Field of the Invention The invention relates to a pharmaceutical formulation of the novel polymorphic form 3 of ixazomib citrate of formula I:

I (Form 3)

Form 3, as compared to the hitherto known form 1 of ixazomib citrate of formula I, disclosed in the patent WO 2009/154737, has turned out to be a polymorphically more stable form, which also makes it more suitable for use in ixazomib citrate formulation.

Background Art

Ixazomib is a novel member of the group of proteasome inhibitors with a structure belonging to the group of peptide boronic acids, now also known under the commercial name of Ninlaro. Ixazomib citrate is currently approved for use in combination with lenalidomide and dexamethasone, intended for the treatment of patients with multiple myeloma after at least one prior therapy.

An advantage of ixazomib citrate, compared e.g. to bortezomib is that thanks to stabilization of the boronic acid in the form of a mixed ester-anhydride with citric acid the substance can also be administered in the oral form. Thus, ixazomib citrate is the first and so far the only orally administered drug of this kind, used for the treatment of multiple myeloma.

Boronic acids are sometimes difficult to prepare in the pure form. In conditions that are favorable for dehydration, boronic acids form cyclic anhydrides and are often sensitive to light. Therefore, boronic acids are advantageously stabilized with a complexing agent, e.g. an a- or β-hydroxy acid (WO2009/154737), or by preparation of precursors with azanediylbis alcohols (WO 2012/177835, WO 2011/087822A1), which enhances their stability and makes it possible to prepare a drug form, suitable for oral administration. Ixazomib citrate and a method of its preparation was first described in the patent application WO 2009/154737.

A preparation method of isomers of ixazomib citrate form 1 or 2 from boroxine III is described in the patent application WO 2009/154737 and is illustrated by Diagram 1. Di ram 1

II (form 2)

Boroxine III, or its free boronic acid is subjected to a reaction with citric acid in a solvent at an elevated temperature; after cooling, the crystallized product is isolated by filtering. Depending on the execution conditions of this reaction, form 1 of formula I, or form 2 of formula II can be obtained, both characterized by NMR, MS, X-ray powder diffraction and the DSC (differential scanning calorimetry) and TGA (thermogravimetric analysis) methods

If after a reaction of boroxine III with citric acid in ethyl acetate at 74°C the reaction mixture is subjected to uncontrolled cooling, it may lead to formation of the 5-member isomeric form 1 (melting point 198.8°C) while controlled cooling of the reaction mixture to the laboratory temperature or to 40°C leads to the formation of the more stable isomeric form 2 (melting point 219.9°C). Form 2 can also be prepared through a reaction of the compound III with citric acid and crystallization from various solvents (tetrahydrofuran, acetonitrile, methyl /so-butyl ketone, 2-methyltetrahydrofuran, acetone) and subsequent addition of the ethyl acetate as an antisolvent.

Disclosure of the Invention

The principle of the invention is a pharmaceutical formulation containing ixazomib citrate in crystalline form 3 as the active ingredient and at least one pharmaceutically acceptable auxiliary substance. Form 3 is a new polymorphic form of ixazomib citrate of formula I and exhibits the characteristic reflections in an X-ray powder patterns with the use of CuKa radiation: 5.4; 10.9; 12.4; 18.7 and 22.6 ± 0.2° 2-theta.

These characteristic and the other measured reflections are presented in Table 1. The X-ray pattern is included in the Appendix as Figure 1.

Table 1 : Table of characteristic peaks:

Pos. Rel. Int.

[°2Th.] d [A] [%]

5.44 16.226 100.0

7.47 11.824 6.1

10.91 8.106 29.6

12.06 7.334 6.7

12.44 7.112 15.5

16.42 5.393 6.4

17.19 5.153 8.3

18.68 4.746 29.2

19.02 4.663 10.2

19.46 4.557 7.5

20.77 4.274 10.4

21.47 4.135 5.8

21.98 4.041 4.1

22.60 3.931 22.2

23.54 3.776 7.3 Pos. Rel. Int.

[°2Th.] d [A] [%]

24.31 3.659 3.1

25.14 3.540 6.3

25.64 3.471 4.0

26.34 3.380 8.5

26.63 3.345 6.6

28.06 3.178 2.9

29.56 3.019 2.2

31.13 2.871 2.7

33.27 2.691 4.2

34.31 2.611 2.7

34.89 2.570 6.9

The new form 3 of ixazomib citrate of formula I proved to be a chemically and polymorphically stable form of isomer I of ixazomib citrate in pre-formulation experiments. Contrary to that, form 1 of ixazomib citrate of formula I, indicated in the patent WO 2009/154737, turned out to be polymorphically unstable under certain conditions and its conversion to ixazomib citrate of form 2 of formula II was observed. In a preferred embodiment, the pharmaceutical formulation according to the invention is packed in air-tight packages as an AI/AI blister pack.

The excipients are preferably processed in such a way as to have a low content of moisture, e.g. less than 4%.

Detailed description of the Invention

The present invention relates to preparation of the solid pharmaceutical dosage form comprising ixazomib citrate in crystalline form 3, which can preferably be packed into a gas non-permeable packaging.

One embodiment of the present invention comprises a pharmaceutical formulation with ixazomib citrate form 3 with an acceptable stability. Pharmaceutical formulations are preferably packed into a gas non-permeable packaging. Preferred gas non- permeable packaging is AI/AI blister.

A pharmaceutical formulation comprising ixazomib citrate form 3 typically comprises one or more excipients. Though in general various excipients could be used, it is especially favorable to use excipients with low amount of residual water. In this invention an excipient with low amount of residual water is defined as an excipient, which contains not more than 4% w/w of water. The water content can be measured by a loss on drying apparatus. An example of such apparatus is for example from the firm Sartorius. Amount of water is measured at conditions 105°C for 10 minutes.

One of the excipients, which may be used to prepare a pharmaceutical formulation comprising ixazomib citrate form 3 is a filler. Suitable fillers that can be used in preparation of pharmaceutical formulation of ixazomib citrate form 3 may be selected from, but not restricted to calcium hydrogen phosphate, microcrystalline cellulose, monosaccharides, oligosaccharides and sugar alcohols like glucose, fructose, saccharose, lactose monohydrate, lactose anhydrous, mannitol, erythritol, sorbitol, maltitol, xylitol and lactitol, compressible sugar and mixtures thereof. Preferred fillers are microcrystalline cellulose, calcium hydrogen phosphate anhydrous, lactose and mannitol. Most preferred are mannitol and a low moisture microcrystalline cellulose containing no more than 4% w/w of water. The amount of filler used to prepare the composition comprising ixazomib citrate form 3 may comprise 40 - 99% in such a way that the sum of API, filler and all other excipients reaches 100% of the final composition.

The other excipient, which may be used to prepare a pharmaceutical formulation comprising ixazomib citrate form 3 is glidant. Suitable glidants that can be used in preparation of pharmaceutical formulation of ixazomib citrate form 3 may be selected from, but not restricted to magnesium silicate, magnesium oxide, magnesium trisilicate, colloidal silicon dioxide, hydrophobic colloidal silica, sodium stearate, talc and mixtures thereof. Preferred glidants are colloidal silicon dioxide and talc. The amount of glidant used to prepare the composition comprising ixazomib citrate form 3 may be 0.1 - 0%. The other excipient, which may be used to prepare a pharmaceutical formulation comprising ixazomib citrate form 3 is lubricant. Suitable lubricants that can be used in preparation of pharmaceutical formulation of ixazomib citrate form 3 may be selected from, but not restricted to hydrogenated castor oil, light mineral oil, myristic acid, palmitic acid, zinc stearate, stearic acid, hydrogenated vegetable oil, polyethylene glycol, glyceryl monostearate, glyceryl palmitostearate, sodium lauryl sulfate, sodium stearyl fumarate, magnesium stearate and mixtures thereof. Preferred lubricants are stearic acid and magnesium stearate. The amount of lubricants used to prepare the composition comprising ixazomib citrate form 3 may be 0.1 - 10%.

In addition to the above stated, a pharmaceutical formulation comprising ixazomib citrate form 3 may include also other excipients. Examples of other excipients that can be used in preparation of pharmaceutical formulation of ixazomib citrate form 3 may be selected from binders, surfactants, disintegrants etc.

A pharmaceutical formulation comprising ixazomib citrate form 3 is typically an encapsulated product. Suitable capsule shell materials used for encapsulation of pharmaceutical formulation of ixazomib citrate form 3 may be selected from both animal as well as vegetable origin. Some non-binding examples of capsule shell materials of animal origin may be selected from animal protein materials like gelatin. Some non-binding examples of capsule shell materials of vegetable origin may be selected from plant polysaccharides like hydroxypropyl methylcellulose, carrageenan and modified forms of starch.

Brief description of the Drawings

Figure 1 : X-ray powder pattern of ixazomib citrate of form 3.

Figure 2: DSC record of ixazomib citrate of form 3.

Figure 3: TGA record of ixazomib citrate of form 3. Examples

HPLC purity

HPLC column: Ascentis Express C-18 100 x 4.6 mm, 2.7 pm

Mobile phase: A 0.05 mol/l acetic acid, pH adjusted with an ammonia solution to 5.0

B: methanol

Gradient- Time Flow % A % B

(min) (ml/min)

0 0.8 89 11

14 0.8 5 95

15 0.8 5 95

16 0.8 89 11

20 0.8 89 11

Analysis time: 20 minutes

Injected quantity: 5 μΙ

Sample 15°C

temperature:

Column 25°C

temperature:

Detection: UV 230 nm

Sample 5 mg of a sample of the substance is dosed into a 10ml preparation: volumetric flask and dissolved in 2 ml of methanol. The flask is filled with water up to the line and stirred.

Analytes: Compound: Retention time (min) Negligibility threshold

TBTU 2.9 0.03%

DCBA 5.0 0.03%

IXA-2 5.2 0.03%

IXA-2 amide 6.3 0.03%

N7 10.1 0.03%

IXA-4 10.2 0.03%

X-ray powder diffraction

The diffractogram was obtained using an XPERT PRO MPD PANalytical powder diffractometer, used radiation CuKa (λ = 0.1542 nm (1.542 A)), excitation voltage: 45 kV, anode current: 40 mA, measured range: 2 - 40° 2Θ, increment: 0.02° 2Θ at the reflection dwell time of 300 s. For the correction of the primary array 0.02 rad Soller slits, a 10 mm mask and a 1/4° fixed anti-dispersion slit were used. The irradiated area of the sample is 10 mm, programmable divergence slits were used. For the correction of the secondary array 0.02 rad Soller slits and a 5.0 anti-dispersion slit were used. The measurement was carried out with a flat sample applied onto a Si plate.

The records of the differential scanning calorimetry (DSC) were measured using a DSC Pyris 1 device made by the company Perkin Elmer. The sample charge in a standard Al pot was between 3 and 4 mg and the heating rate was 10°C/min. The temperature program that was used consists of 1 min of stabilization at the temperature of 20°C and then of heating up to 250°C at the heating rate of 10°C/min. As the carrier gas 4.0 N2 was used at the flow of 20 ml/min.

The records of the thermogravimetric analysis (TGA) were measured using a TGA 6 device made by the company Perkin Elmer. The sample charge in a corundum pot was 15-17 mg and the heating rate was 10°C/min. The temperature program that was used consists of 1 minute's stabilization at the temperature of 20°C and then of heating up to 300°C at the heating rate of 10°C/min. As the carrier gas 4.0 N2 was used at the flow of 20 ml/min. Preparative example - preparation of ixazomib citrate of form 3

3.00 g (6.06 mmol) of 2,5-dichloro-N-[2-({(1 R)-3-methyl-1-[(3aS,4S _l 6S,7aR)-3a ₎ 5 _I 5- trimethylhexahydro-4,6-methano-1 ,3,2-benzodioxaborol-2-yl]butyl}amino)-2- oxoethyl]benzamide of formula V, 0.41 g (6.67 mmol) of boric acid and 1.28 g (6.67 mmol) of citric acid are dosed into a flask. The mixture is stirred in 15 ml of acetone at the room temperature for 22 h. 50 ml of ethyl acetate is added to the mixture. After removal of a part of the solvent (15 ml) by distillation and spontaneous cooling of the reaction mixture, ixazomib citrate of formula I is obtained by aspiration. After drying in a vacuum drier (16 h at 40°C) the yield of the reaction is 91% wt. and HPLC purity of the product 98.9%.

The XRPD pattern is shown in Fig. 1 , the characteristic peaks are presented in Table 1.

The DSC record contains an endothermic curve that corresponds to the melting point Tonset = 212.2°C. The record is shown in Fig. no. 2 in the Appendix.

The TGA record indicates a weight loss in the temperature range of 20 to 200°C of approx. 1.3%.

The record is shown in Fig. no 3 in the Appendix.

Comparative Example 0

Ixazomib citrate form 1 was mixed with microcrystalline cellulose, standard moisture and packed into a standard polyethylene (PE) bag. The bag was put into the stress testing chamber for 7 days at 80°C and 75% relative humidity. After 7 days the amount of total impurities were measured by HPLC in order to analyze chemical purity. In addition, in order to analyze physical stability of polymorph, XRPD analysis was performed.

The standard polyethylene bag did not exhibit enough protection. High amount of impurities were formed (12.1%) and in addition, polymorphic form changed from form 1 into form 2. Microcrystalline cellulose, standard moisture in combination with standard polyethylene packaging does not exhibit adequate protection of ixazomib citrate.

Comparative Example 1

Ixazomib citrate form 1 was mixed with microcrystalline cellulose, standard moisture and packed into AI/AI bag. The bag was put into the stress testing chamber for 7 days at 80°C and 75% relative humidity. After 7 days the amount of total impurities were measured by HPLC in order to analyze chemical purity. In addition, in order to analyze physical stability of polymorph, XRPD analysis was performed. Significant chemical degradation and polymorphic transformation were observed similar as the same formulation mixture packed in PE. mg/bag

Ixazomib citrate form 1 4.00

Microcrystalline cellulose, standard moisture 86.00

Packaging AI/AI bag

Total impurities (HPLC) 8.6%

Form of Ixazomib citrate (XRPD) form 2

Example 1 Ixazomib citrate form 3 was mixed with microcrystalline cellulose, standard moisture and packed into AI/AI bag. The bag was put into the stress testing chamber for 7 days at 80°C and 75% relative humidity. After 7 days the amount of total impurities were measured by HPLC in order to analyze chemical purity. In addition, in order to analyze physical stability of polymorph, XRPD analysis was performed.

By comparing Comparative Example 1 with Example 1 it is clear that ixazomib citrate form 3 performs considerably better than ixazomib citrate form 1. Ixazomib citrate form 3 exhibits considerably better chemical purity than ixazomib citrate form 1 (5.5% vs. 8.6%, respectively). In addition, ixazomib citrate form 3 does not change its physical form, while ixazomib citrate form 1 converts to form 2.

In addition, by comparing those results with Comparative example 0, it can also be noticed that the use of the AI/AI bag significantly improves stability of ixazomib citrate. Comparative Example 2

Ixazomib citrate form 1 was mixed with microcrystalline cellulose, low moisture and packed into AI/AI bag. The bag was put into the stress testing chamber for 7 days at 80°C and 75% relative humidity. After 7 days the amount of total impurities were measured by HPLC in order to analyze chemical purity. In addition, in order to analyze physical stability of polymorph, XRPD analysis was performed. Comparing HPLC and XRPD data from table below with those for comparative example 1 , it seems that using of low moisture microcrystalline cellulose provides formulation with better chemical and physical stability

Example 2 Ixazomib citrate form 3 was mixed with microcrystalline cellulose, low moisture and packed into AI/AI bag. The bag was put into the stress testing chamber for 7 days at 80°C and 75% relative humidity. After 7 days the amount of total impurities were measured by HPLC in order to analyze chemical purity. In addition, in order to analyze physical stability of polymorph, XRPD analysis was performed. mg/bag

Ixazomib citrate form 3 4.00

Microcrystalline cellulose, low moisture 86.00

Packaging AI/AI bag

Total impurities (HPLC) 1.4%

Form of Ixazomib citrate (XRPD) form 3

By comparing Comparative Example 2 with Example 2 it is clear that ixazomib citrate form 3 performs considerably better than ixazomib citrate form 1. Ixazomib citrate form 3 exhibits considerably better chemical purity than ixazomib citrate form 1 (1.4% vs. 1.7%, respectively) and the form is polymorphically stable. Moreover, using of low moisture excipient provides chemically and physically stable product based on comparing XRPD and HPLC data in Example 1 and 2.

Example 3

Form 3 of ixazomib citrate was stirred either with mannitol or with microcrystalline cellulose with a low moisture content for 15 minutes. Then, talc was added and the mixture was stirred for another 10 minutes. Finally, magnesium stearate was added and the mixture was stirred for another 3 minutes so that a mixture for processing into capsules could be prepared. The prepared mixture was subsequently manually processed into gelatin capsules of size 4. The gelatin capsules were packed in AI/AI blister packs. mg mg mg mg mg mg in 1 in 1 in 1 in 1 in 1 in 1 capsule capsule capsule capsule capsule capsule

Form 3 of ixazomib

4.00 4.00 3.00 3.00 2.3 2.3 citrate

Mannitol 84.00 85.00 85.70

Microcrystalline

84.00 85.00 85.70 cellulose, low moisture Talc 1.00 1.00 1.00 1.00 1.00 1.00

Magnesium stearate 1.00 1.00 1.00 1.00 1.00 1.00

Total 90.00 90.00 90.00 90.00 90.00 90.00

Gelatin capsules of

size 4

Blister pack material AI/AI AI/AI AI/AI AI/AI AI/AI AI/AI