WO1996001645A1

WO1996001645A1 - Use of muramyl peptide compounds

Info

Publication number: WO1996001645A1
Application number: PCT/GB1995/001619
Authority: WO
Inventors: Philip Ledger
Original assignee: Peptech(Uk) Limited
Priority date: 1994-07-11
Filing date: 1995-07-10
Publication date: 1996-01-25
Also published as: BG101126A; HU9700071D0; JPH10505580A; CN1155245A; ZA955763B; AU2893595A; GB9413935D0; CZ4797A3; CA2194678A1; SK2697A3; IL114542A0; EP0768888A1; HUT77290A

Abstract

Muramyl peptide compounds, particularly N-acetyl-D-glucosaminyl-(β1-4)-N-acetylmuramyl-L-alanyl-D-isoglutamine (GMDP), are useful in the treatment or prophylaxis of inflammatory dermatological conditions such as psoriasis and in the treatment or prophylaxis of immune-related diseases of the skin and mucous membranes.

Description

USE OF MURA YL PEPTIDE COMPOUNDS

The present invention relates to the treatment of inflammatory dermatological conditions and in particular to the treatment of psoriasis.

Psoriasis is a non-infective, usually chronic inflammatory skin disease occurring in about 2% of the population. It has a number of clinical manifestations, the most common of which is raised, red, roughened plaques covered by silvery scales. The nails are involved in about 50% of cases, and arthritic involvement may occur. The external changes in the skin are associated with histological changes in the disposition of the epidermis, and vascularisation of sub-epidermal tissues. Infiltration of lymphocytes commonly occurs. The occurrence of psoriasis results from a combination of environmental and genetic factors. Numerous studies have demonstrated a range of changes in functionality of the epidermis and immune system of psoriatics, but no comprehensive theory yet exists which can accounts for all the observed abnormalities.

Current therapy for psoriasis can be topical (including steroids, coal tar, dithranol, vitamin D3 derivatives) oral (including retinoids, methotrexate, cyclosporine) or phototherapy (UVB alone, or UVA with psoralen) . Unfortunately, the more effective preparations (eg. steroids, methotrexate, cyclosporine) have the potential to cause severe side effects. The less potent, palliative preparations, which tend to be topical, although being less dangerous, are frequently messy and inconvenient to use. It is therefore evident that an effective, safe, oral treatment for psoriasis is a very desirable medication and would have extreme utility.

It has now been discovered that various muramyl peptide derivatives are useful in the treatment of psoriasis.

It has long been known that non-specific stimulation of the immune system can be brought about by exposure to bacteria, or components extracted from bacterial cell walls. The specific components responsible for this activity were identified as sugar-containing peptides of the cell wall, and further biochemical analysis of the peptide identified then as the peptidoglycan component of the cell wall . The smallest effective synthetic molecule was found to be an N-acetylmuramyl-L-alanyl-D- isoglutamine (Merser et al , Biochem . Biophys . Res . Comm. 66 1316 (1975)) . The ability of this compound (now frequently referred to as "prototype muramyl dipeptide" or "prototype MDP") to protect mice against bacterial infection ( Klebsiella pneumonia) has been described (Chedid eϋ al , Proc . Na t ' l . Acad . Sci . USA, 74 2089 (1977) ) .

Subsequently, a wide variety of analogues of prototype muramyl dipeptide were synthesised, some of which have been proposed as treatments for the restoration of immune function or the non-specific stimulation of the immune system. These analogues, and prototype MDP itself, are muramyl peptide compounds.

Various authors have dealt with the use of muramyl peptides and analogues thereof as adjuvants, including Azuma et al (Adv. Exp . Med . Biol . 319, 253-263 (1992)) , who teach that MDPs are effective for use as immunoadjuvants for the potentiation of antigenicity of recombinant or component vaccines .

Allison et al { Semin . Immunol . 2(5) 369-374 (1990)) teach that an adjuvant formulation consisting of a synthetic MDP analogue in a squalane-Pluronic polymer emulsion elicits cell-mediated immunity and antibodies of protective isotypes and augments responses to various antigens.

Burke (Rev. Infect . Dis . , 13, Suppl. 11, pS906-911, Nov- Dec 1991) teaches that MTP-PE was found to be particularly useful as an adjuvant with a Herpes simplex virus subunit vaccine.

Allison et al (Mol . Immunol . , 28(3) 279-284 (1991)) relates to the use of MDP analogues with antigens to elicit cell mediated immunity in influenza, hepatitis B virus, herpes simplex virus, lentivirus and tumour vaccines.

Muramyl peptides have also been proposed for use as anti viral agents (Ikeda et al , Antiviral Res 5:207-15 (1985)) and in the treatment of cancers (Phillips NC and Tsao, M- S, Cancer Immunol Immunother. 33:85-90 (1991)) .

In the teaching of these documents, little is disclosed concerning the use of muramyl peptide compounds for diseases of the skin, and none of these have involved psoriasis or other inflammatory conditions . Most skin applications have involved the potential anti-cancer benefits of this class of compound. For example, Talmadge, JE et al ( Cancer Res 46:1160-3 (1986)) found that the muramyl peptide analogue MTP-PE was able to retard the growth of primary skin cancers. In another study (Greenhalgh D and Gamelli, RL, Journal of Trauma 27:510-4 (1987)), the use of MDP was examined in wound healing. However, in this case neither beneficial nor deleterious effects were seen. Elsewhere, the local injection of MDP with an antigen has been shown to enhance the subsequent cutaneous "delayed type hypersensitivity" response to that antigen (Tsujimoto, M et al , Microbiol Immunol . 23:933-936 (1979)) .

US-A-4357322 discloses the use of various muramyl and desmethylmuramyl dipeptides in treating inflammation. No mention, however, is made of GMDP or psoriasis.

In a first aspect of the present invention there is provided the use of a muramyl peptide compound in the preparation of an agent for the treatment or prophylaxis of an inflammatory dermatological condition.

Many muramyl peptide compounds useful in this invention fall within general formula I:

wherein:

R¹ represents a hydrogen atom or a C₁-C₂₂ acyl group; R² represents a hydrogen atom or a C_τ-C₂₂ acyl group;

R³ represents a hydrogen atom or a C,-C₆ alkyl group;

R⁴ represents a C_τ-C₂₁ alkyl group or a C₅ or C₁₀ aryl group;

R⁵ represents a hydrogen atom; and

R represents the residue of an amino acid or a linear peptide built up of from 2 to 6 amino acid residues, at least one of the residues being optionally substituted with a lipophilic group;

other than prototype muramyl dipeptide and desmethylmuramyl dipeptide.

Preferred acyl groups for R¹ and R² are C^Cg acyl groups such as acetyl; it will be appreciated that the carbon count in the acyl group does not include the carbonyl moiety. Preferred alkyl groups for R³ are C^ , alkyl groups such as methyl and ethyl. Preferred alkyl groups for R⁴ and C^Cg alkyl groups, particularly C^-d alkyl groups, such as methyl or ethyl; phenyl is a preferred aryl group.

R preferably represents a mono-, di- or tri-peptide. The proximal peptide residue (or the only peptide residue, if there is only one) is preferably that of an L-amino acid. Examples include:

L-alanyl L-tryptophanyl

L-valyl L-lysyl L-leucyl L-ornithyl

L-isoleucyl -arginyl L-α-aminobutyryl -histidyl

L-seryl L-glutamyl

L-threonyl -glutaminyl L-methionyl L-aspartyl

L-cysteinyl L-asparaginyl

L-phenylalany1 L-prolyl

L-tyrosyl L-hydroxyprolyl

L-alanyl is preferred, as is L-threonyl.

The next amino acid from the proximal end of the peptide is preferably of the D-configuration. It is preferably acidic and may be D-glutamic or D-aspartic acid or a mono-, di- or mixed

alkyl ester, amide or C₁-C₄ alkyl amide thereof. (The expression "mixed" is illustrated when one carboxyl group is amidated and the other esterified. D-isoglutamine and D- glutamate are preferred.

A third amino acid residue from the proximal end of the chain, if there is one, is preferably of the L- configuration, as indicated above in relation to the proximal amino acid residue. L-alanyl and L-lysyl are preferred.

The amino acid residue or linear peptide is optionally substituted with at least one lipophilic group. The lipophilic group may be a C₁₀-C₂₂ acyl group such as stearoyl or a di- (C₁₀-C₂₂ acyl) -sπ-glycero-3' -hydroxy- phospheryloxy-group wherein for example each of the C_1Q-C₂₂ acyl groups can be a palmitoyl group. The lipophilic group may alternatively (or in addition, as more than one substitution may be present) be a C^C^, ester group, such as a C₂-C₆ ester group: a butyl ester is an example.

Examples of muramyl dipeptides within the scope of general formula I include: muroctasin, otherwise known as MDP-Lys (L18) (N²- (N- acetylmuramyl-L-alanyl-D-isoglutaminyl) -N⁶-stearoyl- L-lysine) ;

MTP-PE (N-acetyl-muramyl-L-alanyl-D-isoglutaminyl-L- alanyl-2- (1' ,2' -dipalmitoyl-sn-glycero-3' -hydroxy- phosphoryloxy) ethylamide, monosodium) ,*

murabutide (N-acetylmuramyl-L-alanyl-D-glutamine-cϋ- N-butyl ester) ,- and

t-MDP (N-acetylmuramyl-L-threonyl-D-isoglutamine) .

The preparation of muroctasin is disclosed in EP-A- 0021367 and US-A-4317771. The preparation of MTP-PE is disclosed in EP-A-0025495. The preparation of murabutide is described in Lefrancier et al , J. Med. Chem. . 25 87

(1982) . The preparation of t-MDP can be prepared by methods known in the art. Patent publications which give details of the preparations of muramyl peptide compounds generally include BE-A-0834753 , BE-A-0834754, BE-

A-0847103, BE-A-0849214, DE-A-2710455, DE-A-2922533, DE-

A-2747379, DE-A-2912865, FR-A-2355505, FR-A-2358159, FR-

A-2375249, EP-A-0004512, EP-A-0002677, JP-A-54063016, JP- A-54073729, JP-A-55019236, US-A-4082735 and US-A-4082736.

(The preparation of prototype muramyl dipeptide is disclosed in DE-A-2450355 and US-A-4235771. ) All the documents referred to in this specification are incorporated herein by reference.

Not all muramyl dipeptides useful in the present invention fall within general formula I. Many fall within general formula II, which represents a very much preferred group of compounds for use in the invention:

II

wherein:

R represents a residue of an amino acid or a linear peptide built of from 2 to 6 amino acid residues, at least one of the residues being optionally substituted with a lipophilic group; and

n is 1 or 2.

Preferred values for R are as described above in relation to general formula I. It is particularly preferred that the peptide R correspond to the peptide in prototype MDP (L-Ala-D-isoGln) . Alternatively, in another preferred embodiment, R may represent L-Ala-D-Glu.

The preferred value for n is 1.

Compounds of general formula II are disclosed in US-A- 4395399 and the preferences set out in that document are equally preferred in the present invention. Additionally, in this invention, the group R may be substituted lipophilically as described above.

One of the most preferred compounds for use in the present invention falls within general formula II and is N-acetyl-D-glucosaminyl- (βl-4 ) -N-acetylmuramyl-L-alanyl- D-isoglutamine (GMDP), the structure of which is:

GMDP

This compound (Compound II in US-A-4395399) , also known as glycopin, has already undergone preclinical toxicity testing and pharmacokinetic investigations required for licensing for clinical use in the USSR (as it then was) . The acute toxicity in mice, measured by the LD_S0 test is 7 g/kg. This figure shows the compound to be almost an order of magnitude less toxic than muroctasin which has an LD₅₀ value in mice of 625 g/kg.

While the pyrogenicity of GMDP is sufficiently low to make it suitable for use in the present invention, and not to have prevented its clinical evaluation for other purposes, it may in some circumstances be preferable to use an even less pyrogenic analogue. Such an analogue is available, and is N-acetyl-D-glucosaminyl- (01-4) -N- acetylmuramyl-L-alanyl-D-glutamic acid (GMDP-A) , which is Compound III in US-A-4395399, and whose structure is as follows:

GMDP -A

Other preferred compounds within the scope of general formula II include:

N-acetyl-D-glucosaminyl- (31-4) -N acetylmuramyl-L-alanyl- L-isoglutamine (GMDP-LL) which has the structure:

GMDP-LL

N-acetyl-D-glucosaminyl- (jSl-4) -N acetylmuramyl-L-alanyl- D-glutamine n-butyl ester (GMDP-OBu) which has the structure:

GMDP-OBu

N-acetyl-D-glucosaminyl- (/31-4) -N acetylmuramyl-L-alanyl- D-isoglutaminyl-L-lysine (GMDP-Lys) which has the structure:

GMDP-Lys

N^α- [N-acetyl-D-glucosaminyl- (01-4) -N-acetylmuramyl-L- alanyl-D-isoglutaminyl] -N'-stearoyl-L-lysine (GMDP-

Lys (St)) which has the structure:

GMDP-Lys (St)

Other useful compounds include :

N^α- [N-Acetyl-D-glucosaminyl- (01--4) -N-acetyl -muramyl -L- alanyl-γ-D-glutamyl] -N^€-stearoyl-L-lysine which has the structure :

GMDPA-Lys(St)

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-L-alanyl- D-glutamic acid dibenzyl ester which has the structure:

GMDPA(OBzl)

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-N-methyl- L-alanyl-D-isoglutamine which has the structure:

Me -GMDP

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl- (01--4) - N-acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-bis- (L- alanyl-D-isoglutamine) which has the structure:

( GMDP )

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl- (01--4) - N-acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-bis- (L- alanyl-D-glutamic acid) which has the structure:

(GMDPA) N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl- (01--4) - N-acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-bis- (L- alanyl-D-isoglutaminyl-L-lysine) which has the structure:

(GMDP Lys)₂

N-acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl- (01--4) N-acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-bis- [L alanyl-D-isoglutaminyl-N^£-stearoyl-L-lysine] :

[GMDP-Lys (St) ]₂ N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-L alanyl-D-isoglutamine 1-adamantyl ester which has the structure :

GMDP -Ad

L-Threonyl-N^e- [N-Acetyl-D-glucosaminyl- (01--4) -N-acetyl - muramyl -L-alanyl -γ-D-isoglutaminyl] -L-lysyl-L-prolyl-L- arginine which has the structure :

GMDP-tuftsin E

N-Acetyl-D-glucosaminyl- (01--4) -N-acetyl-muramyl-L- alanyl-γ-D-isoglutaminyl-L-threonyl -L-lysyl-L-prolyl-L- arginine which has the structure:

GMDP-tuftsin A

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-L-alanyl- α-D-glutamyl-L-lysyl-L-threonyl-N^£-stearoyl-L-lysyl-L- prolyl-L-arginine which has the structure:

GMDPA-tuftsin lipophilic

N^£- [N-Acetyl-D-glucosaminyl- (01--4) -N-acetyl -muramyl -L- alanyl-γ-D-isoglutaminyl] -L-lysyl-L-histidyl-L-glycine amide which has the structure :

GMDPA-bursin

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-L-alanyl - D-isoglutaminyl-L-glutamyl-L-tryptophan which has the structure:

GMDP-thymogen I

N-Acetyl-D-glucosaminyl- (01--4) -N- ace tylmuramyl- L-alanyl - D-isoglutaminyl- e -aminohexanoyl-L-glutamyl-L-tryptophan which has the structure:

GMDP-thymogen II

N^a- [N-Acetyl-D-glucosaminyl- (01--4) -N-acetyl-muramyl-L- alanyl-D-isoglutaminyl] -N^£-stearoyl-L-lysyl-L-glutamyl-L- tryptophan which has the structure:

GMDP-thymogen III

N-acetylmuramyl-L-threonyl-D-isoglutamine which has the structure:

Thr -MDP

N-acetylmuramyl -L-alanyl -D-glutamine n-butyl ester which has the structure :

Murabutide

In the above structures, the following abbreviations are used:

Bzl - benzyl;

Me methyl,*

Ahx - e-aminohexanoyl

The most preferred compound is GMDP followed by GMDP-A, and murabutide. Glucosaminyl-muramyl dipeptides within the scope of general formula II can be prepared relatively cheaply and in reasonably large quantities by the process disclosed in US-A-4395399. The preparation disclosed is based on the extraction and purification of the disaccharide component from the bacterium Micrococcus lysodecticus and its subsequent chemical linkage to a dipeptide synthesised for example by conventional peptide chemistry. However, the disaccharide may equally well be chemically synthesised using standard sugar chemistry.

Inflammatory dermatological conditions treatable, or preventable, by means of the invention include all types of psoriasis, including discoid or plaque psoriasis, flexural psoriasis, scalp psoriasis, palmar/plantar psoriasis, guttate psoriasis, erythrodermic psoriasis and pustular psoriasis, psoriatic arthritis and changes in the nails resulting from psoriasis.

The effect of GMDP in psoriasis has been studied in clinical trials, which are described in more detail in Example 1 below. The PASI (psoriasis area and severity index) of treated individuals tended to fall during treatment, and a number of individuals even showed complete clearing of lesions. Articular symptoms of psoriatic arthritis were also improved by GMDP. Individuals receiving placebo tablets showed minimal improvement, some worsening or no change.

As with many treatments for psoriasis, the exact mechanism by which compounds useful in the invention causes improvement is not known. In fact, it is extremely surprising that muramyl peptide compounds should have this beneficial effect as muramyl peptides are generally considered to be pro-inflammatory immunostimulants, whereas regression of inflamed lesions would generally be considered as requiring anti- inflammatory treatment. It has even been described in the literature that treatment with interferon, another "immunostimulator" can in fact exacerbate psoriasis (Funk J; Langeland T; Schrumpf E; Hanssen LE Br J Dermatology 125: 463-5 (1991) , Pauluzzi P, Kokelj , F, Perkan, V, Pozzato, G, Moretti, M. Acta Dermatol Venereol 73:395 (1993)) .

Some experimental studies have been performed which provide insight into the possible mechanism of action of muramyl peptide compounds, particularly GMDP, in the skin, and also address the potential scope cf the invention. However, the effectiveness of the invention is not affected by the relevance of these experiments or the accuracy of their interpretation.

Thus, as is described in detail in Example 2 below, the muramyl peptide compound GMDP was applied to the skin of mice in solution in ethanol. At control sites, ethanol alone was applied. Some groups of animals received irradiation with ultra violet light (UVB) or received an application of cis urocanic acid (cUCA) , both treatments known to provoke changes in the cutaneous immune system.

Like UVB and cUCA, GMDP treatment caused a loss of ATPase staining and retraction of dendritic processes of the epidermal dendritic cells, which is generally associated with a loss of immunological function. i.e., the GMDP reduced the potential immunoreactivity of the skin. In this respect, it is observed that UVB phototherapy alone is a treatment for psoriasis, thereby supporting the efficacy of muramyl peptide compounds in the invention.

In other experiments, it was determined that unlike UVB, GMDP does not cause migration of dendritic cells from the epidermis to draining lymph nodes.

From these experiments it can be concluded that GMDP is having a fundamental effect on dendritic Langerhans cells, which are the primary immune component of the epidermis. Since there is evidence to support a role for Langerhans cells in the pathogenesis of psoriasis (Placek et al , Acta Derm Venereol (Stockh) 68:369-77 (1988)), it is possible that a down-regulation of the activity of these cells is able to reduce the severity of the disease. The experiments with the mice were performed by topical application of GMDP, but GMDP is known to be orally bioavailable, and so GMDP orally administered, as in the clinical trial, could be expected to exert an effect in the skin.

Because of the demonstrated effect on the cutaneous immune system on the one hand and an immune system- related human skin disease (psoriasis) on the other, it can be expected that muramyl peptides will have utility in the treatment of a range of immunologically based inflammatory skin diseases for which it has never previously been proposed. Moreover, as the mucous membranes lining the buccal cavity, the vagina and the uterine cervix also contain Langerhans cells, these too are target organs for muramyl peptide treatment. In the second aspect of the present invention there is provided the use of muramyl peptide compound in the preparation of an agent for the treatment or prophylaxis of immune-related diseases cf the skin and mucous membranes. These include, but are not restricted to, endogenous eczema (otherwise known as atopic eczema or atopic dermatitis) , seborrhoeic eczema, pompholyx, contact dermatitis, urticaria, erythroderma, lichen planus, vitiligo and alopoecia areata.

The efficacy of muramyl peptide compounds in the invention has been demonstrated using oral administration. The formulation in this instance consisted of tablets containing pharmaceutically acceptable excipients, namely lactose, starch, polyvidone, magnesium stearate and talc. Muramyl peptide compounds may be formulated for sustained and/or delayed delivery if desired. Gastric coating is another option.

The precise oral dosage for administration will always be that deemed suitable by the clinician or physician. Subject to that, a daily oral dosage in the range of from 0.1 to 100 mg per day (or per unit dose) may be found acceptable, with a range of 0.5 to 50 mg being preferred. Within this preferred range, an optimal daily dosage would be within the range 2 to 30 mg or indeed 2 to 20 mg.

In addition, the duration of administration may be varied. The duration will of course depend, to some extent, on dosage level, i.e. lower dose results in longer required duration of dosage. In general terms, the duration of dosage will be in the range of 1-60 days, preferably 1-30 days and most preferably 1-14 days. It has been demonstrated that muramyl peptide compounds do have an affect on the cutaneous immune system after topical administration. Thus, despite the advantages inherent in an oral dosage form, it may be determined that for certain specific instances a topical formulation of muramyl peptide compound(s) will be preferred, when for example functioning of the gastrointestinal tract of a patient is compromised by disease or surgery, or in the case of particularly recalcitrant skin diseases where a particularly high local concentration of muramyl peptide compound is desired.

According to a third aspect of the invention, there is provided a topical formulation of a muramyl peptide compound.

The formulation, which may be presented as an ointment, lotion or cream, may contain pharmaceutically acceptable excipients or carriers, with due regard being taken of the ability of the formulation effectively to release the muramyl peptide into the skin. The formulation may even enhance the passage of said muramyl compounds by the incorporation of so called permeation enhancers.

Muramyl peptide compounds may be used either singly or in combination with each other in the invention. Also, muramyl peptide compounds may be used in combination with other compounds, whether formulated together or separately; for example, a muramyl peptide compound may be administered orally and another compound administered topically. When used in combination, either with each other or with other compounds, administration can be simultaneous, separate or sequential.

In a final aspect, the present invention provides a method for the prophylaxis or treatment of an inflammatory dermatological condition, comprising administering to a patient a muramyl peptide compound.

Preferred features of each aspect of the invention are as for each other aspect, mutatis mutandis .

The invention will now be illustrated by the following non-limiting examples and drawings, in which:

FIGURE 1 : is a plot showing changes in psoriasis severity and area index (PASI) during the course of treatment with GMDP or placebo.

EXAMPLE 1

The use of GMDP in the treatment of psoriasis,

A Open label trial

A preliminary trial in the use of GMDP for psoriasis was conducted in 8 patients who received GMDP in doses of 10 or 20 mg for a period of 9 to 18 days. In general, effective reduction of the cutaneous symptoms of psoriasis was observed. One of the patients had the variant of psoriasis known as psoriatic arthritis, and this patient observed a reduction in joint pain and morning stiffness of joints.

B Placebo controlled trial

METHODS

Nineteen individuals with psoriasis (plaque psoriasis, pustular psoriasis or erythrodermic psoriasis) were randomised either to oral treatment with GMDP tablets (at a dose of 20 mg per day for 10 days, followed by 20 mg every other day for a further ten days, (i.e. treatment on days 1,2,3,4,5,6,7,8,9,10,12,14,16,18 and 20) or an identical placebo tablet. The trial was "double blind", in that neither the patient nor the investigator knew which preparation (GMDP or placebo) was given to particular patients. Common practice in modern clinical trials, this double blinding is particularly important in psoriasis trials where a strong psychological element can cause improvement in patients who "know" they are receiving a potential treatment.

The severity and area of the psoriasis in all of the patients was measured at entry to the trial and at intervals out to about 20 days according to the internationally recognised PASI (psoriasis area and severity index) system (Frederiksson and Pettersson, Dermatologica 157:238-244 (1978)) . Changes in individual patients are shown in Fig 1. In this graph, the starting condition of patients was standardised at "100%", and then at subsequent examinations the PASI score is shown as a percent of starting score. It is clear that the PASI of treated individuals tended to fall during treatment, and a number of individuals even showed complete clearing of lesions. Individuals receiving placebo tablets showed minimal improvement, some worsening or no change. At the time of last examination, the mean score for treated patients was 6.0 and the mean score for control patients was almost twice that, 11.7. EXAMPLE 2

The use of GMDP in the treatment of psoriasis combined with the sequential use of other psoriasis treatments.

In a double blind, placebo-controlled clinical trial of GMDP, 14 patients received active (GMDP) treatment (30 mg/day for 10 days) . Of these, all except one subject showed improvement as measured by a decrease in their PASI score.

Following initial improvement during the 10 days' treatment with GMDP, several of the patients elected to receive further psoriasis therapy other than GMDP. This included UV irradiation, topical salicylic acid, oral magnesium sulphate and vitamin A derivatives. Improvement continued in these patients, clearly demonstrating ^■ that GMDP treatment can be safely and effectively followed by other treatments, if that is considered appropriate by the administering physician.

EXAMPLE 3

The effect of GMDP on ATPase expression by epidermal dendritic cells in the mouse.

METHOD

The method used in this experiment has been described in detail by Norval et al (Norval, M, Gilmour, J W, and Simpson T J, P otoderma ol Photoimmunol Photomed 7:243-8 (1990) )

GMDP was dissolved in ethanol at 1 mg/ml and 0.1 mg/ml. Twenty microlitres of this solution, or vehicle (ethanol) control was painted on to the dorsal sides of the ears of mice which had previously been "stripped" with adhesive tape to remove the superficial barrier layers. Other mice were irradiated with a dose of UVB (144 mJ/cm²) known to influence Langerhans cell (LC) ATPase expression. In another experiment of this type, the positive control was cis-urocanic acid (cUCA) , a substance generated in the epidermis under the influence of UVB, and believed to be implicated in the mediation of UVB-induced changes in LC function.

Twenty four hours later mice were killed, epidermis was removed from the dorsal surface of the ears, and stained to reveal ATPase activity. Cells showing staining were counted and expressed as cells/mm². The morphology of the cells was also noted.

RESULTS AND DISCUSSION

Results are summarised in Tables 2 and 3. GMDP at the two doses studied significantly reduced the number of ATPase positive cells as compared to vehicle controls. The positive control treatments (UVB irradiation and c- UCA) also reduced cells, as expected.

TABLE 2

Treatment No of ATPase -ve cells/mm2 (mean±SD)

Ethanol 420 (30)

GMDP 1 mg/ml 350 (20)

GMDP 0.1 mg/ml 325 (20)

UVB 160 (25) TABLE 3

Treatment No of ATPase +ve cells/ππr_2

(mean+SD)

Ethanol 445 (30)

GMDP 1 mg/ml 350 (30)

GMDP 0.1 mg/ml 280 (20) c-UCA 325 (30)

EXAMPLE 4

The effect of GMDP on the migration of epidermal dendritic cells to draining lymph nodes.

In this example, the ability of GMDP to provoke migration of dendritic epidermal cells was examined.

Mice were treated with ethanol, GMDP at 1 mg/ml in ethanol, or UVB at 96 mJ/cm.2. Forty eight hours later mice were killed, the auricular ("draining") lymph nodes excised, and dendritic cells purified and counted.

RESULTS AND DISCUSSION

Results are summarised in Table 4.

TABLE 4

Treatment No of dendritic cells per lymph node (mean±SD)

Ethanol 1750 (400)

GMDP 1 mg/ml 2200 (250)

UVB 8000 (1800)

UVB significantly enhanced the number of dendritic cells in lymph nodes. GMDP showed no significant effect.

Claims

1. The use of a muramyl peptide compound in the preparation of an agent for the treatment or prophylaxis of an inflammatory dermatological condition.

2. The use as claimed in claim 1, wherein the muramyl peptide compound is a compound of general formula I:

wherein:

R¹ represents a hydrogen atom or a C₁-C₂₂ acyl group;

R² represents a hydrogen atom or a d-C^ acyl group;

R³ represents a hydrogen atom or a

alkyl group; R⁴ represents a C_x-C₂₁ alkyl group or a C₆ or C₁₀ aryl group;

R⁵ represents a hydrogen atom; and

R represents the residue of an amino acid or a linear peptide built up of from 2 to 6 amino acid residues, at least one of the residues being optionally substituted with a lipophilic group.

3. The use as claimed in claim 2, wherein the muramyl peptide compound is: muroctasin, otherwise known as MDP-Lys (L18) (N²- (N- acetylmuramyl-L-alanyl-D-isoglutaminyl) -N⁶-stearoyl-L- lysine) ,*

MTP-PE (N-acetyl-muramyl-L-alanyl-D-isoglutaminyl-L- alanyl-2- (1' ,2' -dipalmitoyl-sn-glycero-3 ' -hydroxy- phosphoryloxy) ethylamide, monosodium) ;

murabutide (N-acetylmuramyl-L-alanyl-D-glutamine-α-N- butyl ester) ,* or

t-MDP (N-acetylmuramyl-L-threonyl-D-isoglutamine)

. The use as claimed in claim 1, wherein the muramyl peptide compound is:

II wherein:

n is 1 or 2 5. The use as claimed in claim 1, wherein the muramyl peptide compound is N-acetyl-D-glucosaminyl- (01-4) -N- acetylmuramyl-L-alanyl-D-isoglutamine (GMDP) .

6. The use as claimed in claim 1, wherein the muramyl peptide compound is N-acetyl-D-glucosaminyl- (01-4) -N- acetylmuramyl-L-alanyl-D-glutamic acid (GMDP-A) .

7. The use as claimed in claim 1, wherein the muramyl peptide compound is:

N-acetyl-D-glucosaminyl- (01-4) -N acetylmuramyl-L- alanyl-L-isoglutamine (GMDP-LL) ,-

N-acetyl-D-glucosaminyl- (01-4) -N acetylmuramyl-L- alanyl-D-glutamine n-butyl ester (GMDP-OBu) ;

N-acetyl-D-glucosaminyl- (01-4) -N acetylmuramyl-L- alanyl-D-isoglutaminyl-L-lysine (GMDP-Lys) ; or

N^a- [N-acetyl-D-glucosaminyl- (01-4) -N-acetylmuramyl-L- alanyl-D-isoglutaminyl] -N^£-stearoyl-L-lysine (GMDP- Lys (St) ) .

8. The use as claimed in claim 1, wherein the muramyl peptide compound is:

N*- [N-Acetyl-D-glucosaminyl- (01--4) -N-acetyl-muramyl-L- alanyl-γ-D-glutamyl] -N^e-stearoyl-L-lysine (GMDPA- Lys (St) ) ;

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-L- alanyl-D-glutamic acid dibenzyl ester (GMDPA(OBzl) ₂) ; N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-N- methyl-L-alanyl-D-isoglutamine (Me-GMDP) ;

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl- (01-- 4) -N-acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl- bis- (L-alanyl-D-isoglutamine) ( (GMDP)₂) ,-

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl- (01-- 4) -N-acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl- bis- (L-alanyl-D-glutamic acid) ((GMDPA)₂) ;

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyi- (01-- 4) -N-acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl- bis- (L-alanyl-D-isoglutaminyl-L-lysine) ( (GMDP Lys)₂) ,*

N-acetyl-D-glucosaminyl - ( 01 - -4 ) -N-acetylmuramyl- (01- - 4 ) -N-acetyl -D-glucosaminyl - ( 01 - -4 ) -N-acetylmuramyl - bis - [L- alanyl -D- isoglutaminyl -N^£ - stearoyl -L-lysine] ( [GMDP-Lys (St ) ] ₂) ;

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-L- alanyl-D-isoglutamine 1-adamantyl ester (GMDP-Ad) ;

L-Threonyl-N^£- [N-Acetyl-D-glucosaminyl- (01--4) -N- acetyl-muramyl-L-alanyl-γ-D-isoglutaminyl] -L-lysyl-L- prolyl-L-arginine (GMDP-tuftsin E) ;

N-Acetyl-D-glucosaminyl- (01--4) -N-acetyl-muramyl-L- alanyl-γ-D-isoglutaminyl-L-threonyl-L-lysyl-L-prolyl- L-arginine (GMDP-tuftsin A) ;

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-L- alanyl-cY-D-glutamyl-L-lysyl-L-threonyl-N^e-stearoyl-L- lysyl-L-prolyl-L-arginine (GMDPA-tuftsin lipophilic) ; N^£- [N-Acetyl-D-glucosaminyl- (01--4) -N-acetyl-muramyl-L- alanyl-γ-D-isoglutaminyl] -L-lysyl-L-histidyl-L-glycine amide (GMDPA-bursin) ;

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-L- alanyl-D-isoglutaminyl-L-glutamyl-L-tryptophan (GMDP- thymogen I) ;

N-Acetyl-D-glucosaminyl- (01--4) -N-acetylmuramyl-L- alanyl-D-isoglutaminyl-e-aminohexanoyl-L-glutamyl-L- tryptophan (GMDP-thymogen II) ;

N⁰- [N-Acetyl-D-glucosaminyl- (01--4) -N-acetyl-muramyl-L- alanyl-D-isoglutaminyl] -N^£-stearoyl-L-lysyl-L-glutamyl- L-tryptophan (GMDP-thymogen III) ,*

N-acetylmuramyl-L-threonyl-D-isoglutamine (Thr-MDP) ; or

N-acetylmuramyl-L-alanyl-D-glutamine n-butyl ester (murabutide) .

9. The use as claimed in any one of claims 1 to 8, wherein the inflammatory dermatological condition is psoriasis.

10. The use as claimed in claim 9, wherein the psoriasis is discoid or plaque psoriasis, flexural psoriasis, scalp psoriasis, palmar/plantar psoriasis, guttate psoriasis, erythrodermic psoriasis or pustular psoriasis, psoriatic arthritis, or involves changes in the nails resulting from psoriasis.

11. The use of muramyl peptide compound in the preparation of an agent for the treatment or prophylaxis of immune-related diseases of the skin and mucous membranes.

12. The use as claimed in claim 11, wherein the muramyl peptide compound is as defined in any one of claims 2 to 8.

13. The use as claimed in claim 11, wherein the immune-related disease is endogenous eczema (otherwise known as atopic eczema or atopic dermatitis) , seborrhoeic eczema, pompholyx, contact dermatitis, urticaria, erythroderma, lichen planus, vitiligo or alopoecia areata.

14. A topical formulation of a muramyl peptide compound.

15. A formulation as claimed in claim 14 which is an ointment, lotion or cream.

16. A method for the prophylaxis or treatment of an inflammatory dermatological condition, which comprises administering to a patient a muramyl peptide compound.

17. A method as claimed in claim 16, wherein the muramyl peptide compound is as defined in any one of claims 2 to 8.

18. A method as claimed in claim 16 or claim 17, wherein the inflammatory dermatological condition is psoriasis.

19. A method as claimed in claim 18, wherein the psoriasis is discoid or plaque psoriasis, flexural psoriasis, scalp psoriasis, palmar/plantar psoriasis, guttate psoriasis, erythrodermic psoriasis or pustular psoriasis, psoriatic arthritis, or involves changes in the nails resulting from psoriasis.

20. A method as claimed in any one of claims 16 to 19, wherein the muramyl compound is administered at a daily dose of from 0.1 to 100 mg.

21. A method as claimed in claim 20, wherein the daily dose is from 0.5 to 50 mg.

22. A method as claimed in claim 21, wherein the daily dose is from 2 to 30 mg.

23. A method as claimed in claim 22, wherein the daily dose is from 2 to 20 mg.

24. A method as claimed in any one of claims 16 to 23, wherein the muramyl peptide compound is administered for 1-60 days.

25. A method as claimed in claim 24, wherein the muramyl peptide compound is administered for 1-30 days.

26. A method as claimed in claim 25, wherein the muramyl peptide compound is administered for 1-14 days.

27. A method as claimed in any one of claims 16 to 26, wherein the muramyl peptide compound is administered together with at least one other therapeutic agent used in the treatment or prophylaxis of an inflammatory dermatological condition. 28. A method as claimed in claim 27, wherein the two agents are administered simultaneously, separately or sequentially.

29. A pharmaceutical composition comprising a muramyl peptide compound together with at least one other therapeutic agent used in the treatment or prophylaxis of an inflammatory dermatological condition, for simultaneous, separate or sequential use in the treatment or prophylaxis of an inflammatory condition.

30. A pharmaceutical composition as claimed in claim

29, modified by any one or more of the features of claims 2 to 10.

31. A pharmaceutical formulation as claimed in claim 29 or claim 30, wherein the other therapeutic agent is salicylic acid, magnesium sulphate or a vitamin A derivative.