Field of the invention

The present invention relates to solid forms of Obeticholic Acid and hydrates or solvates thereof and processes for preparation of the same.

Background of the invention

Obeticholic Acid is chemically described as (3a, 5β, 6a, 7a)-6-Ethyl-3, 7- dihydroxycholan-24-oic acid and structurally represented by formula (I) as given below:

(I)

Obeticholic Acid (OCA) is a first-in-class Farnesoid X receptor (FXR) agonist. It is a potential molecule for the treatment of primary biliary cirrhosis (PBC).

U.S. Patent No. 7,138,390 discloses Obeticholic Acid and a process for its preparation. However, this patent does not disclose any polymorphic form of the product obtained by the said process.

The patent application, US20130345188 describes another process for preparation of Obeticholic Acid. This patent also discloses various crystalline and non-crystalline forms of Obeticholic Acid.

The PCT application, WO2016107575 discloses Obeticholic Acid Form A. Active pharmaceutical ingredients (APIs) may exist in a variety of different solid forms, for example, as solvates, hydrates, co-crystals, salts and the like. APIs may also be prepared in different solid forms, in that they may be amorphous, may exist as different crystalline forms, and/or in different solvation or hydration states. It is known in the art that different solid forms are different in physicochemical behaviour. By varying the form of an API, it is possible to vary the physical properties thereof. For instance, solid forms of an API typically have different solubilities such that a more thermodynamically stable solid form is less soluble than a less thermodynamically stable solid form or vice-a-versa.

Solid forms can also differ in properties such as shelf-life, bioavailability, morphology, vapor pressure, density, color, and compressibility. Accordingly, variation of the solid state of an API is one of many ways in which to modulate the physical and pharmacological properties thereof.

The existence and possible number of solid forms for a given compound cannot be predicted, and there are no standard procedures that may be used to prepare solid forms of a substance. However, the discovery of new solid forms hydrates or solvates of an active pharmaceutical ingredient provides broader scope to a formulation scientist for formulation optimization, for example by providing a product with different properties, e.g., better processing or handling characteristics, improved dissolution profile, or improved shelf-life. So, there is a need for solid forms of Obeticholic Acid and hydrates or solvates thereof. Object of the invention

It is an object of the present invention to provide solid forms of Obeticholic Acid and hydrates or solvates thereof.

It is another object of the present invention to provide a process for preparation of solid forms of Obeticholic Acid and hydrates or solvates thereof.

It is yet another object of the present invention to provide pharmaceutical composition comprising an effective amount of solid forms of Obeticholic Acid and hydrates or solvates thereof. Brief description of the drawing

Figure- 1 : The powder X-ray diffraction (PXRD) pattern of crystalline Form-a of Obeticholic Acid

Figure-2: The differential scanning calorimetry (DSC) thermogram of crystalline Form-a of Obeticholic Acid

Figure-3: The PXRD pattern of crystalline Form-β of Obeticholic Acid

Figure-4: The PXRD pattern of crystalline Form-γ of Obeticholic Acid

Figure-5: The DSC thermogram of crystalline Form-γ of Obeticholic Acid

Figure-6: The PXRD pattern of crystalline Form-δ of Obeticholic Acid Figure-7: The Infrared Spectrum (IR) of crystalline Form-a of Obeticholic Acid

Description of the invention

Accordingly, the present invention describes solid forms of Obeticholic Acid.

In one embodiment, the present invention is directed to crystalline Form-a of Obeticholic Acid. The crystalline Form-a of Obeticholic Acid has substantially the same PXRD (powder X- ray diffraction) pattern, as illustrated in Figure- 1. The crystalline Form-a of Obeticholic Acid is characterized by PXRD pattern having characteristic X-ray diffraction peaks at 4.97, 5.32, 6.30 7.26, 7.73, 8.93, 9.96, 10.57, 12.26, 12.44, 12.62, 15.81, 16.43, 17.91 and 20.50 degree 2Θ ± 0.2 degree 2Θ. In a preferred embodiment, the crystalline Form-a of Obeticholic Acid is further characterized by PXRD pattern having characteristic X-ray diffraction peaks at 4.97, 5.32 and 10.57 degree 2Θ ± 0.2 degree 2Θ.

The crystalline Form-a is further characterised by differential scanning calorimetry (DSC) thermogram as illustrated in Figure-2. The crystalline Form-a of Obeticholic acid has characteristic endothermic peak at about 100.1°C with onset at about 93.1°C. The crystalline Form-a of Obeticholic Acid is also characterised by Infrared (IR) Spectrum as illustrated in Figure-7.

The crystalline Form-a of Obeticholic Acid is having an infrared spectrum in KBr comprising one or more characteristic peaks selected from absorption bands at 3448.71, 2956.72, 2935.52, 2870.53, 2366.89, 2345.80, 1710.27, 1463.82, 1411.70, 1377.05, 1331.83, 1245.61, 1202.01, 1162.03, 1099.31, 1063.05, 974.76, 854.38, and 735.53 cm ^"1 .

The present invention is also directed to a process for the preparation of crystalline Form- α of Obeticholic Acid.

The crystalline Form-a of Obeticholic Acid of the present invention is obtained by stirring Obeticholic acid in a mixture of non-polar and polar solvent or alone in a non- polar solvent followed by removal of solvent.

The non-polar solvent is selected from the group of aromatic or aliphatic hydrocarbons and the polar solvent is selected from the group of ester, ketone, ether, alkanol, and chlorohydrocarbon or mixtures thereof. In a preferred embodiment the crystalline Form-a is obtained by slurring Obeticholic Acid in n-heptane for about 24 hrs.

The process for preparing crystalline Form a of Obeticholic Acid comprises of the steps of: a) providing Obeticholic acid in n-heptane to obtain a reaction mixture, b) slurring the reaction mixture of step a) at room temperature, and c) isolating the crystalline Form a of Obeticholic Acid.

The crystalline Form-a of Obeticholic Acid isolated from n-heptane may be a heptane solvate. With regard to the presence of solvents in a solid state form, it is understood that the content of solvent i.e. stoichiometric/ non-stoichiometric ratio will often depend on, inter alia, the drying conditions for the solid state form. Thus in some embodiments the content of n-heptane in Form-a of Obeticholic Acid is in the range of 3% to 0.5%.

The crystalline Form-a is also prepared by dissolving Obeticholic Acid in a mixture of toluene and ethanol at about 50° C followed by slow solvent removal by evaporation at ambient conditions.

In another embodiment, the present invention is directed to crystalline Form-β of Obeticholic Acid.

The crystalline Form-β of Obeticholic Acid has substantially the same PXRD pattern, as illustrated in Figure-3. The crystalline Form-β of Obeticholic Acid is characterized by PXRD pattern having characteristic X-ray diffraction peaks at 4.95, 5.31, 6.31, 7.21, 7.72, 8.90, 9.92, 10.94, 12.28, 12.69, 13.84, 14.47, 15.77, 16.48, 17.36, 18.51, 19.22, 20.91, and 22.72 degree 2Θ ± 0.2 degree 2Θ.

In a preferred embodiment, the crystalline Form-β of Obeticholic Acid is further characterized by PXRD pattern having characteristic X-ray diffraction peaks at 13.84 and 14.47 degree 2Θ ± 0.2 degree 2Θ.

The present invention is also directed to a process for the preparation of crystalline Form- β of Obeticholic Acid.

The Crystalline Form-β of Obeticholic Acid of the present invention is obtained by dissolving Obeticholic Acid in a non-polar solvent followed by addition of another solvent which may be non-polar or polar, preferably non-polar, followed by removal of solvent.

The process for preparing crystalline Form β of Obeticholic Acid comprises of the steps of: a) providing Obeticholic acid in toluene and heating at 70 ⁰ C to obtain a solution, b) adding hexane to the solution of step a) at about 25°C and stirring for about 12 hours, and c) isolating the crystalline Form β of Obeticholic Acid. The non-polar solvent is selected from the group of aromatic or aliphatic hydrocarbons and the polar solvent is selected from the group of ester, ketone, ether, alkanol, and chlorohydrocarbon or mixtures thereof.

In another embodiment, the present invention is directed to crystalline Form-γ of Obeticholic Acid.

The crystalline Form-γ of Obeticholic Acid has substantially the same PXRD pattern, as illustrated in Figure-4. The crystalline Form-γ of Obeticholic Acid is characterized by PXRD pattern having characteristic X-ray diffraction peaks at 6.18, 6.81, 7.39, 9.96, 10.88, 11.01, 12.60, 13.66, 13.83, 14.03, 14.85, 15.91, 17.54, 17.67, 18.61, 18.71, 19.39, 19.99, 20.71, 21.54, 21.82, 23.15, 24.65, and 24.95 degree 2Θ ± 0.2 degree 2Θ.

In a preferred embodiment, the crystalline Form-γ of Obeticholic Acid is further characterized by PXRD pattern having characteristic X-ray diffraction peaks at 6.18, 6.81, 13.66, 17.54, 18.71 and 19.39 degree 2Θ ± 0.2 degree 2Θ.

The crystalline Form-γ is further characterised by differential scanning calorimetry (DSC) thermogram as illustrated in Figure-5. The crystalline Form-γ of Obeticholic acid has characteristic endothermic peak at about 81.8°C with onset at about 77.7°C.

The present invention is also directed to a process for the preparation of crystalline Form- γ of Obeticholic Acid.

The crystalline Form-γ of Obeticholic Acid of the present invention is obtained by dissolving Obeticholic acid in a mixture of non-polar and polar solvent followed by removal of the solvent mixture.

The process for preparing crystalline Form γ of Obeticholic Acid comprises of the steps of: a) providing Obeticholic acid in a mixture of toluene and ethanol and heating at about 60 ⁰ C to obtain a solution b) cooling the solution of step a) at about 25 °C, and c) isolating the crystalline Form γ of Obeticholic Acid. The non-polar solvent is selected from the group of aromatic or aliphatic hydrocarbons. The polar solvent is selected from the group of ester, ketone, ether, alkanol, chlorohydrocarbon and a mixture thereof.

In another embodiment, the present invention is directed to crystalline Form-δ of Obeticholic Acid.

The crystalline Form-δ of Obeticholic Acid has substantially the same PXRD (powder X- ray diffraction) pattern, as illustrated in Figure-6. The crystalline Form-δ of Obeticholic Acid is characterized by PXRD pattern having characteristic X-ray diffraction peaks at 18.00 degree 2Θ(± 0.2 degree 2Θ. The present invention is also directed to a process for the preparation of crystalline Form- δ of Obeticholic Acid.

The crystalline Form-δ of Obeticholic Acid of the present invention is obtained by slurring Obeticholic acid in a polar solvent, preferably water followed by removal of solvent. The process for preparing crystalline Form δ of Obeticholic Acid comprises of the steps of: a) providing Obeticholic acid in water to obtain a reaction mixture, b) slurring the reaction mixture of step a) at about 50°C for about 25 hours, and c) isolating the crystalline Form δ of Obeticholic Acid. The non-polar solvent of the present invention is selected from the group of aromatic hydrocarbon more preferably toluene, xylene, ethyl benzene etc., aliphatic hydrocarbon more preferably n-hexane, n-heptane, n-pentane, cyclohexane, methyl cyclohexane etc., or mixtures thereof.

The polar solvent of the present invention is selected from the group of ester more preferably ethyl acetate, isopropyl acetate, butyl acetate etc.; ketone more preferably acetone, methyl isobutyl ketone (MIBK), butanone etc.; ether more preferably methyl tert-butyl ether (MTBE), dioxane, tetrahydrofuran, diisopropyl ether, etc.; alkanol more preferably, methanol, ethanol, propanol, isopropanol, butanol, 2-butanol, pentanol etc.; amide more preferably dimethyl formamide, N-methylpyrrolidone etc.; nitrile more preferably acetonitrile etc. ; chlorohydrocarbon more preferably dichloromethane, chloro benzene etc.; and water; or combinations thereof. The solid forms of Obeticholic Acid of the present invention are isolated using techniques such as decantation, filtration by gravity or suction, centrifugation, or slow solvent evaporation or any other suitable technique known in the art and optionally the isolated solid are washed with a solvent, such as an anti-solvent or the solvent, to reduce the amount of entrained impurities. Obeticholic acid used in the present invention is purchased from commercial sources or prepared from processes known in the art.

In one more embodiment, the present invention also provides a pharmaceutical composition comprising solid forms of Obeticholic Acid of the present invention along with one or more pharmaceutically acceptable carriers, excipients, or diluents. The solid forms of Obeticholic Acid of the present invention are used as Farnesoid X receptor (FXR) agonist for prevention or treatment of an FXR mediated disease or condition.

The solid forms of Obeticholic Acid of the present invention are used in preparing pharmaceutical compositions for prevention or treatment of an FXR mediated disease or condition. Such pharmaceutical compositions are prepared by the methods known in the literature.

The present invention is further illustrated with the following non-limiting examples.

Example-1: Preparation of crystalline Form-q of Obeticholic acid

0.74 g (1.75 mmol) Obeticholic acid was taken in 9.0 ml toluene and heated to 50 °C. Thereafter 2.0 ml ethanol was added to the reaction mixture followed by stirring at 50 °C for 5-10 minutes to obtain a clear solution. The clear solution was allowed to stand at ambient conditions for one week. The precipitated crystals were collected by filtration and dried under vacuum at 50 °C to yield 0.62 g of crystalline Form -a of Obeticholic Acid.

Example-2: Preparation of crystalline Form-q of Obeticholic acid

1.2 g (2.85 mmol) Obeticholic acid was slurried in 40 ml n-heptane at 25-30°C for 24-25 hrs. The solid was filtered and dried under vacuum at 50°C for 7-8 hrs to yield 1.0 g of crystalline Form-a of Obeticholic Acid.

Example-3: Preparation of crystalline Form-β of Obeticholic Acid

2.1 g (4.99 mmol) Obeticholic acid was dissolved in 25 ml toluene at 70 °C and refluxed for 20-30 minutes. The solution was cooled to 25°C. A white emulsion appeared on addition of 30 ml hexane. The slurry obtained was stirred for 15 hrs and filtered under vacuum. The white wet cake was dried under vacuum for 4 hrs to yield 1.0 g of crystalline Form-β of Obeticholic Acid.

Example-4: Preparation of crystalline Form-γ of Obeticholic Acid

2.0 g (4.73 mmol) Obeticholic acid was dissolved in 10 ml toluene at 60 °C, followed by addition of 1.5 ml ethanol. The solution was cooled to 25 °C and allowed to stand at ambient conditions. A few hexagonal crystals appeared after 4 days. The crystals were collected, grounded and dried under vacuum for lhr to yield 1.95 g of crystalline Form-γ of Obeticholic Acid.

Example-5: Preparation of crystalline Form-δ of Obeticholic Acid 2.1 g (4.99 mmol) Obeticholic acid was slurried in 30 ml demineralized water and stirred at 50 °C for 25 hrs and filtered. The wet cake was dried under vacuum at 50°C for 5 hrs to yield 2.1g of crystalline Form-δ of Obeticholic Acid

Example-6: Preparation of crystalline Form-q of Obeticholic acid

2.2 g (5.23 mmol) Obeticholic acid was slurried in 74 ml n-heptane at 25-30°C for 24-25 hrs. The solid was filtered and dried under vacuum at 50°C for 7-8 hrs to yield 2.1 g of crystalline Form-a of Obeticholic Acid. Example-7: Preparation of crystalline Form-δ of Obeticholic Acid

5.3 g (12.6 mmol) Obeticholic acid was slurried in 80 ml demineralized water, seeded and stirred at 45°C to 50 °C for 25 hrs, and filtered. The wet cake was dried under vacuum at 50°C for 5 hrs to yield 5.1g of crystalline Form-δ of Obeticholic Acid.