Field of the Invention The invention relates to novel solid forms of amorphous dolutegravir of formula I, their preparation methods and use in a drug form. These solid forms can be advantageously used to increase the chemical and polymorphic stability of amorphous dolutegravir.

(I)

Dolutegravir is indicated in combination with other antiretroviral medications for the treatment of adult and adolescent patients over 12 years of age infected by the human immunodeficiency virus (HIV). Dolutegravir inhibits HIV integrase by binding to the active site of the integrase and by blocking the transfer processes of integration of the retroviral deoxyribonucleic acid (DNA), which is important for the replication cycle of HIV.

Background Art Dolutegravir is first mentioned in the patent application WO2006116764, which does not mention any details of the character of the solid form of the product. The patent application WO2010068253 already describes crystalline sodium salts of dolutegravir, the anhydrous salt and monohydrate. There, these salts are characterized with the use of XRPD and IR. The anhydrous sodium salt in a crystalline form is also included in the original medication Tivicay. The last known solid form, i.e. the amorphous sodium salt of dolutegravir, is described in the patent application WO2013038407, using the XRPD, DSC, TGA, IR and Raman spectroscopy methods. Preparation of other salts has not been published yet. Disclosure of the Invention

The amorphous form of dolutegravir is easy to obtain with the use of various preparation methods. The glass transition temperature of amorphous dolutegravir is not relatively low; however, stabilization in the form of a solid solution or dispersion contributes to its chemical as well as polymorphic stabilization. At higher temperatures and elevated relative humidity, especially solid solutions of dolutegravir are more stable and recrystallization and chemical degradation of dolutegravir cannot occur. For stabilization of the amorphous form of dolutegravir solid solutions and dispersions with chemicals can be used that can provide a higher glass transition value and thus higher chemical and polymorphic stability. Chemical compounds that can be used in this manner comprise polymers, copolymers, saccharides, oligosaccharides, polysaccharides, fats, waxes and urea, preferably polymers. The prepared solid solution or solid dispersion then exhibits higher polymorphic and chemical stability at elevated temperatures and increased relative humidity.

The invention provides a mixture in the form of a melt, containing dolutegravir and at least one pharmaceutically acceptable excipient. The selection of the excipient for this mixture is governed by the requirement for stability of the end product. A preferred excipient is such where the final mixture achieves a glass transition temperature higher than 40°C, more preferably higher than 70°C. Suitable excipients for dolutegravir are hydroxypropyl cellulose, hydroxypropyl methylcellulose, hypromellose acetate succinate, l-ethenyl-2-pyrrolidinone homopolymer (e.g. povidone PVP K30), polyvinyl caprolactam-polyvinyl acetate- polyethylene glycol copolymers (e.g. Soluplus™), poly(methacrylic acid, methyl methacrylate) 1:2 (e.g. Eudragit S100, Eudragit L100), a- hydro-ro-hydroxypoly(oxy-l,2-ethanediyl) (e.g. PEG 6000), ethyl ester of acetic acid with l-ethenyl-2-pyrrolidinone (e.g. Copovidone VA64), D-(+)-glucose, D-(+)-saccharose or urea, especially hypromellose acetate succinate, Eudragit SI 00, Eudragit LI 00 and Povidone PVP K30.

Brief Description of the Drawings

Fig. 1: DSC record of the solid solution of dolutegravir - HPMC AS

Fig. 2: DSC record of the solid solution of dolutegravir - PVP K30

Fig. 3: DSC record of the solid solution of dolutegravir - Eudragit SI 00 Fig. 4: XRPD pattern of the solid solution of dolutegravir - HPMC AS

Fig. 5: XRPD pattern of the solid solution of dolutegravir - PVP K30

Fig. 6: XRPD pattern of the solid solution of dolutegravir - Eudragit SI 00 Detailed description of the invention

A crystalline solid substance is characterized by a regular long-distance structure arrangement. On the other hand, amorphous solid substances do not exhibit this arrangement. The molecular arrangement of an amorphous solid substance may be represented by "frozen liquid" with rheological properties of a solid substance.

A solid mixture, consisting at least of two components - the active pharmaceutical ingredient (API) and another at least one chemical compound (matrix), can have several forms. To make the explanation of used terms simpler, the matrix for API stabilization is considered to consist of one component only. In fact, this matrix may consist of one, two, or more components (chemical compounds). As components of a matrix for solid mixtures, compounds of the type of polymers, copolymers, saccharides, oligosaccharides, polysaccharides, fats, waxes or urea can be preferably used.

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

A typical "amorphous solid dispersion" then represents a solid composition where the active pharmaceutical ingredient (API) and the matrix show an amorphous character, measured by XRPD. Measured by differential scanning calorimetry this "amorphous solid dispersion" exhibits at least two glass transitions (Tg), one for the dispersed component (pharmaceutically active ingredient) and the other one for the matrix while the number of Tg's depends on the number of the components of the matrix.

In case that both the amorphous components (API and matrix) are mixed on the molecular level and the resulting solid mixture shows just one glass transition temperature (Tg), measured by differential scanning calorimetry, it is a special solid mixture, referred to as a "solid solution".

As mentioned above, compared to crystalline solid substances, amorphous solid substances have a different internal structure and a larger surface area, and therefore they exhibit a higher solubility. If the solubility and biological availability of pharmaceutically active substances need to be increased, it is more preferable to prepare them in an amorphous form. If the temperature of a crystalline material reaches the melting point, its phase changes from the solid phase to the liquid phase. When this melt is cooled again, the crystalline structure is restored. However, if the melt is cooled at a sufficiently high rate, crystallization may be prevented by formation 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 a much higher mobility than in the vitreous state, as described by Remington in the publication: The Science and Practice of Pharmacy, Pharmaceutical Press, 21 ^nd edition.

Since molecules in the vitreous state also exhibit certain mobility, it is advantageous 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, the amorphous form of the API should be preferably stabilized by increasing of the glass transition temperature (Tg) 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 will be polymorphically and chemically more stable at elevated temperatures a higher relative humidity. Even in cases when the glass transition temperature is not increased, the existence of a solid solution, or solid dispersion, may substantially contribute to stabilization of the API.

The glass transition temperature of amorphous dolutegravir is 91°C and in its non-stabilized condition it may be subject to degradation during storage at an elevated temperature and humidity. For this reason, it is advantageous to stabilize the amorphous form of dolutegravir in the form of a solid solution or solid dispersion to prevent chemical degradation and recrystallization. The prepared solid mixture then exhibits higher polymorphic and chemical stability at elevated temperatures and increased relative humidity.

A possibility of stabilizing amorphous dolutegravir consists in creating solid compositions with polymers, copolymers, saccharides, oligosaccharides, polysaccharides, fats, waxes and urea, preferably especially with polymers. These polymers may come from the group of polymers that are soluble or insoluble in water. Typical polymers soluble in water for stabilization 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 polymers insoluble in water for stabilization of dolutegravir are methylcellulose, ethylcellulose, polymethacrylates, hypromellose phthalate, hypromellose succinate, hypromellose acetate succinate (HPMC AS), cellulose acetate phthalate, carboxymethyl cellulose etc. An advantage of these polymers is the fact that their solubility is dependent on the pH value of the solution and their use makes it possible to influence releasing of the pharmaceutically active ingredient depending on pH of the alimentary tract.

There are a number of preparation methods of stabilized amorphous forms of dolutegravir. One of the preparation methods of stabilized amorphous forms of dolutegravir consists in the dissolution process. In a common dissolution process the active substance is dissolved in a solvent or in any mixture of solvents. The solvent may be water or any organic solvent. As an example of suitable organic solvents methanol, ethanol, ethyl acetate, isopropyl alcohol, acetone, dichloromethane, tetrahydrofuran etc. may 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 matter is produced. The solvent can be removed by means of a rotary vacuum evaporator, fluid granulation, spray drying, electrospinning, solvent freeze-drying etc.

Other options of preparation of stabilized amorphous substances are methods without the use of a solvent. In these processes the active pharmaceutical ingredient (dolutegravir) is mixed with a stabilizing substance (e.g. a polymer). This mixture is heated up and melted, producing a melt. Common temperatures for the formation of 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 its processing. The melt is subsequently cooled down, which produces an amorphous solid substance. As some examples of these processes hot melt extrusion, hot melt granulation, high shear mixer, fluid bed granulation without the use of a solvent etc. may be mentioned.

This invention focuses on the preparation of a pharmaceutical mixture containing amorphous dolutegravir with polymers, copolymers, saccharides, oligosaccharides, polysaccharides, fats, waxes and urea, preferably especially with polymers. For the preparation of polymer stabilized amorphous solid forms of dolutegravir the following polymers can be advantageously used: polyvinyl pyrrolidone (PVP), copovidone (Kollidon VA64), hydroxypropyl cellulose (Klucel), hydroxypropyl methylcellulose (Methocel), derivatized hydroxypropyl methylcellulose (e.g. HPMC AS), derivatives of polymethacrylate (Eudragit LI 00, Eudragit SI 00) and copolymers of polyvinyl caprolactam - polyvinyl acetate - polyethylene glycol (Soluplus™), especially hypromellose acetate succinate, Eudragit LI 00, Eudragit SI 00 and Povidone PVP K30.

The most commonly used polymers in this invention are polyvinyl pyrrolidone (PVP K30) with the molecular weight of approx. 50,000 Da (g/mol), Methocel E5 (HPMC) with the molecular weight of approx. 22,000 Da (g/mol), Eudragit SI 00 with the molecular weight of approx. 125,000 Da (g/mol), Eudragit LI 00, copovidone (Kollidon VA64), hydroxypropyl cellulose (HPC, Klucel), Soluplus™ and hypromellose acetate succinate (HPMC AS-LF). Out of the group of saccharides and the other substances glucose, saccharose, galactose or urea can be advantageously used.

For the preparation of the amorphous solid forms of dolutegravir (API) the method of removing the solvent by means of a rotary vacuum evaporator or lyophilization (freeze-drying of solvents) was used. Out of all the prepared mixtures Table 1 presents the best solid solutions together with the results of the DSC and X-ray powder analyses.

Table 1:

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

According to the results of the DSC analyses, dolutegravir forms the most stable solid solutions with HPMC AS (Fig. 1), PVP K30 (Fig. 2) and Eudragit SI 00 (Fig. 3). A comparison of the Tg values from the DSC measurements showed that dolutegravir formed the most stable solid solution with Eudragit S100 (Tg 122.3°C).

Also, the results of the X-ray powder analysis proved the presence of only the amorphous form of dolutegravir in the solid solutions with the polymers HPMC AS (Fig. 4), PVP K30 (Fig. 5) and Eudragit SI 00 (Fig. 6).

Load tests were used to observe and compare stability of these three solid solutions containing amorphous dolutegravir.

Amorphous dolutegravir stabilized in the form of a solid solution with HPMC AS exhibits chemical stability under load conditions and no degradation of the API occurs. Partial crystallization of the API only occurs under the extreme load of 80°C at the relative humidity of 75%; under normal conditions the solid solution of dolutegravir - HPMC AS shows polymorphic stability. All the results concerning the stability testing of the solid solution of dolutegravir - HPMC AS are summarized in Table 2. Table 2:

Amorphous dolutegravir stabilized in the form of a solid solution with Povidone PVP K30 only exhibits polymorphic stability under load conditions at a reduced relative humidity. Partial crystallization of the amorphous API occurs at an elevated relative humidity. Chemical stability of amorphous dolutegravir also significantly increases in the solid solution forms and even under extreme load conditions there is no increase of the contents of impurities (see Table 3).

Table 3:

Solid solution of dolutegravir - PVP K30, Tg = 96.1°CHPLC = 99.08%

X-ray HPLC

25°C, 0% RH, 10 days amorphous API 99.06%

25°C, 100% RH, 10 days mixture of amorphous and crystalline

API 99.05%

50°C 0% RH, 3 days amorphous API 99.07%

50°C, 75% RH, 3 days mixture of amorphous and crystalline

API 99.09%

80°C, 0% RH, 3 days amorphous API 98.99%

80°C, 75% RH, 3 days mixture of amorphous and crystalline 99.07%

Amorphous dolutegravir stabilized in the form of a solid solution with Eudragit SI 00 exhibits extreme polymorphic stability under load conditions; no crystalline API was detected under any load conditions and dolutegravir remains in the amorphous form even being loaded by 80°C and the relative humidity of 75%. Chemical stability of amorphous dolutegravir also significantly increases in the solid solution form and a slight increase of the contents of impurities is only observed under the conditions of 80°C and the relative humidity of 75%. All the results concerning the stability testing of the solid solution of dolutegravir - Eudragit SI 00 are summarized in Table 4.

Table 4:

The prepared amorphous solid substances containing dolutegravir, stabilized by polymers, saccharides, oligosaccharides, polysaccharides or urea in accordance with this invention can be used for the preparation of pharmaceutical compositions, especially solid drug forms, e.g. tablets. Such pharmaceutical mixtures can contain at least one excipient from the group of fillers (e.g. lactose), binders (e.g. microcrystalline cellulose), disintegrants (e.g. sodium salt of croscarmellose), lubricants (e.g. magnesium stearate), surfactants etc. These tablets can be coated with common coating compounds, e.g. polyvinyl alcohol or polyethylene glycol.

List of analytical methods

Measurement parameters of XRPD: The diffractograms were measured using 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° 20, increment: 0.02° 2Θ, the measurement was carried out on a flat powder sample that was applied on a Si plate. For the setting of the primary optical equipment programmable divergence slits with the irradiated area of the sample of 10 mm, 0.02 rad Soller slits and a ¼° anti-diffusion slit were used. For the setting of the secondary optical equipment an X'Celerator detector with maximum opening of the detection slot, 0.02 rad, Soller slits and a 5.0 mm anti-diffusion slit were used.

The records of differential scanning calorimetry (DSC) were measured using a Discovery DSC device made by TA Instruments. The sample charge in a standard Al pot (40 μΚ) was between 4 and 5 mg and the heating rate was 5°C/min. The temperature program that was used consists of 1 min of stabilization at the temperature of 0°C and then of heating up to 250°C at the heating rate of 5°C/min (amplitude = 0.8°C and period = 60 s). As the carrier gas 5.0 N ₂ was used at the flow of 50 ml/min.

Chemical purity was measured with the use of liquid chromatography (HPLC):

Device: Waters Acquity UPLC, spectrophotometric detection

Sample preparation: 4.0 mg of the tested sample is dissolved in 10.0 ml of 40% acetonitrile

Column: - dimension: 1 = 0.10 m,□ = 2.1 mm

- stationary phase: Acquity BEH Phenyl (Waters), 1.7 μηι particles

- column temperature: 30°C.

Mobile phase: _^ 4: 10 mM ammonium dihydrogen phosphate, pH 2.5

B: Methanol

Gradient elution:

Detection: spectrophotometer 258 nm Injected quantity: 1.0 μΐ

Sample temperature: 20°C

Examples

The purpose of the following examples is to further elucidate the invention without limiting its scope.

Amorphous dolutegravir was prepared by dissolution of dolutegravir in a volatile solvent and subsequent quick evaporation on a rotary vacuum evaporator. The chemical purity of dolutegravir prepared this way was 98.2% (HPLC), the glass transition temperature was 91°C and XRPD confirmed its amorphous form.

Example 1

Preparation of the amorphous solid form of dolutegravir with HPMC AS

2.5 mg of dolutegravir was dosed into a 250ml flask together with 2.5 g of hydroxypropyl methylcellulose acetate succinate. The mixture was dissolved in a mixture of dichloromethane and methanol at an elevated temperature and under stirring. The completely clear solution was stirred for another 30 minutes at an elevated temperature and subsequently it was completely evaporated on a rotary vacuum evaporator. The final product was further dried in a vacuum drier at 40°C for 12 hours. The glass transition temperature of the solid solution prepared this way was 88.8°C (DSC record in Fig. 1). The X-ray powder pattern of the solid solution of dolutegravir - hydroxypropyl methylcellulose acetate succinate is shown in Figure 4. The HPLC purity of the solid solution prepared this way was 99.01%. Example 2

Preparation of the amorphous solid form of dolutegravir with PVP K30

5 g of dolutegravir was dosed into a 500ml flask together with 5 g of povidone PVP K30. The mixture was dissolved in a mixture of dichloromethane and methanol at an elevated temperature and under stirring. The completely clear solution was stirred for another 30 minutes at an elevated temperature and subsequently it was completely evaporated on a rotary vacuum evaporator. The final product was further dried in a vacuum drier at 40°C for 12 hours. The glass transition temperature of the solid solution prepared this way was 96.1°C (DSC record in Fig. 2), the chemical purity was 99.08% (HPLC). The X-ray powder pattern of the solid solution of dolutegravir - povidone PVP K30 is shown in Figure 5.

Example 3

Preparation of the amorphous solid form of dolutegravir with Eudragit S100

2.5 g of dolutegravir was dosed into a 250ml flask together with 2.5 g of Eudragit SI 00. The mixture was dissolved in a mixture of dichloromethane and methanol at an elevated temperature and under stirring. The completely clear solution was stirred for another 30 minutes at an elevated temperature and subsequently it was completely evaporated on a rotary vacuum evaporator. The final product was further dried in a vacuum drier at 40°C for 12 hours. The glass transition temperature of the solid solution prepared this way was 52.5°C (DSC record in Fig. 3), the chemical purity was 99.03% (HPLC). The X-ray powder pattern of the solid solution of dolutegravir - Eudragit SI 00 is shown in Figure 6. Example 4

Pharmaceutical composition of the product - core

The following ingredients were placed into a homogenizer: solid solution of dolutegravir - povidone PVP K30, mannitol, microcrystalline cellulose, povidone and water. The mixture was homogenized for 15 min at 20 rpm. Finally, sodium stearyl fumarate and sodium glycolate was added and the mixture was homogenized for another 3 min at 20 rpm. The tabletting matter produced in the above mentioned way was compressed in a rotary tabletting machine and used for the production of cores with the approximate weight of 310 mg. The obtained cores may possibly be coated (a mixture of hypromellose, PEG, talc, titanium dioxide, iron oxide).