueous layer which was evaporated down 
to a low bulk when a brown solid precipitated. The solid was extracted 
into hot methanol and decolourised and evaporated to give a brown solid 
which was converted to the title dihydrochloride, m.p. 
297.degree.-300.degree. C. 
EXAMPLE 34 
2-(3-Methylthio-4-methoxyphenyl)-1H-imidazo-[4,5-c]pyridine dihydrochloride 
3-Methylthio-4-methoxybenzoic acid (obtained by diazotization of 
3-amino-4-methoxybenzoic acid, followed by treatment with methylmercaptan) 
was suspended in dry toluene and thionyl chloride (1.1 eq) was added 
slowly to it. The mixture was refluxed for 3.5 hours. T.l.c. indicated 
reaction to be complete. The solvent was removed in vacuo to leave a dark 
brown residue. 
The acid chloride obtained above was suspended in the minimum quantity of 
dry ether and added portionwise to a suspension of 3,4-diaminopyridine (1 
eq) in dry pyridine and triethylamine. The resulting mixture was refluxed 
for 5 hours. T.l.c. indicated the reaction to be complete. 
The cooled reaction mixture was filtered through hyflo and the filtrate 
evaporated in vacuo. The residue was triturated with ether and then 
dissolved in methanol. 
The solid that separated was filtered off and the methanol filtrate was 
evaporated under reduced pressure to give a viscous oil. NMR indicated 
this to consist mainly of the intermediate amide. This oil was dissolved 
in ethylene glycol and the solution obtained heated at 200.degree. for 4 
hours. T.l.c. indicated reaction to be complete. 
The cooled reaction mixture was poured into water. A white solid 
precipitated and was filtered and dried. The solid was triturated into 
ethyl acetate/ether to give a solid which was converted to the title 
dihydrochloride, m.p. 275.degree.-277.degree. C. 
EXAMPLE 35 
2-(3-Methylsulphinyl-4-methoxyphenyl)-1H-imidazo[4,5-c]pyridine 
The compound obtained in Example 34, was oxidised using hydrogen peroxide 
(2 eq) in a manner analogous to that described in Example 21. The title 
compound was obtained as a white solid, m.p. 227.degree.-229.degree. C. 
EXAMPLE 36 
2-(3-Methylsulphinylphenyl)-1H-imidazo[4,5-c]pyridine hydrochloride 
The compound prepared in Example 30, was oxidised by the method described 
in Example 23 above, to obtain the title compound as a white solid, m.p. 
250.degree.-252.degree. C. 
EXAMPLE 37 
2-(2-Allyloxy-4-methoxyphenyl)-1H-imidazo[4,5-c]pyridine hydrochloride 
(a) 2-Allyloxy-4-methoxybenzoyl morpholide 
To a stirred solution of 2-allyloxy-4-methoxy benzoyl chloride (14 g) in 
dry toluene was added morpholine (12 ml) and stirring continued for 1 
hour. 
Toluene was removed under reduced pressure, 2N hydrochloric acid (20 ml) 
was added to the residue and the mixture was extracted with ethyl acetate. 
The combined extracts were washed successively with sodium bicarbonate 
solution and water and dried over magnesium sulphate before filtering and 
evaporating to yield a yellow oil. 
(Purity was certified by thin layer chromatography and the structure 
confirmed by N.M.R.) 
(b) 2-(2-Allyloxy-4-methoxyphenyl)-1H-imidazo[4,5-c]pyridine hydrochloride 
To a mixture of 2-allyloxy-4-methoxybenzoyl morpholide (9 g) and 
3,4-diaminopyridine (3.9 g) was added dropwise, with stirring, phosphorus 
oxychloride (16.5 ml). 
The mixture was heated under reflux for 3 hours before excess phosphorus 
oxychloride was removed under reduced pressure. Water (50 ml) was added to 
the residue and the solution made alkaline with ammonia before extraction 
with chloroform. The combined extracts were dried over magnesium sulphate 
before filtering and evaporating to yield a beige coloured solid which was 
purified by column chromatography (silica gel; chloroform/methanol, 19:1) 
to give the free base (m.p. 123.degree.-125.degree. C.) of the title 
compound. The free base was taken up in acetone and treated with ethereal 
hydrochloric acid to precipitate the hydrochloride salt, m.p. 
175.degree.-180.degree. C. (decomp). 
EXAMPLE 38 
2-(2,4-Dimethoxyphenyl)-1H-imidazo[4,5-c]pyridineN.sup.5 -oxide hydrate 
To a solution of 2 equivalents of m-chloroperbenzoic acid in methylene 
chloride at room temperature was added 
2-(2,4-dimethoxy-phenyl)-1H-imidazo[4,5-c]pyridine. After stirring for 1 
hour the yellow solution was refluxed for a further 3 hours. It was then 
concentrated and chromatographed directly on silica gel, eluting with 
chloroform-methanol mixtures. Recrystallisation from ethanol-petrol gave 
the title compound, m.p. 224.degree.-225.degree. C. (dec). 
EXAMPLE 39 
2-(2,4-Dimethoxyphenyl)-4-chloro-1H-imidazo[4,5-c]pyridine 
A suspension in phosphorus oxychloride of the N-oxide obtained in the 
preceding Example was stirred at 80.degree. C. for 3 hours. Excess 
phosphorus oxychloride was then removed in vacuo and the residue 
partitioned between chloroform and dilute ammonium hydroxide. After drying 
the organic phase over magnesium sulphate, the solvent was evaporated and 
the residue recrystallised from aqueous ethanol, m.p. 
203.degree.-204.degree. C. 
EXAMPLE 40 
3-Methyl-2-(2,4-dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine and its 
hydrochloride 
A mixture of 2,4-dimethoxybenzoic acid and 3-methylamino-4-amino-pyridine 
(prepared from 3-bromo-4-nitropyridine-N-oxide and methylamine followed by 
reduction) in phosphorus oxychloride was refluxed for 4 hours. After 
cooling the solid was triturated with ether and then partitioned between 
chloroform and saturated sodium bicarbonate. After drying over magnesium 
sulphate the solvent was evaporated and the residue chromatographed on 
silica gel. Recrystallisation from benzene-petrol gave the title base, 
m.p. 162.degree.-163.degree. C. An acetone solution of the base was 
treated with ethereal HCl to give the title hydrochloride, m.p. 
235.degree.-237.degree. C. 
EXAMPLE 41 
1-Methyl-2-(2,4-dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine and its 
dihydrochloride 
The title base was prepared from 4-methylamino-3-amino-pyridine (prepared 
from 4-chloro-3-nitropyridine and methylamine followed by reduction) and 
2,4-dimethoxybenzoic acid in phosphorus oxychloride as described in 
Example 40, m.p. 180.degree.-181.degree. C. An acetone solution of the 
base was treated with ethereal HCl to give the title hydrochloride m.p. 
225.degree.-227.degree. C. 
EXAMPLE 42 
2-(3,4-Dihydroxyphenyl)-1H-imidazo[4,5-c]pyridine hydrochloride 
2-(3,4-Dimethoxyphenyl)-1H-imidazo[4,5-c]pyridine was stirred at reflux in 
glacial acetic acid and 48% HBr for 8 hours. After cooling, the 
precipitate was filtered and recrystallised from 2N HCl to give the title 
compound m.p. 320.degree.-323.degree. C. (dec). 
EXAMPLE 43 
2-[4-Methoxy-2-(3-dimethylaminopropoxy)phenyl]-pyridine hydrochloride 
(a) 2-[4-Methoxy-2-(3-chloropropoxy)phenyl]-1H-imidazo[4,5-c]pyridine 
A mixture of 3,4-diaminopyridine and 2-(3-chloropropoxy)-4-methoxybenzoic 
acid in phosphorus oxychloride was stirred at reflux for 4 hours. The 
excess phosphorus oxychloride was then removed in vacuo and the residue 
carefully treated with water before basifying with dilute ammonia 
hydroxide and extracting with chloroform. The crude product was then 
dissolved in ethyl acetate, decolourised with charcoal and triturated with 
ethereal HCl to give the title compound m.p. 174.degree.-176.degree. C. 
(b) 
2-[4-Methoxy-2-(3-dimethylaminopropoxy)phenyl]-1H-imidazo-[4,5-c]-pyridine 
hydrochloride 
A solution of the compound obtained in stage (a) in 33% 
dimethylamine/ethanol was stirred at 100.degree. C. for 8 hours. The 
volatiles were then removed in vacuo and the residue partitioned between 
chloroform and saturated sodium bicarbonate. After drying over magnesium 
sulphate, the solvent was evaporated and the residue recrystallised from 
benzene/petrol to give the title base. The ethanol solution of the base 
was treated with ethereal HCl to give the title hydrochloride as a 
hydrate, m.p. 206.degree.-208.degree. C. 
EXAMPLE 44 
2-[4-Methoxy-2-(3-iso-propylamino-propoxy)phenyl]-1H-imidazo-[4,5-c]pyridin 
e hydrochloride 
The above compound was prepared by reacting the product of stage (a) of 
Example 42 and isopropylamine in ethanol at 100.degree. C. for 8 hours as 
described in stage (b) of Example 43, m.p. 217.degree.-219.degree. C. 
(hydrate). 
EXAMPLE 45 
2-[4-Methoxy-2-(3-tert-butylaminopropoxy)phenyl]1H-imidazo-[4,5-c]pyridine 
hydrochloride 
The above compound was prepared by reacting the product of stage (a) of 
Example 43 and tert-butylamine in ethanol at 100.degree. C. for 8 hours as 
described in stage (b) in Example 43, m.p. 252.degree.-253.degree. C. 
(hydrate). 
EXAMPLE 46 
2-(2,4-Dimethoxyphenyl)-4-amino-1H-imidazo[4,5-c]pyridine 
The compound is prepared by treatment of the corresponding 4-chloro 
compound with ammonium hydroxide. 
EXAMPLE 47 
2-(2,4-Dimethoxyphenyl)-4-hydroxy-1H-imidazo[4,5-c]pyridine 
This compound is prepared by treatment of the corresponding 4-amino 
compound with nitrous acid. 
EXAMPLE 48 
2-(2,4-Dimethoxyphenyl)-4-methoxy-1H-imidazo[4,5-c]pyridine 
This compound is prepared by 4-methoxylation of the corresponding 4-chloro 
compound. 
EXAMPLE 49 
2-(2,4,5-trimethoxyphenyl)-1H-imidazo[4,5-c]pyridine dihydrochloride 
This compound was prepared in an analogous manner to that described in 
Example 1, m.p. 258.degree.-260.degree. C. 
EXAMPLE 50 
2-(2-methylsulphinyl)-1H-imidazo[4,5-c]pyridine hydrochloride 
This compound was prepared from the compound of Example 29, in an analogous 
manner to that described in Example 21, m.p. 243.degree.-245.degree. C. 
The following examples illustrate pharmaceutical formulations according to 
the present invention wherein the active compound may be any compound of 
formula (I') defined above, for example, 
2-(2-methoxy-4-methylsulphinylphenyl)-1H-imidazo[4,5-c]pyridine. 
EXAMPLE A 
Tablet Formulation 
______________________________________ 
Active compound (as base) 
100 mg 
Lactose 100 mg 
Sodium starch glycollate 
20 mg 
Polyvinylpyrrolidone 4 mg 
Magnesium stearate 2 mg 
226 mg 
______________________________________ 
Mix the active compound with the lactose and the sodium starch glycollate. 
Granulate the mixture with a solution of polyvinylpyrrolidone in 50% 
aqueous alcohol. Dry the granulate and mix in the magnesium stearate. 
Compress to tablets of average weight 226 mg. 
EXAMPLE B 
Capsule Formulation 
______________________________________ 
Active compound (as base) 
100 mg 
Lactose 100 mg 
Starch 30 mg 
Methylcellulose 4 mg 
Stearic Acid 4 mg 
238 mg 
______________________________________ 
Mix the active compound with the lactose and the starch. Granulate with a 
solution of the methylcellulose in water. Dry and mix in the stearic acid. 
Fill 238 mg into a hard gelatin capsule. 
EXAMPLE C 
IV Injection (Freeze Dried) 
______________________________________ 
Active compound (as hydrochloride) 
50 mg 
Mannitol 50 mg 
Water for Injection to 2 ml 
______________________________________ 
Dissolve the active compound in the Water for Injections. Sterilise the 
solution by passage through a membrane filter, 0.2.mu. pore size, 
collecting the filtrate in a sterile glass receiver. Fill into sterile 
glass 2 ml vials under aseptic conditions and secure with aluminium seals. 
The injection is reconstituted before administration by the addition of a 
convenient volume of Water for Injection or sterile saline solution when a 
large volume infusion is required. 
EXAMPLE D 
IV Injection (Multidose vial) 
______________________________________ 
Active compound (as hydrochloride) 
250 mg 
Benzyl Alcohol 0.075 ml 
Water for Injection 5 ml 
______________________________________ 
Dissolve the benzyl alcohol in Water for Injection. Add and dissolve the 
active compound. Make up to volume with Water for Injection. Pass through 
a membrane filter, 0.2.mu. pore size, collecting the filtrate in a sterile 
glass receiver. Fill into sterile glass vials. Close the vials with 
sterile rubber closures and secure with aluminium seals. 
EXAMPLE E 
Suppository 
______________________________________ 
Compound (as base) 100 mg 
Suppository Base (Massa 2 g 
Esterinum C) to 
______________________________________ 
Melt the suppository base at 40.degree. C. Incorporate the active compound 
in fine powder form in the molten base and mix until homogeneous. Pour the 
mixture into suitable moulds, 2 g per mould and allow to set. 
BIOLOGICAL ACTIVITY 
Determination of in vitro Inotropic Activity 
Male guinea-pigs (Halls 275-350 g) having been allowed free access to food 
and water were killed by a blow to the head. The heart was rapidly excised 
and washed with Krebs-Henesleit solution containing the 
.beta.-adrenoceptor antagonist carazolol (5.times.10.sup.-8 M) and gassed 
with 95% O.sub.2 : 5% CO.sub.2 at 34.degree. C. The heat was transferred 
to a petri dish containing the same buffer kept at a constant temperature 
(34.degree. C.) throughout the dissection. Fresh buffer was used for each 
dissection and washings were discarded after use. A single right 
ventricular papillary muscle was employed from each heart; the tendinous 
end ligated to a stainless steel hook and the lower end ligated and cut 
away from the ventricle wall and attached to a perspex clamp such that the 
tissue was in contact with a platimum punctate electrode. The stainless 
steel hook was suspended from a Grass FT.03 transducer which recorded 
isometric tension. The preparation was placed in a 20 ml pyrex organ bath 
containing buffer gassed with 95% O.sub.2 : 5% CO.sub.2 and maintained at 
34.degree. C. 500 mg loading tension was applied to the preparation. 
Stimulation was effected by rectangular pulses of Imsec duration at 1.5 Hz 
at 30% above the threshold voltage (1-5 volts) by a SRI stimulator. The 
transducer inputs were coupled to a potentiometric recording device by a 
6-channel Grass transducer coupler. After 90 minutes, preparations unable 
to sustain uniform contractions beyond this period were rejected. After 
observing both a stable baseline and contractile force (usually 15 
minutes) additions of test compounds were made in a cumulative fashion in 
0.5 log.sub.10 unit intervals over the range of 10.sup.-9 M to &gt;10.sup.-3 
M (final bath concentration) or the limit of solubility which ever is the 
greater. 
The following compounds were tested and found, in the concentration range 
specified above, to have positive inotropic activity and to be capable of 
eliciting at least 75% increase in the basal contractile force (F.sub.c). 
The compounds may be ranked as follows: 
______________________________________ 
Potency for 75% increase 
F.sub.c lying within the range: 
Compounds of Example Nos: 
______________________________________ 
(1) &gt;10.sup.-3 M 3,22,35,38,40,41,50 
(2) 10.sup.-4 -10.sup.-3 M 
1,7,21,23,29,32,34 
(3) 10.sup.-5 -10.sup.-4 
8,10 
______________________________________ 
Determination of in vivo Inotropic and Vasodilatory Activity 
The compounds of Examples 1,2 and 21 were tested in comparison with 
amrinone and Vardax. In anaesthetised, open-chest beagles, bolus 
intravenous injections of the test compound (see Table below) produce a 
dose-related positive inotropic stimulation (as measured by the increase 
in the rate of change of the left ventricular pressure--dp/dt) over the 
dose range of 0.003-3.0 mg/kg. This is accompanied by a dose-related 
increase in aortic blood flow, and a fall in systemic blood pressure (see 
Table below). 
______________________________________ 
Compound ED.sub.50 INO 
ED.sub.30 VASO 
______________________________________ 
Example 2 2.0 mg/kg 5.1 mg/kg 
Example 1 0.13 mg/kg 0.24 mg/kg 
Example 21 0.063 mg/kg 0.19 mg/kg 
Vardax 1.0 mg/kg 2.11 mg/kg 
Amrinone 1.0 mg/kg 2.0 mg/kg 
______________________________________ 
Determination of Phosphodiesterase Inhibitory Activity 
The determination of phosphodiesterase inhibitory activity was effected by 
a procedure based on that of Thompson and Appleman (Biochme., 10, 311 
(1971)). .sup.3 H-cAMP (5 uM) is incubated at 37.degree. C. for 30 minutes 
with the 1000Xg supernatent of a 10% (w/v) homogenate of guinea pig heart 
in 50 mM-Tris/HCL pH7+5 mM-mgCI.sub.2 in either the presence or the 
absence of the compound of Example 21 which, in the former case, is 
dissolved in Tris buffer to give final concentrations of 100 uM, 1 mM and 
10 mM. Phosphodiesterase enzyme in the homogenate hydrolyses .sup.3 H-cAMP 
to .sup.3 H-5'-AMP which is further converted to .sup.3 H-adenosine by a 
5'-nucleotidase added to the incubation mixture. After a period of 
incubation unchanged .sup.3 H-cAMP is removed by adding ion exchange resin 
to the mixture and centrifuging. The .sup.3 H in the supernatent is 
assayed by liquid scintillation counting and gives a quantitative measure 
of adenosine formation (i.e. cAMP hydrolysis). Comparison of the .sup.3 
H-adenosine formed in the presence and absence of test compound gives a 
measure of the PDE-inhibitory activity of the compound. At 100 .mu.M, 1 mM 
and 10 mM, the compound of Example 21 exhibited no PDE inhibitory 
activity. 
Cardiovascular and anti-aggregating actions of the compound of Example 21 
(Compound A) in the anaesthetised rhesus monkey 
Rhesus monkeys of both sexes (7.3-9 kg, body weight) were sedated with 
phencyclidine, subsequently anaesthetised with thiopentone and maintained 
with sodium pentobarbitone. Catheters were placed in the left femoral 
artery to record blood pressure and in the left femoral vein for 
administration of drugs. A further catheter was placed in the 
contralateral femoral artery for the removal of blood samples. Heart rate 
was recorded from ECG (standard lead II). A left ventricular catheter was 
introduced via the left carotid artery to measure left ventricular 
pressure. All cardiovascular parameters were displayed on a polygraph 
(Grass, model 7D). Rectal temperature of the anaesthetised monkey was 
maintained at 37.degree.-38.degree. C. via a heated table-pad. 
(i) Ex vivo inhibition of platelet aggregation 
Blood samples (3 ml) were withdrawn into syringes containing trisodium 
citrate (0.315% w/v final concentration), and spun for 2 seconds. The 
platelet rich-plasma was transferred to a Born-type aggregometer and 
incubated for 1 min (at 37.degree. C.) prior to the addition of sufficient 
ADP to induce sub-maximal (1.5-3 .mu.M) or near maximal (8-12 .mu.M) 
aggregation. Inhibition of aggregation was calculated with reference to at 
least 2 control samples prior to intravenous infusion of compound A. The 
sequence of administration of compound A was randomized between 
experiments. The effective dose of compound A which caused 50% inhibition 
of aggregation is 1.0 mg/kg i.v. (approximately). 
(ii) In vitro inhibition of platelet aggregation 
Blood was freshly collected into siliconized (Siloclad; Clay Adams) plastic 
(Sterlin Ltd.) tubes containing trisodium citrate (3.15%; 0.1 volume with 
0.9 volume blood) and centrifuged (200 g for 15 min) at room temperature. 
The platelet-rich plasma (PRP) was withdrawn into plastic containers and 
kept at room temperature. Inhibition of platelet aggregation was 
determined in a Born-type aggregometer by incubating aliquots (0.5 ml) of 
the PRP for 1 min at 37.degree. C. with or without compound A prior to 
addition of sufficient adenosine diphosphate (ADP). Dose-inhibition curves 
were constructed for each compound and the ID.sub.50 (dose causing 50% 
inhibition) was calculated as the dose required to reduce the aggregation 
to 50% of its control amplitude. The ID.sub.50 for compound A is 1 mg/ml 
(approximately). 
Toxicity Studies 
In preliminary toxicity studies, the effects of intravenous administration 
of compound A (see above) to female Wistar rats has been determined. 
Animals were randomly distributed into groups of five, each group receiving 
a single administration of drug. One group served as a control and 
received the vehicle only. Observations on behaviour were made at 5 
minutes and 20 minutes, at 1, 3, 41/2 hours and at 2, 4 and 6 days 
following drug administration. 
The findings of these studies are tabulated below. 
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DOSE OBSERVATION MORTALITY 
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35 mg/kg 
Flushing, Slight -- 
hypothermia (&lt; 1.degree. C.) 
70 mg/kg 
Hypoactivity, ataxia, 
-- 
slow respiration 
100 mg/kg 
Hypothermia (&lt; 2.degree. C.) 
-- 
deep slow respiration, 
ataxia, flushing, hypoactivity 
140 mg/kg 
Hypoactivity, hypothermia, 
2/5 within 3h 
(2-3.degree. C.) ataxia 
4/5 within 2 days 
200 mg/kg 
Hypoactivity, ataxia, 
5/5 within 5-30 
convulsions minutes 
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