RU2758436C1 - Method for obtaining amorphous co-evaporates of cladribin with cyclodextrins - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for producing amorphous co-evaporate containing (a) cladribine, (b) cyclodextrin and (c) an organic solvent, said method comprising the steps of: (i) dissolving cyclodextrin in an aqueous alcoholic solution, (ii) dissolving cladribine in aqueous alcoholic solution of cyclodextrin, (iii) removing the solvent to obtain the final amorphous co-volatilized substance containing less than 2% residual solvent.

EFFECT: new method for preparing an amorphous complex of cladribine with cyclodextrin has been developed, which makes it possible to obtain a highly stable amorphous complex that can be used in medicine for the production of solid dosage forms containing cladribine.

8 cl, 7 dwg, 10 ex

Description

Technology area

The invention relates to the chemical-pharmaceutical industry and relates to a method for producing amorphous co-evaporates of cladribine and a method for their use.

State of the art

Cladribine (2-chlorodeoxyadenosine, 2-CdA) was developed in the late 1970s. Research Institute of Scrips (La Jolla, California) and was used, in particular, for the treatment of hemato-oncological diseases. Cladribine is a synthetic chlorinated analogue of deoxyadenosine with the following structure:

In addition to the chemotherapeutic effect, cladribine also has an immunosuppressive effect, especially on the adaptive component of the immune system, characterized by pronounced lymphopenia of peripheral B cells (CD19 +) and CD4 +, and partially CD8 + T cells.

Cladribine is a prodrug taken up by cells with specific transport proteins. In cells, it undergoes phosphorylation by deoxycytidine kinase (DCK) to form mononucleotide 2-chlorodeoxyadenosine-5'-monophosphate (2-CdAMP), which is subsequently phosphorylated to form 2-chlorodeoxyadenosine-5'-triphosphate (2-CdATP), which itself is active connection.

In resting cells, 2-CdATP causes single strand breaks in DNA, rapid consumption of nicotinamide adenine dinucleotide, ATP depletion, and cell death. In dividing cells, 2-CdATP interferes with DNA synthesis by inhibiting ribonucleotide reductase and competes with deoxyadenosine triphosphate for incorporation into DNA by DNA polymerases.

In most cell types, the active triphosphorylated form is inactivated by dephosphorylation of 5β-nucleotidase, but in lymphocytes, especially in B cells, the kinase: phosphatase ratio is high, so that the drug remains active and predominantly inhibits these cells, while other cell types remain intact.

Changes in the expression levels of deoxycytidine kinase (DCK) and 5'-nucleotidase (5'-NT) between immune cell subtypes may explain differences in the sensitivity of immune cells to cladribine. Due to these levels of expression, cells of the innate immune system are less affected than cells of the adaptive immune system.

One of the characteristic properties of cladribine is its instability in an acidic environment. Cladribine belongs to the so-called "acid-labile drugs", that is, substances that quickly decompose in an acidic environment. Even at a physiological temperature of 37 ° C, the t1 / 2 value of cladribine is defined as equal to 1.6 h for solutions with a pH of 2.0 and only 0.37 h for solutions with a pH of 1.0 (Tarasiuk A., Skierski J., Kazimierczuk Z . Stability of 2-chloro-2'-deoxyadenosine at various pH and temperature. Archivum Immunologiae et Therapiae Experimentalis, 01 Jan 1994, 42 (1): 13-15).

Since the main site of absorption for oral drugs is the low pH stomach, absorption of acid-sensitive drugs in the stomach is difficult. The acidic pH of the stomach can be adjusted, for example, with enteric formulations or with a buffer or substances that lower the pH of the stomach. These standard procedures have proven ineffective for cladribine (F. Albertioni, G. Juliusson & J. Liliemark. On the bioavailability of 2-chloro-2 ^′ -deoxyadenosine (CdA). The influence of food and omeprazole. European Journal of Clinical Pharmacology v. 44, pp. 579-582, 1993).

To protect cladribine at low pH, Schultz et al. Proposed the use of a cyclodextrin-clabribine complex (US patent No. 6,194,395). Cyclodextrins contribute significantly to the stability of cladribine in solution at pH 1.4 and maintain more than 80% of the active ingredient for almost 5 hours and about 70% of the active ingredient for 8 hours, i.e. throughout the experiment, while the loss of cladribine dissolved in solution in the absence of cyclodextrins was about 50% after about 3 hours, and after 8 hours about 15% of the active substance remained in the solution. Based on the results obtained, it was proposed to use complexes of cladribine with cyclodextrins to obtain stable liquid and solid dosage forms.

However, Schultz et al. Described only a method for preparing a solid dosage form by melt extrusion, in which cladribine and cyclodextrin are mixed with other accessory ingredients and then heated to melt. The broad dose range from 1 to 15 mg of cladribine and from 100 to 500 mg of cyclodextrin presented in the patent includes many combinations that may be useful as mixtures but not for complexing. For example, the ratio of 1 mg cladribine to 500 mg cyclodextrin contains too much cyclodextrin so that the drug cannot easily leave the complex and perform its therapeutic function. On the other hand, 15 mg of cladribine and only 100 mg of cyclodextrin will not be enough to complex a given amount of cladribine.

In addition, the ratio of cladribine to cyclodextrin 1: 500 actually does not allow for an oral dosage form with a higher content of active ingredient. Even the claimed protection of cladribine from degradation at low pH is likely to depend on the API (active pharmaceutical ingredient): cyclodextrin ratio and is not a common characteristic of cyclodextrin.

Another method for preparing the cladribine-cyclodextrin complex is as follows: (i) dissolving cyclodextrin in water, (ii) adding cladribine and stirring for 15-18 hours, followed by (iii) removing undissolved cladribine by filtration and (iv) lyophilizing the filtrate for 97 -118 hours (US No. 8785415).

This method of obtaining a complex of cladribine: cyclodextrin takes from 112 to 136 hours.

A similar method for preparing the cladribine-cyclodextrin complex is described in US No. 7,888,328. The resulting product is characterized by the authors as a mixture consisting of 30-40% amorphous complex of cyclodextrin and cladribine, where cladribine is located inside the “pore” of cyclodextrin, and 60-70%, where cladribine is located outside the “pore” of cyclodextrin (inclusion and non-inclusion complexes). Unfortunately, the ratio of the components in the known complexes has not been confirmed by any analytical method.

Also, it has not been proven that amorphous forms of cyclodextrin affect the solubility of cladribine. For a clear conclusion, for example, there is no comparison of the solubility of the amorphous form itself or other polymorphic forms with the amorphous form in the form of a cyclodextrin complex.

The two above-mentioned methods for preparing a complex of cladribine with cyclodextrin, regardless of the nature of the complex formed, are practically identical, and both use lyophilization to obtain a complex of cyclodextrin with cladribine.

Lyophilization is a labor-intensive process characterized by high capital costs for technical equipment and operations. Because of its cost, lyophilization is used rather in the production of, for example, parenteral drugs, vaccines, proteins or substances susceptible to heat damage in general using standard methods. It is rarely used in the manufacture of oral preparations due to cost and is essentially limited to the production of oral dispersible formulations.

The aim of the present invention was to eliminate the disadvantages of the above-mentioned methods for preparing a cladribine complex and to provide a reliable, cost-effective, safe and easy-to-use industrial technology for the production of a cladribine-cyclodextrin complex, which provides a product with the same physicochemical properties as lyophilized cladribine complex ...

The technical result of the claimed invention is the development of a simple instrumental implementation of a method for producing an amorphous complex of cladribine-cyclodextrin (co-evaporate) used for the preparation of an oral dosage form.

In experiments aimed at exploring the possibility of replacing lyophilization with a cheaper and more reliable method, it was found that (i) the use of an aqueous-alcoholic solution lowers the temperature required to dissolve cladribine and significantly shortens the time required to dissolve cladribine in a cyclodextrin solution, ( ii) co-evaporate of cladribine with cyclodextrins make it possible to obtain a highly stable amorphous complex with satisfactory solubilizing properties such that (iii) the obtained amorphous co-evaporate exhibits physicochemical properties identical to the sample obtained in accordance with the example given in US patent 8785415, and in 7 888 328 shows the same dissolution profile as the original composition in buffers with pH 1.0, 2.0, 4.5 and 6.8, while the total time to obtain amorphous co-evaporate, as well as the cost of its preparation an order of magnitude lower than when obtaining a complex of cladribine in accordance with the above patents.

Summary of the invention

The present invention relates to a method for preparing an amorphous complex of cladribine with cyclodextrin (co-evaporate), comprising:

a) cladribine,

b) cyclodextrin and

c) additional residual organic solvent.

In this case, the method for producing amorphous co-evaporate includes the following stages:

(i) dissolving cyclodextrin in an aqueous alcoholic solution,

(ii) dissolving cladribine in an aqueous alcoholic solution of cyclodextrin, and

(iii) complete removal of the solvent in a vacuum evaporator.

Another object of the present invention is an oral dosage form comprising:

(a) amorphous co-evaporate according to the present invention; and

(b) pharmaceutically acceptable excipients.

Preferably, the oral dosage form is in the form of tablets, more preferably in the form of uncoated tablets. The tablets are preferably prepared by direct compression.

Co-evaporate is a complex of API (active pharmaceutical ingredient) and polymeric excipient (s) (excipient (s)) obtained by removing a volatile organic solvent in which both the drug (API) and the excipient have been previously dissolved.

The term "cladribine" in the context of this document refers to cladribine in the form of its pharmaceutically acceptable solvates, hydrates, enantiomers, polymorphs, or mixtures thereof. Preferably, cladribine is used in crystalline form.

In addition to cladribine, co-evaporate contains cyclodextrin and, in some cases, organic solvent residues.

Typically, the term "cyclodextrin" refers to cyclic oligosaccharides with a molecular weight of about 1000 Da, which are composed of six to eight glucose units linked by an α-1,4-glycosidic bond. The molecular structure of cyclodextrin resembles a truncated cone with a hydrophilic outer surface and a non-polar inner cavity.

In the present invention, hydroxypropyl-β-cyclodextrin (hydroxypropylated β-cyclodextrin, HPβCD) is preferably used. HP-β-cyclodextrin is a circular molecule of seven glucose units linked by α-1,4-glycosidic bonds, with an average degree of substitution of 3 to 6, more preferably 4 to 5, especially 4.6. The average degree of substitution refers to the number of substituents per cyclodextrin ring. An average substitution degree of 4 to 5, in particular 4.6, results in excellent dissolution properties.

In addition, a cyclodextrin with a bulk density of 150-700 milligrams / cm ² , more preferably 200-350 milligrams / cm ² , is preferably used.

In addition, it is particularly preferred that cyclodextrins in the form of an amorphous cyclodextrin hydrate are used in all embodiments of the present invention.

In addition to cladribine and dextrin, co-evaporate contains a residual organic solvent. In general, any organic solvent capable of dissolving cladribine and cyclodextrin (at least partially, but preferably completely) is suitable for preparing a co-volatilized substance.

Water is not considered an organic solvent.

In a preferred embodiment, an organic solvent is used with a relative dielectric constant (ε) of 3-40, preferably 4-38, more preferably 5-35, even more preferably 8-32, measured at 20 ° C.

In general, suitable organic solvents can be selected from C3-C6 ketones, C5-C9 aliphatic or aromatic hydrocarbons, optionally substituted, for example, halogen, C3-C6 ester, C2-C6 alcohol, C2-C6 ether, dimethylacetomide, dimethylformamide , dimethyl sulfoxide, N-methyl-2-pyrrolidone (NMP) and mixtures thereof. Preferably, the organic solvent is an alcohol, preferably a C2-C6 alcohol, more preferably ethanol and isopropyl alcohol. Ethanol is particularly preferred.

Finally, another aspect of the present invention is the use of an organic solvent with a relative dielectric constant of 3-40, measured at 20 ° C.

Typically, the organic solvent may contain mixtures of two or more of the above solvents.

The method for preparing co-evaporate according to the present invention includes the steps of:

i) dissolving cyclodextrin in an aqueous-alcoholic solution;

ii) dissolving cladribine in hydroalcoholic cyclodextrin;

iii) removing the solvent (in whole or in part).

In step (i), the cyclodextrin is completely dissolved in the aqueous alcohol solution.

In step ii) cladribine is gradually added and completely dissolved in a solution of organic solvent and water with stirring. The dissolution can be carried out at an elevated temperature. Temperatures of 25-80 ° C are preferably used, more preferably 25-60 ° C, optimally 25-40 ° C.

The amount of organic solvent used in steps i) and ii) to dissolve cladribine and dextrin usually affects the process in terms of process time and cost.

In a preferred embodiment, cladribine is dissolved in an amount of 0.1-38 mg / ml of an aqueous alcoholic solution, more preferably 0.5-30 mg / ml, even more preferably 0.5-25 mg / ml, most preferably 1-20 mg / ml. In this case, the alcohol content in the aqueous-alcoholic solution is from not less than 5 vol.% To not more than 95 vol.%.

In a preferred embodiment, dextrin is dissolved in an amount of 10-1000 mg / ml of an aqueous alcoholic solution, more preferably 20-500 mg / ml, even more preferably 35-400 mg / ml, most preferably 40-350 mg / ml.

The organic solvent is completely or partially removed, so that the remaining amount of the solvent is contained in the resulting co-evaporate. Preferably, the co-evaporate contains a residual organic solvent in an amount of 0.1-10% w / w, more preferably 0.5-5% w / w, even more preferably 0.6-4% w / w, optimally 0 , 7-2.0% w / w based on the total weight of the evaporated solids.

In another preferred embodiment, the starting compounds and process conditions are selected so that the resulting amorphous co-evaporate contains:

(a) 0.1-30 wt%, preferably 1-20 wt%, more preferably 5-15 wt% cladribine,

(b) 70-99.9 wt%, preferably 80-99 wt%, more preferably 85-95 wt% cyclodextrin, and

(c) 0-20 wt%, preferably 0.1-10 wt%, more preferably 0.5-5 wt% organic solvent based on the total weight of co-evaporate.

In step iii), the organic solvent can be removed at elevated temperature and / or under reduced pressure. The solvent can be removed at a pressure of 0.1-1000 mbar, preferably 1-200 mbar, more preferably 5-100 mbar, even more preferably 10-50 mbar, in particular 30-40 mbar. On a laboratory scale, the time for step iii) can be about 0.5-2.0 hours, preferably about 90 minutes. The removal of the organic solvent can be carried out, for example, in a vacuum rotary evaporator, for example a Rotavapor Büchi®.

Preferably, the solvent is removed at a temperature of 30-70 ° C, preferably 30-65 ° C, more preferably 30-45 ° C. Evaporation time lasts from tens of minutes to hours. Residual solvent in amorphous co-evaporate is determined by gas chromatography.

The process of the present invention, as shown above, results in the formation of an amorphous co-evaporate containing cladribine, cyclodextrin and a residual organic solvent.

The term "amorphous co-evaporate" is used for the purposes of the patent application to mean a solid that does not exhibit crystalline properties under RPD (X-ray powder diffractometry) conditions. Compared with crystalline forms, it has an undeniable advantage due to its higher solubility.

The inventive method leads to obtaining a stable, rapidly soluble amorphous complex obtained by co-evaporation of cladribine and cyclodextrin (co-evaporate) in the form of a material of white or translucent (milky white) color. Co-evaporate exhibits physicochemical properties (FTIR spectra (Fourier transform infrared spectroscopy), RPD, 13 C NMR, TG / DTA) equivalent to the sample obtained in accordance with the example given in US patents 8,785,415 and 7,888,328.

The present invention also relates to other co-evaporates that can be obtained by the claimed method. With regard to said co-evaporates, all of the above remarks regarding preferred embodiments apply (eg, with respect to the type and amount of organic solvent, type and amount of cladribine, as well as the type and amount of cyclodextrin, solvent removal conditions, etc.).

The resulting co-evaporate of the present invention can be administered in the form of pharmaceutical preparations.

Preferably, the oral dosage form is in the form of tablets, more preferably in the form of uncoated tablets. The tablets are preferably prepared by direct compression.

One or more pharmaceutically acceptable excipients such as fillers, binders, lubricants, lubricants, release agents, and disintegrants may be used in the pharmaceutical composition of the present invention. With regard to the aforementioned pharmaceutically acceptable excipients, the application contains references to the book "Lexikon der Hilfsstoffe fur Pharmazie, Kosmetik und angrenzende Gebiete" published by G.P. Fiedler, 4th edition, Edito Cantor, Aulendorf and earlier editions, and Guide to Pharmaceutical Excipients, 3rd edition, edited by Arthur H. Kibbe, American Pharmaceutical Association, Washington, USA. and Pharmaceutical Press Service, London.

Brief Description of Drawings

The invention is illustrated by the following drawings.

FIG. 1 shows the structures of cladribine hydrate and its location in the basal cell.

FIG. 2 shows a comparison of the RPD of the used forms of cladribine, mechanical mixture, HPbCD and the diffraction pattern of the obtained amorphous co-evaporate. On the basis of the RPD, it is impossible to distinguish the co-evaporate obtained in accordance with this patent from the sample in accordance with US patent 7888328, therefore only one typical diffractogram of the final product is shown, regardless of the method of preparation.

FIG. 3 shows the results of the analysis of co-evaporate and the sample by the TG / DTA method in accordance with US patent 7,888,328.

FIG. 4 shows the FTIR spectra of cladribine, HPbCD, mechanical mixture, co-evaporate and sample in accordance with US patent 7,888,328.

FIG. 5 shows the 13 C NMR spectra of a mechanical mixture of cladribine / HPbCD, standard HPbCD, co-evaporate and a sample in accordance with US patent 7,888,328.

FIG. 6 shows the detection of residual 13C ethanol in co-evaporate by liquid-phase NMR.

FIG. 7 shows the results of a comparative dissolution of co-evaporate and a sample in accordance with US patent 7,888,328 in dissolution solutions with pH 1.2 and 6.8.

Implementation of the invention

Below is a more detailed description of the claimed invention. The present invention can be subjected to various changes and modifications that are clear to a person skilled in the art based on reading this description. Such changes do not limit the scope of the claim.

All reagents used are commercially available, all procedures, unless otherwise stated, were carried out at room temperature or ambient temperature, that is, in the range from 18 to 25 ° C.

Example 1 Preparation of cladribine co-evaporate with cyclodextrin using the known crystal form of cladribine I (TW 201117816 A): 6000 mg of hydroxypropyl-β-cyclodextrin (HPBCD) was dissolved in 15 ml of distilled water. After dissolution, 96% ethanol was added to the solution in a volume ratio of water: ethanol 3: 2. Finally, 500 mg of the crystalline form of cladribine I was added, the resulting suspension was heated and stirred at 25-35 ° C using a magnetic stirrer until a clear solution was obtained. The time required for the dissolution of cladribine was approximately 15 minutes. The weight ratio of HPBCD: API was 12: 1. Then the sample was placed on a rotary evaporator with a water bath temperature of 40 ° C, where it was dried in vacuum for 1 hour. Then the sample was placed in a dry oven and dried overnight at 45 ° C.

Example 2. Obtaining co-evaporate of cladribine with cyclodextrin using the amorphous form of cladribine: 6000 mg of hydroxypropyl-β-cyclodextrin (HPBCD) was dissolved in 15 ml of distilled water. After dissolution, 96% ethanol was added to the solution in a volume ratio of water: ethanol 3: 2. Finally, 500 mg of the amorphous form of cladribine was added, the resulting suspension was heated and stirred at about 25-35 ° C using a magnetic stirrer until a clear solution was obtained. The time required for the dissolution of cladribine was approximately 7 minutes. The weight ratio of HPBCD: API was 12: 1. Then the sample was placed on a rotary evaporator with a water bath temperature of 40 ° C, where it was dried in vacuum for 1 hour. Then the sample was placed in a dry oven and dried overnight at 45 ° C.

The amorphous form of cladribine was obtained in accordance with Example 3 in patent application WO 2011/054179 A1. The presence of an amorphous form of cladribine was confirmed by RPD.

Example 3 Preparation of cladribine co-evaporate with cyclodextrin using a new hydrated cladribine polymorph: 1200 mg of hydroxypropyl-β-cyclodextrin (HPBCD) was dissolved in 15 ml of distilled water. After dissolution, 96% ethanol was added to the solution in a volume ratio of water: ethanol 3: 2. Finally, 100 mg of a new crystalline form of cladribine hydrate was added, the resulting suspension was heated and stirred at about 25-35 ° C. using a magnetic stirrer until a clear solution was obtained. The weight ratio of HPBCD: API was 12: 1. The time required for the dissolution of cladribine was about 8 minutes. The sample was then placed on a rotary evaporator with a water bath temperature of 45 ° C, where it was dried under vacuum for 1 hour. Then the sample was placed in a dry oven and dried overnight at 40 ° C.

The crystal structure of the new cladribine polymorph and its spatial structure were confirmed by XRD and XRD (Fig. 1).

The use of cladribine of different crystallinity does not affect the production of co-evaporate, but only affects the time required for the dissolution of the crystalline form in a cyclodextrin solution in a water-alcohol solution. To obtain a new crystalline form, 100 mg of form I of cladribine was dissolved with stirring in an excess of solvent - 10 ml of 96% EtOH, 15 ml of distilled H ₂ O at an elevated temperature (60 ° C). The solution was concentrated by evaporation in vacuo to a volume of 10 ml. The concentrated solution was poured in a continuous thin layer onto a Petri dish and allowed to evaporate freely at room temperature.

The structure of cladribine monohydrate was characterized by structural analysis of a single crystal with a Cu-Kα radiation source and at a measurement temperature of 200 K. Cladribine monohydrate crystallizes in the orthorhombic system in space group P212121. Chiral center configuration - C11-R; C13-S; C14-R; C31-R; C33-S; C44-R. Lattice parameters of cladribine monohydrate:

a = 7.1448 (2) Å

b = 13.4926 (4) Å

c = 26.5439 (6) Å

α = 90.00 °

β = 90.00 °

γ = 90.00 °

V = 2558.88 (12) Å3

Z = 8

R = 0.0395

Density (g / cm ³ ) = 1.577

Example 4. Obtaining a sample in accordance with example 2 of US patent 7888328 (comparative example)

17.25 g of hydroxypropyl-β-cyclodextrin (to obtain an approximately 17% solution) was dissolved in 82.5 ml of distilled water, then 1875 mg of cladribine was added, the mixture was stirred at 48 ° C for nine hours, after which it was stirred for another 9 hours at room temperature. Any undissolved cladribine was removed by filtration. After filtration, the solutions were poured into vials for lyophilization, partially capped and lyophilized in accordance with the conditions described in the patent.

Example 5. X-ray powder diffractometry

X-ray powder diffractometry of cladribine, cladribine-cyclodextrin co-evaporates prepared according to Examples 1 and 3, and a sample prepared according to Example 2 of US patent No. 7,888,328 was performed using standard normal radiation Cu-Kα. Reflection peaks were recorded in the 2-theta range of 5-40 degrees and 5-80 degrees, respectively. XRD results of both cladribine crystalline forms tested are shown in FIG. 2a (the X-ray of Form I is shown at the top of the figure, the X-ray of cladribine monohydrate is at the bottom). FIG. 2b illustrates the RPD of the HPbCD (Hydroxypropyl-beta-cyclodextrin) standard. FIG. 2c illustrates an X-ray diffraction pattern of a mechanical mixture obtained by simply mixing crystalline Form I of cladribine and HPbCD. Due to the high concentration of HPbCD, which partially masks the cladribine response, the peaks corresponding to cladribine are indicated by vertical lines for better orientation. FIG. 2d illustrates XRD of co-evaporate. Regardless of the crystal structure of the starting cladribine, all samples of co-evaporates, and the sample prepared in accordance with the example of US patent No. 7,888,328 show XRD of an amorphous product.

Based on the data obtained, it can be unambiguously asserted that neither the use of a substance with a different crystal structure, nor the method of obtaining a sample, affect the amorphous nature of the final product.

Example 6. Thermogravimetric Analysis / Differential Thermal Analysis (TGA / DTA)

The TGA profiles of cladribine, HPbCD, mechanical mixture, co-evaporate, and a sample prepared in accordance with US Pat. No. 7,888,328 at 25-300 ° C. are shown in FIG. 3a. The TGA curve of cladribine indicates that the degradation process begins at a temperature of about 200 ° C (Fig. 3a). In the case of HPbCD, due to dehydration, the weight loss was approximately 6% in the temperature range of 30 to 140 ° C. TG analysis of a sample in accordance with US Pat. No. 7,888,328 showed a water loss in the range 20-100 ° C and a degradation process starting at about 250-200 ° C). The TG curve of the mechanical mixture shows a multi-stage decomposition path. The first phase in the range of room temperature - 100 ° C is associated with the loss of water from HPbCD, and the second phase, observed at temperatures above 200 ° C, is associated with the decomposition of cladribine. Based on a comparison of the TG decomposition phase for the co-vaporized substance and the sample in accordance with US Pat. No. 7,888,328, both samples decompose more slowly than the mixture. The demonstrated higher thermal stability of the complex is a sign of interaction between HPbCD and cladribine. The TGA of co-evaporate shows a similar result to the TGA of the sample in accordance with US Pat. No. 7,888,328. To better understand the thermal behavior of the samples, DTA was performed (FIG. 3b). Cladribine standard in differential scanning calorimetry (DSC) demonstrates two endothermic phenomena. The first endothermic event at a temperature of about 206 ° C characterizes the onset of thermal decomposition of cladribine and corresponds to a transition to a molten state. With a second endothermic event, at about 212 ° C, the formation of a degradation product of cladribine is likely.

The DTA profile HPbCD corresponds to water loss.

The DTA curves of co-evaporate and the sample in accordance with US Pat. No. 7,888,328 show an endothermic phenomenon due to water loss in the HPbCD (40-140 ° C). In addition, both samples exhibit endothermic events at approximately 200 ° C, which can be caused by residual unbound cladribine. The absence of thermal phenomena typical of pure cladribine means the loss of the crystalline nature of cladribine when it is included in the complex. This is indirect evidence of the interaction of cladribine with HPbCD. Both test specimens, i.e. both co-evaporate and the sample in accordance with US Pat. No. 7,888,328 can be considered similar based on the results of the TG / DTA assays.

Example 7. Fourier transform spectroscopy (FTIR spectra)

To obtain a sample, 0.58 g of potassium bromide was weighed and ground in a mortar with 0.005 g of a sample of the dosage form obtained in accordance with Example 1 and Example 4. The mixture was weighed again and quantitatively transferred to a press, made into a tablet, placed in a Petri dish and stored in the dehumidifier. A tablet containing 0.58 g of potassium bromide was used to measure the reference spectrum. The reference spectrum of a potassium bromide tablet serving as a background was measured using a Bruker Vertex 80 spectrometer. The spectra of the tablets of both prepared samples were then measured with a background reading. The results are shown in FIG. 4a-4e. FIG. 4a shows the FTIR spectrum of crystalline Form I of cladribine. FIG. 4b shows the FTIR spectrum of the HPbCD standard. FIG. 4c shows a mechanical mixture made by simply mixing cladribine with HPbCD. The IR spectrum of the mechanical mixture can be interpreted as the “sum” of the spectra of pure cladribine and pure HPbCD with sharp vibrational bands for pure cladribine, which indicates that the molecules are structurally defined and regular (in the crystal field). This is a clear demonstration of the presence of two separate phases - crystalline cladribine and HPbCD. In contrast, the FTIR spectra of co-evaporate (Fig. 4d) and the sample in accordance with US patent 7,888,328 (Fig. 4e) show clear differences, especially with respect to the markers of the crystalline phase of cladribine observed in the mechanical mixture. The origin of the amorphous phase can be explained by the interaction of cladribine with HPbCD, which protects cladribine molecules from crystallization. As seen in FIG. 4d and 4e, the FTIR spectra of the compared samples showed no significant change and the samples can be considered very similar based on the FTIR spectra.

Example 8 The behavior of the solid phase 13 C NMR was investigated using a solid state NMR spectrometer Bruker Avance III HD 500 WB / NMR. Solid state NMR spectra of a mechanical mixture of cladribine with HPbCD, cladribine co-evaporate and a sample prepared in accordance with US Pat. No. 7,888,328 are shown in FIG. 5a and 5b and indicate that there is no intermolecular interaction between cladribine and HPbCD and that the mixture consists of differently located molecular domains of each individual component. Comparison of the spectra in Fig. 5b (top to bottom - the spectrum of the sample in accordance with US patent 7888328, standard HPbCD, co) indicates that there is no shift for the HPbCD signals, and practically no cladribine resonances are detected (in the spectral region of approximately 40 ppm, 120 ppm and 160 ppm) ... This indicates the absence of the crystalline domain of cladribine and that the sample consists of cladribine dispersed at the molecular level in HPbCD. As seen in FIG. 5b, no differences were found between the spectra of co-evaporate and the sample according to US Pat. No. 7,888,328, and therefore the samples can be considered similar.

Example 9. Detection of Residual Solvent

Residual solvent was determined by gas chromatography and the data obtained were confirmed by liquid NMR. For determination by gas chromatography, a gas chromatograph with a flame ionization detector and helium (99.999%) as a carrier gas was used. The presence of a trace amount of ethanol in an amount close to the detection limit of the instrument was demonstrated using a gas chromatograph. Even liquid phase NMR did not show the presence of residual ethanol. Only the use of 13C-Ethanol in the preparation of the co-evaporated substance made it possible to detect trace amounts of solvent in the sample (Fig. 6). Based on these measurements, it can be argued that the co-evaporate obtained by the inventive method contains only trace amounts of residual solvent and, therefore, approaches the composition of the sample prepared in accordance with the method according to US patent 7888328, which was obtained only from an aqueous solution of cyclodextrin.

Example 10. Comparative dissolution

Comparative dissolution was performed in three basic dissolution buffers (0.1 M HCl, pH 1.0; in acetate buffer, pH 4.5, and phosphate buffer, pH 6.8) using dissolution instrument II, at 50 rpm , at 37 ° C. Samples were taken at 5 minute intervals. Mavenclad 10 mg was used as a reference product, the tested product was tablets prepared from amorphous co-evaporate using excipients listed in the package insert for the original product (Mavenclad). FIG. 7 shows a comparison of the dissolution profiles in buffers with pH 1.0 and 6.8, and the dissolution profile in a buffer with pH 1.0 is considered discriminatory due to the high sensitivity of cladribine to low pH levels. As seen in FIG. 7, both test formulations show consistency of dissolution parameters in both dissolution buffers used.

Claims (17)

1. A method of obtaining an amorphous complex of cladribine with cyclodextrin, including: (i) dissolving cyclodextrin in an aqueous alcohol solution, (ii) dissolving cladribine in an aqueous-alcoholic solution of cyclodextrin, (iii) complete or partial removal of the solvent. 2. The method according to claim 1, characterized in that the resulting amorphous complex contains: a) cladribine, b) cyclodextrin and c) optionally residual organic solvent. 3. The method according to PP. 1 and 2, characterized in that the resulting amorphous complex contains: a) 1-20 wt%, preferably 5-15 wt% cladribine, b) 80-99 wt%, preferably 85-95 wt% cyclodextrin; and c) 0-10 wt%, preferably 0.5-2 wt% organic solvents. 4. A method according to any one of claims. 1-3, characterized in that alcohol C2-C6 is used for the preparation of an aqueous-alcoholic solution. 5. The method according to claim 4, characterized in that ethanol or isopropyl alcohol is used as the alcohol. 6. The method according to any one of claims. 1-5, characterized in that in step (iii) the solvent is removed at a temperature of 30-60 ° C and a pressure of 0.1-1000 mbar, preferably 1-200 mbar, more preferably 5-100 mbar, even more preferably 10-50 mbar, in particular 30-40 mbar. 7. A method according to any of the preceding claims, wherein the cyclodextrin is hydroxypropylated beta-cyclodextrin. 8. A method according to any one of claims, characterized in that the obtained amorphous complex of cladribine with cyclodextrin is used for the preparation of pharmaceutical compositions for oral administration.

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