PDE IV inhibiting compounds, compositions and methods of...

Details PDE IV inhibiting compounds, compositions and methods of... PDE IV inhibiting compounds, compositions and methods of...

2000-02-25

2001-03-20

Davis, Zinna Northington (Department: 1625)

Drug, bio-affecting and body treating compositions

Designated organic active ingredient containing

Having -c-, wherein x is chalcogen, bonded directly to...

C546S266000

Reexamination Certificate

active

06204275

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to compounds and pharmaceutical compositions for the treatment of diseases by raising the level of cyclic adenosine-3′,5′-monophosphate (cAMP) through the inhibition of phosphodiesterase IV (PDE IV).
Many hormones and neurotransmitters modulate tissue function by elevating intracellular levels of 3′,5′-cyclic adenosine monophosphate (cAMP). The cellular levels of cAMP are regulated by mechanisms which control synthesis and breakdown. The synthesis of cAMP is controlled by adenyl cyclase which may be directly activated by agents such as forskolin or indirectly activated by the binding of specific agonists to cell surface receptors which are coupled to adenyl cyclase. The breakdown of cAMP is controlled by a family of phosphodiesterase (PDE) isoenzymes, which also control the breakdown of guanosine 3′,5′-cyclic monophosphate (cGMP). At least seven members of the family have been described (PDE I-VII), the distribution of which varies from tissue to tissue. This suggests that specific inhibitors of PDE isoenzymes could achieve differential elevation of cAMP in different tissues [for reviews of PDE distribution, structure, function and regulation, see Beavo & Reifsnyder (1990) TIPS, 11:150-155, Nicholson et. al. (1991) TIPS, 12: 19-27, and Torphy and Undem (1991) Thorax, 46: 512-523].
The availability of PDE isotype selective inhibitors has enabled the role of PDEs in a variety of cell types to be investigated. In particular it has been established that PDE IV controls the breakdown of cAMP in many inflammatory cells, for example, basophils (Peachell P. T. et al., (1992) J. Immunol., 148: 2503-2510) and eosinophils (Dent G. et al., (1991) Br. J. Pharmacol., 103: 1339-1346) and that inhibition of this isotype is associated with the inhibition of cell activation. Furthermore, elevation of cAMP in airway smooth muscle has a spasmolytic effect. Consequently PDE IV inhibitors are currently being developed as potential anti-inflammatory drugs particularly for the prophylaxis and treatment of asthma, by achieving both anti-inflammatory and bronchodilator effects.
The application of molecular cloning to the study of PDEs has revealed that for each isotype there may be one or more isoforms. PDE IV has been shown to exist in four isoforms (A, B, C and D) to date, each coded for by a separate gene in both rodents (Swinnen J. V. et al., (1989) Proc. Natl. Acad. Sci. USA, 86: 5325-5329) and man (Bolger G. et al., (1993) Mol. Cell Biol., 13: 6558-6571).
The existence of multiple PDE IVs raises the prospect of obtaining inhibitors that are selective for individual isoforms, thus increasing the specificity of action of such inhibitors. This assumes that the different PDE IV isoforms are functionally distinct. Indirect evidence in support of this comes from the selective distribution of these isoforms in different tissues (Swinnen et al., 1989; Bolger et al., 1993; Obernolte R. et al., (1993) Gene, 129: 239-247, ibid) and the high degree of sequence conservation amongst isoforms of different species.
To date, full length cDNAs for human PDE IVA, B and D (Bolger et al., 1993 ibid; Obernolte et al., 1993 ibid; Mclaughlin M. et al., (1993) J. Biol. Chem., 268: 6470-6476) and rat PDE IVA, B and D (Davis R. et al., (1989) Proc. Natl. Acad. Sci. USA, 86: 3604-3608; Swinnen J. V. et al., (1991) J. Biol. Chem., 266: 18370-18377), have been reported, enabling functional recombinant enzymes to be produced by expression of the cDNAs in an appropriate host cell. These cDNAs have been isolated by conventional hybridization methods. However using this approach, only partial cDNAs for both human and rat PDE IVC have been obtained. (Bolger et al., ibid. 1993 and Swinnen et al., ibid. 1989 and International Patent Specification No. WO 91/16457.)
The design of PDE IV inhibitors for the treatment of inflammatory diseases such as asthma, has met with limited success to date. Many of the PDE IV inhibitors which have been synthesised have lacked potency and/or inhibit more than one type of PDE isoenzyme in a non-selective manner. PDE IV inhibitors that are relatively potent and selective for PDE IV, are reported to be emetic as well. Indeed this side effect has been so universal that experts have expressed their belief that the emesis experienced upon administration of a PDE IV inhibitor may be mechanism based.
The compounds described herein are potent inhibitors of PDE TV at concentrations that exhibit little or no inhibitory action on other PDE isoenzymes. These compounds inhibit the human recombinant PDE IV enzyme and also elevate cAMP in isolated leukocytes. Certain compounds prevent inflammation in the lungs induced by carrageenan, platelet-activating factor (PAF), interleukin-5 (IL-5) or antigen challenge. These compounds also suppress the hyperresponsiveness of airway smooth muscle seen in inflamed lungs. Advantageously, compounds according to the invention have good oral activity, and at orally effective doses exhibit little or none of the side-effects associated with known PDE IV inhibitors, such as rolipram. The compounds of the invention are therefore of use in medicine, especially in the prophylaxis and treatment of asthma and other inflammatory conditions.
SUMMARY OF THE INVENTION
A compound represented by formula I:
or a pharmaceutically acceptable salt thereof wherein:
each R
a
independently represents a member selected from the group consisting of: H, C
1-6
alkyl and haloC
1-6
alkyl;
R
b
represents a member selected from the group consisting of: H, C
1-6
alkyl, haloC
1-6
alkyl;
each R
1
independently represents a member selected from the group consisting of: C
1-10
alkyl, aryl, heteroaryl, substituted C
1-10
alkyl, substituted aryl and substituted heteroaryl, wherein the substituents are 1-6 members selected from the group consisting of: C
1-4
alkyl, halo, hydroxy, haloC
1-4
alkyl, CN, C
1-4
alkoxy, C
1-4
alkylthio, C
1-4
alkyl-SO
2
— and H
2
NSO
2
—; and
when present, each R
2
independently represents a member selected from the group consisting of: halo, C
1-6
alkyl, haloC
1-6
alkyl and CN.
DETAILED DESCRIPTION OF THE INVENTION
The terms used herein have the following meanings unless otherwise indicated.
Heteroaryl is a member selected from the group consisting of pyridyl and thiazolyl.
Halo includes F, Cl, Br and I.
Alkyl and the alkyl portion of alkoxy include linear, branched and cyclic structures, with the indicated number of carbon atoms. Thus, examples of C
1-6
alkyl include methyl, ethyl, propyl, 2-propyl, s- and t-butyl, butyl, pentyl, hexyl, 1,1-dimethylethyl, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. Similarly, C
1-6
alkoxy is intended to include alkoxy groups of from 1 to 6 carbon atoms of a straight, branched, or cyclic configuration. Examples of alkoxy groups include methoxy, ethoxy, propoxy, isopropoxy, cyclopropyloxy, cyclohexyloxy, and the like. Likewise, C
1-6
alkylthio is intended to include alkylthio groups of from 1 to 6 carbon atoms of a straight, branched or cyclic configuration. Examples of alkylthio groups include methylthio, propylthio, isopropylthio, cycloheptylthio, etc. By way of illustration, the propylthio group signifies —SCH
2
CH
2
CH
3
.
HaloC
1-6
alkyl means an alkyl group in which one or more hydrogen atoms have been replaced by halogen atoms, with up to complete substitution of all hydrogen atoms with halo groups, e.g., —CF
3
, —CF
2
CF
3
and the like.
The invention encompasses compounds of Formula I useful in the treatment of disease by inhibition of PDE IV:
or a pharmaceutically acceptable salt thereof wherein:
each R
a
independently represents a member selected from the group consisting of: H, C
1-6
alkyl and haloC
1-6
alkyl;
R
b
represents a member selected from the group consisting of: H, C
1-6
alkyl, haloC
1-6
alkyl;
each R
1
independently represents a member selected from the group consisting of: C
1-10
alkyl, aryl, heteroaryl, substituted C
1-10
alkyl, substituted aryl and substituted heteroaryl, wherein the substituents are 1-6 members selec

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