GB2217596A - Anti-arthritic liposome composition - Google Patents

Description

2217596 7 1_ PHARMACEUTICAL PREPARATION CONTAINING FELBINAC This invention

relates to a pharmaceutical preparation containing 4- biphenylacetic acid (BPAA), also sometimes known as felbinac, useful in the treatment of arthritis.

BPAA is the active metabolite of fenbufen, a drug of the non-steroidal antiinflammatory class (i.e. an NSAID) and which is widely prescribed for a variety of conditions, including arthritis. BPAA itself, however, has hitherto not been generally used in therapy, although recently there has become available a BPAA-containing gel for topical application in the treatment of arthritis.

The present invention has developed out of research work which we have conducted to find an improved delivery system for BPAA in the treatment of arthritis.

one commonly practised method for treating arthritis is intra-articular therapy, in which the active agent is directly injected into the region of the inflamed joint. However, we have found that in the case of BPAA, conventional injectable solutions or suspensions of the drug have little or no effect in reducing the inflammation of arthritic joints.

In contrast to these discouraging results, we have now found in accordance with this invention that liposomal preparations of BPAA can provide a considerable reduction in joint inflammation and that this desirable effect is exceptionally long-lasting.

These advantageous properties of liposomal preparations of BPAA were not at all predictable. The use of liposomes as carriers for drugs has been suggested for many years, and as long ago as 1979, De Silva and his coworkers used a liposome formulation to deliver steroidal antiinflammatory agents to arthritic knee joints (De Silva et al, Lancet, 1, 1320, 1979). However, up to the present, no effective liposomal preparation of 2- an antiinflammatory drug for use in intra-articular therapy is available on the market.

Thus, the present invention broadly provides a liposomal preparation useful in intra-articular therapy and comprising BPAA as active ingredient.

As is well known, liposomes are formed when phospholipids or other suitable amphipathic molecules are allowed to swell in water or aqueous solutions to form (usually) multilayer structures comprised of many bilayers separated from each other by aqueous material. The liposomal preparations of the present invention may be prepared by any of the methods known in the art using phospholipids or other amphipathic lipids suitable for this purpose. The use of egg lecithin as the source of the phospholipid is however particularly preferred because it has a low phase transition temperature and will therefore form liposomes at room temperature when in the presence of aqueous material. Other suitable phospholipids which may be used herein include, for example, other natural lecithins such as soya bean lecithin, and saturated and unsaturated synthetic lecithins for example dimyristoyl phosphatidyl choline, dipalmitoyl phosphatidyl choline, distearoyl phosphatidyl choline, dioleyl phosphatidyl choline and dilinoleyl phosphatidyl choline.

In general, the lipid to BPAA weight ratio in the liposomal preparations of this invention will lie in the range of 7:1 to 15:1 for a useful therapeutic effect in vivo, with the preferred weight ratio of lipid to BPAA being from 9:1 to 11:1.

The liposomal preparations of this invention may optionally include one or more pharmaceutically acceptable adjuvants which are known to impart advantageous properties to liposomal preparations, for example:

V 3- (a) substances which are known to provide a negative charge on the liposomes, for example, egg phoshatidic acid or dicetyl phosphate; (b) substances known to provide a positive charge, for example, stearyl amine, or stearyl amine acetate; (c) substances shown to effect the physical properties of the liposomes in a more desirable way; for example, sterols such as cholesterol, ergosterol, phytosterol, sitosterol, sitosterol pyroglutamate, 7- dehydrocholesterol, lanosterol, or caprolactam, will affect membrane rigidity; (d) substances known to have antioxidant properties to improve the chemical stability of the liposome components, such as tocopherol, propyl gallate, ascorbyl palmitate, or butylated hydroxy toluene.

The preferred embodiments of this invention incorporate cholesterol to increase the packing of the molecules, generally in a lipid to cholesterol weight ratio of from 1:1 to 10:1, preferably from 4:1 to 7:1.

It has been found that the particle size of the liposomal preparations may have a significant effect on their efficacy. Thus, on the one hand it appears that the particles should be small enough to be phagocytosed by the synovial cells, whilst on the other hand they should not be so small that they escape from the synovial cavity into the systemic circulation. In general, therefore, we prefer that the liposomal particle size should be within the range from 0.1 to 5.0 gm, preferably from 0.5 to 3.0 gm.

The liposomal preparation of this invention may be made by methods known to those skilled in the art. Thus, for example, the BPAA, selected lipid and any optional ingredients, may be dissolved in chloroform or other suitable organic solvent which is then evaporated off. When the resulting material is dispersed in a suitable aqueous medium such as distilled water, isotonic saline or buffer solution, a multilamellar liposome suspension is formed. The particle size of the liposomal suspension can, if necessary, then be adjusted, as by filtration and/or ultrasonication. The usual steps (eg filter sterilization of the individual components and the maintenance of aseptic processing conditions) preferably should be taken to ensure the sterility of the liposomal suspension. Alternatively, the liposomal suspension may be sterilized postpreparation if the liposomal particle size required is less than 0.2 gm in diameter.

The thus-prepared liposomal suspension may be filled into vials for use as such, but to avoid the risk of unacceptable degradation on storage it is preferred that it be dehydrated, for example freeze-dried by conventional methods, ready for reconstitution at the time of use. The dehydrated lipid-drug mixture preferably is stored under nitrogen until required for use. It is reconstituted by the addition of an aqueous vehicle for injection such as, for example, 5% dextrose, 5% sorbitol, isotonic saline or phosphate-buffered saline. It is preferred that the pH of the injectable formulation should be within the range of 6.5 - 8.5, more preferably 6.8 - 7.8, the desired pH level being achieved preferably by appropriate addition of buffered saline.

The BPAA-containing liposomal preparations of this invention have potential for the treatment of arthritis or as an intravenous analgesic. For the treatment of arthritis the preparations preferably would be administered by direct injection into the joint cavity at a dosage rate of about 10-20 mg of BPAA about every two months depending on the size of the inflamed joint being treated.

The invention is illustrated by the Examples which follow:

I 1 1 5_ ExamDle 1 A multilamellar liposomal preparation was made having the following composition:

Egg lecithin Cholesterol BPAA 2.5 g 0.6 g 0.25 g The components were initially dissolved in 50 ml chloroform in a round bottomed flask. The solvent was then removed in a rotary evaporator at 400-450C, to leave a lipid/sterol/BPAA film in the flask. Next, the film was hydrated at room temperature by the addition of 25 ml of phosphate- buffered saline (pH 8.0). After vigorous shaking to disperse the film, the resultant liposome suspension had a particle size of about 1-2 gm, a final pH of 6.85 and a BPAA concentration of about 10.0 mg/M1.

A sterile 1.0 mi injection of the thus prepared liposomal preparation was then injected into an inflamed rabbit knee joint ("acute" arthritis model) which had been irritated two days previously with a mixture of poly-D-lysine and hyaluronic acid (PDL/HA). The other knee joint of the rabbit, which had also been injected with the same irritant mixture two days previously, was at the same time injected with a control saline solution.

The diameters of both joints were then periodically measured over the ensuing weeks. The results of this experiment are shown graphically in Figure 1 of the accompanying drawings.

As can be seen from Fig. 1, the size of both knee joints increased rapidly and substantially following the injection of the irritant mixture. The control joint, injected with saline solution at day 2, remained at substantially the same enlarged size until day 72 when it was injected with a further dose of irritant, 6- resulting in its size rapidly increasing still further. The knee joint which had been injected with the BPAAcontaining liposomal preparation of this invention also remained enlarged for a week or so following the injection, but its size then reduced steadily and substantially until about day 45. Between day 45 and day 72, there was only a small increase in the size of the joint, and when at day 72 the joint was then likewise injected with a further dose of the irritant mixture, the resultant size of the joint was still less than with the control joint.

The "scatter" in the individual points shown in the graph of Fig. 1, particularly the apparent variations in joint sizes between day 2 and day 10, is almost certainly a reflection of the difficulty which was experienced in measuring the joint in precisely the same position on each occasion.

The weight of the rabbit at the start of this test was 2.24 kg and at day 73 was 2.19 kg.

The data shown in Fig. 1 holds out the promise that the BPAA-liposomal preparations of this invention will provide a prolonged relief for patients with severely arthritic joints from a single injection of the preparation.

Comparative ExamDle 1 Following the general procedure of Example 1, 1 ml of a sterile solution of the ethanolamine salt of BMA (equivalent to 5 rag/ml of BMA) in an aqueous vehicle was inserted into an inflamed rabbit knee joint, and the diameter of the joint was periodically measured and compared with the diameter of the other knee joint injected with a saline solution as control. The results of this experiment are shown graphically in Figure 2 of the accompanying drawings.

7- From Figure 2, it is observed that there was ac tually no statistically significant decrease at all in the diameter of the knee joint which had been injected with the BPAA solution until about day 12, whereafter the diameter decreased but only to the level of the knee joint injected with the saline control.

Figure 2 illustrates that BPAA solutions are ineffective for relieving arthritis in this rheumatoid arthritis model.

Comparative ExamDle 2 In a further experiment, again following the general procedure of Example 1, a phosphate-buffered aqueous suspension containing 10 mg/mi of BPAA was tested in the rheumatoid arthritis model, by injection of 0.5 ml of the BPAA suspension into the inflamed rabbit knee joint.

The results of this experiment are shown in Figure 3 of the accompanying drawings, and from which it will be seen that up to about 4 days the knee joint treated with the BPAA suspension decreased at about the same, slight, rate as the knee joint injected with the saline control, whereafter the diameter of the BPAA injected knee actually increased somewhat, possibly indicating that BPAA in suspension could actually be an irritant.

Figure 3 illustrates that BPAA suspensions also are ineffective in this rheumatoid arthritis model.

ExanDle 2 The same liposomal preparation used in Example 1 was tested for efficacy in a "chronic" arthritis model (antigen-induced).

The procedure used was as follows:

8_ Day 0 Intra-dermal injections of an emulsion of 5 x 1 ml aliquots of Freund's Complete Adjuvant with ovalbumin (at 10 mg/ml) into back of rabbit.

Day 14 Repeat of above sensitisation Day 28 Injection of challenging dose of ovalbumin (1 mg) intra- articularly Day 30 Intra-articular injections of BPAA liposomal preparation and control saline Day 118 Further injection of challenging dose of ovalbumin (1 mg) intra- articularly The diameters of the BPAA-injected and control knee joints were periodically measured over the ensuing weeks, and the results are plotted in Figure 4 of the accompanying drawings, wherein time is measured from the first injection of a challenging dose of ovalbumin ie Day 0 on graph is the twenty eighth day of the experiment. Figure 4 shows that the BPAA- injected knee joint declined quite rapidly in diameter until at about day 20 post-injection it was substantially not enlarged. Thereafter, up until about day 78 post-injection, there was no significant enlargement of the knee joint. Only then was it apparent that the beneficial effects of the BPAA injection were beginning to wear off. In contrast, the diameter of the control knee joint (saline injection) declined more slowly over the first about 40 days postinjection when it remained substantially constant but at a higher level than the BPAA-injected knee joint.

2 1 g-

Claims (10)

CLAIMS:

1. A liposomal preparation useful in intraarticular therapy and comprising 4-biphenylacetic acid (BPAA) as an active ingredient.

2. A preparation according to Claim 1, wherein the ratio of BPAA to lipid used to form the liposome is from 1:7 to 1:15 by weight, preferably from 1:9 to 1:11 by weight.

3. A preparation according to claim 2, wherein said lipid is egg lecithin.

4. A preparation according to any preceding claim, comprising also cholesterol in a lipid-tocholesterol weight ratio of from 1:1 to 10:1, preferably from 4:1 to 7:1.

5. A preparation according to any preceding claim, wherein the liposome particle size is from 0.1 to 5.0 gm, preferably from 0.5 to 3.0 gm.

6. A preparation according to any preceding claim, comprising also an aqueous carrier for injection.

7. A lipid-BPAA mixture suitable for constitution with an aqueous carrier for injection, and formed by dehydrating a liposomal preparation according to any preceding claim.

8. A lipid-BPAA mixture which forms a liposomal preparation upon addition of an aqueous vehicle, and comprising the product formed by dissolving BPAA and a lipid in an organic solvent and then evaporating off said organic solvent.

1 c 10- g. The use of a liposomal preparation according to any one of Claim 1-6 in intra-articular therapy.

10. A liposomal preparation containing BPAA, substantially as described in Example 1 or Example 2 herein.

Published 1989 at The Patent Office, State House, 66.71 High Holborn, London WCIR 4TP. Rather copies maybe obtained from The Patent Ofnce. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87