Patent Application
20120237610
This invention concerns the development of solutions for intra-articular injection for the treatment of articular degeneration, in particular osteoarthritis.
It proposes combining a viscosupplementation agent, such as hyaluronic acid or one of its salts, with a fibroblast growth medium of defined composition, and possibly another polysaccharide, to advantage of natural origin.
In some limb joints, the opposing bony extremities, protected by articular cartilage, are enclosed within a capsule lined by connective tissue, called the synovial membrane.
Synovial fluid is the viscous fluid which fills the articular cavity; it is composed of hyaluronic acid (HA), secreted by fibroblast cells of the synovial membrane (synoviocytes), and interstitial fluid filtered from the blood plasma. The functions of synovial fluid are to reduce the friction by lubricating the joint, absorb shocks, provide oxygen and nutrients to the chondrocytes of the articular cartilage, and eliminate carbon dioxide and metabolic waste from the latter, since the cartilage is not vascularised.
Osteoarthritis is a common degenerative articular condition with a multifactorial aetiology, involving loss of material from the articular cartilages. As the condition develops, a reduction is observed in the concentration and molecular weight of the HA present in the synovial fluid. This phenomenon is explained by a reduction in endogenous synthesis of hyaluronic acid and by the inflammation which generates free radicals, responsible for the oxidative degeneration.
These alterations cause a reduction in the viscoelastic properties of the HA and gradually lead to the loss of its essential function of protecting the joint. They can result in erosion of the cartilage, the presence of fragments of cartilage or bone within the articular cavity, pain and stiffness.
Viscosupplementation is a well-established therapeutic option consisting of injecting HA into the joint concerned to help lubricate it better, increase mobility and reduce pain. Depending on the severity of the osteoarthritis, series of 3 to 5 weekly injections, e.g. into the knee, are effective for 6 months to 1 year in the majority of patients. This therapeutic option is extremely useful, particularly for patients who do not tolerate, or no longer respond to conventional treatment such as anti-inflammatories and oral analgesics, but whose disease does not yet justify prosthetic treatment.
Improvement to viscosupplementation solutions has, up until now, concerned increasing the residence time of HA in the joint, with the objective of increasing its efficacy.
Processes of chemical modification of HA, cross-linking HA (WO 2007/070547), or combining HA with a polyol (WO 2009/024670) have been described for slowing down the in vivo mechanical or thermal degradation of the HA gel or its breakdown by radicals.
Nevertheless, the intra-articular persistence of HA viscosupplementation products, whether modified or not, the half-life of which is a few days, is still very much shorter than their period of therapeutic efficacy, which depends, indeed, on several cumulative roles:
There is thus an obvious need to develop new therapeutic solutions for the treatment of articular degeneration, particularly of osteoarthritis.
Given this situation, the Applicant has taken a completely new approach. It is intended that this invention should act at two distinct levels to re-establish good articular function, notably for treating articular degeneration, particularly osteoarthritis.
This invention therefore concerns a composition for injection combining a viscosupplementation agent and a fibroblast growth medium to revitalise the cellular components of the articular connective tissues, particularly synoviocytes and chondrocytes, and consequently ensure their cellular regeneration and stimulate their endogenous synthesis (of hyaluronic acid and GAGs, fundamental functional constituents of joints).
More precisely, the components likely to play the role of viscosupplementation agent in an intra-articular injectable composition according to the invention are chosen from the following list: hyaluronic acid, chondroitin sulphate, keratan, keratan sulphate, heparin, cellulose and its derivatives, chitosan, xanthans, galactomannan, the alginates and their respective salts.
In practice, the commonly used viscosupplementation agent in this intra-articular application is hyaluronic acid or one of its salts. For this reason, in a particular embodiment, the targeted composition only contains hyaluronic acid or one of its salts as the viscosupplementation agent, combined with the fibroblast growth medium.
An alternative embodiment would use hyaluronic acid or one of its salts as the main viscosupplementation agent in the planned composition, combined with at least one other polysaccharide, to advantage of natural origin to ensure its biocompatible, non-immunogenic character. This other polysaccharide is to advantage a polysulphated glycosaminoglycan—particularly chondroitin sulphate, keratan, keratan sulphate, or even heparin, cellulose and its derivatives, chitosan, the xanthans, galactomannan, the alginates and their respective salts. The composition contains in addition the fibroblast growth medium, and possibly other constituents.
In practice, it therefore involves combining a mechanical action of lubricating and protecting the joint with a trophic action of fibroblastic stimulation encouraging cell synthesis in the synovial membrane and articular cartilage. The first action is ensured by the viscosupplementation agent, to advantage hyaluronic acid—cross-linked or not, or one of its salts,—possibly combined with one or more other polysaccharides of natural origin. The second action is provided by the fibroblast growth medium as defined below.
As is known, the hyaluronic acid used in this invention may occur in different forms: as salts, derivatives such as esters or amides, and in a linear or chemically cross-linked form. All these forms can be envisaged for this invention. While cross-linking increases the lifespan of hyaluronic acid molecules within the organism, these modifications however affect its physical/chemical characteristics, biological properties and potential immunogenicity.
As indicated for hyaluronic acid, the polysaccharide or polysaccharides, to advantage of natural origin, may or may not be cross-linked, grafted or not grafted, using cross-linking and grafting techniques described in the prior art.
As a technical solution is required for the joint structures that is as neutral as possible, that is to say a biomimetic solution, non cross-linked hyaluronic acid, and its physiologically acceptable salts, are preferred for the first component as this molecule is a natural component of the synovial fluid. By physiologically acceptable salts of hyaluronic acid we mean particularly sodium and potassium salts, as well as mixtures of them.
The viscosupplementation agent, to advantage hyaluronic acid, is present in the composition preferably at a concentration of between 1 and 100 mg/ml, to advantage between 10 and 25 mg/ml.
The second essential component of the composition according to the invention is a fibroblast growth medium.
For this invention, a fibroblast growth medium is defined as a complete medium not only keeping fibroblasts alive but also stimulating their multiplication and synthesis within the cells (components of the extracellular matrix and synovial fluid).
Conducting a functional growth assay can determine whether a given medium is a fibroblast growth medium according to the invention. A suitable functional assay known to those working in the field is particularly colorimetric observation of the density of living cells using the reagent WST-1 and reading results at 450 nm (Berridge, M. V. et al. (1996): The Biochemical and Cellular Basis of Cell Proliferation Assays That Use Tetrazolium Salts. Biochemica 4, 15-19.)
As an example, a fibroblast growth medium is available commercially: this is the DMEM standard culture medium (Sigma) supplemented with 10% by weight of FCS (foetal calf serum) cell growth factor.
Generally speaking, such media contain extracts of animal or cellular origin which do indeed stimulate the growth of fibroblasts, but which have the disadvantage of not having a determined composition or of containing untraceable exogenous elements such as FCS, bovine pituitary extracts, the cell growth factors EGF (epidermal growth factor), FGF (fibroblast growth factor), insulin or cholera toxin, hydrocortisone, piperazine, etc.
To advantage, the fibroblast growth medium used in this invention does not contain cell growth factors or biological extracts of animal or cellular origin, in particular if these are not traced or traceable and/or are not of a defined composition.
The expression “not traced” or “not traceable” means that the source of the biological material in question and/or the treatment undergone by the latter cannot be established or checked.
In practice, the said medium to advantage contains no biological extract of animal or cellular origin, no cell compound or growth factor or hormone.
In a preferred embodiment, a fibroblast growth medium as compatible as possible with the natural environment of the joint, i.e. a medium containing biomimetic and/or biocompatible constituents (biological materials naturally present in the organism or neutral to it which do not induce allergic or inflammatory reactions), is introduced into the joint by intra-articular injection. To advantage, this medium includes components of the basic substance of connective tissue.
Such a medium will specifically provide fibroblasts with optimised nutrition in the form of vitamins, trace elements, amino acids, mineral salts, simple sugars (such as glucose, ribose, deoxyribose) and/or complex sugars (such as HA), and natural growth factors in the form of the constituents of nucleic acids (nitrogen containing bases and pentoses, needed to form nucleotides, and nucleosides). To advantage, it will also have a physiological pH between 6.5 and 7.9, preferably between 7.4 and 7.6 and an osmolarity between 280 and 450 mOsm, preferably between 300 and 350 mOsm.
It should be noted that HA can be both a component of the growth medium and the viscosupplementation agent. The difference is in the form of the HA (necessarily a physiological hyaluronate salt in the medium) and its quantity (much lower quantities in the medium).
To stimulate the growth of fibroblasts, such a medium can be enriched using a substance which is exogenous to the organism but of natural, traceable origin and well defined composition. A substance meeting this definition is for example a mixture of peptides extracted from milk, or MPC complex (Milk Peptide Complex), obtained by successive precipitation from milk then the separation of certain proteins subjected to enzyme hydrolysis.
This substance, in the form of a dehydrated powder, is added to the medium to advantage at between 0.5 to 5 mg/ml, to greater advantage at 4 to 5 mg/ml.
As an example, a complex medium meeting such a definition has been developed by the Applicant and combines about sixty components in precisely defined quantities as follows:
As demonstrated below, such an enriched medium has a capacity in vitro to stimulate the growth of fibroblasts for several days. Moreover, it allows stimulated growth of the fibroblasts in the presence of serum. It is therefore a particularly suitable candidate for an intra-articular injection, in as far as part of the synovial fluid is a filtrate of blood plasma.
In addition, as demonstrated in this application, the incubation of fibroblasts in this medium increases the capacity of these cells to resist oxidative stress, i.e. it has anti-oxidant properties. Thus, in vitro, the enriched medium exerts an inhibitory effect on excess mitochondrial production of reactive oxygen species (superoxide ion) by fibroblasts exposed to a respiratory chain inhibitor (antimycin A). The expression kinetics of a fluorescent oxidation assay (DCFDA) is also significantly reduced for human fibroblasts pre-incubated in the growth medium and subjected to chemical oxidative stress, (AAPH), compared with control fibroblasts pre-incubated in standard DMEM. The anti-oxidant properties of the fibroblast growth medium also means that it has a role in protecting hyaluronic acid against oxidative degradation within the joint, which could increase the persistence of this compound in situ and prolong the therapeutic efficacy of the viscosupplementation.
Thus, the “fibroblast growth medium” according to the invention, which could also be called a “complete natural environment for the survival and growth of fibroblasts”, must have the following characteristics:
A composition according to the invention may in addition contain other ingredients or excipients, currently used in this application, particularly derivatives or purified fractions of HA. Nevertheless, according to a particular embodiment, the composition for injection consists only of the two components described above: firstly a viscosupplementation agent, to advantage hyaluronic acid possibly combined with one or more other polysaccharides of natural origin, and secondly a fibroblast culture medium.
As already stated, this composition is for intra-articular injection into a subject's joint cavity.
For this invention, the term “subject” designates a mammal, preferably a human, but may also designate an animal receiving veterinary treatment, particularly domestic animals or those used for recreational purposes (e.g. dogs, cat or horses).
In principle, all joints can be treated using a composition according to the invention. The knee is a joint particularly targeted in human subjects. In the dog, the hip is a joint frequently treated, while in the horse, to advantage it is the carpus, fetlock or hock.
According to a preferred embodiment, the composition, to advantage aqueous, is in the form of a gel, owing to application as an injection, the object of the invention. Remarkably, this restriction is perfectly compatible with the fibroblast growth media described above, which can be formulated as gels by incorporating hyaluronic acid, without adding exogenous excipients.
To even greater advantage, the composition is in the form of a monophasic hydrogel, i.e. a hydrogel as a single homogeneous phase. The viscosity of the composition obtained can be easily adjusted, particularly by adjusting the composition and the quantity of hyaluronic acid to obtain rheological properties similar to those of synovial fluid.
As an example, it has been shown that a composition according to the invention, with osmolarity between 300 and 350 mOsm, pH between 7.4 and 7.6 and a concentration of hyaluronic acid of molecular weight 1.3 to 1.8 MDa, of between 10 and 25 mg/ml was perfectly compatible with the application intended.
The composition for injection according to the invention may also form part of a kit including, in addition, syringes to contain the said composition. These may for example be single dose syringes of 2 to 20 ml. In such a kit, the 2 essential components of the composition can be presented as a mixture in the same syringe, or in 2 distinct syringes for extemporaneous mixing.
Given the injectable character and the intended treatment, such a composition is to advantage sterilised, cold sterilisation being used advantageously to avoid denaturing the components present. This may be performed by 0.22 μm membrane filtration for the fibroblast growth medium, and by separate sterilisation for the hyaluronic acid using a process known to those working in the field.
Another alternative consists of providing the composition for injection in the form of a powder (HA and fibroblast growth medium), in vials made of glass, polypropylene, polyethylene or any other material which can withstand sterilisation by ionising radiation or thermal flash sterilisation. In this embodiment, the monophasic hydrogel is reconstituted by adding sterile water to the vial, using a (sterile) syringe, before injecting the product into the joint. In this case, the product must be reconstituted between 2 to 72 hours before the injection.
Given their complementary mode of action, the two components of the composition according to the invention may be mixed and/or administered simultaneously, separately or spread over time.
A direct application for the composition according to the invention is treatment of articular degeneration, in particular osteoarthritis.
A composition according to the invention is therefore intended to be used as a medical device and/or medicinal product.
The invention will now be illustrated in a non-exhaustive manner by the following examples supported by the attached figures.
Protocol
Results
In conclusion, it appears that the fibroblast growth medium used according to the invention allows survival and stimulates the growth of normal human fibroblasts in the absence of exogenous growth factors.
Protocol
Results
In conclusion, it is evident that the medium exerts an inhibitory effect on excess mitochondrial production of reactive oxygen species (superoxide ion) by fibroblasts exposed to a respiratory chain inhibitor (antimycin A). The expression kinetics of a fluorescent oxidation assay (DCFDA) is also significantly reduced for human fibroblasts pre-incubated in the growth medium and subjected to chemical oxidative stress, (AAPH), compared with control fibroblasts pre-incubated in standard DMEM.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0959205 | Dec 2009 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2010/052397 | 11/8/2010 | WO | 00 | 5/31/2012 |
