Field of the Invention The invention relates to amorphous forms of obeticholic acid (OCA) of formula I, with the systematic name (3a,5p,6a,7a)-6-ethyl-3,7-dihydroxycholan-24-ic acid, a method of their preparation and their use for the preparation of a pharmaceutical composition.

Background Art

Obeticholic acid is a semi-synthetic bile acid analog with an agonistic effect on the farnesoid X receptor (FXR). It is designed for the treatment of liver diseases, e.g. primary biliary cirrhosis (PBC), nonalcoholic steatohepatitis (NASH) or primary sclerosing cholangitis (PSC).

Obeticholic acid was first mentioned in the patent application WO2002072598. The application describes its isolation by means of column chromatography, which generally yields substances of an amorphous character, no more detailed data concerning the product character being published in this patent application.

It was followed by two process patent applications WO2006122977 and US20090062526 concerning synthesis of obeticholic acid. The patent application WO2006122977 describes preparation of amorphous obeticholic acid by reprecipitation through the ammonium salt. The patent application WO2013192097 describes two solid forms of obeticholic acid: crystalline form C and amorphous form 1. It describes preparation of crystalline form C and subsequently its reprecipitation through the sodium salt to form 1 of obeticholic acid. The said patent application also mentions other crystalline forms of obeticholic acid, which however are not suitable for use in the pharmaceutical industry for various reasons. Further, the application mentions examples of the contents of a pharmaceutical composition comprising obeticholic acid.

The patent application WO2017008773 describes preparation of crystalline form 1-2. Crystalline form 1-2 of obeticholic acid exhibits high purifying capability, robust preparability and good filterability. This crystalline form of obeticholic acid can be advantageously used for the preparation of an amorphous form of obeticholic acid.

Many pharmaceutical solid compounds can exist in different solid forms that are considered as polymorphs, hydrates/solvates, salts or cocrystals having different crystal units and thus different physicochemical characteristics as the melting point, solubility, dissolution rate as well as bioavailability. To distinguish individual solid phases of a compound, several solid- state analytic methods can be used, e.g. the X-ray powder diffraction, solid-state NMR, Raman spectroscopy as well as thermoanalytical techniques.

Discovering novel solid forms (polymorphs, solvates/hydrates, salts, cocrystals) of an active pharmaceutical ingredient offers an opportunity to select a suitable modification with desirable physicochemical characteristics and processability, and to improve the characteristics of the pharmaceutical product. For this reason, there is an obvious need of new solid forms (polymorphs, solvates/hydrates, salts, cocrystals, amorphous forms, stabilized amorphous forms) of obeticholic acid.

Disclosure of the Invention

An object of this invention are amorphous forms of obeticholic acid and their use for the preparation of a pharmaceutical composition. Both the amorphous obeticholic acid alone and amorphous obeticholic acid stabilized with various pharmaceutically acceptable excipients, e.g. polymers, copolymers, saccharides, oligosaccharides, polysaccharides, fats, waxes or urea, advantageously especially polymers, can be used for the drug form. Amorphous forms stabilized this way can form solid compositions (solid dispersions, amorphous solid dispersions or solid solutions).

The invention relates to solid forms of amorphous obeticholic acid with at least one pharmaceutically acceptable excipient, which may be selected from the group of polymers, saccharides, oligosaccharides, polysaccharides, fats, waxes or urea. The amorphous obeticholic acid is advantageously stabilized with hydroxypropyl methylcellulose (hypromellose, HPMC), hypromellose acetate succinate (HPMC AS) derivatives of polymethacrylate, (Eudragit El 00, Eudragit LI 00, Eudragit SI 00), polyvinyl pyrrolidone (Povidone, PVP), copovidone (Kollidon) or copolymers of polyvinyl caprolactam - polyvinyl acetate - polyethylene glycol (Soluplus).

In principle, one of the main characteristics of solid solutions is their capability of increasing the chemical and physical stability. All the above mentioned excipients are commonly used for the preparation of drug forms.

Compared to crystalline forms, amorphous forms exhibit a clear advantage of their higher solubility and thus higher bioavailability.

An object of the invention is an amorphous form of obeticholic acid stabilized with at least one pharmaceutically acceptable polymer. An amorphous form stabilized this way exhibits a glass transition temperature of at least 40°C, more preferably at least 70°C, even more preferably at least 100°C.

The pharmaceutically acceptable polymer is preferably selected from the group that consists of hydroxypropyl cellulose, hydroxypropyl methylcellulose, hypromellose acetate succinate, Methocel E5, povidone PVP K30, Soluplus, PEG 6000, copovidone VA64, Eudragit S100, Eudragit L100 and Eudragit E100.

Stabilized amorphous forms of obeticholic acid in accordance with the present invention exhibit a characteristic amorphous halo in an X-ray powder pattern with the use of CuKa radiation.

In some embodiments of the invention the content of obeticholic acid to the polymer is in the weight ratio of 1 : 0.5 to 1 : 5, preferably 1 : 1 to 1 : 3.

Another object of the invention is a preparation method of a stabilized amorphous form of obeticholic acid comprising dissolution of obeticholic acid with a pharmaceutically acceptable polymer in a suitable solvent selected from the group of methanol, ethanol, 2-propanol, tert- butanol, ethyl acetate, acetone, dichloromethane, tetrahydrofuran, water or their mixtures, and subsequent removal of the solvent, providing the amorphous form. The solvent is preferably selected from a group that consists of methanol, dichloromethane, tert-butanol, water or their mixture.

Another object of the invention is a preparation method of a stabilized amorphous form of obeticholic acid comprising mixing of obeticholic acid with a pharmaceutically acceptable polymer and subsequent heating of this mixture, producing a melt and providing an amorphous form.

Another object of the invention is the use of a stabilized amorphous form of obeticholic acid in accordance with the present invention for the preparation of a pharmaceutically acceptable composition.

Another object of the invention is a pharmaceutical composition comprising and amorphous form of obeticholic acid stabilized with at least one pharmaceutically acceptable polymer. The pharmaceutical composition in accordance with the present invention can preferably have the form of a tablet. Such pharmaceutical composition can further comprise at least one excipient from the group of binders (e.g. microcrystalline cellulose), disintegrants (e.g. sodium carboxymethyl starch), lubricants (e.g. magnesium stearate), surfactants etc.

Another object of the invention is a pharmaceutical composition comprising a solid solution of an amorphous form of obeticholic acid stabilized with at least one pharmaceutically acceptable polymer, the ratio of obeticholic acid to the polymer being in the weight range of 1 : 0.5 to 1 : 5, preferably 1 : 1 to 1 : 3.

Another object of the invention is a solid solution of obeticholic acid with povidone PVP K30 in the weight ratio of OCA : polymer 1 : 0.5 to 1 : 3, characterized by a differential scanning calorimetric curve with a glass transition temperature of 111 to 125 °C.

Another object of the invention is a solid solution of obeticholic acid with Eudragit El 00 in the weight ratio of OCA : polymer 1 : 1 to 1:3, characterized by a differential scanning calorimetric curve with a glass transition temperature of 58 to 78°C.

Another object of the invention is a solid solution of obeticholic acid with Eudragit SI 00 in the weight ratio of OCA : polymer 1 : 1 to 1:3, characterized by a differential scanning calorimetric curve with a glass transition temperature of 101 to 109°C.

Another object of the invention is a solid solution of obeticholic acid with Soluplus in the weight ratio of OCA : polymer 1 : 1 to 1 :3, characterized by a differential scanning calorimetric curve with a glass transition temperature of 57 to 75°C.

Another object of the invention is a solid solution of obeticholic acid with Kollidon VA64 in the weight ratio of OCA : polymer 1 : 1 to 1 :3, characterized by a differential scanning calorimetric curve with a glass transition temperature of 91 to 92°C.

Another object of the invention is a solid solution of obeticholic acid with Methocel E5 in the weight ratio of OCA : polymer 1 : 1, characterized by a differential scanning calorimetric curve with a glass transition temperature of 82°C. Another object of the invention is a solid solution of obeticholic acid with HPMC AS in the weight ratio of OCA : polymer 1 : 1, characterized by a differential scanning calorimetric curve with a glass transition temperature of 93 to 94°C.

Another object of the invention is optimized preparation of obeticholic acid alone. Amorphous obeticholic acid can be advantageously prepared from crystalline form 1-2 described in the invention WO2017008773. Crystalline form 1-2 exhibits high purifying capability, robust preparability and good filterability.

Amorphous forms can be advantageously used for the preparation of a pharmaceutical composition. Amorphous forms have higher solubility than crystalline forms, thus exhibiting higher bioavailability. Amorphous obeticholic acid can be advantageously stabilized in the form of a solid solution with a pharmaceutically acceptable polymer.

Detailed description of the Invention A crystalline solid substance is characterized with a regular structural arrangement for a long distance. Conversely, amorphous solid substances do not exhibit this arrangement. The molecular arrangement of an amorphous solid substance can be represented by a "frozen liquid" with rheological properties of a solid substance. A solid mixture consisting of at least two components - the active pharmaceutical ingredient (API) and another at least one chemical compound (matrix) can take several forms. To facilitate clarification of the used terms, the matrix for stabilization of the API is only assumed to consist of one component. In fact, this matrix may consist of one, two or more components (chemical compounds). Substances of the type of polymers, copolymers, saccharides, oligosaccharides, polysaccharides, fats, waxes or urea can be advantageously used as matrix components for solid mixtures.

The term "solid dispersion" represents a solid composition of an active pharmaceutical ingredient (API) that is dispersed in a matrix, this matrix exhibiting a crystalline character.

A conventional "amorphous solid dispersion" represents a solid composition where the active pharmaceutical ingredient (API) and the matrix exhibit an amorphous character as detected by XRPD. When subjected to differential scanning calorimetry, this "amorphous solid dispersion" exhibits at least two glass transitions (Tg), one for the dispersed component (active pharmaceutical ingredient) and the other for the matrix, the number of Tg's depending on the number of the matrix components. If both the amorphous components (API as well as matrix) are mixed on the molecular level and the resulting solid mixture only exhibits one glass transition (Tg) temperature in differential scanning calorimetry, it is a special solid composition referred to as a "solid solution". As mentioned above, amorphous solid substances have a different internal arrangement from crystalline solid substances and a larger surface, thus exhibiting higher solubility. If solubility and bioavailability of active pharmaceutical ingredients needs to be increased, they should be prepared in an amorphous form. When the temperature of a crystalline material achieves the melting point, the phase will change from the solid to liquid phase. Re-cooling of this melt will cause arrangement of the crystal structure again. However, if the melt is cooled sufficiently quickly, crystallization can be prevented by the occurrence of a subcooled solution. The subcooled solution is cooled to achieve the glass transition (Tg), the molecules are kinetically frozen and the subcooled liquid solidifies into glass. Molecules in a subcooled liquid have much higher mobility than in the glass state, as described by Remington in the publication: The Science and Practice of Pharmacy, Pharmaceutical Press, 21 ^st edition.

Since molecules have certain mobility in the glass state, it is convenient for the glass transition temperature to be at least 20°C, preferably 30°C and most preferably at least 40°C above the temperature of the actual storage conditions. For this reason, it is advantageous to stabilize the amorphous form of the API by increasing the glass transition (Tg) temperature to prevent recrystallization and chemical degradation. By preparing a solid mixture, we are able to increase this glass transition temperature to prepare the API in a form that is polymorphically and chemically more stable at elevated temperatures and increased relative humidity.

Amorphous obeticholic acid has the glass transition temperature of 93 °C and in its non- stabilized form it may suffer from chemical degradation during storage at an elevated temperature and humidity. For this reason, it is advantageous to stabilize the amorphous form of obeticholic acid by increasing the glass transition (Tg) temperature to prevent chemical degradation and recrystallization. The prepared solid mixture is then polymorphically and chemically more stable even at elevated temperatures and relative humidity.

A possible approach to stabilization of amorphous obeticholic acid consists in producing solid mixtures with polymers, copolymers, saccharides, oligosaccharides, polysaccharides, fats, waxes and urea, preferably especially with polymers. These polymers can come from the groups of polymers that are soluble or insoluble in water. Typical polymers that are soluble in water are polyvinyl pyrrolidone (povidone), copovidone, polyvinyl alcohol, hydroxypropyl methylcellulose (hypromellose), hydroxypropyl cellulose, polyethylene glycol, copolymers of polyvinyl caprolactam - polyvinyl acetate - polyethylene glycol (Soluplus) etc. Typical solvents that are insoluble in water are methylcellulose, ethylcellulose, polymethacrylates, hypromellose phthalate, hypromellose succinate, hypromellose acetate succinate (HPMC AS), cellulose acetate phthalate, carboxymethyl ethylcellulose etc. An advantage of these polymers is the fact that their solubility depends on pH of the solution and their use makes it possible to influence releasing of the active pharmaceutical ingredient depending on the pH value of the alimentary tract. A number of techniques can be used to prepare stabilized amorphous forms of obeticholic acid. One of the preparation techniques of stabilized amorphous forms of obeticholic acid is the dissolution process. In a common dissolution process, the active ingredient is dissolved in a solvent or in any mixture of solvents. The solvent can be water or any organic solvent. As an example of suitable organic solvents, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2- butanol, tert-butanol, ethyl acetate, acetone, dichloromethane, chloroform, tetrahydrofuran, etc. can be mentioned. In the next step, a substance stabilizing the active pharmaceutical ingredient is added to this solution or suspension. The solvent is quickly removed and amorphous solid mass is produced. The solvent can be removed by means of a rotary vacuum evaporator, fluid granulation, spray drying, electrospinning, freezing of the solvent etc.

Other possibilities of preparation of stabilized amorphous substances are represented by techniques without the use of a solvent. In these processes, the active pharmaceutical ingredient (obeticholic acid) is mixed with a stabilizing substance (e.g. a polymer). This mixture is heated up and melted, producing a melt. Common temperatures to produce a melt vary in the range of 20°C - 40°C above the Tg temperature when the mixture is melted and has a suitable viscosity for processing. The melt is subsequently cooled down, which provides an amorphous solid substance. As some examples of these techniques, hot melt extrusion, hot melt granulation, high shear mixer, fluid bed granulation without the use of a solvent etc. can be mentioned.

For the preparation of a stabilized amorphous form of obeticholic acid a solvent removal technique (e.g. with the use of a rotary vacuum evaporator, spray drying or lyophilization) or preparation via melt (hot melt extrusion) can be used.

The preparation method of a stabilized amorphous form of obeticholic acid using the solvent removal principle comprises the following steps:

a/ dissolving or dispersing obeticholic acid and a polymer in a solvent or mixture of solvents;

b/ removing the solvent or the mixture of solvents.

For the dissolution in step a/, common organic solvents or water, or their mixtures can be used. To remove solvents in step b/, evaporation at a reduced pressure, spray drying or lyophilization can be used.

The preparation method of a stabilized amorphous form of obeticholic acid using the hot melt extrusion comprises the following steps:

a/ mixing obeticholic acid with a pharmaceutically acceptable polymer;

hi heating the mixture of step a/ to produce melt and to obtain an amorphous form.

The presence of the polymer increases physical stability of the amorphous form of the active pharmaceutical ingredient. An amorphous form is generally an irregular arrangement of a substance. This invention focuses on preparation of a pharmaceutical mixture comprising amorphous obeticholic acid with polymers, copolymers, saccharides, oligosaccharides, polysaccharides, fats, waxes and urea, preferably especially with polymers. The following polymers can be advantageously used to prepare polymer-stabilized amorphous forms of obeticholic acid: polyvinyl pyrrolidone (PVP), copovidone (Kollidon VA64), hydroxypropylcellulose (Klucel), hydroxypropyl methylcellulose (Methocel), derivatized hydroxypropyl methylcellulose (e.g. HPMC AS), derivatives of polymethacrylate (Eudragit LlOO, Eudragit SlOO, Eudragit E100) and copolymers of polyvinyl caprolactam - polyvinyl acetate - polyethylene glycol (Soluplus). Polyvinyl pyrrolidone (PVP K30), Methocel E5 (HPMC), Eudragit SlOO, Eudragit LlOO, copovidone (Kollidon VA64), hydroxypropylcellulose (HPC, Klucel), Soluplus and hypromellose acetate succinate (HPMC AS-LF) can be advantageously used.

For the preparation of stabilized amorphous solid forms of obeticholic acid (API), the technique of removing the solvent with a rotary vacuum evaporator, spray drying or lyophilization (freezing of solvents) were used. The products prepared this way are presented in Table 1 together with the results of DSC and X-ray powder analyses.

Table 1:

Weight ratio Preparation

Polymer DSC X-ray

(OCA : polymer) method

PVP K30 1 : 0.5 evaporation Tg 111°C amorphous API

PVP K30 ¹ 1 evaporation Tg l l6°C amorphous API

PVP K30 ¹ 1 lyophilization Tg 117°C amorphous API

PVP K30 ¹ 3 spray drying Tg 125°C amorphous API

Eudragit SlOO ¹ 1 evaporation Tg 109°C amorphous API

Eudragit SlOO ¹ 3 lyophilization Tg 101°C amorphous API

Eudragit E100 ¹ 1 evaporation Tg 69°C amorphous API

Eudragit E100 ¹ 1 spray drying Tg 78°C amorphous API

Eudragit E100 ¹ 3 spray drying Tg 58°C amorphous API

Soluplus ¹ 1 evaporation Tg 75°C amorphous API

Soluplus ¹ 3 evaporation Tg 57°C amorphous API

Copovidone VA64 ¹ 1 evaporation Tg 91°C amorphous API

Copovidone VA64 ¹ 3 lyophilization Tg 92°C amorphous API

HPMC AS LF ¹ 1 lyophilization Tg 93°C amorphous API

HPMC AS MF ¹ 1 lyophilization Tg 94°C amorphous API

Methocel E5 ¹ 1 evaporation Tg 82°C amorphous API A differential scanning calorimetry (DSC) measurement makes it possible to distinguish a solid dispersion and a solid solution. In the case of a solid solution, the amorphous solid substance only exhibits one glass transition (Tg) value in the record. The prepared amorphous substances in the weight ratio of 1 : 2 (API : polymer) formed stable solid solutions whose stability increases with the increasing Tg value (Hancock and Zografi, 1997).

According to the results of DSC analyses, obeticholic acid forms the most stable solid solutions with povidone PVP K30, Eudragit SI 00 or Copovidone VA64. With respect to sensitivity of the API (especially at higher temperatures) and possible degradation of the API during melting, solid solutions with polymers that have a lower glass transition temperature are also usable as such a high temperature does not need to be applied to melt them. This is mainly the case of Soluplus, Eudragit El 00 or Methocel E5. The results of the X-ray powder analysis confirmed an amorphous character of the substances of all the prepared mixtures of obeticholic acid and the polymers.

Load tests were used to monitor and check stability of amorphous obeticholic acid and the prepared solid solutions of obeticholic acid. Amorphous obeticholic acid has the glass transition temperature of 93°C. To compare the behavior under load conditions, solid solutions of obeticholic acid with different glass transition temperatures were selected.

In particular, a solid solution of obeticholic acid with Eudragit El 00 was selected in the weight ratio of OCA : Eudragit E100 1 : 3, with the glass transition temperature of 58°C. Further, a solid solution of obeticholic acid with Eudragit El 00 was selected in the weight ratio of OCA : Eudragit El 00 1 : 1, with the glass transition temperature of 78°C.

Further, a solid solution of obeticholic acid with Soluplus was selected in the weight ratio of OCA : Soluplus 1 : 3, with the glass transition temperature of 57°C.

Further, a solid solution of obeticholic acid with Soluplus was selected in the weight ratio of OCA : Soluplus 1 : 1, with the glass transition temperature of 75°C.

Further, a solid solution of obeticholic acid with Copovidone VA64 was selected in the weight ratio of OCA : Copovidone VA64 1 : 3, with the glass transition temperature of 92°C. Further, a solid solution of obeticholic acid with Eudragit SI 00 was selected in the weight ratio of OCA : Eudragit SI 00 1 : 3, with the glass transition temperature of 101°C.

Further, a solid solution of obeticholic acid with povidone PVP K30 was selected in the weight ratio of OCA : PVP K30 1 : 3, with the glass transition temperature of 125°C.

The results of the stability testing of amorphous obeticholic acid and solid solutions of obeticholic acid are summarized in Table 2.

Table 2:

Amorphous OCA, Tg = 93 °C

DSC

40°C, 0% RH, 7 days amorphous sample; Tg = 93 °C

40°C, 0% RH, 30 days amorphous sample; Tg = 93 °C

40°C, 75% RH, 7 days amorphous sample; Tg = 93°C

40°C, 75% RH, 30 days amorphous sample; Tg = 93°C

60°C, 0% RH, 3 days amorphous sample; Tg = 94°C

60°C, 75% RH, 3 days amorphous sample; Tgl = 69°C, Tg2 = 92°C

Solid solution of OCA : Eudragit E100 1 : 1, Tg = 78 °C

DSC

40°C, 0% RH, 7 days solid solution; Tg = 80°C

40°C, 0% RH, 30 days solid solution; Tg = 79°C

40°C, 75% RH, 7 days solid solution; Tg = 77°C

40°C, 75% RH, 30 days solid solution; Tg = 76°C

60°C, 0% RH, 3 days solid solution; Tg = 87°C

60°C, 75% RH, 3 days solid solution; Tg = 78°C

Solid solution of OCA : Eudragit El 00 1 : 3, Tg = 58 °C

DSC

40°C, 0% RH, 7 days solid solution; Tg = 59°C

40°C, 0% RH, 30 days solid solution; Tg = 63 °C

40°C, 75% RH, 7 days solid solution; Tg = 58°C Amorphous OCA, Tg = 93 °C

DSC

°C, 75% RH, 30 days solid solution; Tg = 60°C

°C, 0% RH, 3 days solid solution; Tg = 58°C

°C, 75% RH, 3 days solid solution; Tg = 59°C

Solid solution of OCA : Soluplus 1 : 1, Tg = 75 °C

DSC

°C, 0% RH, 7 days solid solution; Tg = 77°C

°C, 0% RH, 30 days solid solution; Tg = 74°C

°C, 75% RH, 7 days solid solution; Tg = 68°C

°C, 75% RH, 30 days solid solution; Tg = 54°C

°C, 0% RH, 3 days solid solution; Tg = 86°C

°C, 75% RH, 3 days amorphous sample; Tgl = 58°C, Tg2 = 94°C

Solid solution of OCA : Soluplus 1 : 3, Tg = 57 °C

DSC

°C, 0% RH, 7 days solid solution; Tg = 74°C

°C, 0% RH, 30 days solid solution; Tg = 69°C

°C, 75% RH, 7 days solid solution; Tg = 61°C

°C, 75% RH, 30 days solid solution; Tg = 60°C

°C, 0% RH, 3 days solid solution; Tg = 66°C

°C, 75% RH, 3 days solid solution; Tg = 63°C

Solid solution of OCA : Copovidone VA64 1 : 3, Tg = 92 °C

DSC

°C, 0% RH, 7 days solid solution; Tg = 92°C

°C, 0% RH, 30 days solid solution; Tg = 96°C

°C, 75% RH, 7 days solid solution; Tg = 103 °C

°C, 75% RH, 30 days solid solution; Tg = 104°C

°C, 0% RH, 3 days solid solution; Tg = 93 °C

°C, 75% RH, 3 days solid solution; Tg = 104°C Amorphous OCA, Tg = 93 °C

DSC

Solid solution of OCA : Eudragit S 100 1 : 3, Tg = 101 °C

DSC

40°C, 0% RH, 7 days solid solution; Tg = 126°C

40°C, 0% RH, 30 days solid solution; Tg = 132°C

40°C, 75% RH, 7 days solid solution; Tg = 138°C

40°C, 75% RH, 30 days solid solution; Tg = 138°C

60°C, 0% RH, 3 days solid solution; Tg = 127°C

60°C, 75% RH, 3 days solid solution; Tg = 138°C

Solid solution of OCA : PVPK30 1 : 3, Tg = 125 °C

DSC

40°C, 0% RH, 7 days solid solution; Tg = 127°C

40°C, 0% RH, 30 days solid solution; Tg = 128°C

40°C, 75% RH, 7 days solid solution; Tg = 142°C

40°C, 75% RH, 30 days solid solution; Tg = 142°C

60°C, 0% RH, 3 days solid solution; Tg = 127°C

60°C, 75% RH, 3 days solid solution; Tg = 142°C

The stability testing shows that amorphous obeticholic acid (OCA) starts to degrade under higher temperature (60°C) and increased humidity (75% RH) loading and after three days, DSC analysis shows a less stable form of obeticholic acid. This means that it is physically less stable than obeticholic acid stabilized in the form of a solid solution with a pharmaceutically acceptable excipient.

All the tested solid solutions of obeticholic acid show high physical stability under all the tested conditions.

What is surprising is that solid solutions that have a glass transition temperature below the tested temperature are physically stable. E.g. a solid solution of obeticholic acid with Eudragit El 00 was selected in the weight ratio of OCA : Eudragit El 00 1 : 3, which has the glass transition temperature of 58°C, behaves like this and under the temperature load of 60°C it remains amorphous at both the tested relative humidity values, the glass transition temperature being more or less the same. Another such example is a solid solution or obeticholic acid with Soluplus in the weight ratio of OCA : Soluplus 1 : 3, which has the glass transition temperature of 57°C, where the loading with a higher temperature and a low relative humidity results in an increase of the glass transition temperature, namely to 74°C (40°C / 0% RH / 7 days), or 66°C (60°C / 0% / 3 days), respectively.

Another phenomenon that can be observed during load testing is "maturation", i.e. rising of the glass transition temperatures of selected solid solutions due to a higher temperature, or higher relative humidity.

E.g. the glass transition temperature of a solid solution of obeticholic acid with Eudragit SI 00 in the weight ratio of 1 : 3, which was originally 101 °C, rises to 126°C due to the solution being stored for 7 days at 40°C and 0% relative humidity. This solid solution also has a similar temperature (127°C) after being stored for 3 days at 60°C and 0% relative humidity. An even higher glass transition temperature of this sample was measured when it was exposed to the conditions of 40°C and 75% relative humidity for 7 days or 60°C and 75% relative humidity for 3 days.

Also, a solid solution of obeticholic acid with Copovidone VA64 in the weight ratio of 1 : 3 with the original glass transition temperature of 92°C increased its glass transition temperature to 103°C or 104°C after maturation at 40°C and 75% relative humidity for 7 days or at 60°C and 75% relative humidity for 3 days, respectively.

A similar phenomenon was also observed in the case of a solid solution of obeticholic acid with PVP K30 in the weight ratio of 1 : 3, which originally had the glass transition temperature of 125°C. After maturation at 40°C and 0% relative humidity for 7 days, or 60°C and 0% relative humidity for 3 days, respectively, the glass transition temperature was the same and almost identical to the original condition, 127°C. However, after maturation at 40°C and 75% relative humidity for 7 days, or 60°C and 75% relative humidity for 3 days, respectively, the glass transition temperature rose to the unified value of 142°C.

Another object of the invention is optimized preparation of obeticholic acid alone. Amorphous obeticholic acid can be advantageously prepared from crystalline form 1-2 of obeticholic acid, described in the patent application WO2017008773. Crystalline form 1-2 exhibits high purifying capability, robust preparability and good filterability. For the preparation of the amorphous form of obeticholic acid, the procedure based on precipitation through the ammonium salt of obeticholic acid, described in the patent application WO2006122977 was first used, but the product obtained this way, when crystalline for 1-2 of obeticholic acid was used as the input material, had lower chemical purity than the input material and higher contents of residual solvents. Therefore, the procedure required optimization. The problem of higher contents of residual solvents was solved by the use of higher equivalents of ammonia and subsequently phosphoric acid. The use of a higher equivalent of ammonia also accelerated dissolution, which means that obeticholic acid was only exposed to higher temperature for the time necessary for dissolution, the subsequent reaction was carried out at lower temperatures, which contributes to lower degradation and lower reduction of chemical purity. A dosage change during the reaction also contributed to solving the problem of the decrease of chemical purity. In the original procedure, the solution of the ammonium salt of obeticholic acid was dosed to phosphoric acid. Obeticholic acid is less stable in an acidic environment and it gets degraded. Therefore, it is convenient to avoid this procedure when obeticholic acid is exposed to the action of an excess of phosphoric acid. If, conversely, phosphoric acid is dosed to the mixture of the ammonium salt of obeticholic acid, the environment does not get over-acidified, pH of the reaction mixture is easier to control and no degradation of obeticholic acid occurs. This optimized procedure using all the changes can be used to obtain a product with the same chemical purity as the purity of the input material, preferably even higher. The experiments are described in the embodiment examples.

The amorphous solid forms of obeticholic acid prepared according to this invention can be used for the preparation of pharmaceutical compositions, especially solid drug forms, e.g.. tablets. Such pharmaceutical compositions can comprise at least one excipient from the group of binders (e.g. microcrystalline cellulose), disintegrants (e.g. sodium carboxymethyl starch), lubricants (e.g. magnesium stearate), surfactants etc. These tablets can be coated with conventional layers of e.g. polyvinyl alcohol or polyethylene glycol. Brief description of the Drawings

Fig. 1: DSC record of the amorphous form of obeticholic acid (OCA)

Fig. 2: DSC record of a solid solution of OCA : PVP K30 1 : 3 Fig.3: DSC record of a solid solution of OCA : Eudragit SI 00 1 : 3

Fig. 4: DSC record of a solid solution of OCA : Eudragit E100 1 : 1

Fig. 5: DSC record of a solid solution of OCA : Eudragit E100 1 : 3

Fig. 6: DSC record of a solid solution of OCA : Soluplus 1 : 1

Fig. 7: DSC record of a solid solution of OCA : Soluplus 1 : 3

Fig. 8: DSC record of a solid solution of OCA : Copovidone VA64 1 : 3

Fig. 9: DSC record of a solid solution of OCA : HPMC AS 1 : 1

Fig. 10: DSC record of a solid solution of OCA : Methocel E5 1 : 1 Examples

Obeticholic acid was prepared in accordance with the procedure disclosed in the patent application WO2002072598. The product isolated by means of column chromatography, as mentioned in this application, was confirmed to have an amorphous character. Amorphous obeticholic acid was further prepared by means of the optimized procedures described in Examples 1 and 2. All the products were verified for *H and ¹³ C NMR.

The laboratory temperature refers to the temperature of 25°C ± 3°C.

The embodiment examples below are only used to illustrate and clarify the invention and are by no means intended to restrict the protection scope, which is only delimited by the wording of the patent claims.

Example 1

Preparation of an amorphous form of obeticholic acid

A mixture of 40 ml of water and 844 μΐ of 25% ammonia was poured into a 100 ml vessel of an EasyMax reactor. At the laboratory temperature, 2 g of obeticholic acid, form 1-2 were added to the stirred mixture (300 rpm) and the acid was dissolved during 5 min. The obtained mixture was maintained at 5°C and subsequently, a solution of phosphoric acid (697 μΐ, 85%) in 1 ml of water was added by dripping during 2 minutes. After the addition, the reaction mixture was stirred for another 1 hour at 5°C and then the obtained solid substance was filtered and washed with 3 x 10 ml of water. The solid substance was dried for 20 h in a vacuum drier at 40°C. The amount of 1.79 g of amorphous obeticholic acid with the glass transition (Tg) temperature of 94°C was obtained. Example 2

Preparation of an amorphous form of obeticholic acid

The amount of 20 g of obeticholic acid, form 1-2, was dosed into a 500-ml Radleys reactor and then an ammonia solution was poured to it (8.9 ml of 23% ammonia in 400 ml of water). The mixture was stirred at the laboratory temperature for 30 min until dissolution and then its temperature was adjusted to 5°C. A solution of 6.74 ml of 85% phosphoric acid in 10 ml of water was continually added during 2 h. After the addition, the reaction mixture was stirred for another 1 h at 5°C and then the obtained solid substance was filtered and washed with 3 x 100 ml of water. The product was dried for 20 h in a vacuum drier at 40°C. The amount of 18.2 g of amorphous obeticholic acid with the glass transition (Tg) temperature of 93°C was obtained.

Example 3

Preparation of an amorphous form of obeticholic acid stabilized with PVP K30

Obeticholic acid (500 mg) and povidone K30 (250 mg) were dissolved in a mixture of methanol (3 ml) and dichloromethane (2 ml) by means of ultrasound. The obtained solution was subsequently evaporated in a rotary vacuum evaporator, which provided amorphous foam. DSC confirmed a solid solution with the glass transition (Tg) temperature of 111°C. Example 4

Preparation of an amorphous form of obeticholic acid stabilized with PVP K30

Obeticholic acid (500 mg) and povidone K30 (500 mg) were dissolved in a mixture of methanol (3 ml) and dichloromethane (2 ml) by means of ultrasound. The obtained solution was subsequently evaporated in a rotary vacuum evaporator, which provided amorphous foam. DSC confirmed a solid solution with the glass transition (Tg) temperature of 116°C.

Example 5

Preparation of an amorphous form of obeticholic acid stabilized with PVP K30

Obeticholic acid (5 g) and povidone 30 (5 g) were dissolved in 300 ml of a mixture of water and tert-butanol in the ratio of 1 : 1 by means of ultrasound. The obtained solution was frozen in liquid nitrogen and subsequently lyophilized. DSC confirmed a solid solution with the glass transition (Tg) temperature of 1 17°C. Example 6

Preparation of an amorphous form of obeticholic acid stabilized with PVP K30

Obeticholic acid (50 g) and povidone K30 (150 g) were dissolved in 150 ml of methanol by means of ultrasound. The obtained solution was subsequently spray dried in a Buchi spray drier. DSC confirmed a solid solution with the glass transition (Tg) temperature of 125°C.

This product was further exposed to maturation conditions at the temperatures of 40°C to 60°C and a relative humidity below 30%, ideally below 15%. The product was stabilized and the obtained solid solution exhibited the glass transition (Tg) temperature of 142°C. Example 7

Preparation of an amorphous form of obeticholic acid stabilized with Eudragit S100

Obeticholic acid (500 mg) and Eudragit SI 00 (500 mg) were dissolved in 50 ml of methanol by means of ultrasound. The obtained solution was subsequently evaporated in a rotary vacuum evaporator, which provided amorphous foam. DSC confirmed a solid solution with the glass transition (Tg) temperature of 109°C.

Example 8

Preparation of an amorphous form of obeticholic acid stabilized with Eudragit S100

Obeticholic acid (3 g) and Eudragit SI 00 (9 g) were dissolved in 250 ml of a mixture of water and tert-butanol in the ratio of 1 : 1 by means of ultrasound. The obtained solution was frozen in liquid nitrogen and subsequently lyophilized. DSC confirmed a solid solution with the glass transition (Tg) temperature of 101°C.

This product was further exposed to maturation conditions at the temperatures of 40°C to 60°C and a relative humidity below 30%, ideally below 15%. The product was stabilized and the obtained solid solution exhibited the glass transition (Tg) temperature of 127°C.

If this product is exposed to maturation conditions at the temperatures from 40°C to 60°C and relative humidity of 75%, the product gets stabilized and the glass transition (Tg) temperature of the final solid solution is up to 138°C. Example 9

Preparation of an amorphous form of obeticholic acid stabilized with Eudragit E100

Obeticholic acid (3 g) and Eudragit LI 00 (3 g) were dissolved in 50 ml of methanol by means of ultrasound. The obtained solution was subsequently evaporated in a rotary vacuum evaporator, which provided amorphous foam. DSC confirmed a solid solution with the glass transition (Tg) temperature of 69°C.

Example 10

Preparation of an amorphous form of obeticholic acid stabilized with Eudragit E100

Obeticholic acid (20 g) and Eudragit LI 00 (20 g) were dissolved in 500 ml of methanol by means of ultrasound. The obtained solution was subsequently spray dried in a Buchi spray drier. DSC confirmed a solid solution with the glass transition (Tg) temperature of 78°C. Example 11

Preparation of an amorphous form of obeticholic acid stabilized with Eudragit E100

Obeticholic acid (20 g) and Eudragit LI 00 (60 g) were dissolved in 700 ml of methanol by means of ultrasound. The obtained solution was subsequently spray dried in a Buchi spray drier. DSC confirmed a solid solution with the glass transition (Tg) temperature of 58°C.

Example 12

Preparation of an amorphous form of obeticholic acid stabilized with Soluplus

Obeticholic acid (2 g) and Soluplus (2 g) were dissolved in a mixture of methanol (12 ml) and dichloromethane (4 ml) by means of ultrasound. The obtained solution was subsequently evaporated in a rotary vacuum evaporator, which provided amorphous foam. DSC confirmed a solid solution with the glass transition (Tg) temperature of 75°C.

Example 13

Preparation of an amorphous form of obeticholic acid stabilized with Soluplus

Obeticholic acid (2 g) and Soluplus (6 g) were dissolved in a mixture of methanol (36 ml) and dichloromethane (12 ml) by means of ultrasound. The obtained solution was subsequently evaporated in a rotary vacuum evaporator, which provided amorphous foam. DSC confirmed a solid solution with the glass transition (Tg) temperature of 57°C. Example 14

Preparation of an amorphous form of obeticholic acid stabilized with copovidone VA64

Obeticholic acid (2 g) and copovidone VA64 (2 g) were dissolved in a mixture of methanol (12 ml) and dichloromethane (8 ml) by means of ultrasound. The obtained solution was subsequently evaporated in a rotary vacuum evaporator, which provided amorphous foam. DSC confirmed a solid solution with the glass transition (Tg) temperature of 91 °C.

Example 15

Preparation of an amorphous form of obeticholic acid stabilized with copovidone VA64

Obeticholic acid (2 g) and copovidone VA64 (6 g) were dissolved in 250 ml of a mixture of water and tert-butanol in the ratio of 1 : 1 by means of ultrasound. The obtained solution was frozen in liquid nitrogen and subsequently lyophilized. DSC confirmed a solid solution with the glass transition (Tg) temperature of 92°C.

Example 16

Preparation of an amorphous form of obeticholic acid stabilized with HPMC AS LF

Obeticholic acid (1 g) and HPMC AS LF (1 g) were dissolved in 50 ml of a mixture of water and tert-butanol in the ratio of 1 : 1 by means of ultrasound. The obtained solution was frozen in liquid nitrogen and subsequently lyophilized. DSC confirmed a solid solution with the glass transition (Tg) temperature of 93°C.

Example 17

Preparation of an amorphous form of obeticholic acid stabilized with HPMC AS MF Obeticholic acid (1 g) and HPMC AS MF (1 g) were dissolved in 50 ml of a mixture of water and tert-butanol in the ratio of 1 : 1 by means of ultrasound. The obtained solution was frozen in liquid nitrogen and subsequently lyophilized. DSC confirmed a solid solution with the glass transition (Tg) temperature of 94°C. Examples 18

Preparation of an amorphous form of obeticholic acid stabilized with Methocel E5

Obeticholic acid (2 g) and methocel E5 (2 g) were dissolved in a mixture of methanol (50 ml) and dichloromethane (50 ml) by means of ultrasound. The obtained solution was subsequently evaporated in a rotary vacuum evaporator, which provided amorphous foam. DSC confirmed a solid solution with the glass transition (Tg) temperature of 82°C. Example 19

Preparation of amorphous forms of obeticholic acid stabilized with a polymer by extrusion

Solid solutions of obeticholic acid with all the above mentioned polymers can also be prepared by melting (hot melt extrusion). Obeticholic acid was first mixed with a polymer at the particular ratio, then the mixture was homogenized for at least 5 min and subsequently extruded at the temperature shown in Table 3. The extrudates were subsequently ground in a hammer mill with a 1-mm sieve and analyzed by means of XRPD. Table 3:

Example 20

Pharmaceutical composition of 10 mg of the product - cores

Ingredients were placed into a homogenizer: obeticholic acid, microcrystalline cellulose and sodium carboxymethyl starch. The mixture was homogenized for 15 min at 20 rpm. Finally, magnesium stearate was added and the mixture was homogenized for another 3 min at 20 rpm. The tableting matter obtained in the above mentioned manner was compressed on a rotary tableting machine and used for the production of cores with the approximate weight of 200 mg. The resulting cores may possibly be coated (a mixture of hypromellose, PEG , talc, titanium dioxide, iron oxide).

Example 21

Pharmaceutical composition of 10 mg of the product - cores

Ingredients were placed into a homogenizer: amorphous form of obeticholic acid stabilized with povidone PVP K30, microcrystalline cellulose and sodium carboxymethyl starch. The mixture was homogenized for 15 min at 20 rpm. Finally, magnesium stearate was added and the mixture was homogenized for another 3 min at 20 rpm. The tableting matter obtained in the above mentioned manner was compressed on a rotary tableting machine and used for the production of cores with the approximate weight of 200 mg. The resulting cores may possibly be coated (a mixture of hypromellose, PEG , talc, titanium dioxide, iron oxide).

Example 22

Pharmaceutical composition of 10 mg of the product - cores

Substance Ouantitv - core /ma/

Amorphous form of obeticholic acid stabilized with Eudragit 40.0

S 100 in the weight ratio of 1 : 3

Microcrystalline cellulose 146.0

Sodium carboxymethyl starch 12.0

Magnesium stearate 2.0 Ingredients were placed into a homogenizer: amorphous form of obeticholic acid stabilized with Eudragit SI 00, microcrystalline cellulose and sodium carboxymethyl starch. The mixture was homogenized for 15 min at 20 rpm. Finally, magnesium stearate was added and the mixture was homogenized for another 3 min at 20 rpm. The tableting matter obtained in the above mentioned manner was compressed on a rotary tableting machine and used for the production of cores with the approximate weight of 200 mg. The resulting cores may possibly be coated (a mixture of hypromellose, PEG , talc, titanium dioxide, iron oxide).

Example 23

Pharmaceutical composition of 10 mg of the product - cores

Ingredients were placed into a homogenizer: amorphous form of obeticholic acid stabilized with Eudragit El 00, microcrystalline cellulose and sodium carboxymethyl starch. The mixture was homogenized for 15 min at 20 rpm. Finally, magnesium stearate was added and the mixture was homogenized for another 3 min at 20 rpm. The tableting matter obtained in the above mentioned manner was compressed on a rotary tableting machine and used for the production of cores with the approximate weight of 200 mg. The resulting cores may possibly be coated (a mixture of hypromellose, PEG , talc, titanium dioxide, iron oxide).

Example 24

Pharmaceutical composition of 10 mg of the product - cores

Substance Ouantitv - core /ma

Amorphous form of obeticholic acid stabilized with Soluplus 20.0

in the weight ratio of 1 : 1

Microcrystalline cellulose 166.0 Sodium carboxymethyl starch 12.0

Magnesium stearate 2.0

Ingredients were placed into a homogenizer: amorphous form of obeticholic acid stabilized with Soluplus, microcrystalline cellulose and sodium carboxymethyl starch. The mixture was homogenized for 15 min at 20 rpm. Finally, magnesium stearate was added and the mixture was homogenized for another 3 min at 20 rpm. The tableting matter obtained in the above mentioned manner was compressed on a rotary tableting machine and used for the production of cores with the approximate weight of 200 mg. The resulting cores may possibly be coated (a mixture of hypromellose, PEG , talc, titanium dioxide, iron oxide). List of analytical methods

The records of differential scanning calorimetry (DSC) were measured with a Discovery DSC device made by TA Instruments. The charge of the sample in a standard Al pot (40 μϋ) was between 4-5 mg and the heating rate was 5°C/min. The used temperature program consists of 1 stabilization minute at 0°C and then of heating up to 220°C at the heating rate of 5°C/min (amplitude = 0.8°C and period = 60 s). 5.0 N ₂ was used as the carrier gas at the flow of 50 ml/min.

Measuring parameters of XRPD: The diffractograms were measures with an X'PERT PRO MPD PANalytical diffractometer, used radiation CuKa (λ = 1,542 A), excitation voltage: 45 kV, anode current: 40 mA, measured range: 2 - 40° 2Θ, increment: 0.02° 2Θ, increment dwell: 200 s, the measurements were carried out with a flat powder sample applied on a Si plate. For the setting of the primary optical system programmable divergence slits with the irradiated sample area of 10 mm, 0.02 rad Soller slits and a ¼° anti-dispersion slit were used. For the setting of the secondary optical system an X'Celerator detector with the maximum opening of the detection slot, 0.02 rad Soller slits and a 5.0 mm anti-dispersion slit were used.