WO2008111092A1

WO2008111092A1 - Crystalline temozolomide monohydrate and process for preparation thereof

Info

Publication number: WO2008111092A1
Application number: PCT/IN2008/000134
Authority: WO
Inventors: Bijan Panda; Golak Chandra Maikap; Shiv Kumar Agarwal; Manoj Kumar Singh; Manu Jaggi; Ashwini Nangia; Nanubolu Jagadeesh BABU; Srinivasulu AITIPAMULA; Lingireddy Sreenivas REDDY
Original assignee: Fresenius Kabi Oncology Limited
Priority date: 2007-03-09
Filing date: 2008-03-10
Publication date: 2008-09-18

Abstract

A crystalline Temozolomide Monohydrate. A process for preparing the same comprising: i) dissolving Temozolomide, having a purity of 50-70% in acetone at a temperature of about 50-55°C; ii) optionally adding activated carbon to the solution of step i); iii) filtering the activated carbon from the mixture of step ii); iv) evaporating the filtrate of step iii) to obtain a solid substance; v) dissolving the solid substance obtained in step iv) in a mixture of acetone and water in the ratio of 3:1 v/v at a temperature from about 50°C to reflux temperature; vi) optionally adding activated carbon to the solution of step v); vii) cooling the mixture of step vi) to ambient temperature; viii) filtering the activated carbon from the mixture of step vii); ix) cooling the filtrate of step viii) to a temperature of 0-5 °C and collecting the crystals and drying the filtrate of step viii) to give the crystalline Temozolomide Monohydrate.

Description

CRYSTALLINE TEMOZOLOMIDE MONOHYDRATE AND PROCESS FOR PREPARATION THEREOF

FIELD OF THE INVENTION

The present invention relates to a novel crystalline Temozolomide Monohydrate and a process for preparation thereof.

The present invention further relates to pharmaceutical compositions comprising the novel crystalline Temozolomide Monohydrate, useful for treatment of cancers of various origins.

BACKGROUND OF THE INVENTION

Temozolomide, which is chemically known as 3,4-dihydro-3-methyl-4-oxoimidazo[5,l-d]- as-tetrazine-8-carboxamide and represented by formula (I),

(I) is used to treat cancerous tumors in the brain of adult patients. Temozolomide is marketed under the brand name TEMOD AR^®, which is available as a Capsule in strengths of 5mg, 20 mg, 100 mg, 140 mg, 180 mg, and 250 mg for treatment of adult patients with newly diagnosed Glioblastoma Multiforme, concomitantly with radiotherapy and then as maintenance treatment. It is also indicated for the treatment of adult patients with Refractory Anaplastic Astrocytoma i.e. patients who have experienced disease progression on a drug regimen containing Nitrosourea and Procarbazine.

Temozomide per se was first disclosed by Lunt et. al in US 5,260,291, which apart from claiming the molecule i.e. Temozolomide also discloses a process for preparation thereof as well as pharmaceutical compositions comprising the same for treatment of malignant neoplasms, e.g. carcinomas, melanomas, sarcomas, lymphomas and leukaemias, and in the treatment of glioma and mycosis fungoides at doses which are generally between 0.1 and 200, preferably between 1 and 20, mg/kg body weight per day.

US 5,260,291 discloses a method for synthesis of Temozolomide (I) by cyclization of 5- diazo-lH-imidazole-4-carboxamide of formula (II) with methyl isocyanate, the chemistry of which is depicted below and which, is further illustrated in Examples 1, 4, and 9 therein.

(H) (I) Example 1 of US 5,260,291 states that the Temozolomide obtained after reaction of 5-diazo- lH-imidazole-4-carboxamide of formula (II) with methyl isocyanate is isolated from anhydrous diethyl ether and dried in air to give a light brown microcrystalline solid having a melting point of 21O⁰C (with effervescence) and darkening from 160° to 21O⁰C.

Example 4 of US 5,260,291 similarly states that Temozolomide obtained after reaction of 5- diazo-lH-imidazole-4-carboxamide of formula (II) with methyl isocyanate is isolated from ethyl acetate to give a cream colored solid having a melting point of 212⁰C (with effervescence). It is further stated that the material thus obtained can be recrystallised from three different solvent systems to give three different polymorphic forms having different IR spectra. For e.g.

(i) Colorless needles of Temozolomide having characteristic IR spectrum peaks at υ_max 3410, 3205 1758, 1730 and 1678 cm^"1 and having a melting point of 21O⁰C (with effervescence) is obtained on recrystallisation from a 3:1 v/v mixture of acetone and water; (ii) White microcrystals of Temozolomide having characteristic IR spectrum peaks at υ_max 3430, 3200, 1740 and 1675 cm^'1, and having a melting point of 210 ⁰C (with effervescence) is obtained on recrystallisation from a 1 :3 v/v mixture of acetone and water; and (iii) A granular solid of Temozolomide having characteristic IR spectrum peaks at υ_max 3450, 3380, 3200, 1742, 1688 and 1640 cm^"1, and having a melting point of 215 ⁰C (darkening from 200⁰C) is obtained on recrystallisation from hot water.

Example 9 of US 5,260,291 similarly states that Temozolomide obtained after reaction of 5- diazo-lH-imidazole-4-carboxamide of formula (II) with methyl isocyanate in a mixture of dichloromethane and n-methylpyrrolid-2-one and on isolation from diethyl ether gives a pale purple solid having a melting point 202-203⁰C (with decomposition). Further, an additional polymorphic form was also disclosed, which was obtained by dissolving Temozolomide in acetonitrile, filtering, concentration of the filtrate to dryness, and trituration of the resulting residue with diethyl ether. Temozolomide thus obtained is stated to be an orange-tinged solid, having a melting point of about 200⁰C (with decomposition).

However, apart from melting point and Infrared spectrum US 5,260,291 does not provide any other solid state characteristics of Temozolomide, such as X-ray (Powder) diffraction pattern, Differential Scanning Calorimetry and Solid state NMR, obtained by different isolation or crystallization methods.

Very specifically, various crystalline forms of Temozolomide have been disclosed in US 2005/0187206 Al, which provides nine crystalline forms referred to as Form I, Form II, Form III, Form IV, Form V, From VI, Form VII, Form VIII and Form IX, which posses distinct X-ray (Powder) diffraction pattern and Infrared spectrum. The present inventors have found that a novel crystalline form of Temozolomide, especially a novel crystalline Temozolomide Monohydrate could be prepared by a selective method which forms the subject matter of the present invention.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

Fig-1 represents a characteristic X-ray (Powder) Diffraction Pattern of the crystalline Temozolomide Monohydrate of the present invention.

Fig-2 represents a characteristic Differential Scanning Calorimetry Thermogram of the crystalline Temozolomide Monohydrate of the present invention.

Fig-3 represents a characteristic Infra Red Spectrum of the crystalline Temozolomide Monohydrate of the present invention.

Fig-4 represents the intrinsic dissolution profile of the crystalline Temozolomide Monohydrate of the present invention.

Fig-5 represents the intrinsic dissolution profile of the known crystalline form IH of Temozolomide, as disclosed in US2005/0187206.

Fig-6 represents the Plasma concentration profile of the crystalline Temozolomide Monohydrate of the present invention and the known crystalline form III of Temozolomide, as disclosed in US2005/0187206 in Wistar rat upto 8 hours.

Fig-7 represents the Plasma concentration profile of the active metabolite (MTIC) of the crystalline Temozolomide Monohydrate of the present invention and the known crystalline form III of Temozolomide, as disclosed in US2005/0187206 in Wistar rat upto 8 hours. Fig-8 represents the Plasma concentration profile of a Capsule Blend of Temozolomide prepared from the crystalline Temozolomide Monohydrate of the present invention and the Reference Listed Drug (TEMOD AR^®) in Wistar rat upto 24 hours.

Fig-9 represents the Plasma concentration profile of a Capsule Blend of Temozolomide prepared from crystalline Temozolomide Monohydrate of the present invention and the Reference Listed Drug (TEMODAR^®) in Wistar rat upto 8 hours.

SUMMARY OF THE INVENTION In particular, it was found that crystallization of Temozolomide from a mixture of water and water-miscible solvents affords a crystalline material, which is different from the known polymorphic forms reported in US 5,260,291 and US 2005/0187206 Al. The new crystalline form on the basis of single crystal X-Ray studies and as well as water content has been confirmed to be a monohydrate form of Temozolomide, which hitherto is not known and hence novel.

The novel crystalline Temozolomide Monohydrate has water content in range of 8 to 9% and exhibits a Differential Scanning Calorimetry Thermogram having a characteristic endotherm and exotherm at about 74⁰C to about 78⁰C and about 198⁰C to about 214⁰C respectively, which is as depicted in Fig-2.

The Infra Red spectrum of the crystalline Temozolomide Monohydrate has characteristic peaks at υ_max 3414, 3285, 3171, 3131, 3026, 2908, 2777, 2361, 1743 and 1673 cm^"1, which is as essentially depicted in Fig-3.

The novel crystalline Temozolomide Monohydrate exhibits characteristic 2Θ and ^/-spacing values in its X-Ray (Powder) Diffraction Pattern as summarized in Table-I and as depicted in Fig-1. Table -I: X-ray (Powder) Diffraction Reflections In 2Θ Values And Interplanar Distance (d) Of The Crystalline Temozolomide Monohydrate Of The Present Invention

Typically the novel crystalline Temozolomide Monohydrate is prepared by crystallization of Temozolomide from a mixture of water and water-miscible organic solvents, which are selected from aliphatic nitriles such as acetonitrile and propionitrile; ketones such as acetone, methyl isobutyl ketone and methyl ethyl ketone; and cyclic ethers such as tetrahydrofuran and dioxane etc. The water-miscible organic solvent and water are typically employed in a proportion of between 1 : 1 v/v to 4:1 v/v. Amongst the water-miscible organic solvents, acetone is most preferred. Specifically, it was found that the novel crystalline Temozolomide monohydrate could be conveniently obtained by crystallization of Temozolomide from a mixture of acetone and water in a definite ratio of 3:lv/v under certain specific conditions. More particularly, it was found that the crystalline Temozolomide monohydrate could be obtained by dissolving Temozolomide in a mixture of acetone and water in a ratio of 3:1 v/v at a temperature of about 50-55 ⁰C followed by cooling the mixture to 0-5 ⁰C and collecting the crystals of Temozolomide monohydrate.

Very specifically, it was found that the crystalline Temozolomide monohydrate could not be obtained when solvents other than acetone in admixture with water are employed for crystallization of Temozolomide. Amongst the other solvents employed such as ethyl acetate, acetonitrile, Tetrahydrofuran, N, N Dimethyl Formamide, etc., such solvents in admixture with water were found to produce other crystalline forms of Temozolomide, in many instances the crystalline forms III and VIII as disclosed in US 2005/0187206 were formed. More surprisingly, it was found that even when a mixture of acetone and water was employed for crystallization of Temozolomide, the formation of the crystalline

Temozolomide was largely dependent on the ratio of the individual solvents in the mixture with a proportion of acetone and water in a v/v ratio of 3:1 specifically forming the crystalline Temozolomide monohydrate whereas, other proportions were found to give a crystalline product different from the monohydrate form of the present invention.

The crystalline Temozolomide monohydrate prepared by the abovementioned process has water content in the range of 8-9 % w/w and is found to be stable for upto 3 months under accelerated stability conditions.

In accordance with the objectives, there is provided a new crystalline Monohydrate form of Temozolomide having a characteristic X-ray (Powder) Diffraction Pattern, Differential Scanning Calorimetry Thermogram and a characteristic Infra Red Spectrum as depicted in Fig-1, Fig-2 and Fig-3 respectively. According to another aspect there is provided a process for the preparation of the abovementioned novel crystalline Temozolomide monohydrate, comprising the steps of: i) dissolving Temozolomide, having a purity of 50-70% in acetone at a temperature of about 50-55⁰C; ii) optionally adding activated carbon to the solution of step i); iii) filtering the activated carbon from the mixture of step ii); iv) evaporating the filtrate of step iii) to obtain a solid substance; v) dissolving the solid substance obtained in step iv) in a mixture of acetone and water in the ratio of 3:1 v/v at a temperature from about 50 ⁰C to reflux temperature; vi) optionally adding activated carbon to the solution of step v); vii) cooling the mixture of step vi) to ambient temperature; viii) filtering the activated carbon from the mixture of step vii); ix) cooling the filtrate of step viii) to a temperature of 0-5 ⁰C and collecting the crystals and drying the filtrate of step viii) to give the crystalline Temozolomide

Monohydrate.

According to a further aspect there is provided pharmaceutical compositions comprising the novel crystalline Temozolomide monohydrate and pharmaceutically acceptable excipients. Such pharmaceutically acceptable excipients include diluents, fillers, binding agents, disintegrants, preservatives, lubricants, colouring and flavoring agents and the like. The oral route is the preferred route for administration. The composition according to the present invention, for oral administration, also include capsules of absorbable materials such as gelatin containing one or more of the active substances with or without the addition of diluents or excipients. The pharmaceutical compositions prepared with the novel crystalline monohydrate form are used in the treatment of various forms of cancer and solid tumors. Pharmacokinetic Studies On The Crystalline Temozolomide Monohydrate Prepared As

Per The Method Of The Present Invention

Discussed hereinbelow are some of the non-clinical studies carried out by the present inventors on the novel crystalline monohydrate form of Temozolomide, prepared as per the method of the present invention, the details of which have been discussed in detail hereinbefore. These studies include the intrinsic dissolution studies conducted on the crystalline hydrate form and the known form III of Temozolomide, as disclosed in

US2005/0187206 and also the pharmacokinetic studies conducted on the two polymorphic forms and their metabolites along with the Reference Listed Drug.

The intrinsic dissolution rate is defined as the dissolution rate of pure substances under the condition of area constant surface. The measurement of intrinsic dissolution rate is a tool that is used to characterize the bulk drug substances and excipients. The dissolution rate and bioavailibility of a drug substance are influenced by its solid-state properties i.e. crystallinity, amorphism, polymorphism, hydration, solvation, particle size, and particle surface area. The measured intrinsic dissolution rate is dependent on these solid-state properties.

Dissolution studies were carried out for the novel monohydrate form and form III of Temozolomide using the belowmentioned parameters:

Apparatus: USP II (Paddle)

Volume: 500 ml

Medium: Water

RPM: 50 The results obtained for the intrinsic dissolution of the monohydrate form and form III of the drug have been tabulated in Table II and III respectively and depicted in Fig 4 and Fig 5 respectively. Table-II: Intrinsic dissolution rate of crystalline Temozolomide monohydrate

Table -Ill.'Intrinsic dissolution rate of known crystalline Form III of Temozolomide as disclosed in US 2005/0187206.

The intrinsic dissolution rate of Temozolomide monohydrate of the present invention was found to be 0.73124 mg/min/cm² and that of the known form III, as disclosed in US 2005/0187206 was found to be 0.7125 mg/min/cm² thereby showing that the intrinsic dissolution properties of the two forms are comparable.

The non-clinical studies carried out also included the determination of the pharmacokinetics of the crystalline Temozolomide monohydrate of the present invention, and its comparison with the pharmacokinetics of the known form III of Temozolomide, as disclosed in US 2005/0187206 and the Reference Listed Drug (RLD). Incidentally, the marketed composition of Temozolomide actually conforms to the polymorphic Form III as disclosed in US 2005/0187206. Hence, the pharmacokinetics of the crystalline Temozolomide monohydrate was compared with that of Form III and the marketed composition.

In all the studies, wherever a comparison of the abovementioned studies with a conventional, approved and marketed composition of Temozolomide, was required TEMOD AR^®, was used.

The Pharmacokinetic study was conducted in male Wistar rats under fasting conditions. Care and handling of animals were in accordance with Institutional Animal Ethics Committee (IAEC). Each composition was orally administered as a 0.4% suspension in methylcellulose to the group of seven animals separately at a dose of 30 mg/kg.

Blood samples were taken from the retro-orbital plexus at various time points Plasma was separated immediately by centrifugation and stored at -20°C prior to analysis. Temozolomide from the plasma was extracted via Liquid-Liquid Extraction and analyzed using Liquid Chromatography Mass Spectrometry (LC-MS/MS) technique. Pharmacokinetic parameters were determined using the WinNonlin software 5.0.1 (Pharsight Corporation). Non-compartment model was used to fit the data. Distribution and elimination were represented by the following parameters area under the curve (AUC_aii), total body clearance (Cl_obs), apparent volume of distribution (Va) and plasma half life (Ty₂).

Temozolomide is an alkylating agent of the imidazotetrazine derivative that exhibits broad spectrum antitumor activity against murine tumors. It exerts its antitumor activity through linear triazine MTIC. Temozolomide is chemically converted to MTIC both in vitro and in vivo. It is believed that Temozolomide exerts its antitumor activity via its biologically active degradation product MTIC; hence, it was imperative to determine plasma concentration of both Temozolomide and MTIC in plasma when its PK profile was studied.

The pharmacokinetic profile of the two polymorphs i.e. the novel monohydrate form and form III of Temozolomide after single oral dose of 30 mg/kg has been summarized in Table- IV and depicted in Fig 6.A comparative pharmacokinetic profile of the active metabolite (MTIC) of both forms has also been studied and summarized in Table IV and depicted in Fig

7.

Table-IV: Pharmacokinetic Parameters of Crystalline Temozolomide Monohydrate of the Present Invention and Form III Of Temozolomide, as disclosed in US2005/018206 and their metabolites

Non-Transposed Final Parameters

Upon comparison of the pharmacokinetic properties of the monohydrate form of Temozolomide with the RLD, as the C₀, AUC₃Ii, T_1/2 values at each dose of the two compositions are comparable; the Pharmacokinetics of the said two compositions can be concluded to be comparable across the dose, the details of which are summarized in Table-V and depicted in Fig 8 and Fig 9. v

Table -V: Pharmacokinetic Parameters Of The Capsule Blend of The Crystalline Temozolomide Monohydrate Of The Present Invention and Capsule Blend of the RLD

Non-Transposed Final Parameters

The invention is further illustrated by way of the following example, which should not be construed as limiting the scope of the invention. It would be evident from the following illustrative non limiting examples that Temozolomide monohydrate could not be obtained when solvents other than acetone admixed with water is used for crystallization of Temozolomide.

Example 1

Temozolomide (5gm) was added to a mixture of acetone and water (700ml) in the ratio of 3:1

(v/v) and stirred at 20-25⁰C to for about 30 minutes to dissolve the material. Activated carbon

(lgm) was added to the solution and the mixture agitated at 20-25⁰C for another 1 hour. The mixture was then filtered and the filtrate stirred at -5 to O⁰C for 4-5 hours. The solid material crystallizing out was then filtered and dried at 25-3O⁰C under vacuum to give crystalline Temozolomide Monohydrate, having the characteristic X-ray (Powder) diffraction pattern as depicted in Table-I and Fig-1; the characteristic Differential Scanning Calorimetry Thermogram as depicted in Fig-2; and Infra Red spectrum as depicted in Fig-3.

Example 2

Temozolomide (lgm) was added to a mixture of acetonitrile and water (26ml) in the ratio of 3:1 (v/v) and stirred at 55 ⁰C for about 30 minutes to dissolve the material. Activated carbon (lgm) was added to the solution and the mixture agitated at 20-25⁰C for another 1 hour. The mixture was then filtered and the filtrate stirred at 0-5⁰C for 2-3 hours. The solid material crystallizing out was then filtered and dried at 25-3O⁰C under vacuum to give crystalline Temozolomide form III as disclosed in US2005/0187206.

■ Example 3

Temozolomide (lgm) was added to a mixture of tetrahydrofuran and water (90ml) in the ratio of 3:1 (v/v) and stirred at 55 ⁰C to for about 30 minutes to dissolve the material. Activated carbon (lgm) was added to the solution and the mixture agitated at 20-25⁰C for another 1 hour. The mixture was then filtered and the filtrate stirred at 0-5⁰C for 2-3 hours. The solid material crystallizing out was then filtered and dried at 25-3O⁰C under vacuum to give crystalline Temozolomide form III as disclosed in US2005/0187206.

Example 4

Temozolomide (lgm) was added to a mixture of N,N dimethylformamide and water (40ml) in the ratio of 3:1 (v/v) and stirred at 55 ⁰C for about 30 minutes to dissolve the material. Activated carbon (lgm) was added to the solution and the mixture agitated at 20-25⁰C for another 1 hour. The mixture was then filtered and the filtrate stirred at 0-5⁰C for 2-3 hours. The solid material crystallizing out was then filtered and dried at 25-3O⁰C under vacuum to give crystalline Temozolomide form III as disclosed in US2005/0187206. Example 5

Temozolomide (lgm) was added to a mixture of acetone and water (140ml) in the ratio of 3:1 (v/v) and stirred at room temperature for about 30 minutes to dissolve the material. Activated carbon (lgm) was added to the solution and the mixture agitated at 20-25⁰C for another 1 hour. The mixture was then filtered and the filtrate stirred at 0-5⁰C for 2-3 hours. The solid material crystallizing out was then filtered and dried at 25-3O⁰C under vacuum to give crystalline Temozolomide form IX as disclosed in US2005/0187206.

Claims

1. A crystalline Temozolomide Monohydrate.

2. The crystalline Temozolomide Monohydrate Form as claimed in claim 1, exhibiting an x-ray powder diffraction pattern characterized by 20 angle and d values as represented in the following table.

3. The crystalline Temozolomide Monohydrate Form as claimed in claim 1, characterized by a Differential Scanning Calorimetry Thermogram having a characteristic endotherm and exotherm at about 74⁰C to about 78⁰C and about 198⁰C to about 214⁰C respectively.

4. The crystalline Temozolomide Monohydrate Form as claimed in claim 1, characterized by an Infra Red Spectrum having characteristic peaks at υ_maχ 3414, 3285, 3171,

3131, 3026, 2908, 2777, 2361, 1743 and 1673 cnT¹.

5. The crystalline Temozolomide Monohydrate Form as claimed in claim 1, further characterized by an x-ray powder diffraction pattern as represented in Fig-1.

6. The crystalline Temozolomide Monohydrate Form as claimed in claim 1, further characterized by a Differential Scanning Calorimetry Thermogram as represented in Fig-2.

7. The crystalline Temozolomide Monohydrate Form as claimed in claim 1, further characterized by an Infra Red Spectrum as represented in Fig-3.

8. A process for preparing Monohydrate Form of Temozolomide as defined in claim 1, which comprises the steps of: i) dissolving Temozolomide, having a purity of 50-70% in acetone at a temperature of about 50-55⁰C; ii) optionally adding activated carbon to the solution of step i); iii) filtering the activated carbon from the mixture of step ii); iv) evaporating the filtrate of step iii) to obtain a solid substance; v) dissolving the solid substance obtained in step iv) in a mixture of acetone and water in the ratio of 3 : 1 v/v at a temperature from about 50⁰C to reflux temperature; vi) optionally adding activated carbon to the solution of step v); vii) cooling the mixture of step vi) to ambient temperature; viii) filtering the activated carbon from the mixture of step vii); ix) cooling the filtrate of step viii) to a temperature of 0-5 ⁰C and collecting the crystals and drying the filtrate of step viii) to give the crystalline Temozolomide Monohydrate.

9. A process according to claim 8, wherein the acetone and water are typically employed in a proportion of 3 : 1 v/v.

10. A pharmaceutical composition comprising the crystalline Temozolomide Monohydrate along with pharmaceutically acceptable excipients adapted for administration to patients for treatment of various medical conditions.

11. A pharmaceutical composition according to claim 10, wherein the pharmaceutically acceptable excipients are selected from diluents, fillers, binding agents, disintegrants, preservatives, lubricants, colouring and flavoring agents.

12. The pharmaceutical composition according to claim 10, adapted for administration to patients for treatment of medical conditions selected from cancerous tumors in the brain, Glioblastoma Multiforme concomitantly with radiotherapy and Refractory Anaplastic Astrocytoma.

13. A method of treating a medical condition in which treatment with Temozolomide is beneficial, the method comprising administering a pharmaceutically effective amount of the crystalline Temozolomide monohydrate to a mammal in need thereof.