Background of the invention and prior art Cyclooxygenase (COX, also referred to as prostaglandin endoperoxide H synthase, PGHS) is the rate-limiting enzyme in prostaglandin synthesis in the body, and exists as two isoforms, COX-1 and COX-2. They have two enzymatic functions, namely a cyclooxygenase function that converts arachidonic acid to prostaglandin G2 (PGG2), with formation of an oxygen- containing ring structure, and a peroxidase activity that converts PGG2 to prostaglandin H2 (PGH2). PGH2 in turn acts as the precursor of various eicosanoids, including PGE2, PGF2a, PGD2, prostacyclin and thromboxane A2.

Eicosanoids are commonly known as pivotal regulators of immune and inflammatory processes (Gong C, et al, Brain Res. 2001 901: 38-46). It is known that aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) block the enzymatic activity of both isoforms. This is at least part of the underlying mechanism of the anti-inflammatory activity of aspirin and other NSAIDs, prostaglandins being, in general, inflammation stimulating substances.

The enzymes COX-1 and COX-2 are encoded by separate genes located on different chromosomes. The COX-1 gene is larger, and its structure facilitates continuous transcription of a stable message, so that it is a constitutive, housekeeping enzyme, present in most cells and tissues. The COX-2 gene is smaller, and is consistent with its characterization as an

immediate-early stage gene that is rapidly upregulated during inflammation and other pathological processes. COX-2 normally is not detectable in most tissues, but can be induced by mitogens, cytokines and certain inflammatory agents.

A consequence of the over expression or over-activity of either or both of COX-1 and COX-2 is pain. The source or cause of the pain may be inflammation, tissue damage through injury, muscle damage through injury, over-exertion, etc. , burns, chemical exposure, toxic substance ingestion or the like, all of which are associated with increases in the COX-2 activity at the site of origin of the pain.

Treatment of inflammation in a patient by administration of NSAIDs is well known. These inhibit both isoforms due to their occupancy of the COX active site, preventing access by arachidonic acid. The resulting local inhibition of prostaglandins, however, is believed to be the underlying cause of unwanted gastro-intestinal side effects such as stomach bleeding and ulceration. This is attributed to inhibition of COX-1, whereas the isoform COX-2 is the one closely associated with inflammation since it mediates production of prostaglandin.

Various selective inhibitors of COX-2 have accordingly been developed, such as celecoxib and rofecoxib, to treat inflammation, with reduced gastro-intestinal side effects. The COX-2 selective inhibitors, however, have been reported to cause different side effects, most notably in the cardiac area. One concern is the reported increased risk of myocardial infarction and thrombosis in patients on selective COX-2 inhibitors. This increase may be a consequence of the reduction of the formation of prostaglandin PGiz as a result of selective COX-2 inhibition, whilst leaving the thromboxane A2 producing activity of COX-1 unaffected. PG12 functions as an inhibitor of platelet aggregation, whilst thromboxane A2 functions as a promoter of platelet aggregation. Celecoxib, in particular, has been shown to lower prostacyclin without affecting thromboxane. This tips the balance of prostacyclin/thromboxane in favour of thromboxane leading to increased vascular and thrombotic events (Bing RJ et

al, J Am Coll Cardiol 2002 39: 521-2). A large-scale study with the COX-2- specific inhibitor rofecoxib (Vioxx Gastrointestinal Outcomes Research [VIGOR] trial) revealed that rheumatoid arthritis patients taking rofecoxib had a greater incidence of cardiovascular events than patients taking the NSAID naproxen (DeMaria AN, Am J Cardiol 2002 89: 33-8).

Certain pathophysiological conditions, including ischemia and hypoxia, are associated with increased expression of COX-2 in the brain. It has been shown that topical administration of lipopolysaccharide (LPS) caused a time- dependant dilatation of cerebral arterioles that was inhibited by the selective COX-2 inhibitor NS-398 (Brian JE Jr. et al, Stroke 1998 29: 2600-6).

Vasodilatation is one of the cardinal manifestations of inflammation in the brain. In an experimental model of brain inflammation COX-2 was shown to be expressed in endothelial cells and it has been suggested that it plays a role in the development of fever during brain inflammation suggesting a role for COX- 2 in meningitis, encephalitis (Cao C et al, J Neurosci 1999 19: 716-25).

COX-2 has also been suggested to be the key element controlling the generation of proinflammatory mediators involved in the progression of Alzheimer's disease (AD). In mouse studies, rofecoxib was shown to significantly reverse LPS-induced retention deficit. LPS is known to induce the in vivo synthesis and release of inflammatory mediators such as IL-1, IL-6 and PGE2 (Jain NK et al, 2002 Behavioural Brain Research 133: 369-376).

Inhibitors of COX-2 have also been shown to be effective as therapeutic agents in experimental autoimmune neuritis.

A procedure or composition which when administered to mammalian patients, modulates the expression of the COX-2 gene should, therefore, provide a basis for a treatment or inhibition of the progression of a variety of pain-causing disorders in mammalian patients, and of the pain associated therewith.

It is an object of the present invention to provide a method for treating a mammalian subject to modulate pathological COX-2 expression, and thereby alleviate COX-2-related disorders, with reduced adverse side effects.

Summary of the invention The present invention provides, from one aspect, a process to alleviate a cyclooxygenase-related pain-causing disorder in a mammalian subject, by reducing the pathological expression of the COX-2 gene in the mammalian patient, by administration thereto of bodies, such as liposomes, beads or similar particles, which carry as a major component on their surface certain phospholipids and/or synthetic mimetics thereof. These bodies may carry as a minor component on their surface an inactive constituent.

Thus according to the present invention there is provided a method for treating a COX-2 related pain-causing disorder comprising administering to a patient a pharmaceutically acceptable synthetic, semi-synthetic or natural bodies having a three-dimensional core structure of conformation and size corresponding to mammalian apoptotic cells and/or bodies and expressing or expressible on the surface thereof a ligand selected from, phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphatidic acid, distearoylphosphatidylserine, dipalmitoylphosphatidylserine, cholesterol, sphingomyelins, or combinations thereof, capable of effectively reducing the COX-2 expression in the mammalian patient.

Brief description of the drawings Figure 1 shows the mRNA levels of cyclooxygenase (COX) -2 by polymerase chain reaction (PCR) in a macrophage established cell line system, Example 1 below.

Detailed Description of the Invention In a preferred embodiment, the invention is directed to a composition comprising bodies having a three-dimensional core structure of conformation and size corresponding to mammalian apoptotic cells and/or bodies and expressing or expressible on the surface thereof ligands such as phosphatidylserine which are chosen so as to interact with certain receptors on the cells of the mammalian body, on administration to a mammalian patient, with the result that the COX-2 expression in the patient is modulated.

"Modulating"is defined to mean reducing, physiologically restoring, normalizing or controlling.

As a result of their interacting with certain receptors on the cells of the mammalian body, it is believed that the compositions of the present invention initiate a series of events in the immune system of the mammalian body. While it is not intended that the present invention should be limited by any particular theory of its mechanism or mode of action, it is believed that the bodies of the composition are phagocytosed by antigen presenting cells (APCs) of the immune system with consequent alteration of the cytokine profile of the APCs in favour of COX-2 expression reduction.

In addition, the COX-2 down-regulation effected by the present invention may be the result of analgesic mechanisms in the patient's body. Accordingly, the compositions of the invention are indicated for use in analgesia, pain management and anti-pruritic therapy.

According to preferred aspects of the present invention, synthetic and semi-synthetic bodies carrying ligands selected from phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphatidic acid, distearoylphosphatidylserine, dipalmitoylphosphatidylserine, cholesterol, sphingomyelins, or combinations thereof, on their surface are administered to patients with accompanying beneficial effects of modulating COX-2 expression.

These synthetic and semi-synthetic bodies are three dimensional bodies having shapes and dimensions ranging from those resembling mammalian cells to shapes and dimensions approximating to apoptotic bodies produced by the apoptosis of mammalian cells (typically but not exclusively spheroidal, cylindrical, ellipsoidal, including oblate and prolate spheroidal, serpentine, reniform etc. , and having diameters of about 20 nanometres to about 500 microns), and having COX-2 expression reducing ligands on the surface thereof, to the extent of at least 10% by weight. The structure of aforementioned ligands may be synthetically altered and include all, part of or a modified version of the original ligand.

Another preferred embodiment is a method for treating non- inflammation related pain involving excessive COX-2 expression in a mammalian patient comprising administering to a mammalian patient a non- toxic, effective, excessive-COX-2-expression-treating amount of liposomal or non-liposomal bodies as defined above, wherein the pain is inhibited and/or reduced.

Examples of three-dimensional body portions include liposomes, solid beads, hollow beads, filled beads, particles, granules, microspheres, or beads of biocompatible materials, natural or synthetic, such as polyethylene glycol, polyvinylpyrrolidone, polystyrene, poly (methylmethacrylate), etc. , polysaccharides such as hydroxyethyl starch, hydroxyethylcellulose, agarose and the like, as commonly used in the pharmaceutical industry. The beads may be solid or hollow, or filled with biocompatible material.

Suitable substances for derivatisation to attach the phospholipid (s) to three-dimensional bodies are commercially available e. g. from Polysciences Inc., 400 Valley Road, Warrington, PA 18976, or from Sigma Aldrich Fine Chemicals.

Preferred compositions of matter for use in the present invention are liposomes, which may be composed of a variety of lipids. Liposomes, or lipid vesicles, are sealed sacs, in the micron or sub-micron range, the walls of which consist of suitable amphiphiles. They normally contain an aqueous medium.

Liposomes are vesicles which can be unilamellar (single membrane) or multi- lamella (onion-like structures characterized by multiple membrane bilayer, each separated from the next by an aqueous layer). The bilayer is composed of two lipid monolayers having a hydrophobic"tail"region and a hydrophilic "head"region. In the membrane bilayer, the hydrophobic (nonpolar)"tails"of the lipid monolayers orient toward the center of the bilayer, whereas the hydrophilic (polar)"heads"orient toward the aqueous phase. For use in the present invention, the liposomes are composed, to the extent of at least 10% by weight, of phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphatidic acid, distearoylphosphatidylserine, dipalmitoylphosphatidylserine, cholesterol, and sphingomyelin. Such liposomes are prepared and treated so that the active polar head groups are presented exteriorly on the liposomal body.

Thus a preferred embodiment of this invention provides a process of treating COX-2 related pain-causing disorders comprising administering to a mammalian patient synthetic or semi-synthetic bodies carrying ligands on their surface, namely liposomes or non-liposomal bodies which expose or can be treated or induced to expose one or more phospholipid ligands, selected from phosphatidylserine, phosphatidylethanolamine, phosphatidylinositol, phosphatidic acid, distearoylphosphatidylserine, dipalmitoylphosphatidylserine, cholesterol, and sphingomyelin, optionally with a minor portion (up to less than 50% by weight) of another, active or inactive constituent. The most preferred active phospholipids to be used in the present invention are phosphatidyiserine, phosphatidylethanolamine, phosphatidylinositol, phosphatidic acid, even more preferably a liposome constituted to the extent of about 50-100% phosphatidylserine, phosphatidylethanolamine, phosphatidylinositol, phosphatidic acid, the balance being phosphatidylcholine

or other such biologically acceptable phospholipid (s) active or inactive phospholipid. More preferred are liposomes constituted to the extent of 65- 90% by weight, most preferably 70-80% by weight, with the single most preferred embodiment being about 75% by weight of active phospholipids, the balance being the other inactive phospholipids such as PC. It is also within the scope of the present invention to use bodies having a mixture of the aforementioned phospholipids having chemically active head groups, this mixture comprising at least 10%, preferably at least 50% and most preferably 60-90% of the aforementioned active phospholipids. Mixtures of liposomes of different aforementioned phospholipids having chemically active head groups, and mixtures of such liposomes with liposomes of inactive and/or with liposomes of phospholipids acting through a different mechanism can also be used, provided that the total amount of active phospholipid remains above the minimum of about 10% and preferably above 50% and most preferably 60-90% of active phospholipid in the total mixture.

It is contemplated that the patient may be a mammal, including but not limited to humans and domestic animals such as cows, horses, pigs, dogs cats and the like.

Phospholipids are amphiphilic molecules (i. e. amphiphiles), meaning that the compound comprises molecules having a polar water-soluble group attached to a water-insoluble hydrocarbon chain. The amphiphiles serving as the layers of the matrix have defined polar and apolar regions. The amphiphiles can include in addition to the phospholipids providing the active head groups in the process of the invention, other, naturally occurring lipids used alone with the phospholipid carrying the active head group, or in a mixture with another. The amphiphiles serving as the layer (s) of the liposomes can be inert, structure-conferring synthetic compounds such as polyoxyethylene alkylethers, polyoxyethylene alkylesters and saccharosediesters.

Methods of preparing liposomes of the appropriate size are known in the art and do not form part of this invention. Reference may be made to various textbooks and literature articles on the subject, for example, the review article "Liposomes as Pharmaceutical Dosage Forms", by Yechezkel Barenholz and Daan J. A. Chrommelin, and literature cited therein, for example New, R. C.

"Liposomes: A Practical Approach", IRL Press at Oxford University Press (1990).

The diameter of the ligand-carrying liposomes of the preferred embodiment of this invention is from about 20 nanometers to about 500 microns, more preferably from about 20 nanometers to about 1000 nanometers, more preferably from about 50 nanometers to about 500 nanometers, and most preferably from about 80 nanometers to about 120 nanometers. Such preferred diameters will generally correspond to the diameters of mammalian apoptotic bodies or apoptotic cells (typically from about 20 nanometres to 500 microns as measured along the longest axis).

The ligand-carrying bodies may be suspended in a pharmaceutically acceptable carrier, such as physiological sterile saline, sterile water, pyrogen-free water, isotonic saline, and phosphate buffer solutions, as well as other non-toxic compatible substances used in pharmaceutical formulations.

Preferably, the ligand-carrying bodies are constituted into a liquid suspension in a biocompatible liquid such as buffered saline and administered to the patient in any appropriate route which introduces it to the immune system, such as intra-arterially, intravenously, intra-dermally or most preferably intramuscularly or subcutaneously.

It is contemplated that the ligand-carrying bodies may be freeze-dried or lyophilized so that they may be later resuspended for administration. A protectant such as sucrose or trehalose is preferably included in any such freeze-dried composition, to protect the liposomes from damage on re- suspension. This invention is also directed to a kit of parts comprising

lyophilized or freeze-dried ligand-carrying bodies and a pharmaceutically acceptable carrier, such as physiological sterile saline, sterile water, pyrogen-free water, isotonic saline, and phosphate buffer solutions, as well as other non-toxic compatible substances used in pharmaceutical formulations.

A preferred manner of administering the ligand-carrying bodies to the patient is a course of injections, administered daily, several times per week, weekly or monthly to the patient, over a period ranging from a week to several months. The frequency and duration of the course of the administration is likely to vary from patient to patient, and according to the condition being treated, its severity, and whether the treatment is intended as prophylactic, therapeutic or curative. Its design and optimization is well within the skill of the attending physician. Intramuscular injection is most preferred. One particular injection schedule, in at least some of the indications of the invention, is an injection of an appropriate amount of bodies on day 1, a further injection on day 2, a further injection on day 14, and then"booster"injections at monthly intervals.

The quantities of ligand-carrying bodies to be administered will vary depending on the nature of the mammalian disorder it is intended to treat and on the identity and characteristics of the patient. It is important that the effective amount of ligand-carrying bodies is non-toxic to the patient, and is not so large as to overwhelm the immune system. When using intra-arterial, intravenous, subcutaneous or intramuscular administration of a liquid suspension of ligand-carrying bodies, it is preferred to administer, for each dose, from about 0.1-50 ml of liquid, containing an amount of ligand-carrying bodies generally equivalent to 10%-1000%, preferably 10%-100%, of the number of leukocytes normally found in an equivalent volume of whole blood or the number of apoptotic bodies that can be generated from them. Generally, the number of ligand-carrying bodies administered per delivery to a human patient is in the range from about 500 to about 2.5 x 1012 (<250 ng of bodies, in the case of liposomes, pro-rated for density differences for other embodiments of bodies), more preferably from about 1,000 to about 1,500, 000,000, even

more preferably 10,000 to about 100,000, 000, and most preferably from about 200,000 to about 20,000, 000.

The invention is indicated for use anywhere where COX-2 inhibitors known in the art have been previously shown to be effective. Preferred areas of treatment where the present invention is indicated are: (a) an increase in COX-2 activity resulting in conditions including, but not limited to pancreatitis, endometriosis, and adenomyosis; (b) the inducement of analgesia and the treatment of pain, especially pain unrelated to or not substantially related to inflammation."Analgesia"is defined as alleviation of pain, acute and chronic, induced by all known mechanisms, including but not limited to pain related to postoperative pain, cancer, neuropathic pain, and complex regional pain syndrome.

The source or cause of the pain may include but is not limited to, tissue damage through injury, muscle damage through injury, over-exertion, etc., burns, chemical exposure, toxic substance ingestion or the like, all of which are associated with increases in COX-2 expression at the site of origin of the pain; (c) treatment and-prophylaxis of the symptoms of mammalian neuroinfectious diseases including but not limited to meningitis and encephalitis.

In an alternative embodiment of the invention, the compounds of this invention may be administered prior to, in conjunction with or subsequent to administration of a pharmaceutically effective amount of a known COX-2 inhibitor, such as celecoxib (Celebrex (g)) or rofecoxib (Vioxx@). When said alternative embodiment is employed, the pharmaceutical effective amount of the COX-2 inhibitor is administered to reduce excessive COX-2 activity. A pharmaceutically acceptable amount is well known in the art.

Thus the present invention is applicable for treatment of substantially any excessive COX-2 expression-related non-inflammatory pain condition.

COX-2 is constitutively expressed in neurons. Excessive COX-2 expression may result from cell damage such as physical injury, chemical injury and pressure on body organs resulting from tumour growth or organ enlargement due to malignancies or other disorder. Such pain is experienced substantially instantaneously, as a result of excessive COX-2 at the site, the consequent release of pain"Substance P", from the peripheral sensory nerve endings, to the nerves and the spinal cord and thence to the brain. In contrast, pain due to inflammation is slow to build as the inflammation develops and becomes chronic rather than acute.

Another example of a disorder well-suited to treatment according to the invention is post-herpetic neuralgia resulting from shingles where extreme pain develops as an after-effect. Persons developing hyperalgesia (extreme sensitivity to pain) are also suitably treated by the invention.

Pressure due to organ enlargement is effectively a mechanical pressure, the pain from which is non-inflammatory and intractable. Organ linings, e. g. of the liver, contain cells with substance P, which is released in association with excessive expression of COX-2 therefrom. Similarly, bone pressures associated with cancer growths create pain by similar mechanisms. These are tratable according to the invention.

See Vanagash et al., Progr. in Neurobiology, 2001 July : 64: 327-63, contents incorporated herein.

See also Camu F et al., Drugs. 2003; 63 Suppl 1: 1-7; Ruoff et al., J.

Pain Symptom Manage. 2003 Feb; 25 (2 Suppl) : S21-31; Kiefer et al., Cum.

Opin Investig Drugs 2002 Sep; 3 (9): 1348-58; and Sinatra R, J. Pain Symptom Manage. 2002 July ; (1 Suppl) : 518-27, all of which are incorporated herein by reference.

The invention is further described for illustrative purposes in the following specific example.

Example U937 is a monocytic leukemia cell line that can be differentiated into macrophages by administration of a phorbol ester. Treatment of these macrophages with lipopolysaccharide (LPS), a component of the cell wall of Gram-negative bacteria, stimulates a response in U937 cells, with the upregulation of expression of a number of molecules including COX-2. This provides an experimental system for the assessment of COX-2 related therapies. The macrophages can be grown in culture medium in the presence of a suspected COX-2 affecting composition, and the expression of RNA or DNA of the COX-2 measured. Liposomes of size 100 20 nanometers were prepared as according to standard methods known in the art with one set comprising 75% phosphatidylserine (PS): 25% phosphatidylcholine (PC) and the other comprising of 100% PC. A stock concentration of 2.93 x lol4 liposomes per ml was used and which was then diluted in PBS to give a working concentration of 2.93 x 108.

U937 cells were cultured by growing in RPMI medium with 10% fetal calf serum (FCS) and 1 % penicillin/streptomycin at 37°C, 5% C02. They were seeded into 6 well plates at a concentration of 5 x 105 cells per ml with 2 mis of cells added'per well and differentiated into macrophages by treating with 150nM phorbol myristate acetate (PMA) for 2-3 days. The cell media is then

replaced after macrophages have differentiated and replaced with complete media for 24hrs prior to liposome addition so as to allow any up-regulation of genes/proteins induced by PMA to be reduced. System compared with PGJ2, a known inhibitor of COX-2. PGJ2 is the most potent natural ligand for the PPAR-gamma receptor which is involved in the regulation of genes related to cell differentiation, apoptosis etc. PPAR-gamma has been shown to be expressed on a variety of immune cells, including T and B cells as well as macrophages and dendritic cells, TNF-a and IL-1 ß. PGJ2 has also been shown to significantly suppress IL-1 ß-induced COX-2 expression.

The cells were then treated as follows : Phosphate buffered saline (PBS) -as a negative control<BR> 100ng/ml Lipopolysaccharide (LPS) -as a positive control LPS + 12 x 106 75% PS: 25% PC liposomes LPS + 12 x 106 100% PC liposomes LPS + 10pM 15-deoxy-Prostaglandin J2 (PGJ2) The cells were then incubated at 37°C, 5% C02. After 18hrs the media was collected, the cells were rinsed with PBS and lysed with 1 ml of Tri-Reagent TM (Sigma) for mRNA analysis. COX-2 and GAPDH mRNA were extracted and detected with reverse transcription-polymerase chain reaction as (RT-PCR) and carried out using standard methods known in the art (Adderley SR, Fitzgerald DJ, J Biol Chem, Vol. 274, Issue 8,5038-5046, February 19,1999). The reaction was performed using the following primers: Human 847bp COX-2 Primers Sense: 5'TCC TTG CTG TTC CCA CCC ATG 3' Antisense: 5'CAT CAT CAG ACC AGG CAC CAG 3' Human GADPH Primers Sense: 5'CCA CCC ATG GCA AAT TCC ATG GCA 3'

Antisense: 5'TCT AGA CGG CAG GTC AGG TCC ACC 3' With the GADPH included as an experimental control for each sample.

Results Lane 1 on gel contains markers that confirm the size of the COX-2/GADPH bands. There is a constant band in all lanes of the GADPH gel as this is a housekeeping gene and provides a control for the loading of the gel. The control (lane 5) indicates those cells that were not treated with LPS and shows a very low level of COX-2 expression. LPS treatment causes a measurable increase in COX-2 mRNA production (lane 2) when compared with control. A known COX-2 inhibitor PGJ2 (lane 6) causes a significant reduction in LPS- induced COX-2. PS liposomes (lane 3) in this system caused a greater reduction in COX-2 production than PGJ2, while PC liposomes (lane 4) had little effect.