Process for preparing (15α,16α,17β)-estra-1,3,5(10)-triene-3,15,16,17-tetrol (estetrol) monohydrate

Abstract

The present invention relates to a process for preparing (15α,16α,17β)-estra-1,3,5(10)-triene-3,15,16,17-tetrol monohydrate, also known as estetrol monohydrate, having formula (I). [Formula 1] JPEG2026503158000010.jpg2674

Description

[Technical Field]

[0001] The present invention relates to the field of processes for the synthesis of active ingredients (APIs) for pharmaceutical use, and in particular to a process for the industrial-scale preparation of the compound (15α,16α,17β)-estra-1,3,5(10)-triene-3,15,16,17-tetrol monohydrate, also known as estetrol monohydrate. [Background technology]

[0002] Estetrol is an active ingredient with pharmacological activity that makes it useful for hormone replacement therapy (HRT), female contraception, or the treatment of autoimmune disorders associated with hormonal imbalance. The compound is a natural product isolated from human urine and has been known for many years. It was first described in the paper "Synthesis of epimeric 15-hydroxyestriols, new and potential metabolites of estradiol," J. Fishman et al., JOC Vol. 33, No. 8, August 1968, pp. 3133-3135 (compound Ia in the figure on page 3133).

[0003] The structural formula of estetrol is reported below: [ka]

[0004] Positions 15, 16, and 17 of the steroid skeleton (highlighted in the formula reported above) each have one hydroxyl group with a defined spatial configuration, as shown in the structural formula above, i.e., the hydroxy groups at positions 15 and 16 have an α configuration, while the hydroxy group at position 17 has a β configuration.

[0005] The presence of impurities in an active ingredient below set limits is an essential requirement for its use in pharmaceutical formulations. The limits recognized by international guidelines for pharmaceutical substances are 0.1% for unknowns and 0.15% for identified ones. Therefore, the ability to meet these limits is a fundamental characteristic for defining an industrially applicable process. Regardless of the yield, any process that provides an API with impurity contents that do not meet the above limits is not industrially useful, as the resulting API will not be able to obtain marketing authorization from the relevant authorities (EMA, FDA, etc.).

[0006] In the case of estetrol, the scientific and patent literature has so far focused on processes aimed at producing high yields of the compound suitable for industrial use and with the high purity required for pharmaceuticals. In particular, one of the aims of industrial processes is to avoid the presence of the 15β,16β,17β isomers of the compound having the structural formula shown below, from which estetrol must be purified and used in pharmaceutical formulations. [ka]

[0007] Patent application WO2004 / 041839A2 (page 6, lines 5-10) describes a process for obtaining estetrol, the purity of which can reach 99% with the sum of the single impurities not exceeding 1%.

[0008] Subsequent applications relating to the production of estetrol are, for example, WO2012 / 164096A1, WO2013 / 034780A1, WO2013 / 050553A1, WO2015 / 040051A1, WO2015-086643A1, and WO2021 / 044302A1; for example, WO2015 / 040051A1 shows in the examples the achievement of estetrol / isomer 15β,16β,17β ratios of up to 99:1.

[0009] Other requirements in the pharmaceutical industry relate to the stability and processability of the compound of interest.

[0010] Active molecules may be more stable when provided in the form of salts, complexes or solvates, from which the molecules can be easily released under metabolic conditions. In addition, active molecules are almost always formulated with excipients to produce administrable compositions, in which the excipients perform various functions, such as controlling the release rate of the active component, masking unpleasant tastes, and making the dosage unit into a manageable weight and volume.

[0011] One useful form of estetrol is the monohydrate, i.e., a solvate of water and the compound in a 1:1 stoichiometric ratio. Estetrol monohydrate can be represented as follows: [ka]

[0012] The above-mentioned patent publications refer to the synthesis process of estetrol, and salts or solvates of the compound are only mentioned in addition, or not at all, such as in WO2015-086643A1. None of the above-mentioned publications report a reproducible method for preparing estetrol monohydrate at an industrial level and with the required purity level.

[0013] Patent application WO 2021 / 058716 A1 in the name of the present applicant describes a method for producing estetrol monohydrate, which comprises dissolving anhydrous estetrol in a water-miscible organic solvent, mixing the resulting solution with water, removing the organic solvent by distillation to obtain a suspension, maintaining the suspension under stirring, then filtering, washing, and finally drying the solid under reduced pressure. While the method of WO 2021 / 058716 A1 is reliable and consistently provides estetrol monohydrate of a quality and purity suitable for the intended use, it involves the use of an organic solvent that must be distilled off and then recovered, adding time and cost to the overall process. Furthermore, great care must be taken to ensure that the solvent is completely removed and not included in the final dosage unit.

[0014] The object of the present invention is to provide a process for the preparation of estetrol monohydrate suitable for industrial use, which avoids the use of organic solvents while providing a pharmaceutical quality compound. Summary of the Invention

[0015] The object of the present invention is to provide an industrially applicable process for the preparation of estetrol monohydrate without the need to resort to purification techniques.

[0016] The present invention relates to a process for converting anhydrous estetrol to estetrol monohydrate by contacting the estetrol with pure water in either liquid or vapor form. [ka] [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 shows the DRX diffractograms of estetrol monohydrate obtained under different conditions using the first embodiment of the process of the present invention. [Figure 2] FIG. 2 shows the DRX diffractograms of estetrol monohydrate obtained under different conditions using the first embodiment of the process of the present invention. [Figure 3] FIG. 3 shows the DRX diffractogram of estetrol monohydrate obtained using the second embodiment of the process of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention relates to a process for the preparation of estetrol monohydrate starting from anhydrous estetrol.

[0019] Anhydrous estetrol can be produced according to any of the processes known in the prior art. One preferred method is the method comprising steps A) to D) of WO2021 / 058716A1. Anhydrous estetrol can be used in both crystalline and amorphous form.

[0020] By "pure water" in this specification and claims, it is intended to mean distilled water.

[0021] In a first embodiment, the present invention resides in a process comprising contacting anhydrous estetrol with purified water according to the following steps: a) preparing a suspension of anhydrous estetrol in water and stirring for at least 5 minutes to obtain a suspension of estetrol monohydrate; b) filtering the suspension of estetrol monohydrate obtained in step a) to produce wet estetrol monohydrate; c) drying the wet estetrol monohydrate of step b) to obtain estetrol monohydrate.

[0022] The stirring in step a) is carried out at a temperature between 5 and 90°C, preferably between 15 and 35°C.

[0023] The inventors studied the time course of the conversion of anhydrous estetrol to estetrol monohydrate by preparing a slurry of the anhydrous compound in water, sampling the slurry at various times, drying the samples, and analyzing them by XRPD. An example of the results obtained is shown in the different diffractograms in Figure 1. The analysis shows that the signal corresponding to anhydrous estetrol disappears after stirring in water for just a few minutes, indicating a rapid conversion to estetrol monohydrate.

[0024] The drying in step c) is carried out at a pressure of less than 800 mbar, preferably less than 500 mbar, more preferably less than 250 mbar, at a temperature between 15 and 50°C, preferably between 15 and 35°C.

[0025] In a second embodiment, the present invention resides in a process for converting anhydrous estetrol to estetrol monohydrate by a simple conditioning procedure, which comprises a first step d) of exposing the anhydrous estetrol powder to an atmosphere having a relative humidity (RH) of at least 75% at a temperature between 20 and 25°C for at least 24 hours, and a second step e) of recovering the estetrol monohydrate powder.

[0026] At the end of step d), the conversion is complete and the estetrol monohydrate powder can be easily recovered in step e) and is ready for use in pharmaceutical formulations without further processing.

[0027] Step d) is preferably carried out in an atmosphere having a RH of at least 90% and, independently of the RH, preferably for at least 36 hours.

[0028] The present invention is further illustrated by the following examples.

[0029] Experimental equipment, methods and conditions HPLC: Agilent Model 1260 Infinity Chromatography System; UV Detector Model G1315C DAD VL+

[0030] Method HPLC: Chromatography conditions: -Column: Supelco discovery C18 150 x 4.6 mm, 5 μm -Flow rate: 1mL / min -Detector: UV280nm -Injection volume: 25μl -Temperature: 22℃ Mobile phase A: 4.29 g / L of CH3COONH4 solution in water / methanol / acetonitrile 90 / 6 / 4 Mobile phase B: 38.6 g / L of CH3COONH4 solution in water / methanol / acetonitrile 10 / 54 / 36

[0031] [Table 1]

[0032] XPRD: XRPD analysis was performed using a Bruker D2 Phaser (2nd version) powder diffractometer operating in Bragg-Brentano geometry with a rotating multisampler and a linear SSD detector (Lynxeye). The X-ray source was an X-ray tube with a copper anode operated at 30 kV and 10 mA. For the analysis, X-rays with a wavelength corresponding to the mean Kα of copper (λ = 1.54184 Å) were used. Kβ radiation was filtered with a nickel filter.

[0033] A "zero background" silicon sample holder with a flat surface was used on which the sample was spread to form a thin layer, and the sample holder was rotated at a speed of 60 rpm during the analysis.

[0034] Scans were performed over the 2θ range of 4–40° with 2θ increments of 0.016° and an acquisition time of 1.0 s for each increment.

[0035] Diffractograms were processed using Bruker DIFFRAC.EVA software.

[0036] Note The water used in the experimental description is to be understood as pure water unless otherwise stated.

[0037] Example 1 This example relates to the first embodiment of the process of the invention, the hydration of anhydrous estetrol by slurry in water.

[0038] 3.0 g of pure crystalline anhydrous estetrol was placed in a 100 mL flask.

[0039] Purified water (30 mL, 10 V / w) was added, and the mixture was stirred at 20-25 °C using a mechanical stirrer.

[0040] Slurry samples were taken after 5 minutes, 1 hour and 4.5 hours.

[0041] The sample was filtered under vacuum, dried on the filter for 10 minutes and analyzed by XRPD.

[0042] The results of the XRPD studies are reported in Figures 1 and 2.

[0043] In Figure 1, the lower diffractogram, indicated as time zero (t = 0 h), refers to the starting anhydrous estetrol, the three middle diffractograms refer to samples taken at the times indicated, while the upper diffractogram was obtained using a sample of pure estetrol monohydrate prepared according to the process described in WO2021 / 058716A1 and is included as a reference.

[0044] FIG. 2 is an enlarged view of the vertical axis of the two diffractograms of FIG. 1 at t=0 h and t=4.5 h, in which the disappearance of the anhydrous estetrol peak and the appearance of the estetrol monohydrate peak can be more easily seen.

[0045] The final sample of the slurry after 4.5 hours was estetrol monohydrate (white crystals, HPLC purity=100%).

[0046] The list of XRPD peaks is reported in Table 1 below. [Table 2]

[0047] The list of peaks in Table 1 corresponds to the data reported in WO2021 / 058716A1 for estetrol monohydrate, to the usual approximation of ±0.2°.

[0048] Example 2 This example relates to the hydration of estetrol anhydride in a 100% RH chamber, which is the second embodiment of the process of the present invention.

[0049] 3.0 g of pure estetrol anhydride was placed as a thin layer in a crystallization apparatus.

[0050] The crystallization apparatus was placed in a glass desiccator filled with water at 20 < T < 25 °C at the bottom.

[0051] Some samples of the powder were collected after 3.5 hours, 7 hours, 24 hours, and 48 hours and analyzed by XRPD. The obtained diffractograms are reproduced in Figure 3. The diffractogram at time 0 (t = 0 h) refers to estetrol anhydride, and the upper diffractogram added as a reference was obtained using a sample of pure estetrol monohydrate prepared according to the process described in WO2021 / 058716A1. The four intermediate diffractograms are recorded for the samples obtained after the indicated processing times.

[0052] [[ID=​​​​​​​​​​​​​​

Claims

1. 1. A process for converting estetrol to estetrol monohydrate, comprising: 【Chemistry 1】 1. A method comprising contacting anhydrous estetrol with pure water in either liquid or vapor form.

2. 10. The method of claim 1, wherein the anhydrous estetrol is contacted with purified water in liquid form, a) preparing a suspension of anhydrous estetrol in water and stirring for at least 5 minutes to obtain a suspension of estetrol monohydrate; b) filtering the suspension of estetrol monohydrate obtained in step a) to produce wet estetrol monohydrate; c) drying the wet estetrol monohydrate of step b) to obtain estetrol monohydrate. A method comprising:

3. 3. The method of claim 2, wherein step a) is carried out at a temperature between 5 and 90°C.

4. 4. The method according to claim 3, wherein step a) is preferably carried out at a temperature between 15 and 35°C.

5. 3. The method of claim 2, wherein step c) is carried out at a pressure of less than 800 mbar.

6. 6. The method of claim 5, wherein step c) is carried out at a pressure of less than 500 mbar.

7. 7. The method of claim 6, wherein step c) is carried out at a pressure of less than 250 mbar.

8. 3. The process of claim 2, wherein step c) is carried out at a temperature of 15 to 50°C.

9. 9. The method of claim 8, wherein step c) is carried out at a temperature between 15 and 35°C.

10. 10. The method of claim 1, wherein the anhydrous estetrol is contacted with pure water in vapor form, d) exposing the anhydrous estetrol powder to an atmosphere having a relative humidity (RH) of at least 75% at a temperature between 20 and 25°C for at least 24 hours; e) recovering the estetrol monohydrate obtained in step d). A method comprising:

11. 11. The method of claim 10, wherein step d) is carried out using an atmosphere having a RH of at least 90%.

12. 11. The method of claim 10, wherein step d) is carried out for at least 36 hours.

13. The method of claim 11, wherein step d) is carried out for at least 36 hours.

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