FR2837099A1 - Compositions that form a gel on contact with physiological liquids, allowing prolonged release of active materials - Google Patents

Abstract

Thermosensitive compositions containing an organic hydrophobic liquid (B), an organo gelling substance (C), the molecules of which can link together by weak bonds, and a biologically active substance (A), the composition forming an organogel when in contact with a physiological liquid after administration to an animal, especially a human.

Description

of a composition to accelerate healing and regeneration

tissue.

  The present invention relates to a thermosensitive chemical composition comprising a hydrophobic organic solvent, a cited organogelling substance, and a bioactive substance, said composition being intended to be administered to a living organism, for delivery

extended with bioactive substances.

  Said composition has the capacity to form an organogel spontaneously or by cooling, once brought into contact with an aqueous medium, and in particular a physiological liquid. Said shaped organogel serves as a support for the prolonged release of bioactive substances by diffusion eVou by erosion eVou progressive biodegradation to said organogel in the organism. The present invention also extends to the uses which can be made of this composition in the therapeutic field and more particularly in the field of prolonged delivery of bioactive substances. The term “thermosensitive composition” means any composition capable of passing from the liquid state to the gel state as a function of the temperature and by organogel any gel whose liquid phase is composed of an organic solvent. Furthermore, by bioactive substance is meant any substance having the capacity to act on a living organism or its functioning in a con

  prevent, cure, relieve or improve the state of said organism.

  The term “hydrophobic organic solvent or liquid” is understood to mean a solvent or a liquid whose molecules or parts of molecules exhibit a certain repulsion with respect to water molecules. Hydrophilic solvent is understood to mean a solvent whose molecules establish interactions

  of attraction with water molecules.

  Gels have long been used in industry

  for the properties given to them by their particular physical structure.

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  In fact, they correspond to an intermediate state of matter because they are composed of both elements in solid form and elements in liquid form. The solid elements forming a three-dimensional structure or matrix, organized in a network of molecules interconnected with each other, this network immobilizing the elements present in liquid form. The gels can be fouled according to the type of bonds which connect the molecules of the solid phase to each other or according to the type of

  solvent, organic or aqueous that makes up the liquid phase.

  We call hydrogels, gels whose liquid phase is an aqueous phase, to differentiate them from organogels whose liquid phase is a

organic phase.

  Gels whose matrix consists of molecules linked together by covalent bonds are generally in a stable and irreversible state once formed. Conversely, gels whose solid matrix is obtained by low energy bonds (such as hydrogen bonds or Van der Waals bonds in particular), generally have reversible gels, that is to say which can pass from state gel in the liquid state in function

  surrounding conditions (pH, temperature, ionic strength, etc.).

  In the case of heat-sensitive gels, the temperature at which the change of state is observed is called the transition temperature. In the particular case of systems exhibiting a hysteresis behavior, the geliliquid transition temperature is different from the temperature of

liquid / gel transition.

  Thus, gels are used in particular in the pharmaceutical industry, for their capacity for retention vis-à-vis bioactive molecules, in particular in the context of the administration of substances.

active by transcutaneous flight.

  This retention property has also been exploited for the use of gels as vectors for prolonged drug delivery. Thus, US Pat. No. 3,932,624 describes the use of a hydrogel intended for the delayed delivery of saralasin. In this patent, the gel is made

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  based on gelatin, which, diluted in a physiological saline solution containing the bioactive substance, will impregnate it to form a gel structure which can be implanted in the body by surgical flight at the subcutaneous level. The implanted gel gradually releases the active substance it contains by progressive erosion of said gel. However, this type of use requires implantation in situ by vole chi ru rgica le. a previously formed gel. This operation therefore remains at the same time

  expensive and restrictive for the patient.

  To overcome this drawback, implantable hydrogels forming in situ have been developed. Thus, US patent N 5,863,551 describes the use of a composition based on N-substituted acrylamide, a binding agent and a complex sugar for the formation of an implantable hydrogel. This porous gel is formed in situ by spontaneous polymerization of complex sugar

  after being injected in liquid form in the desired area.

  The hydrogel thus formed in situ or more exactly in vivo contains at least 80% of water. It is used in order to offer cells in

  development of a stable three-dimensional environment.

  Such in situ formation hydrogels have also been used for delayed drug delivery. Thus, more recently US patent application N 20010007673 describes the use of a hydrogel forming in vivo intended for the delayed delivery of bioactive molecules, in particular proteins. A composition based on alginate, a polyvalent metal ion and the desired active substance, is injected in liquid form and passes into gel form once implanted in the body. Gelfication takes place again by retaining physiological fluids in the matrix formed by the alginate molecules. This hydrogel allows a delayed diffusion of

  the bioactive substance in the fluids of the organism.

  Furthermore, US Pat. No. 5,575,815 describes the intra-cavitary, i.e. intra-arterial or intravenous implantation, of an aqueous liquid composition which transforms or viscosifies into a hydrogel in vivo. The use of this gel for the incorporation of active substances is planned, in particular

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  for angioplasty. The hydrogels used are made of polyether polymers. However, the main drawback of these hydrogels lies in their effectiveness in delivering hydrophilic bioactive substances over long periods of time. This is due in particular to their large proportion of water which gives them a high porosity, leading the hydrophilic bioactive substances present in such gels to be relatively quickly eliminated in the circulation. This diffusion phenomenon is particularly important for very hydrophilic small molecules such as certain hydrophilic drugs or certain hydrophilic peptides for example. The effectiveness of the extended release of

  these substances are therefore reduced.

  The object of the present invention is to provide a new pharmaceutical composition having the capacity to form an organogel allowing the release over long periods of time of active substances. In addition, the object of the present invention is also to provide such a delayed release support which is both biocompatible and biodegradable, making it possible, moreover, to be administered in liquid form, that is to say

  easy, easy, fast and inexpensive.

  Organogels have already been used as a support for the

  delayed release of active ingredient.

  Thus patent application No. WO 97/15287 describes a biodegradable polymer matrix injected subcutaneously or intramuscularly in gel form which gradually releases the active principle which it contains by passing to a liquid state in the organism. This matrix consisting of two hydrophobic copolymers contains an aqueous liquid in which the active ingredient is dissolved. This document discloses the parental administration of a

  hydrophobic organogel which liquefies once injected into the body.

  The present invention, on the contrary, relates to a hydrophobic organogel generated in vivo after having been applied in liquid form. Of

  such gels have already been described in the prior art.

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  Patent application No. WO 94/08623 discloses a hydrophobic organogel containing lecithin and a hydrophobic lecithin solvent used for the delayed release of protein. The gel is formed in vivo, from a solution injected intramuscularly or subcutaneously, by absorption of water from the interstitial medium during the injection. On the contrary, the hydrophobic organogel of the present invention is not

  not form by absorption of surrounding water.

  The present invention relates to a thermosensitive liquid composition with gelling properties comprising an organic liquid.

  hydrophobic, an organogelling substance, and a bioactive substance.

  The organogelling substance is made up of molecules capable of binding together by bonds of low energy so that the self

  assembly of these molecules is advantageously thermoreversible.

  The thermosensitive composition in liquid form according to the invention contains a hydrophobic organic liquid, an organogelling substance whose molecules have the capacity to bind together by low energy bonds, and a bioactive substance. Wile passes into the form of an organogel when it comes into contact with a physiological liquid, when it is administered to an animal body, in particular man, in particular when injected into the organism, for example to the body. using a conventional syringe, by extra vascular parenteral, or intramuscular

subcutaneous.

  By extravascular parenteral flight is meant any penetration flight into the organism other than the digestive tract and the vascular flight

  (veins, arteries and blood vessels).

  The composition of the invention can also be administered by intraocular flight, by intracavital flight or on prostheses prior to their application, by vaginal flight, on an open plate or during a

surgical intervention.

  Numerous documents describe compositions for topical use containing lecithin-based organogels (see for example US N 6,306,383). Lecithin is a mixture of low-weight phospholipids

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  moldculaire. Ibcithins are amphoteric, they are soluble in alcohol and they form an emulsion with water. Ibcithine organogels have been described as vehicles used to facilitate the penetration of low molecular weight molecules (Willimann, H., et al., "Organogel Ibcithine as a matrix for transdermal drug delivery", J. Pharm. Sci., Vol 81, 1992). Ibcithin organogels are obtained by adding a little water to a solution of lecithin in organic solvents such as isop ropyle palm itate or cyclooctane. In these documents, water is added to form the desired gel so that the organogel

  is formb before its application on the skin.

  On the contrary, the organogels of the present invention are in liquid form when administered to a living organism and take the form of gei once they come into contact with physiological liquid. In addition, Ibcithins do not constitute organogGatory substances

  as defined in the context of the present invention.

  The term physiological liquid is understood to mean any liquid circulating in an animal body, such as for example the lymphatic fluid, the tear fluid, the cerebrospinal fluid, the amniotic fluid, the parenteral fluid and the blood. The organogel formed from the composition according to the invention possesses capacities for retaining bioactive molds and more particularly molecules with a weight of less than 100,000 dalton having a hydrophilic character, making it possible to envisage a release of said molds in

  the organism for periods longer than 3 days.

  Finally, said organogel formed in the organism from the composition according to the invention has the capacity to be eliminated slowly by erosion and progressive biodegradation, without toxicity for the organism or it

is implanted.

  This in situ gelification property in accordance with the invention is obtained by the use of a hydrophobic organic solvent, constitute the organic phase with said organogel and by an organoglycerating substance (or

  organogGlator), constitute the solid matrix for said organogel.

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  The molecules constitute this organogelling substance, wind of the type in particular ester derivatives of fatty acids of amino acids which have the capacity to spontaneously self-assemble to form a matrix immobilizing said hydrophobic organic solvent. This molecular self-assembly can be achieved by hydrogen bonds being established between groups of the alcohol (-OH), acid (-COOH), amine (-NH or NH2) type.

  carried by organogelling molecules.

  If necessary, the gelation of the liquid composition is induced by cooling the site of application of the composition or by diffusion of a

  hydrophilic organic solvent added to the composition of the invention.

  The Applicant has selected hydrophilic organic solvents capable of creating weak bonds (e.g. hydrogen poets) with molecules of organogelling substance, and capable of diffusing into

  aqueous media to make the composition according to the invention.

  Thus, the hydrophilic organic solvent introduced into the mixture forming the composition according to the invention will compete with the molecules of organogelling substance, creating with said molecules weak bonds (eg hydrogen poets) preventing the said molecules of s Self-assembling in a dense and united network The composition according to the invention will therefore remain in liquid form while the molecules with said hydrophilic organic solvent will remain linked to the molecules of the organogelator. The use according to the present invention of the reversibility of weak bonds will advantageously allow the organogelling matrix to reassemble as soon as said hydrophilic organic solvent has diffused in

the surrounding environment.

  Thus, when it comes into contact with an aqueous solution and more particularly with physiological liquids such as the interstitial liquid, the lymph or the intraperitoneal liquid for example, said hydrophilic organic solvent present in the composition according to the invention will

  diffuse into said surrounding liquid due to its hydrophilicity.

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  Diffusion to said hydrophilic organic solvent will then allow the self-assembly of the molecules of said organogelling substance. This self-assembly, by creating a structured network, will allow the retention of said hydrophobic organic liquid, passing said composition from the liquid state to the gel state. The present invention therefore provides a simple system of gelation in

  spontaneous sifu, and easy administration.

  Furthermore, the present invention is based on the hysteresis properties observed by the applicant on organogels based on organogelling substances according to the invention. By hysteresis is meant the physical phenomenon observed in particular for gelable compositions, representing the difference between the gel / liquid transition temperature and the liquid / gel transition temperature. These properties make it possible in fact to design a composition in accordance with the invention which is liquid, therefore easily injectable, at ambient temperature (or at a temperature approaching ambient temperature). In addition, these properties also make it possible to produce an organogel according to the invention which, once formed in vivo, will remain in gel form at the body temperature of the organism considered. Indeed, such an organogel, whether formed by diffusion or simple cooling, has a gel / liquid transition temperature higher than the temperature of the injection or application site. Therefore, it

  is perfectly stable in said organism.

  Finally, the present invention has the advantage of providing a support for prolonged release of drugs or other active substances. Indeed, the organogel formed in the organism and in accordance with the present invention comprises a true matrix structure organized that has little affinity for the surrounding aqueous medium and therefore allows a slow release of the active substance by diffusion, erosion or biodegradation progressive organogel audit. The present invention therefore provides a simple, effective and easy-to-administer support allowing a prolonged release in the organism, for a period at least equal to 1 day, of substances such as bioactive substances 2837099 and more particularly of molecules with hydrophilic character of a

weight less than 100,000 dalton.

  In addition, the composition according to the present invention has the advantage of being extremely inexpensive, attempted in terms of manufacturing as described below, than in terms of packaging and administration. The organogelling substances in accordance with the invention are substances whose molecules have the capacity to bond together by low energy bonds, and in particular by hydrogen bonds, allowing the formation of a thermosensitive matrix. These molecules are in particular molecules of low molecular weight having acid ends (

  COOH) or alcohol (-OH) or even amine (-NH2 or -NH) for example.

  In addition, these substances are preferably biocompatible and do not give rise to toxic or dangerous metabolites for

  The organism during their degradation by the latter.

  Preferably, amino acid derivatives or fatty acid ester derivatives of amino acids such as alanine will be used, having both good biocompatibility and satisfactory organogelling power and above all conferring on the gelled system properties of hysteresis. These properties result in a transition from the liquid state to the gel state at a temperature different from that observed during the transition from the gel form to the liquid form of said composition. The Applicant deserves to have noticed that the difference between these two transition temperatures is variable depending on the type of hydrophobic organic solvent used, and the amount

  of organogelling substance used.

  Thus, the applicant has produced compositions in accordance with the invention, the transition temperatures and the differences between these wind temperatures adjustable by simple modification of these two parameters. The results reflecting these wind variations represented on the

Figures 1 and 2.

  Figure 1 shows the diagram of the liquid-gel (solid lines) and gel-liquid (dotted lines) transition temperatures of Nlauroyl L

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  Alanine Methyle ester (LAM) in the presence of benzyl benzoate (circles) or a

  mixture of benzyl benzoate / 5% benzyl alcohol (triangles).

  Figure 2 shows the diagram of the Liquid gel (solid lines) and Gel-liquid (dotted lines) transition temperatures of the LAM in the presence of soybean oil (diamonds) or Labrafac CC (carrel). Preferably, the difference between these two transition temperatures is chosen so that the liquid / gel transition temperature is lower than the body temperature of the living organism considered in the. case I, organogel is administered without hydrophilic organic solvent and the transition temperature

  gel / liquid is above the above temperature.

  Thus, use will preferably be made of alanine ester derivatives such as N-lauroyl L-alanine methyl ester or N-lauroyl L-alamine ethyl ester as

  organogelling substance according to the invention.

  The quantity of organogelling substance depends on the type of hydrophobic organic solvent used and the transition temperature

  that we wish to choose for the organogel according to the invention.

  However, the proportion of this substance is advantageously

  chosen between 0.5 and 50% by weight of the total weight of said composition.

  The Applicant has found that the use as an organogelling substance of N-lauroyl L-alanine methyl ester allows said composition to pass into the gel state by simple cooling below the liquid / gel transition threshold and to remain in the gel state. at a temperature exceeding the liquid / gel transition temperature, in particular the temperature of the living organism Indeed, the Applicant has noticed that the led to orga nogel forms by cooling is stable in the temperature range between the temperature / gel transition temperature and the gel / liquid transition temperature. All of these observations led the applicant to develop a thermosensitive composition with gelling properties having the capacity to pass into gelled form by simple local cooling and to preserve this gelled state at body temperature. In this particular case of the invention, the amount of hydrophilic organic solvent can be

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  extremely reduced, or even zero since the gelation takes place by cooling of said composition and no longer by diffusion to said solvent

hydrophilic organic.

  This embodiment is particularly advantageous since it overcomes the presence of the hydrophilic organic solvent and therefore further simplifies the process for preparing the composition according to

  [The invention and also to reduce its cost price.

  Thus, according to a particular embodiment, the thermosensitive composition according to the invention contains a proportion of N-lauroyl L alanine methyl ester sufficient to allow the passage of said composition from the liquid state to the organogel state by simple cooling.

  of said composition in contact with its injection site in the body.

  Such cooling must be sufficient to change the said composition, applied in liquid form, to its gel form. This cooling, which can be carried out by external apposition of a cold object such as a grace loaf or a cold compress or any other cooling means around the injection site, must allow a local lowering,

  under the liquidelgel transition temperature of said composition.

  The composition according to the invention is therefore preferably in liquid form at the temperature of the site of application, has a gel / liquid transition temperature higher than the body temperature and a liquid / gel transition temperature below the body temperature. consider or the gel implantation area. In fact, the skin temperature can be a few degrees lower than the

  general temperature of the organism.

  In a preferred embodiment, the proportion of N-lauroyl L alanine methyl ester of said composition is sufficient for the liquid / gel transition temperature to be lower than the body temperature (37 C in general) and for the geliliquid transition temperature ,

  is higher than body temperature (37 C in general).

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  Even more preferably, the composition according to the invention must have a lower liquid / gel transition temperature.

  at 30 C and a gel / liquid transition temperature higher than + 35 C.

  Thus, the composition according to the invention is preferably a composition in which the interval between the liquid / gel transition temperature and the gel / liquid transition temperature is advantageously at least 20 ° C., the liquid / gel transition temperature being preferably understood

between +5 C and + 36 C.

  The hydrophobic organic solvents which can be used for the preparation of the composition according to the present invention belong to the group of organic solvents immiscible with water capable of creating an organogel type structure, in the presence of a sufficient amount of the substance mentioned.

  organogelator as described above.

  These solvents are preferably biocompatible, that is to say tolerated by the hose organism, causing little or no reaction

  immune, inflammatory or allergic type for example.

  Finally, it should be noted that it is preferable to use hydrophobic organic solvents which are liquid at room temperature, which simplifies the process of

  manufacture and administration of the composition according to the invention.

  It is preferable to use organic solvents which can be degraded in a slow manner, that is to say, not rapidly metabolized by the

  enzymes present at the injection site, and in particular by lipases.

  Thus, the hydrophobic organic solvents in accordance with the invention belong to the group comprising vegetable oils, semi-synthetic oils and certain fatty acid esters, in particular glycerol (in particular biglycerides and triglycerides). The use of biocompatible vegetable oils such as soybean oil, mas oil, cottonseed oil, peanut oil, olive oil, castor oil, sesame oil or almond oil by

example.

  In a preferred manner, a vegetable oil such as soybean oil having a

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  adequate gelation behavior, slow biodegradability and

excellent biocompatibility.

  Among the fatty acid esters which can be used as hydrophobic organic solvents in accordance with the invention, mention may, for example, be made of ethyl oleate or isopropyl myristate in particular. More preferably, fatty acid esters of glycerol, in particular triglycerides, will be used. Even more preferentially, we will use medium chain triglycerides (less than 18 carbon atoms) such as Labrafac CC comprising two fatty acids of 8 and 10

carbon atoms.

  Among the synthetic or semi-synthetic solvents which can be used as hydrophobic organic solvents in accordance with the present invention, there may be mentioned in particular squalene, benzyl benzoate,

  benzyl chloride, and benzyl benzoate / benzyl alcohol mixtures.

  It is also possible to combine oils and synthetic hydrophobic organic solvents. Hydrophilic organic solvent according to the invention is understood to mean a solvent having a high affinity for aqueous media, that is to say

miscible with water.

  The type of hydrophilic organic solvent capable of being used in the present invention is advantageously a solvent capable of acting as an agent for destabilizing the organogel, that is to say capable of creating falble bonds with the molecules of 'organogelling. Such a solvent is moreover advantageously biocompatible, that is to say tolerated by the organism, so that its diffusion causes little or no immune reaction of the inflammatory or allergic type. We will therefore preferentially use for the realization of the present invention, a solvent having

  is approved for parenteral use.

  Said hydrophilic organic solvent in accordance with the invention will be advantageously used in proportions of less than 60 OJ by weight of said

  composition, and more preferably less than 20%.

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  Mention may be made, among hydrophilic solvents, of solvents such as alcohols such as ethanol, glycerol, propylene glycol, poly (ethylene) glycol of low molecular weight, benzyl alcohol or chlorobutanol and their mixtures. Furthermore, other water-miscible solvents can be envisaged, such as dimethyl sulfoxide (DMSO), N-methyl-pyrrolidone, NN-Dimethylacetamide, furfural, glycerol formal, isopropylidene glycerol, lactate ethyl, acetic acid or lactic acid and their mixtures. These examples are not limiting and it is entirely conceivable to carry out the invention from other hydrophilic organic compounds which would have destabilizing properties of gel, that is to say the capacity to create falble bonds with the organogelling substance according to the invention. The bioactive substances capable of being released into the organism from the organogel according to the present invention advantageously contain substances which are difficult to condition for a sustained release, such as molecules of low molecular weight with a hydrophilic character or very hydrophilic. Advantageously, said bioactive substance will be used in proportions of 0.5 to 70%

  by weight of the composition according to the invention.

  Thus, the Applicant has tested the release from a preformed organogel of dextran molecules labeled with a molecule

  fluorescent:; FITC (FIuoro-lso Thio Cyanate).

  The release profile of dextran was monitored in vitro over 20 days by fluorescence assay as shown in Figure N 3. The fluorescence was measured by regular samples of an aqueous solution of

phosphate buffered saline.

  Thus, one can conceive the release over periods greater than 3 days of proteins, in particular of therapeutic interest such as [interferon oc, 30 interferon, somatostatin, ca lcitonin, heparin, interleukins or

  erythropoetin, peptides, amino acids or vitamins.

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  These examples are by no means limiting and other types of molecules, in particular other proteins, may well be envisaged for such prolonged release from an organogel.

in accordance with the invention.

  It is possible to envisage the release into the body from the organogel according to the invention, of molecules such as certain hormones and in particular certain peptide hormones such as the hormone of

  human growth or thyreotropic hormone.

  Thus, provision may be made to use the present invention for the sustained release into the body of nucleic acids, oligonucleotides or

  nucleic acid derivatives in particular.

  Likewise, it is entirely conceivable to carry out the present invention with the aim of dissolving and then releasing fa, with prolonged hydrophobic bioactive substances, that is to say having a strong affinity

  for the organogel and a falble affinity for the surrounding aqueous medium.

  The present invention can therefore be used for a large number of substances of therapeutic or medical interest for which it is desired.

  prolonged release in the body.

  By way of example, the composition according to the present invention can be

prepared in the following manner.

  In the case of a diffusion gelification system We proceed first to spontaneous dissolution or by heating

  eVou agitation of the organogelator in the hydrophilic organic solvent.

  Then the active substance and the hydrophobic organic solvent (s) are incorporated into this mixture, two cases can then arise: a) Either the active substance is soluble in the organic phase thus formed: In in this case, the active substance is dissolved in the organic phase formed. Solubilization stops spontaneously or by heating, with or

without agitation.

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  It is also possible in this case to provide for the dissolution of said

  active substance directly in the hydrophobic organic solvent.

  b) Either the active substance is little or not soluble in the organic phase: In this case, the active substance is firstly "wetted" by dispersing it in the organic phase formed by the hydrophilic organic solvent and the substance organogelling. After stirring, a suspension of active substance is then formed in the mixture. This suspension can then be added to the other components of the

  composition according to the present invention.

  It is also possible to dissolve the active substance in just enough water. This aqueous solution of active substance will be added to the organic phase formed by the hydrophilic organic solvent and the organogelling substance. The aqueous phase is then emulsified into the organic phase by vigorous stirring. The more vigorous the agitation, the smaller the size of the aqueous particles formed in the organic suspension and the more stable the emulsion. This emulsion will then be able to be used for the preparation of a composition

in accordance with the invention.

  It should be noted, however, that this technique using an emulsion has the advantage of preserving the complex molecules of active substance in an aqueous micro environment, which greatly limits the disturbances to which they can be subjected when subjected to the change of environment. The hydrophobic organic solvent is then added to the mixture obtained above, optionally with stirring and heating.

  moderate until a homogeneous mixture is obtained.

  This homogeneous mixture according to the invention can then be injected into a living organism by extra vascular parenteral flight using a conventional syringe for subcutaneous injections. After a lag time which depends on the formulation chosen, we witness the formation of a

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  hardening at the injection site, proof of training; n v / vo de

the organogel according to the invention.

  If it is not extracted in a surgical manner, said organogel will, depending on its size and the nature of the components which constitute it, be biodbgrade eVou to erode gradually with more or less long maturity in the organism. This progressive biodegradation will lead to the release of the active substance possibly contained in the organogel according to the invention. We preferentially choose to produce such organogels, the

  biodegradation will be understood over periods longer than 3 days.

  In the case of a cooling system in this case, we first mix the organogelling substance

  endowed with properties of hysteresis with the hydrophobic organic solvent.

  Then we proceed to the incorporation of the active substance in this mixture. If the active substance is organosoluble, it will be dissolved in the mixture directly or by gentle agitation. In the case where the active substance is little or not organosoluble, one proceeds as above to the dispersion of the latter in the organic phase or to the production of a stable emulsion of active substance previously dissolved in

  water, in the organic phase formed.

  The composition thus formed is stable and preferably liquid at room temperature. Wile is injected for example by parenteral flies

extravascu la ire.

  Immediately after the injection, a cold object (or any other cooling system) is kept in contact with the injection site for a sufficient time to allow the in situ gelification of the composition according to

the present invention.

  When freezing is completed, the cooling system is removed. The injection site then regains body temperature,

  The organogel according to the invention restart stable at said temperature.

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  The thermosensitive composition with gel-forming properties according to the invention can be used for example for the delayed delivery of bioactive substances over long periods, that is to say over periods of at least one day, generally greater than 3 days. . This composition can therefore serve as a support for the delayed delivery of all types of substances,

  in particular of substances of therapeutic or medical interest.

  It is thus possible to provide for the use of the thermosensitive composition in accordance with the invention for the delayed delivery of drugs which need to be maintained at a constant blood level. This invention therefore turns out to be particularly interesting for medicaments ordinarily administered by several daily intakes intended to maintain a

  effective therapeutic rate in the body.

  One can thus envisage the use of the invention for therapeutic substances such as morphine or drugs acting as

  regulators of the cardiovascular system or the nervous system.

  Similarly, one can conceive of the use of the composition according to the invention with the aim of overcoming certain deficiencies in the organism, in particular in vitamins or hormones. Thus, the present invention can serve as a support for the prolonged delivery of hormones requiring a daily intake, and still today administered by injection, a painful and restrictive mode of administration. Such an organogel release medium, due to its easy administration, its safety and its low cost

  would overcome these constraints for the patient.

  This composition can also be used for the manufacture of a medicament intended to be injected into the organism is flown by the extravascular and in particular by subcutaneous, intradermal, intraperitoneal or intramuscular use, by intra- ocu la ire or intravascu la ire, by vaginal fly, on an open platform or during a surgical intervention. 3 0 Wile may also allow them to manufacture a drug intended to be used as a vehicle for prolonged release of substance (s)

bioactive (s) in the body.

  lg 2337099 Example 1: Formation of an organogel in vivo from a

composition according to the invention.

  s In this example, it is sought to verify that the composition in accordance with the invention is indeed capable of gelation in vivo. Wind tests performed on

the rat.

  Soybean oil and ethanol are used as the hydrophilic organic solvent as the hydrophobic organic solvent in accordance with the invention.

according to the invention.

  The organogelling substance chosen is LAM (N-lauroyl L-alanine methyl ester) The proportions used are summarized in the following table: Product Function Proportions LAM Organogelator 17.2% Soybean oil Organic solvent 68.8% hydrophobic Ethanol Organic solvent 14% hydrophilic We proceed firstly to the dissolution of the organogelator in ethanol. Then add soybean oil to this mixture. The mixture thus obtained is stirred and heated until complete homogenization. This mixture

  remains stable and liquid at room temperature.

  The composition thus obtained is then injected subcutaneously. The injection is done at the back, using a conventional syringe for subcutaneous injection. After 2 hours the animal is sacrificed and a semi-solid gel is extracted from the injection site, demonstrating the

in vivo organogel formation.

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  Example 2: Formation of an organogel in vivo from a

composition according to the invention.

  Soybean oil and ethanol are used as the hydrophilic organic solvent as the hydrophobic organic solvent in accordance with the invention.

according to the invention.

  The organogelling substance chosen is LAM (N-iauroyl, L-alanine methyl ester) The proportions used are summarized in the following table: Product Function Proportions LAM Organogelator 24.6% Soybean oil Organic solvent 57.4% hydrophobic Ethanol Organic solvent 18% hydrophilic injection procedure is identical to that of Example 1, similarly

  that [the appearance of an organogel 2h30 post-injection.

  Example 3: Manufacture of a composition according to the invention containing FlTC-Dextran This composition makes it possible to measure in vitro the gradual release

  of an active substance contained in a preformed organogel.

  The active principle used is FlTC-dextran which will make it possible to measure, by assaying the associated fluorescence, the quantity of dextran released by the organogel according to the invention (cf. FIG. 3) FIG. 3 represents the monitoring over 20 days of the release profile of FlTC-dextran (Molecular weight = 9500) from a gel made up of soybean oil and 30% LAM in PBS at 37 C. Each point represents the

  mean value ± sd (n = 3). The exposed gel surface was 0.64 mm2.

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  Product Function Proportions FlTC-Dextran Active substance 1.3% LAM Organogelator 30% Soybean oil Organic solvent 68.7% hydrophobic The LAM is first dissolved in soybean oil while hot. Then hot flTC-dextran is dispersed in the organic phase formed after having previously been ground in a mortar, until a

homogeneous liquid composition.

  This liquid mixture is then introduced gelified by cooling in a test tube. An aqueous saline solution of

phosphate buffered saline.

  Next, over a period of 20 days, samples of the liquid surrounding the organogel according to the invention are taken. We can then closer the fluorescence emitted by these samples and thus note the prolonged release of FlTC-Dextran in the surrounding medium. In the event that such a gel is administered in vivo and in accordance with the present invention, an organic solvent of the ethanol type should be added in such a way as to inhibit

  the gelation process before injection.

  The results of this assay are summarized in Figure N 3.

  Example 4: Demonstration in vivo of the hysteretic properties of an organogel according to the invention. Example of gelation without hydrophilic solvent. The organogelling solution is prepared from the following constituents: Product Function Proportions LAM Organogelator 40% Benzyl benzoate 1 5% Organic solvent 60% hydrophobic benzyl alcohol

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* The hysteretic properties of this organogel have been previously determined so that the liquid / gel transition temperature is lower

  at 30 C and the gel / liquid transition temperature is above 37 C.

  The organogelling solution is first brought to the liquid state by heating, then a volume of 180 μl of this solution, returned to ambient temperature, is injected subcutaneously into the rat. Once the injection is complete, a 4 C press is applied to the injection site for 3 minutes to lower the temperature and cause freezing. The animal is sacrificed 2 h 30 min after the injection and a visual observation of the shape of the implant is carried out. Then the implant is extracted from the site

injection and weighs.

  In this experiment, the implant had a disc shape

  about 1 cm in diameter and a weight of 130 mg.

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Claims (19)

  1. Thermosensitive composition in liquid form containing - a hydrophobic organic liquid, - an organogelling substance whose molecules have the capacity to bind together by low energy bonds, and - a bioactive substance, which passes in the form of organogel when it comes into contact with a physiological liquid, during its administration to an animal body, in particular man. 2. Composition according to claim 1, characterized in that the formation of the organogel is done by cooling the site of application of said composition. 3. Composition according to claim 1 or 2, characterized in that it also contains a hydrophilic organic solvent capable of creating weak bonds with the organogelling substance, and that the formation of the organogel takes place by diffusion to said hydrophilic organic solvent to the aqueous medium.   4. Composition according to Claim 1 or 2, characterized in that an organogel led has a transition temperature from the liquid state to the gel state below the temperature of the application site in the case where the organogel is administered without hydrophilic organic solvent and a temperature of   transition from the gel state to the liquid state above body temperature.   5. Com position as claimed in claim 4, ca characterized in that an organogel led has a transition temperature from the liquid state to the gel state below 30 C and a transition temperature from the gel state to l liquid state greater than + 35 C. 24 2337099   6. Composition according to one of claims 3 to 5 characterized in that   the proportion of the hydrophilic organic solvent is less than 60%, and   preferably less than 20% by weight of said composition.   7. Composition according to one of claims 3 to 6 characterized in that   Said hydrophilic organic solvent belongs to the group comprising ethanol, glycerol, benzyl alcohol, propylene glycol, Nmethylpyrrolidone and dimethylsulfoxide (DMSO), low molecular weight poly (ethylene) glycol, chlorobutanol, furfural, N -Ndimethyacetamide, glycerol formal, isopropylidene glycerol, ethyl lactate, acetic acid and lactic acid.   8. Composition according to claim 7, characterized in that q ue led it solve nt hydrophilic organic is ethanol.   9. Composition according to one of the preceding claims, characterized in   that said hydrophobic organic liquid belongs to the group comprising vegetable oils, triglycerides, semi-synthetic oils, and   organic solvents immiscible with water.   10. Composition according to claim 9, characterized in that said hydrophobic organic substance is soybean oil, squalene, benzyl benzoate, a triglyceride, or a mixture of benzyl benzoate and benzyl alcohol.   11. Composition according to one of the preceding claims, characterized in   that said biologically active substance belongs to the group comprising proteins, peptides, amino acids, vitamins,   nucleic acids and oligonucleotides.   12. Composition according to claim 11, characterized in that said biologically active substance is chosen from morphine, interferon a, 2837099   I'interferon 0, somatostatin, heparin, interleukins, erythropoetin,   ca lcitonin, human growth hormone, thyreotropic hormone.   13. Composition according to one of the preceding claims, characterized in   what the organogelling substance represents between 0.5 and 50% by weight   the total weight of said composition.   14. Composition according to one of the preceding claims, characterized in   that the organogelling substance is a molecule of low molecular weight having acid, alcohol or amine ends, in particular a derived from amino acids.   15. Composition according to claims 14, characterized in that the   organogelling agent belongs to the group of alanine ester derivatives. i6. Composition according to Claim 15, characterized in that the said organogelling substance is N-lauroyl L-alanine methyl ester or N lauroyl L-alanine ethyle ester.   17. Organogel obtained from the composition according to one of   Claims 1 to 16, characterized in that it remains in stable gel form   between application temperature and gel / liquid transition temperature of said composition.   18. Use of a composition according to one of claims 1 to 17 for   the manufacture of a medicament intended to be injected into the body by extravascular parenteral flight and in particular by subcutaneous, intradermal, intraperitoneal or intramuscular flight, or intended to be administered by intraocular flight or by vaginal flight, on an open dish   or during surgery. 26 2837099   19. Use of a composition according to one of claims 1 to 18 for   the manufacture of a medicament intended to be used as a vector for   prolonged release of bioactive substance (s) in the body.   20. Method for preparing a composition according to claim 1, characterized in that the bioactive substance, optionally in aqueous solution, is added to the mixture constitutes the organogelling substance and hydrophobic organic solvent.   21. Method for preparing a composition according to claim 3 which consists in - dissolving the organogelling substance in the hydrophilic organic solvent, then in   - incorporate the bioactive substance and the hydrobobic organic solvent.   22. The method of claim 21, characterized in that when the bioactive substance is sparingly soluble or not soluble in the organic phase, an aqueous solution of said substance is dispersed with stirring in the organic phase consisting of the organogelling substance and the solvent