Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/0012—Galenical forms characterised by the site of application
  • A61K9/0019—Injectable compositions; Intramuscular, intravenous, arterial, subcutaneous administration; Compositions to be administered through the skin in an invasive manner
  • A61K9/0024—Solid, semi-solid or solidifying implants, which are implanted or injected in body tissue
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
  • A61K47/30—Macromolecular organic or inorganic compounds, e.g. inorganic polyphosphates
  • A61K47/36—Polysaccharides; Derivatives thereof, e.g. gums, starch, alginate, dextrin, hyaluronic acid, chitosan, inulin, agar or pectin
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/2004—Excipients; Inactive ingredients
  • A61K9/2022—Organic macromolecular compounds
  • A61K9/205—Polysaccharides, e.g. alginate, gums; Cyclodextrin
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
  • A61L27/14—Macromolecular materials
  • A61L27/20—Polysaccharides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
  • C08B37/006—Heteroglycans, i.e. polysaccharides having more than one sugar residue in the main chain in either alternating or less regular sequence; Gellans; Succinoglycans; Arabinogalactans; Tragacanth or gum tragacanth or traganth from Astragalus; Gum Karaya from Sterculia urens; Gum Ghatti from Anogeissus latifolia; Derivatives thereof
  • C08B37/0063—Glycosaminoglycans or mucopolysaccharides, e.g. keratan sulfate; Derivatives thereof, e.g. fucoidan
  • C08B37/0072—Hyaluronic acid, i.e. HA or hyaluronan; Derivatives thereof, e.g. crosslinked hyaluronic acid (hylan) or hyaluronates

Definitions

• the present invention relates to a crosslinked hyaluronic acid derivative in which the crosslinking has been achieved by means of reaction with a phosphorus-containing reagent, especially a derivative of an acid of phosphorus( ).
• the invention moreover also relates to methods for producing such a product as well as its use as a slow release depot for administration of hyaluronic acid or a medicament, incorporated in the gel.
• Hyaluronic acid is a high molecular weight polysaccharide, highly viscous in character and consisting of a disaccharide repeating unit of N-acetylglucosamine and glucuronic acid. It occurs naturally in the body of humans and animals, for instance in synovial fluid, vitreous humor and pericardial fluid. In all species, the structure of,,.hyaluronic acid is. the same whereas its molecular weight may vary within wide ranges. Because of its bioresorbability and absence of .
• hyaluronic acid has been found to be useful in medical contexts, e.g for the treatment of articular disorders adversely affecting articular motility, and as a surgical aid in connection with eye surgery and for preventing post-operative adhesions.
• hyaluronic acid has been employed in the form of a viscous aqueous solution.
• the duration is too short and mechanical stabilization too weak so that the desired therapeutic effect is not attained.
• a novel biologically degradable crosslinked hyaluronic acid gel derivative which is produced by means of reacting the hyaluronic acid with a phosphorus-containing reagent, especially a phosphorus(V) acid derivative, and which contains endogenous crosslinks, viz., phosphate esters.
• Phosphate esters occur ubiquitously in vivo.
• phospholipids DNA and RNA.
• the process for the production of the phosphate-crosslinked hyaluronate gels and their properties are superior to the manufacturing processes and properties of prior art crosslinked hyaluronic acid materials.
• the crosslinking reaction time is very short, and the substances require a minimum of purification because the reactive crosslinking reagents are rapidly hydrolyzed.
• the gels are degradable biologically, and the degradation time is variable within wide limits.
• the present gels are completely re-swellable after complete desiccation.
• Phosphate crosslinking of polysaccharides is a known method, primarily for the treatment of starch (see for example Koch H et al., Starke 34 (1982) 16).
• the deriva- tization of starch is a treatment of an insoluble material in a heterogeneous system.
• Phosphate crosslinking of hya ⁇ luronic acid too may be carried out heterogeneously on solid material, for instance in pyridine.
• the reaction prefe&rably chosen is one where hyaluronic acid is treated in a dissolved state with a crosslinking reagent.
• This treatment may be performed in an organic solvent in which the hyaluronic acid has been solubilized, e.g. by way of salt formation with a lipophilic cation.
• an organic solvent in which the hyaluronic acid has been solubilized e.g. by way of salt formation with a lipophilic cation.
• Crosslinking reagents employed are derivatives of phos- phorus(V) acid, in particular halides, oxyhalides or an ⁇ hydrides thereof.
• crosslinking reagents are phosphorus pentachloride, phosphoryl chloride (phosphorus oxychloride) or the corresponding bromide or iodide, phos ⁇ phorus pentoxide and trimetaphosphates.
• the reaction is carried out in an alkaline medium.
• the coupling and the hydrolysis of the phosphorus acid deriva ⁇ tives result in the release of relatively large amounts of acid.
• Both the phosphate esters formed and the hyaluronic acid matrix are sensitive to acidic degradation. It is very important, therefore, that enough base is present already from the very start of the reaction, since it is not possible to make any additions to the viscous gelling system.
• the pH of the initial solution must not be too high because the hyaluronic acid is sensitive to alkaline degradation.
• bases for example nitrogen bases like alkylamines, especially those that are sterically hindered such as triethylamine, tributylamine and methyl- morpholine.
• a preferred preparation for cross- linking in aqueous solution employs basic metal phosphates like trisodium phosphate or tripotassium phosphate.
• the by-products obtained will only be biologically tolerable phosphate salts, there being thus no need to further proceed to purification steps for removing rests of potentially toxic alkalis.
• bases that are weaker than those mentioned above for example pyridine.
• the concentration thereof may vary within a wide range of concentrations.
• a practically useful concentration range is 2-15 % (by weight) of hyaluronic acid in the reaction mixture.
• Already concentrations as low as 1 % will give rise to gel formation, but these gels are of a very liquescent consistency and not very worthwhile for technical purposes.
• a practical upper limit, however, is set due to the circumstance that already at moderate concen ⁇ trations high molecular weight hyaluronic acid will form solutions which are very difficult to work with.
• a hyaluronic acid having a molecular weight ooff ssaa concentration should not exceed about 10 %.
• the molecular weight of the hyaluronic acid employed for the crosslinking may vary within a wide range from some --, thousands to several millions, for example from 20,000 to 5x10 depending on the concentration thereof and on the amount of crosslinking agent. However, a preferred molecular weight range is one between about 100,000 and 4x10 ..
• hyaluronic acid or hyaluronates such as e.g. the sodium salt
• other derivatives of hyaluronic acid may be crosslinked in accordance with this method, such as for instance a partially sulfated hyaluronic acid or esterified hyaluronic acid (see EP 265116).
• hyaluronic acid that has been subjected to some other minor chemical modification such as described in e.g. ' US 4713448.
• the amount of crosslinking agent may vary within* a wide range depending on the molecular weight and concentration of the hyaluronic acid.
• the amount of the latter may vary from 10 to 500 % by weight based on the hyaluronic acid. i .
• the crosslinking reaction may be carried out at room temperature or at a somewhat elevated temperature. However, the reaction at these temperatures is very fast; gel formation will occur already after a few minutes' reaction time at room temperature. For better control of the reaction one will therefor choose a lower temperature, for example within the range of from 0 to 10°C.
• the gel material after having been swollen and finely divided in a physiologically acceptable buffer, will be readily injectable.
• the gel can be heat-sterilized, for instance by autoclaving.
• other preparations in the form of shaped materials may be produced, like for instance films, tubes etc.
• the present gels are capable of complete re-swelling after having been desiccated, for example by freeze-drying. From a manufacturing point of view this is a considerable advantage, for by storing a dry stable inter ⁇ mediate product one will avoid such degradation as would occur if the gel were stored while being swollen in a buffer having a pH greater than 7. Also, it is easy to alter the concentration and swelling medium of the final gel composition.
• the phosphorus content in dried gels will vary from some hundredth percent up to one percent.
• the solids content in a completely swollen gel in aqueous solution varies between 0.1 and 10 %.
• the degree of swelling will be much lower in gels crosslinked in a non- homogeneous system with an incompletely dissolved hyaluronic acid.
• the solids content will be 30 %.
• the gels have a maximum of stability at pH 5.75 but are degradable at biological pH (7.3).
• gels are produced which contain also other components, e.g. pharmaceuticals, this being achieved by adding the desired component to the gel either before or after the crosslinking thereof, to thus obtain for instance a slow-release effect. .
• the gels are used for slow release of soluble hyaluronate in vivo.
• Beneficial effects of local administration of hyaluronic acid, for instance in joints, are well known from the literature.
• One of the problems encountered so far is that the hyaluronate, in spite of its high viscosity, is removed too quickly out of the administration area, by diffusion.
• the degradation products of the present gels are, as earlier mentioned, hyaluronic acid and harmless phosphates, making these gels, when implanted, excellent depots for slow-release of hya ⁇ luronic acid.
• the invention thus relates to a method for crosslinking hyaluronic acid by means of subjecting a solution of hya ⁇ luronic acid or a derivative thereof to treatment with a phosphorus-containing reagent, especially a phosphorus(V) — o —
• phosphorus(V) acid derivatives are at present considered to be halides, oxyhalides or anhydrides, for example phosphorus pen achloride, phosphoryl chloride (phosphorus oxychloride) or the corresponding bromide or iodide, phosphorus pentoxide and trimetaphosphates.
• the invention comprises hyaluronic acid gels containing phosphate ester crosslinks produced as stated above, and the use of such gels as preparations for the administration of medicines and as slow-release depots for administration of hyaluronic acid.
• VL.3x10 high molecular weight sodium hyaluronate
• the gels have been swelled, washed and autoclaved in isotonic S ⁇ rensen buffer pH 5.75 (100 ml Na 2 HP0 4 (9.470 g/1), 900 ml NaH 2 P0 4 .H 2 0 (9.208 g/1) and 5200 mg NaCl per liter of solution).
• the sample was stirred with a glass rod until complete dissolution of the hyaluronate had taken place.
• the 6 % hyaluronate solution thus prepared has a pH of about 12.8 %.
• the resultant gel which had a neutral pH, was cut into thin slices.
• the slices were transferred to one liter of S ⁇ rensen busffer.
• the gel was washed for two days with shaking, the buffer being replaced three times during this period.
• the yield of swollen gel was 35 ml.
• the gel was crushed by being forced through a fine-meshed steel wire net and was filled into syringes which were then autoclaved.
• the soft, slightly cohesive gel could easily be injected through a fine injection needle.
• the non-autoclaved gel had a degradation time of 5 weeks whereas the autoclaved gel was degraded within 3-4 weeks:
• the phosphorus content of the dialyzed dried gel amounted to 0.081 %.
• the solids content of the swollen gel was Ii-4 %.
• the gel thus formed was dialyzed against dist. water for two days; then the material was crushed and freeze-dried. The phosphorus content was 0.10 %.
• the dried gel was allowed to swell in S ⁇ rensen buffer for three days, and was then autoclaved.
• the gel thus obtained was cohesive, homogeneous, entirely clear, fairly mobile.
• the degradation time of the autoclaved gel amounted to 4-5 days.
• the swollen gel had a solids content of 3.6 %.
• the degradation time of the autoclaved gel was 10 days.
• the phosphorus content of the dried gel was 0.085 %.
• a somewhat liquescent gel was obtained.
• the gel was autoclaved on having been swelled in S ⁇ rensen buffer of pH 5.0.
• the * non-autoclaved gel had a degradation time of between 15 and 19 days while after autoclaving the degradation time was 10 days.
• crosslinking was tested in aqueous solutions with various different concentrations of sodium hydroxide as the base.
• Dialyzed salt-free sodium hyaluronate was dried in a petri dish so as to form a clear, planar film.
• the film was allowed to swell for some seconds in a cooled mixture of one part of water and nine parts of triethylamine.
• the swollen film was treated with phosphoryl chloride, either by being dipped into it for some seconds or by being maintained in phosphoryl chloride vapor during about one minute. In both cases a clear, water-insoluble crosslinked film was obtained; in its swollen state it had a solids content of about 30 %.

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• Health & Medical Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Medicinal Chemistry (AREA)
• General Health & Medical Sciences (AREA)
• Veterinary Medicine (AREA)
• Animal Behavior & Ethology (AREA)
• Epidemiology (AREA)
• Public Health (AREA)
• Pharmacology & Pharmacy (AREA)
• Dermatology (AREA)
• Engineering & Computer Science (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)
• Biochemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Transplantation (AREA)
• Biomedical Technology (AREA)
• Neurosurgery (AREA)
• Inorganic Chemistry (AREA)
• Molecular Biology (AREA)
• Medicinal Preparation (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)

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Cited By (12)

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Citations (3)

• 1989
  • 1989-02-08 SE SE8900422A patent/SE8900422D0/xx unknown
• 1990
  • 1990-02-07 WO PCT/SE1990/000077 patent/WO1990009401A1/en not_active Application Discontinuation
  • 1990-02-07 JP JP2503222A patent/JP2836952B2/ja not_active Expired - Fee Related
  • 1990-02-07 EP EP19900903058 patent/EP0408731A1/en not_active Ceased

Patent Citations (3)

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