ES3036185A2 - PREPARATION PROCESS OF (15alpha,16alpha,17beta)-ESTRA-1,3,5(10)-TRIENE-3,15,16,17-TETROL MONOHYDRATE (ESTETROL) - Google Patents

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, which has formula (I).

Description

DESCRIPTION

PREPARATION PROCESS OF (15a.16a.17B)-ESTRA-1.3.5(1Q)-TRIENE-3.15.16.17-TETROL MONOHYDRATE (ESTETROL)

FIELD OF INVENTION

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

STATE OF THE ART

Estetrol is an active ingredient with pharmacological activity that makes it useful for hormone replacement therapy (HRT), female contraception, or in the therapy of autoimmune dysfunctions associated with hormonal imbalances. The compound is a natural product isolated from human urine and has been known for years; it was first described in the article "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 (the compound in the figure on page 3133).

The structural formula of estetrol is reported below:

Each of the 15, 16, and 17 positions of the steroid skeleton (indicated in the formula reported above) possesses a hydroxyl radical that, as indicated in the structural formula above, has a defined spatial arrangement; specifically, the hydroxy groups at positions 15 and 16 have an α configuration, while the hydroxy group at position 17 has the β configuration.

An active ingredient's impurity content below a fixed limit is a mandatory requirement for allowing its use in pharmaceutical preparations; the limits accepted by international guidelines for pharmaceutical substances are 0.1% for unknown substances and 0.15% for identified substances. Therefore, the ability to meet these limits is a fundamental characteristic for defining an industrially applicable process. Any process, regardless of its performance, that produces an API with an impurity content that does not comply with the above limits is not industrially useful, since the relevant authorities (EMA, FDA, etc.) cannot grant the resulting API a marketing authorization.

In the case of estetrol, the scientific and patent literature has so far focused on processes aimed at producing the compound in high yield, suitable for industrial application, and with the high purity required for pharmaceutical products; in particular, one of the objectives of the industrial processes is to avoid the presence of the 15p,16p,17p isomer of the compound, which has the structural formula shown below, from which estetrol for use in pharmaceutical preparations must be purified:

Patent application WO 2004/041839 A2 (page 6, lines 5-10) describes a process for obtaining estetrol with a purity of up to 99%, with the sum of individual impurities not exceeding 1%.

Subsequent applications relating to the production of estetrol are, for example, patent documents WO 2012/164096 A1, WO 2013/034780 A1, WO 2013/050553 A1, WO 2015/040051 A1, WO 2015-086643 A1 and WO 2021/044302 A1; WO 2015/040051 A1, for example, shows in the examples the achievement of an estetrol/15p,16p,17p isomer ratio of up to 99:1.

Other requirements of the pharmaceutical industry are connected with the stability and processability of the compounds of interest.

Active molecules can be more stable when provided in the form of salts, complexes, or solvates, from which the molecule can be readily released under metabolic conditions; furthermore, active molecules are almost invariably formulated with excipients to produce administrable compositions, where the excipients perform various functions, such as controlling the release rate of the active component, masking unpleasant taste, keeping the administration unit to a manageable weight and volume, etc.

A useful form of estetrol is the monohydrate, i.e., a solvate of the compound with water in a 1:1 stoichiometric ratio; estetrol monohydrate can be represented as follows:

Previous patent publications refer to the estetrol synthesis process, and salts or solvates of the compound are mentioned in passing, as in patent document WO 2015-086643 A1, or not at all; none of these publications report a reproducible method for preparing estetrol monohydrate at an industrial scale and with the required level of purity.

Patent application WO 2021/058716 A1, in the name of the present applicant, describes a method for producing estetrol monohydrate, which consists of 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, and then filtering, washing and finally drying the solid under reduced pressure. The method of patent document WO 2021/058716 A1 is reliable and consistently provides estetrol monohydrate of suitable quality and purity for the intended application, but it involves the use of organic solvents that need to be distilled off and then recovered, which adds time and cost to the overall process; in addition, the greatest possible care must be taken to ensure that the solvent is completely removed and not included in the final delivery units.

It is an object of the present invention to provide a process for the preparation of estetrol monohydrate that is suitable for industrial application, providing the compound in pharmaceutical quality, while avoiding the use of organic solvents.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an industrially applicable process for preparing estetrol monohydrate, without having to resort to purification techniques.

The invention relates to a process for the transformation of estetrol into estetrol monohydrate:

by bringing anhydrous estetrol into contact with pure water, either in liquid or vapor form.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1 and 2 show the XRD diffractograms of estetrol monohydrate obtainable with the first embodiment of the process of the invention, under different conditions;

Figure 3 shows the XRD diffractogram of estetrol monohydrate obtainable with the second embodiment of the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a method for the preparation of estetrol monohydrate from anhydrous estetrol.

Anhydrous estetrol can be produced by any of the processes known in the prior art; a preferred method is the one comprising steps A) to D) of patent document WO 2021/058716 A1. Anhydrous estetrol can be used in both crystalline and amorphous forms.

By "pure water" in this description and in the claims, distilled water is intended.

In a first embodiment, the invention consists of a process comprising contacting anhydrous estetrol with pure water, according to the following steps:

a) preparing and stirring a suspension of anhydrous estetrol in water for at least 5 minutes, obtaining a suspension of estetrol monohydrate;

b) filtering the estetrol monohydrate suspension obtained in step a) to produce wet estetrol monohydrate;

c) drying the wet estetrol monohydrate from step b) to obtain estetrol monohydrate.

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

The inventors have studied the time course of the transformation of anhydrous estetrol to estetrol monohydrate by preparing suspensions of the anhydrous compound in water, sampling the suspension at different times, drying the sample, and analyzing it by XRPD; an example of the results obtained is represented by the different diffractograms in Figure 1. The analyses show that the signals corresponding to anhydrous estetrol disappear after only a few minutes of stirring in water, rapidly converting it to estetrol monohydrate.

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

In the second embodiment, the invention consists of a process for transforming anhydrous estetrol into estetrol monohydrate by a simple conditioning procedure, said process comprising a first step d) of exposing the anhydrous estetrol powders for at least 24 hours to an atmosphere with at least 75% relative humidity (RH) at a temperature between 20 and 25 °C, and a second step e) of recovering the estetrol monohydrate powders.

At the end of step d), the transformation is complete and the estetrol monohydrate powders can be simply recovered in step e), ready for use in pharmaceutical formulations, without further processing.

Step d) is preferably carried out in an atmosphere with a relative humidity of at least 90% and, regardless of the relative humidity, preferably for at least 36 hours. The invention will be further illustrated by the following examples.

EXPERIMENTAL INSTRUMENTS, METHODS AND CONDITIONS

HPLC:

Agilent 1260 Infinity Chromatography System; UV Detector Model G1315C DAD VL+

HPLC method:

Chromatographic conditions:

- Column: Supelco discovery C18 150 x 4.6 mm, 5 μm - Flow rate: 1 ml/min

- Detector: UV 280 nm

- Injection volume: 25 μl

- Temperature: 22 °C

- Mobile phase A: 4.29 g/l of CH3COONH4 solution in water/methanol/acetonitrile 90/6/4

- Mobile phase B: 38.6 g/l solution of CH3COONH4 in water/methanol/acetonitrile 10/54/36

XPRD:

XRPD analyses were performed using a Bruker D2 Phaser (2nd edition) powder diffractometer operating in Bragg-Brentano geometry, equipped with a spinning multisampler and SSD type linear detector (Lynxeye). The X-ray source was an X-ray tube with a copper anode operating at 30 KV and 10 mA. For the analysis, X-ray radiation having a wavelength corresponding to the average Ka of copper (A = 1.54184 Å) was used. The Kp radiation was filtered through a nickel filter.

"Zero background" silicon sample holders were used, with a flat surface on which the sample was spread to form a thin layer. During the analysis, the sample holder rotated at a speed of 60 rpm.

The scan was performed in the range of 4-40° 20 with increments of 0.016° 20 and an acquisition time of 1.0 s for each increment.

The diffractograms were processed using Bruker DIFRAC.EVA software.

GRADES

Water used in experimental descriptions should be understood as pure water, unless otherwise indicated.

EXAMPLE 1

This example relates to the first embodiment of the process of the invention, the hydration of anhydrous estetrol by suspension in water.

3.0 g of pure crystalline anhydrous estetrol was placed in a 100 ml flask.

Pure water (30 ml, 10 V/w) was added, and the mixture was stirred using a mechanical stirrer at 20-25 °C.

Suspension samples were taken after 5 min, 1 h and 4.5 h.

Samples were vacuum filtered, dried on the filter for 10 min, and analyzed by XRPD.

The results of XRPD tests are reported in Fig. 1 and 2.

In Fig. 1, the lower diffractogram, indicated as time zero (t = 0 h) refers to the initial anhydrous estetrol, the three intermediate diffractograms refer to the samples taken at the indicated times, while the upper diffractogram has been obtained with a sample of pure estetrol monohydrate prepared according to the process described in patent document WO 2021/058716 A1, and has been added for reference.

Fig. 2 is an enlargement of the vertical axis of the two diffractograms at t = 0 h and t = 4.5 h in Fig. 1, which allows easy verification of the disappearance of the anhydrous estetrol peaks and the appearance of the estetrol monohydrate peaks.

The final sample, after 4.5 h of suspension, was estetrol monohydrate (white crystals, HPLC purity = 100%).

The list of XRPD peaks is listed in Table 1 below:

Table 1

The list of peaks in Table 1 corresponds, to the usual approximation of ±0.2°, to the data reported in patent document WO 2021/058716 A1 for estetrol monohydrate.

EXAMPLE 2

This example relates to the second embodiment of the process of the invention, the hydration of anhydrous estetrol in a chamber with 100% RH.

3.0 g of pure anhydrous estetrol was placed in a crystallizer as a thin layer. The crystallizer was placed in a glass desiccator filled to the bottom with water at 20 < T < 25 °C.

Small powder samples were collected after 3.5 h, 7 h, 24 h, 48 h and analyzed by XRPD. The obtained diffractograms are reproduced in Fig. 3, where the diffractogram at time zero (t = 0 h) refers to anhydrous estetrol, the upper diffractogram, added as a reference, has been obtained with a sample of pure estetrol monohydrate prepared according to the process described in patent document WO 2021/058716 A1, and the four intermediate diffractograms have been recorded on the samples obtained after the indicated treatment times.

The final sample, after 48 h of exposure to a humid atmosphere, was estetrol monohydrate (white crystals, HPLC purity = 100%).

Table 2

The list of peaks in Table 2 corresponds, to the usual approximation of ±0.2°, to the data reported in patent document WO 2021/058716 A1 for estetrol monohydrate.

Claims (12)

CLAIMS 1. Process for the transformation of estetrol into estetrol monohydrate: which involves bringing anhydrous estetrol into contact with pure water, either in liquid or vapor form. 2. The process according to claim 1, wherein anhydrous estetrol is contacted with pure water in liquid form, comprising the following steps: a) preparing and stirring a suspension of anhydrous estetrol in water for at least 5 minutes, obtaining a suspension of estetrol monohydrate; b) filtering the estetrol monohydrate suspension obtained in step a) to produce wet estetrol monohydrate; c) drying the wet estetrol monohydrate from step b), obtaining estetrol monohydrate. 3. Process according to claim 2, wherein step a) is carried out at a temperature between 5 and 90 °C. 4. Process according to claim 3, wherein step a) is carried out at a temperature preferably between 15 and 35 °C. 5. Process according to any one of claims 2 to 4, wherein step c) is carried out at a pressure of less than 800 mbar. 6. Process according to claim 5, wherein step c) is carried out at a pressure of less than 500 mbar. 7. Process according to claim 6, wherein step c) is carried out at a pressure of less than 250 mbar. 8. Process according to any one of claims 2 to 7, wherein step c) is carried out at a temperature between 15 and 50 °C. 9. Process according to claim 8, wherein step c) is carried out at a temperature between 15 and 35 °C. 10. Process according to claim 1, wherein anhydrous estetrol is contacted with pure water in the form of vapor, comprising the following steps: d) exposing anhydrous estetrol powders for at least 24 hours to an atmosphere with at least 75% relative humidity (RH) at a temperature between 20 and 25°C; e) recovering the estetrol monohydrate obtained in step d). 11. Process according to claim 10, wherein step d) is carried out in an atmosphere with an RH of at least 90%. 12. Process according to claim 10 or 11, wherein step d) is carried out for at least 36 hours.