DESCRIPTION of the invention entitled:

"Viscous ophthalmic liquid composition comprising natural gums and extracts"

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The present invention relates to a viscous liquid ophthalmic composition comprising or, alternatively, consisting of natural gums and extracts, in particular at least one mucilage and at least one hydrocolloid, useful, for example, as a humectant and/or for carrying active ingredients, which has peculiar technological characteristics.

STATE OF THE ART

Ophthalmic formulations constitute a series of preparations intended for application on the outer surface of the eye, that is, at the level of the cornea and conjunctiva, and in the periocular area. In the first case, in particular, said formulations are generally in liquid form with an aqueous base, take the name of collyrium or eye drops, and constitute one of the most widely used pharmaceutical forms for the care of the eye and/or for the maintenance of its functionality, when used in the preventive phase.

Among the various formulations of eye drops, an important type are products having mucoadhesive properties, which allow the maintenance of the applied solution on the ocular surface for a prolonged period of time. In particular, said characteristic turns out to be very important in the case of patients who have tired, reddened eyes or who need lenitive action, since the maintenance of active substances on the ocular surface is protracted over time, leading, as a result, to greater effectiveness of the preparation. Among the substances most widely used in obtaining the above-mentioned therapeutic effects are certain plant extracts.

We cannot exclude that there is a direct correlation between the rheological properties of an aqueous solution, and in particular its viscosity, and the mucoadhesive properties of said aqueous solution. This statement can be confirmed especially in the case where the substances that are used to increase the viscosity of the solution consist of polymer chains, of natural, semisynthetic or synthetic origin, capable of coordinating water through the formation of hydrogen bonds.

For example, EP0507224, identifies some specific naturally derived polysaccharides (e.g., xanthan gum, carrageenins, gellan gum) to prepare a controlled-release ophthalmic topical composition by dispersing the micronized active ingredient within said polysaccharides, which, by gelling, slows its release.

W02006068899 describes an ophthalmic composition containing Aloe vera gel as a vehicle for several possible active ingredients and capable of increasing patient compliance in its use due to an improved lenitive effect toward dry eye symptoms. The described composition also contains other components, in particular: buffering agents, which ensure the correct pH value for ocular administration; polymeric materials, for emollient purposes; and salts, such as MgCk and ZnCk , as osmotic agents.

EP2263648 describes an ophthalmic composition delivering cobalamin in an aqueous solution in which the presence of sodium hyaluronate, in combination with other substances, is able to stabilize cobalamin at a pH from 6.0 to 7.5, suitable for non-annoying or irritating ocular administration. In addition to mucoadhesion, ophthalmic formulations, and eye drops in particular, must possess an additional characteristic necessary to ensure their safe use: they must be sterile and maintain sterility throughout their period of use. However, at present, the solutions on the market still suffer greatly from limitations and drawbacks. However, it is important to emphasize the fact that liquid ophthalmic formulations often present, as previously described, a certain degree of viscosity, which is functional with respect to their ability to improve the degree of hydration of the eye, as well as to increase the residence time in situ of the formulation itself, and, consequently, of the actives carried therein. Said viscosity, which is therefore necessary from a technological/functional point of view, can, however, present problems during the terminal phase of filtration, mainly due to the difficulty of a viscous solution in overcoming the tight mesh of the filters used in this operation,

In addition, the passage of the viscous solution through the narrow meshes of the filter results in the application of a shear stress that can lead to structural changes in the viscous system, with alteration of the viscosity degree of the solution itself, thus impairing the functionality of the eye drops during its use.

Terminal sterilization which involves the use of high temperatures, generally above 120°C, for a period of time normally set at about 15 minutes, also has some critical issues.

First, this technique is not suitable in the case of eye drops that also contain thermolabile substances in their formulation. In addition, one must always consider the possibility that high temperatures may also promote reactions between the various elements that make up the eye drops themselves.

In response to these issues, one might try to reduce the viscosity of the solution by increasing the temperature, or by increasing the filtration pressure.

However, both of these two attempts have disadvantages related, in the first case, to the temperatures to which some components may be sensitive, and, in the second case, to the fact that the filters may clog more quickly or be damaged, resulting in the risk of non-sterility of the final product. In addition, as previously mentioned, the mechanical stress induced by the passage of the solution through the filters can lead to an alteration in the viscosity of the filtered solution, even more so when working at high pressures.

Another method used to decrease the viscosity of an aqueous solution containing excipients found in state-of-the- art ophthalmic formulations with the function of improving its mucoadhesion and wetting capacity, may be to add salts, particularly chlorine salts, often used to adjust the osmolarity and pH of the composition itself. In particular, studies by M. Poitier et al. (Mathieu Potier et al. Viscosity of Aqueous Polysaccharide Solutions and Selected Homogeneous Binary Mixtures. Macromolecules, 2020, 53 (23), pp.10514-10525 doi:10.1021/acs.macromol.0c02157) show how the viscosity of an aqueous solution based on a polysaccharide, such as dextrans, semisynthetic derivatives of cellulose, carrageenins and alginates, decreases in the presence of a 0.1 M concentration of NaCI in the solution itself.

This approach, however, while acting positively with respect to the possibility of sterilizing the polysaccharide- containing composition by filtration, could act negatively with respect to the ability of the ophthalmic formulation itself to maintain optimal levels of mucoadhesion and humectant capacities in the eye. There still persists, therefore, a strong need for a viscous ophthalmic aqueous liquid composition containing plant gums and extracts that can be easily sterilized, preferably by a filtration process, free of the limitations and drawbacks just described.

PURPOSES OF THE INVENTION

The purpose of the present invention is to provide an aqueous viscous liquid ophthalmic composition comprising or alternatively consisting of plant gums and extracts, said composition being easily sterilizable by a filtration process .

Another purpose of the invention is the use of said sterilized viscous aqueous liquid ophthalmic composition within ophthalmic pharmaceutical formulations, said composition maintaining its viscosity characteristics unchanged.

Further purpose of the invention is the use of said aqueous viscous liquid ophthalmic composition, and/or pharmaceutical formulations comprising it, in the treatment and/or prevention of eye diseases and/or as artificial tears to be used, for example, to counteract symptoms of dry eye, ensuring the sterility and stability of said composition.

Another purpose of the present invention is the use of said aqueous viscous liquid ophthalmic composition, and/or the pharmaceutical formulations comprising it, to carry specific active ingredients useful in the treatment and/or prevention of eye diseases, always while maintaining the sterility and stability of said composition and said specific active ingredients carried therein.

Another purpose of the present invention is the nontherapeutic use of said viscous aqueous liquid ophthalmic composition.

Further purpose of the present invention is to provide a method for the preparation of said viscous aqueous liquid ophthalmic composition comprising or alternatively consisting of plant gums and extracts, said composition being easily sterilizable by a filtration process.

These and other purposes are achieved by the present invention, which will be described in detail below, without wishing in any way to limit its scope.

DESCRIPTION OF THE INVENTION

It is an object of the present invention an aqueous viscous liquid ophthalmic composition comprising or alternatively consisting of at least one mucilage and at least one hydrocolloid.

Preferably, said composition is characterized by the fact that said at least one mucilage is present in an amount from 0.01 to 10% w/w of the total weight of the composition, preferably in an amount from 0.2 to 1% w/w of the total weight of the composition.

Preferably, said composition is characterized by the fact that said at least one hydrocolloid is present in an amount from 0.01% to 10% w/w of the total weight of the composition, preferably in an amount from 0.2% to 1% w/w of the total weight of the composition.

Preferably, said composition is characterized by the fact that said at least one mucilage and said at least one hydrocolloid are in a ratio [mucilage : hydrocolloid] in the range from 10:1 to 1 :2 to each other, preferably in the range from 5:1 to 3:1.

Preferably, said composition is characterized by the fact that said composition has a dynamic viscosity from 1.01 to 1 .60 mPa-s, at a temperature of 25°C±2°C, and an external pressure of 1 atmosphere.

According to another aspect of the invention, said composition is characterized by the fact that said composition has a dynamic viscosity ranging from 1.01 to 2.20 mPa-s, at a temperature of 25°C±2°C, and an external pressure of 1 atmosphere.

Preferably, said composition is characterized by the fact that said at least one mucilage is selected from the group comprising or, alternatively, consisting of Aloe mucilage, Althaea mucilage, Malva mucilage, Tilia mucilage, Calendula mucilage, Psyllium mucilage, or mixtures thereof.

Preferably, said composition is characterized by the fact that said at least one hydrocolloid is selected from the group comprising or, alternatively, consisting of xanthan gum, guar gum, karaya gum, carob gum, gum arabic, ghetti gum, starch, konjac gum, glucomannan, alginic acid or sodium, potassium or magnesium salts thereof, cellulose derivatives, chitosan, sodium hyaluronate, maltodextrins or mixtures thereof.

Preferably, when said mucilage consists of only Aloe mucilage, said hydrocolloid is gum arabic.

According to one aspect of the present invention, mucilages present in the ophthalmic composition of the invention can be marketed as plant extracts supported on maltodextrins. Examples, not limiting, of such combinations currently commercially available include Althaea Officinalis L. dry extract from root, in combination with corn maltodextrins, and Malva sylvestris L. dry extract from leaves, in combination with corn maltodextrins.

In case these kinds of plant extracts are used, as mucilages, they can be considered as representing, in one compound, the at least one mucilage and the at least one hydrocolloid contained in the viscous liquid ophthalmic composition according to the present invention.

Preferably, said composition is characterized by the fact that the hydrocolloid/mucilage pair is selected from the group comprising or alternatively consisting of xanthan gum/Ma/va mucilage, guar gum/ Althaea mucilage, gum arabic/A/oe mucilage, hydroxypropylmethylcellulose/L/num mucilage, and karaya gum/777/a mucilage, Malva mucilage/sodium hyaluronate, maltodextrins/ Althaea mucilage, hydroxypropylcellulose/ Malva mucilage.

Preferably, said composition is for use in the treatment and/or prevention of eye diseases and/or as eye drops or artificial tears to be used, preferably, to counteract dry eye symptoms.

It is an object of the present invention, an ophthalmic pharmaceutical formulation comprising the composition as given above and, optionally, at least one active ingredient and/or excipient for pharmaceutical use.

It is another object of the invention the non-therapeutic use of the composition according to the present invention. There are no documents known to the Applicant that analyze or exploit particular interactions between different types of mucilages and/or hydrocolloids to obtain advantages in the preparative processes of the formulations and compositions that are objects of the present invention.

The Applicant has found it useful to adopt, during the production stages, a whole series of measures to avoid as much as possible the pollution of the composition, which is nevertheless subjected, as a final step, to a sterilizing treatment.

There are basically two techniques most commonly used to implement this treatment:

- sterilizing filtration of the liquid formulation in controlled contamination environments; and

- terminal sterilization of the product once it is divided into the final containers.

Of the two, sterilizing filtration was adopted here because it was found to be more useful, as it ensures that the unchanged characteristics of the composition are maintained as opposed to the possible negative action brought about by the use of high temperatures in terminal sterilization techniques. Sterilizing filtration is performed here using filters that range in size from about 0.10 micron to about 1 micron, preferably from about 0.20 micron to about 0.80 micron, even more preferably from about 0.30 micron to about 0.50 micron, for example, about 0.22 micron or about 0.45 micron.

A "rheology modifier" is a substance that is capable of modifying the flow properties of a liquid, including viscosity. There are certain types of compounds of plant origin that can boast this ability.

In this regard, the authoritative text by Jean Bruneton (Pharmacognosie 3 ^a ed., TEC Publisher, Paris, France) on pages 36-38, which are considered herein incorporated by reference, attributes to plant-derived polysaccharides the characteristic of gelling aqueous solutions and, therefore, said polysaccharides may fall into the category of rheology modifiers.

Again according to Bruneton, an alternative classification of plant polysaccharides, based on botanical origin, has also been suggested, dividing them into 3 classes (page 38; Monographies): polysaccharides that originate from microorganisms and fungi; polysaccharides that originate from algae; polysaccharides that originate from higher plants.

See also Aspinall, G.O. The Polysaccharides, vol. 1, (1982), vol.2 (1983), vol. 3 (1985), Academic Press, New York; Aspinall, G.O. (1987). Chemical Modification and Selective Fragmentation of Polysaccharides, Acc. Chem. Res., 20, 114-120; Doublier, J. -L. (1993). Rheologie des polyosides en milieu agueux: solutions, gels et melanges, IAA, 111 (01-02), 22-28.

A similar, but more articulated, method of classification is proposed and followed by Marcello Nicoletti (Botanica Farmaceutica, 2007 ed., Edises, Naples, Italy, which is considered incorporated here by reference). In particular, the origin of polysaccharides is better specified and further processing that said polysaccharides may undergo is also taken into account.

According to the method proposed by Nicoletti (see, in the chapter Glycides, pages 52-64, which are considered here in their entirety incorporated for ready reference), the following categories 1-5 are thus recognized: 1. hydrocolloids (or gums) exuding from the plant: examples are gum arable, tragacanth gum, karaja gum, ghatti gum;

2. hydrocolloids (or gums) found in the seeds of plants: examples include starch, guar gum, carob gum, tamarind gum, konjac gum, glucomannan, and the polysaccharides of Linum, Psyllium and Plantaga,

3. algal hydrocolloids: these are extracted from the thallus of red and brown algae from which polysaccharides such as agar-agar, carrageenins, and alginates (alginic acid and its salts of sodium, potassium, calcium, and magnesium) are obtained;

4. hydrocolloids (or mucilages) found in leaves, flowers, and roots: examples include Aloe, Althaea, Malva, Calendula, and 777/a;

5. hydrocolloids found in other various parts of plants, particularly in cell walls, examples include cellulose, hemicellulose, extensin, and pectins. Celluloses, in particular, can undergo subsequent processing to obtain semisynthetic derivatives such as, for example, hydroxymethylcellulose, hydroxyethylpropylcellulose, hydroxyethylpropylmethylcellulose, carboxymethylcellulose and salts thereof.

Finally, an additional class of hydrocolloids can be named, consisting of a number of animal-, biotech- or fermentation-derived substances with a very heterogeneous chemical structure (category 6). These substances, due to their behavior in solution, can also be used as rheological modifiers. They include derivatives obtained by extraction from animal parts or by biotechnological means (such as hyaluronic acid), derivatives from the exoskeleton of crustaceans (such as chitosan), and derivatives from bacterial fermentation (such as xanthan gum).

The Applicant after extensive research and development activity has selected particular mucilages and hydrocolloids to give the compositions that are object of the present invention.

An embodiment of the present invention is directed to an aqueous viscous liquid ophthalmic composition comprising or, alternatively, consisting of at least one mucilage, i.e., a hydrocolloid obtained from leaves, roots or seeds of plants belonging to category 4 of the preceding list, and at least one hydrocolloid, belonging to categories 1-3, 5 and/or 6 as previously described, according to the Nicoletti method. Preferably, said at least one mucilage or hydrocolloid (category 4; Nicoletti) obtained from leaves, flowers and roots is selected from the group comprising or, alternatively, consisting of (non-limiting list, but only illustrative): Aloe, Althaea, Malva, Calendula, Psyllium and Tilia and/or mixtures thereof.

Examples of mucilages are:

- Aloe vera gel powder 200:1; Aloe vera (L.) Burm.f. (Aloe barbadensis Mill.)' CAS No.: 85507-69-3194349-62-9; EINECS/ELINCS: 287-390-8 I 305-181-2 (spontaneous cultivation at maturity of leaves that are dried by spray dryer to give a powder); Relative density: 300-600 g/l; Hygroscopic powder, pH 3.5-5; Excipient: maltodextrin.

- Althaea 30% aqueous dry extract; Althaea officinalis L; ALTHAEA OFFICINALIS root extract; CAS No.: 73049- 65-7; EINECS/ELINCS: 277-254-6. Extraction solvent: water

Preparation type: dry extract, where 90% passes through 300 micron and 98% passes through 200 micron. Althaea (root) 27-33% polysaccharide dry extract (d.e.) excipient maltodextrin, hygroscopic powder, pH 3.5-5.5.

- Malva 25-30% polysaccharide dry extract; Malva sylvestris CAS No.: 84082-57-5; EC No.: 282-003-9; hygroscopic powder, pH 4-6. Extraction solvent: water. Excipient: maltodextrin. Not less than 90% passes through 300 micron, relative density: 400-700 g/l.

As previously specified, when said mucilages are marketed in combination with maltodextrins (see, for example, Althaea and Malva mucilages), said maltodextrins may be considered to constitute the component of the at least one hydrocolloid within the composition according to the present invention.

Preferably, said hydrocolloid (categories 1-3, 5 and/or 6; Nicoletti) is selected from the group comprising or, alternatively, consisting of (non-limiting list, but only illustrative):

- gum arable, gum tragacanth, karaja gum, ghatti gum (ghatti gum is the amorphous, translucent exudate of Anogeissus latifolia, a large tree in the Combretaceae family);

- starch, guar gum, carob gum, tamarind gum, konjac gum, glucomannan, Linum, Psyllium, and Plantago polysaccharides;

- extracts from the thallus of red and brown algae from which polysaccharides such as agar-agar, carrageenins, and alginates (alginic acid and its salts of sodium, potassium, calcium, and magnesium) are obtained;

- cellulose, hemicellulose, extensin, and pectins; celluloses can give, by subsequent processing, semisynthetic derivatives such as hydroxymethylcellulose, hydroxyethylpropylcellulose, hydroxyethylpropylmethylcellulose, carboxymethylcellulose and salts thereof;

- derivatives obtained by extraction from animal parts such as hyaluronic acid, derivatives from crustacean exoskeleton such as chitosan, and derivatives from bacterial fermentation such as xanthan gum

- maltodextrins.

An example would be a guar gum having Minimum 5,000 cps 1 200 mesh CAS No.: 9000-30-0; EC No.: 232-536- 0; pH 5.5-7. Viscosity: (RVT, 1%, 25°C, 20 rpm, 24 hours) min. 5000 mPas. Particle size distribution: min. 90% passes through 200 mesh.

Preferably, when said at least one mucilage consists only of Aloe mucilage, said at least one hydrocolloid is gum arable.

According to the invention, the term "viscous" is used to indicate a degree of viscosity of a solution greater than that of water at a pressure of 1 atmosphere and a temperature of 25°C±2°C, specifically, a dynamic viscosity value greater than 1 .01 mPa-s, at a temperature of 25°C±2°C.

According to the present invention, the term "mucilage" refers to one of the compounds of category 4 as previously described, that is, a hydrocolloid found in the leaves, flowers and roots of certain plants, such as, but not limited to, Aloe vera (leaves), Althaea officinalis (root), Malva sylvestris (leaves), Calendula officinalis (flowers), Tilia tomentosa (leaves and flowers).

Again with regard to genera, it is common knowledge to the person skilled in the art that substances of therapeutic and health interest may be found in different parts of the plant, and this situation is dependent on the plant under consideration. Therefore, the person skilled in the art will know how to conveniently choose, based on the state of the art, and common general knowledge, the part of the plant of interest to be subjected to extraction. Said mucilages can be obtained, from the plant containing them, using all techniques and equipment known to person skilled in the art and present in the state of the art. Commonly, the production process involves an extraction of said mucilages from the chosen plant by employing a solvent; generally said solvent is water.

There are also mucilages on the market, in the form of powders or gels, which are extracted, purified and ready to use; they, too, can be directly used in the making of the present invention. For example, said mucilages may be found commercially in combination with maltodextrins.

When referring to a compound belonging to the other classes described according to the Nicoletti classification method (1-3, 5 and/or 6), the term "hydrocolloid" will be used according to the invention. Examples, not limiting, of these hydrocolloids include: xanthan gum, guar gum, karaya gum, carob gum, gum arabic, alginates, semisynthetic derivatives of cellulose, chitosan, sodium hyaluronate, and maltodextrins.

Also with regard to this type of compounds, they may be extracted and/or produced from the natural starting material according to techniques and equipment known to the person skilled in the art, as well as purchased and directly used in the making of the present invention, when commercially available with the desired/needed degree of purity.

The aqueous ophthalmic composition of the invention has the desired viscosity characteristics that ensure its appropriate degree of mucoadhesion in the treatment of eye diseases.

Specifically, the ophthalmic compositions that are object of the present invention have a dynamic viscosity value ranging from 1.01 mPa's to 2.20 mPa's measured, for example, with a Brookfield model DV1 M viscometer from Brookfield Company (United States of America).

Surprisingly, it has been observed that the composition of the invention, which comprises or alternatively consists of an aqueous solution of at least one mucilage and at least one hydrocolloid, according to the previous definitions, results in obtaining a solution that has both a certain degree of dynamic viscosity ranging from 1.01 mPa-s to 2.20 mPa-s and consequent mucoadhesion, and the possibility of using a room-temperature filtration process for the final sterilization step of the solution.

The sterilizing filtration technique consists, as previously mentioned, of passing the solution to be sterilized through special sterile filters with pore diameters ranging from about 0.10 microns to about 1 micron, preferably from about 0.20 microns to about 0.80 microns, even more preferably from about 0.30 microns to about 0.50 microns, for example, about 0.22 microns or about 0.45 microns.

The composition of the invention, has been shown to pass easily, or at least without too much effort, through the filters normally used for the sterilizing filtration operation; this feature is particularly evident when the compositions of the invention are compared with compositions containing components belonging to only one of the two classes, i.e., only a mucilage or only a hydrocolloid (see the Experimental Section below).

According to the present invention, said at least one mucilage and said at least one hydrocolloid are present in an appropriate concentration with respect to the viscosity of the solution desired. Specifically, said at least one mucilage and said at least one hydrocolloid may each be present in solution in a concentration range from 0.01% to 10% w/w of the total weight of the composition. Preferably, said range is from 0.2% to 1% w/w for each component. Even more preferably, said at least one mucilage and said at least one hydrocolloid are present in a weight ratio [mucilage : hydrocolloid] in a range from 10:1 to 1 :2, preferably in a range from 5:1 to 3:1.

In this document, when we say that at least one mucilage (or at least one hydrocolloid) is present in a given percentage composition range, we mean that whatever the number of mucilages (or hydrocolloids) included within the composition, their total amount is within the indicated concentration range, either as a single mucilage (or hydrocolloid) or as the sum of the different mucilages (or hydrocolloids).

According to a particular aspect, the viscous ophthalmic composition of the present invention can be used to prepare a viscous liquid ophthalmic pharmaceutical formulation by addition of one or more other pharmaceutically acceptable components.

According to this aspect, therefore, at least one or more than one or all components belonging to the following classes may also be optionally added to the composition of the invention: active compounds approved for pharmaceutical, cosmetic, medical, and/or food use such as, but not limited to, antioxidants, vasoconstrictors, lubricants, moisturizers, emollients, and refreshers; buffer systems consisting of organic and inorganic acids approved for pharmaceutical, medical, cosmetic, and food use, such as, but not limited to, citric acid and its sodium, potassium, and magnesium salts; tartaric acid and its sodium, potassium, and magnesium salts; lactic acid and its sodium, potassium, and magnesium salts; phosphoric acid and its sodium, potassium, and magnesium salts; carbonic acid and its sodium, potassium, and magnesium salts; sulfuric acid and its sodium, potassium, and magnesium salts; osmotic pressure regulators approved for pharmaceutical, medical, cosmetic and food use, such as, but not limited to, salts of inorganic acids (e.g., sodium chloride, potassium chloride, magnesium chloride); salts of organic acids (e.g. sodium, potassium, and magnesium salts of citric, tartaric, carbonic, lactic, sulfuric, hydrochloric, and nitric acids); other organic compounds (e.g., glycerin, sorbitol, mannitol xylitol, trehalose, polyols, mono- and di-saccharides); preservatives approved for pharmaceutical, cosmetic, food and medical use, such as, but not limited to, methyl paraben, ethyl paraben, propyl paraben, phenyl ethyl alcohol, phenoxyethanol, benzyl alcohol, benzalkonium chloride, chlorhexidine gluconate, chlorhexidine acetate; other pharmaceutically accepted excipients such as, but not limited to, surfactants, organoleptic correctors, dyes.

According to a preferred aspect of the invention, the pharmaceutical formulation containing the liquid ophthalmic composition of the invention has the composition shown in Table I.

Table I: Qualitative-quantitative composition of an ophthalmic formulation comprising the composition according to the present invention (concentration ranges are expressed as % w/w of total weight of the formulation).

Table I

According to one aspect of the present invention, the viscous ophthalmic composition according to the present invention does not contain preservative excipients (component 6 of Table I). Preferably, when said ophthalmic composition is packaged in single-dose containers, said composition does not contain preservative excipients.

According to another aspect of the present invention, the viscous ophthalmic composition according to the present invention does not contain salts, in particular, it does not contain chloride salts selected from NaCI, KCI, MgC or ZnC , which can decrease the viscosity degree of the solution (component 5 of Table I).

Ophthalmic pharmaceutical formulation comprising the composition of the invention is a further object of the present invention.

The viscous liquid ophthalmic composition of the invention, and the pharmaceutical formulation comprising it, for use in eye diseases and/or as eye drops and/or as artificial tears to be used, for example, in the treatment of dry eye symptoms such as pain, itching, ocular burning, or foreign body sensation in the eyes, is a further object of the invention.

The non-therapeutic use of the ophthalmic composition of the invention, is a further object of the invention.

The composition of the present invention, and the ophthalmic formulations comprising it, are capable of overcoming the technical problem related to the difficulty of sterilization operations by filtration of viscous ophthalmic solutions. Specifically, as will be demonstrated in the experimental section that follows, said composition, containing at least one mucilage and at least one hydrocolloid as previously classified and defined, can be filtered through filters with appropriate pore sizes ranging from 0.10 micron to 1 micron, preferably from 0.20 micron to 0.80 micron, even more preferably from 0.30 micron to 0,50 micron, e.g., 0.22 micron or 0.45 micron, suitable for sterilizing the filtered solution, despite the presence of rheological modifiers that increase its viscosity, while maintaining flow rate and operating pressure values within ranges compatible with processing in industrial plants and without the need to work at high temperatures, above room temperature.

It is an object of the present invention a method of preparation of the solutions involving the following steps:

- (I) preferably, proceed with the weighing of raw materials;

- (ii) in a portion of water, indicatively around 30%-40% of the total, a heating phase is started in the temperature range 30°C-70°C depending on the characteristics of the mucilage and gum to be dispersed. Preferably, when the set temperature is reached, the mucilage and hydrocolloid are added using a mechanical shovel or turbine. Preferably, upon completion of complete dispersion, coarse filtration may optionally be carried out for the purpose of removing any insoluble residue;

- (ill) to the remaining water portion, 60%-70% of the total, again under stirring, the preservatives, salts, active ingredients, and osmotic agent are solubilized in that order. Preferably, the operation generally takes place at room temperature e.g. 25°C±2°C but, optionally, heat can be used to facilitate dissolution;

- (iv) after the dissolution of the solution of (ill) is completed, the two solutions are combined by inserting the solution from (ii) into the solution prepared in (ill); preferably, after the two solutions have been combined, sterilizing filtration is performed.

In other words, it is an object of the present invention a process for the preparation of a composition according to the present invention comprising the steps of:

- (I) weighing raw materials;

- (II) heating, preferably at a temperature between 30°C and 70°C, a portion of water, preferably between 30% and 40% by weight with respect to the total weight of water used; - (Ill) upon reaching the set temperature, adding the at least one mucilage and the at least one hydrocolloid under stirring, preferably using a mechanical shovel or turbine, until they are completely dissolved/dispersed in the aqueous solvent;

- (IV) optionally, filtering said solution/dispersion obtained in step (III) to remove any insoluble residue;

- (V) when provided, add, in the remaining portion of water not used in step (II) and preferably between 60% and 70% by weight with respect to the total weight of water used, the preservatives, salts, active ingredients and osmotic agent, preferably in that order, keeping the system under stirring, preferably using a mechanical shovel or turbine, until a solution is obtained;

- (VI) combining the solution/dispersion obtained in step (III), optionally filtered in step (IV), and the solution obtained in step (V), or the remaining portion of water, to obtain the composition according to the present invention;

- (VII) optionally, proceeding to a sterilizing filtration step.

In step (II) of the described process, the heating temperature, preferably between 30°C and 70°C, is selected according to the characteristics of the at least one mucilage and at least one hydrocolloid chosen.

The step (V) is preferably performed at room temperature, e.g. 25°C±2°C. Optionally, the aqueous phase can be heated, for example in the range of 30°C to 70°C, to facilitate dissolution.

The Applicant has found it useful to adopt sterilizing treatment because it ensures that the unchanged characteristics of the composition are maintained with respect to the possible negative action brought about by the use of high temperatures in terminal sterilization techniques. Sterilizing filtration is performed here using filters that range in size from about 0.10 micron to about 1 micron, preferably from about 0.20 micron to about 0.80 micron, even more preferably from about 0.30 micron to about 0.50 micron, for example, about 0.22 micron or about 0.45 micron.

The laboratory data, given in the experimental section below for illustrative and non-limiting purposes, clearly demonstrate what is described.

DESCRIPTION OF THE FIGURES

Figures 1-3: Osmolarity curves (mean values) as a function of time of ophthalmic compositions according to the invention A1, B1 and C1, Figure 1, Figure 2 and Figure 3 respectively, compositions with preservative (solid line), and simulated tear fluid (dashed line) when left in contact via semipermeable membrane for 24 hours.

Figures 4-6: Osmolarity curves (mean values) as a function of time of ophthalmic compositions according to the invention A2, B2 and C2, Figure 4, Figure 5 and Figure 6 respectively, preservative-free compositions (solid line), and simulated tear fluid (dashed line) when left in contact via semipermeable membrane for 24 hours.

Figure 7: Histograms for the percentage of ophthalmic composition dropped from the inclined plane in the presence (mucin, striped bar) and absence (blank, empty bar) of the mucin film and differential percentage (A%A) calculated as the difference between Ob and Cm (mucoadhesive parameter). Formulations with preservative A1 (top left), B1 (top right), C1 (bottom left) and simulated tear fluid (bottom right), data expressed as mean ± s.d.

Figure 8: Histograms for the percentage of ophthalmic composition dropped from the inclined plane in the presence (mucin, striped bar) and absence (blank, empty bar) of the mucin film and differential percentage (A%A) calculated as the difference between Cb and Cm (mucoadhesive parameter). Formulations without preservative A2 (top left), B2 (top right), C2 (bottom left) and simulated tear fluid (bottom right), data expressed as mean ± s.d.

EXPERIMENTAL SECTION

Example 1 : comparative tests of constant pressure filtration

Solutions were prepared in water containing varying amounts of mucilages (class 4) and hydrocolloids (classes 1- 3, 5 and 6).

Specifically, four types of aqueous solutions containing the following hydrocolloid/mucilage pairs in different concentrations were prepared:

1 . xanthan gum/Ma/va mucilage;

2. guar um/Althaea mucilage;

3. hydroxypropylmethylcellulose/L/num mucilage;

4. karaya gum/777/a mucilage.

Aqueous solutions containing the different percentages of hydrocolloids and/or mucilages were subjected to a sterilizing filtration procedure, through a Supporex® grade ECV filter (Pall Corporation, USA) at constant operating pressure (100 mbar), and flow rates were determined.

The general preparation method, applicable to all combinations of mucilages and hydrocolloids, which are the object of this invention, is described below.

In detail, the solution preparation method involves the following steps:

1 . weighing of raw materials;

2. in a portion of water, indicatively around 30%-40% of the total, a heating phase is started in the temperature range 30°C-70°C depending on the characteristics of the mucilage and gum to be dispersed. When the set temperature is reached, the mucilages and hydrocolloids are added using a mechanical shovel or turbine. At the end of dispersion, coarse filtration can optionally be carried out for the purpose of removing any insoluble residues.

3. To the remaining water portion, 60%-70% of the total, again under stirring, the preservatives, salts, active ingredients and osmotic agent are solubilized in that order. The operation generally takes place at room temperature e.g. 25°C but, optionally, heat can be used to facilitate dissolution.

4. After the dissolution of the solution of step 3 is completed, the two solutions are combined by inserting the solution from step 2 into the solution prepared in step 3. When the combination is complete, sterilizing filtration is performed.

At the plant level, liquid flow is measured with a flowmeter: the one used in our tests is marketed by the company Kobold (Milan, Italy)

The preparation described above can be adapted either on the small or industrial scale by employing dissolution and filtration equipment routinely marketed in industrial settings.

No special adjustments of equipment or methods are necessary; the person skilled in the art will know how to adapt equipment to individual circumstances by resorting to the teachings present in the state of common technology.

The measurements are shown in the following Tables (I l-V) in relation to the composition of the solution.

Table II: Flow rate values recorded for the xanthan gum/Ma/va mucilage composition in relation to the amount of the two components, expressed as a weight/weight percentage of the total composition. Table II

Table III: Flow rate values recorded for the guar gwmIAIthaea mucilage composition in relation to the amount of the two components, expressed as a weight/weight percentage of the total composition.

Table III

Table IV: Flow rate values recorded for the hydroxypropylmethylcellulose (HPMC)//j'num mucilage composition in relation to the amount of the two components, expressed as a weight/weight percentage of the total composition. Table IV

Table V: Flow rate values recorded for the karaya gum/7/7/a mucilage composition in relation to the amount of the two components, expressed as a weight/weight percentage of the total composition.

Table V

As is evident from the data shown in the tables, the flow rate decreases as the amount of the components increases (and thus to the viscosity of the solution) very markedly in the case of the presence of a single component (i.e., up to values as low as 10 L/min for amounts of hydrocolloid and/or mucilage of 0.8% w/w). When both components are present, said decrease is much less pronounced and reaches, in the worst case, 14.7 L/min, remaining more often around 16 L/min, even when the total concentration of rheological modifying agents is 1.6 % w/w (0.8+0.8).

The viscosity values are in the range of 1 .01 - 1 .6 mPa's (dynamic viscosity 1 Pas=1 ,000cP).

Example 2: comparative filtration tests at constant flow rate

Solutions were prepared in water containing varying amounts of mucilages (class 4) and hydrocolloids (classes 1- 3, 5 and 6).

Specifically, four types of aqueous solutions containing the following hydrocolloid/mucilage pairs in different concentrations were prepared:

1 . xanthan gum/Ma/va mucilage;

2. guar gumlAlthaea mucilage;

3. hydroxypropylmethylcellulose/L/num mucilage;

4. karaya gum/777/a mucilage.

The aqueous solutions containing the different percentages of hydrocolloids and/or mucilages were subjected to a sterilizing filtration procedure, through a Supporex® grade ECV filter (Pall Corporation, USA) at a constant flow rate (17 L/min), and the operating pressure was determined.

We report the general method given in the previous point

The measurements are shown in the following Tables (VI-IX) in relation to the composition of the solution.

Table VI: Pressure values recorded for the xanthan gum/Ma/va mucilage composition in relation to the amount of the two components, expressed as a weight/weight percentage of the total composition.

Table VI Table VII: Pressure values recorded for the guar gwmIAIthaea mucilage composition in relation to the amount of the two components, expressed as a weight/weight percentage of the total composition.

Table VII Table VIII: Pressure values recorded for the hydroxypropylmethylcellulose (HPMC)//j'num mucilage composition in relation to the amount of the two components, expressed as a weight/weight percentage of the total composition.

Table VIII Table IX: Pressure values recorded for the karaya gum/7/7/a mucilage composition in relation to the amount of the two components, expressed as a weight/weight percentage of the total composition. karaya gum Tilia mucilage pressure

Table IX

As is evident from the data shown in the tables, the same trend as in Example 1 concerning flow rate is observed here as well: the pressure increases as the amount of the components (and thus to the viscosity of the solution) increases very markedly in the case of the presence of a single component (i.e., up to values exceeding 160 mbar in the case of amounts of hydrocolloid and/or mucilage of 0.8% w/w). When both components are present, said increase is much less marked and reaches 136 mbar in the worst case, remaining more often around 120 mbar, even when the total concentration of rheological modifying agents is 1 .6 % w/w (0.8 + 0.8).

As in the previous example, the viscosity values are in the range of 1.01 - 1.6 mPa-s (dynamic viscosity 1Pas=1,000cP).

Formulation examples comprising the composition according to the present invention

The following are qualitative/quantitative examples of formulations comprising the composition according to the present invention (Table X and Table XI). The amounts of the different components (active ingredients and functional excipients) are expressed as a weight/weight percentage of the total weight of the composition.

Table X

Table XI Compositions according to the present invention: qualitative/quantitative formulas and characterization

Formulation A1 (Table XII): Refreshing eye drops

Table XII: * corresponding to 0.050% pure chlorhexidine digluconate Formulation A2 (Table XIII): Refreshing eye drops - preservative-free formulation.

Table XIII

Formulation B1 (Table XIV): Anti-redness eye drops. Table XIV: * corresponding to 0.050% pure chlorhexidine digluconate

Formulation B2 (Table XV): Anti-redness eye drops - preservative-free formulation

Table XV

Formulation C1 (Table XVI): Artificial tears

Table XVI: * corresponding to 0.050% pure chlorhexidine digluconate

Formulation C2 (Table XVII): Artificial tears - preservative-free formulation

Table XVII Characterization (Table XVIII):

Table XVIII

Filtration tests performed on A1, B1 and C1 formulations according to the present invention

In order to test the feasibility of the filtration sterilization process on a pilot scale, filtration tests of A1 (Althaea), B1 (Aloe) and C1 (Malva) formulations set up in the laboratory were performer, at constant pressure, using Sartorius Sartoscale 25 filters (Germany).

The constant-pressure test, was carried out at a pressure of 1 bar, using compressed air inlet to a tank containing the fluid to be filtered (feed solution). The filtered solution was collected in a beaker placed on a scale, and filtration was stopped when the flow rate value exiting the filter decreased by 10% from the initial flow rate. The value of the flow rate (flow rate = g/hour) is expressed in grams of maximum filtered solution as a function of time. For this test, Sartorius Sartoscale 25 filters having surface area of 4.5 cm ² with double membranes of different porosities were used, and their filter capacity (filter capacity = L/m ² ) was calculated by dividing the liters of filtrate collected in the beaker, (throughput) by the surface area of the filter itself (0.00045 m ² ). Specifically, as shown in Tables XIX, XX, and XXI below, the filter train consists of a 0.65 pm pore size filter (Sartopure® GF Plus, polypropylene) and the sterilization system consists of a 0.45 pm and 0.22pm double membrane filter inserted one after the other within the same filter holder capsule (Sartobran® P 0.2 pm, cellulose acetate).

The results of the test carried out at constant pressure were reported in Tables XIX, XX and XXI, wherein EFA is the value of filter surface area and Area for 230L indicates the filter surface area required to filter a volume of 230 liters.

Table XIX: Filtration results for A1 (Althaea) formulation.

Table XX: Filtration results for B1 (Aloe) formulation.

5 Table XXI: Filtration results for C1 (Mallow) formulation.

Osmolarity studies of formulations A1, A2, B1 , B2, 01 and C2 according to the present invention

Tests were performed for the purpose of measuring osmotic exchange between ophthalmic formulations according to the present invention and simulated tear fluid via permselective dialysis membrane.

Specifically, the previously described formulations A1 and A2, containing Althaea mucilage, B1 and B2, containing Aloe mucilage, C1 and 02, containing Malva mucilage, were tested.

The test was performed using a Biotech regenerated cellulose tubular dialysis membrane (Spectrum™ ) having MWCO of 20 kDa, diameter 10 mm, volume/length: 0.79mL/cm. For this purpose, the membrane was first hydrated in distilled water for 15 minutes; then, a volume of 10 mL of simulated tear fluid composed as follows: (pH= 7.4, iso-osmotic) 2.2 g/L NaHCO ₃ ; 6.26 g/L NaCI; 1.79 g/L KOI; 96.4mg /L MgCl2-6H ₂ O; and 73.5mg/L CaCl2-H2O in distilled water. (Budai-Szucs, M et al 2026).

The membrane filled with simulated tear fluid was then closed at the ends with two knots and immersed in a beaker containing 200 mL of ophthalmic composition according to the invention. The test was conducted under magnetic stirring at 25°C.

At the preset times of 4 hours (T4), 8 hours (T8) and 24 hours (T24), a 1mL sample of eye drops was taken and analyzed for its osmolarity. The simulated tear fluid was analyzed for its osmolarity at the beginning (TO) and end of the experiment (T24).

Osmolarity was measured by automatic osmometer, Osmomat 3000 (Gonotec GmbH).

Figures 1-3 show the osmolarity curves (mean values) as a function of time of ophthalmic compositions according to the invention A1, B1 and C1, respectively, compositions with preservative, and simulated tear fluid when left in contact via semipermeable membrane for 24 hours.

Figures 4-6 show the osmolarity curves (mean values) as a function of time of ophthalmic compositions according to the invention A2, B2 and C2, respectively, preservative-free compositions, and simulated tear fluid when left in contact via semipermeable membrane for 24 hours.

In all cases, the measured osmolarity curves for the various ophthalmic compositions according to the present invention show that tear fluid, having physiological osmolarity of 300 mOsm/kg, reduces its osmolarity after 24 hours in contact with the tested ophthalmic compositions. This phenomenon shows the ability of the ophthalmic compositions to lower the osmolarity of the tear fluid to a value around 200 mOsm/kg.

Since, in the case of a dry eye condition, the osmolarity value of the tear fluid is higher than the physiological value (300 mOsm/kg), the demonstrated ability of the ophthalmic composition according to the present invention to lower this value, even from non-pathological levels, is clear evidence of its effectiveness even in "pathological" conditions, where the concentration of salts will be higher and the osmolarity value higher.

Studies on the mucoadhesiveness of formulations A1 , A2, B1 , B2, C1 and C2 according to the present invention Tests were performed for the purpose of measuring the mucoadhesive properties of ophthalmic formulations according to the present invention against those of simulated tear fluid. Specifically, the previously described formulations A1 and A2, containing Althea mucilage, B1 and B2, containing Aloe mucilage, C1 and C2, containing Malva mucilage, were tested.

Mucoadhesive properties were tested using the "inclined plane" method (Sandri et al 2004).

In detail: the inclined plane apparatus consists of a plane (thermostated to 37°C) having a surface area of 28 cm ² and an inclination angle of 60°; this plane overlies a microbalance (Sartorius L420P, G) connected to a computer equipped with software for recording and processing the data derived from said scale.

Porcine gastric mucin type III (Sigma-Aldrich) was used as the biological substrate. A mucin film was prepared directly on the surface of the inclined plane by placing 2.5 mL of an 8% w/w mucin suspension in simulated tear fluid (pH 7.4) on the surface of the inclined plane, which was kept horizontal at 40°C for 2 hours.

The individual formulations (known and accurately weighed amount) were placed on the inclined plane previously coated with the mucin film, and kept horizontal for 10 seconds. Then the plane was tilted 60°, and the amount of eye drops "dripped" onto the scale was recorded as the curve of grams not adhered to the plane, as a function of time.

In order to measure the contribution of the rheological effect of each sample on the mucoadhesive potential, a blank test was performed using the inclined plane without the mucin film.

The value of the amount of ophthalmic formulation that did not remain adhered on the inclined plane (C%) at the end of the experiment was calculated as a percentage according to the following formula:

C% = (Ct*100)/Ct _o where Ct ₀ =amount (mg) of formulation loaded on the inclined plane; Ct =amount of formulation dropped on the microbalance at the end of the experiment.

The difference between the percentage of ophthalmic composition dropped from the inclined plane, in the absence of a mucin film on the inclined plane (Cb) and in the presence of a mucin film on the inclined plane (Cm), is the mucoadhesion parameter, that is, the ability of the ophthalmic composition to adhere to the surface on which it is deposited. The mucoadhesion parameter is expressed as AA%, and is calculated as the difference between the percentage Cb and the percentage Cm according to the following formula:

AA%= (Cb - Cm) where Cb = C% average percentage of formulation dropped from the white inclined plane in the absence of the mucin film; Cm =C% average percentage of formulation dropped from the inclined plane in the presence of the mucin film.

High values of the differential parameter AA% can be attributed to a high mucoadhesive capacity of the sample. Finally, the same mucoadhesive test was performed using simulated tear fluid, to compare the mucoadhesive property of simulated tear fluid, compared with ophthalmic formulations. The simulated tear fluid was considered as a non-mucoadhesive reference. The composition of the simulated tear fluid (pH= 7.4) is: 2.2 g/L NaHCOs; 6.26 g/L NaCI; 1.79 g/L KCI; 96.4mg/L MgCI ₂ -6H ₂ O; and 73.5mg/L CaCI ₂ -H ₂ O in distilled water. (Budai-Szucs, M et al The test results are shown in Figures 7 and 8 for the formulations with preservative (A1, B1 and C1) and formulations without preservative (A2, B2 and C2), respectively.

The numerical data are given in the following Tables XXII (ophthalmic compositions according to the present invention with preservative A1, B1 and C1) and XXIII (ophthalmic compositions according to the present invention without preservative A2, B2 and C2).

Table XXII - Percentage of ophthalmic composition dropped from the inclined plane in the presence (Cm) and absence (Cb) of the mucin film and differential percentage (A%A) calculated as the difference between Cb and Cm (mucoadhesive parameter). Formulations with preservative, data expressed as mean ± s.d.

Table XXII

Table XXIII - Percentage of ophthalmic composition dropped from the inclined plane in the presence (Cm) and absence (Cb) of the mucin film and differential percentage (A%A) calculated as the difference between Cb and Cm (mucoadhesive parameter). Formulations without preservative, data expressed as mean ± s.d.

Table XXIII

The results obtained show that all ophthalmic formulations according to the present invention possess good mucoadhesive property. In fact, the differential percentage (AA% = Cb - Cm), which is an index of the amount of formulation that remained adhered to the substrate on which it was poured (mucoadhesive potential); was found to be always positive for all compositions. This property is confirmed by significantly different values between the percentage of formulation dropped from the blank inclined plane (Cb) and that dropped from the inclined plane coated by the mucin film (Cm).

In addition, and even more relevant, the differential percentage (AA%) as mucoadhesive potential was higher for all formulations tested than that of simulated tear fluid.