CRYSTALLINE BORTEZOMIB MONOHYDRATE PROCESS

The following specification particularly describes the invention and the manner in which it is to be performed.

INTRODUCTION

Bortezomib (I) is chemically known as [(lR)-3-methyl-l-[[(2S)-l-oxo-3-phenyl-2-[(pyrazinyl carbonyl) amino] propyl] amino] butyl] boronic acid and is represented by the structural Formula I Bortezomib is a modified di-peptidyl boronic acid and can be represented as an N-protected dipeptide and may be written as Pyz-Phe-boro-Leu, which stands for pyrazinoic acid,phenylalanine and Leucine having a boronic acid group in place of carboxylic acid. It is a proteosome inhibitor in organisms and is believed to function as a reversible inhibitor of the chymotrypsin-like activity of the 26S proteasome in mammalian cells. The 26S proteasome is a large protein complex that degrades ubiquitinated proteins. The ubiquitin-proteasome pathway plays a role in regulating the intracellular concentration of specific proteins, maintaining homeostasis within cells.

Inhibition of the 26S proteasome prevents this targeted proteolysis, which can affect multiple signaling cascades within the cell. This disruption of normal homeostatic mechanisms can lead to cell death.

Bortezomib is cytotoxic to a variety of cancer cell types in vitro and causes a delay in tumor growth in vivo in nonclinical tumor models, including multiple myeloma. Bortezomib presently is approved in USA for the treatment of multiple myeloma, relapsed multiple myeloma, and mantle cell lymphoma. A variety of combination therapies have been investigated for treating multiple myeloma, in which Bortezomib is administered with one or more other biologically active substances, such as lenalidomide, dexamethasone, melphalan, predisone, thalidomide, cyclophosphamide,doxorubicin, vincristine, carmustine, pomalidomide, vorinostat, tanespimycin, and perifosine. Other potential uses of bortezomib also have been reported, including treatment of amyloidosis.
It is available in the market under the brand name "VELCADE ™" in the form of injection. Each vial contains 3.5 mg of Bortezomib as a sterile lyophilized powder. Chemistry review section of Summary Basis Of Approval for Bortezomib (NDA 21-602) mentions that the drug substance, drug product and the reconstituted drug product have three different molecular forms. PS-341 (Bortezomib) drug substance exists as the trimeric boroxine in the solid state. When exposed to water, the boroxine hydrolyses to monomeric boronic acid PS-341. The structure of the lyophilized PS-341 drug product has been determined to be symmetrical mannitol ester.

While reconstituted by 0.9% NaCl solution, the reconstituted PS-341 drug product consists of equilibrium between the mannitol ester and the PS-341 boronic acid.

Adams et al in US5780454 discloses Bortezomib, its pharmaceutically acceptable salts, pharmaceutipal composition and use in inhibiting the proteosome function in a mammal. Further, it discloses a process for the preparation of Bortezomib and its analogues.

Gupta et al in US6713446 discloses lyophilized formulation of Bortezomib esters. This patent mentions that Bortezomib prepared by the process as described in US5780454 is white amorphous powder.

US4525309 discloses a process for the homologation of boronic esters by rearrangement of the intermediate boron "ate" complex in the presence of a Lewis acid catalyst to promote the
rearrangement reaction and to minimize epimerization of a-carbon atom.

Pickersgill et al in US7714159 disclose processes for preparing Bortezomib and its intermediates which are boronic ester compounds.

US '159 discloses that the previously reported processes for the preparation of the intermediate
compound of the formula-Ill by Lewis acid promoted rearrangement of boron "ate" complex of the formula ~X employ tetrahydrofuran, an ether solvent that is miscible with water, and requires rigorously dried equipment, solvents, and Lewis acid reagent and such reactions are expensive and difficult to scale up. Further, according to the '159 patent, attempted scale-up of the prior art processes frequently results in further deterioration in diastereomeric ratio of the boronic ester compound either because of exposure of the product to halide ion during concentration of the reaction mixture to remove the tetrahydrofuran solvent and exchange it for a water-immiscible solvent or failure to completely remove the tetrahydrofuran during the subsequent aqueous washes.

US '159 appears to address the problems of the prior art by carrying out the rearrangement of the boron "ate" complex in an ether solvent that has low miscibility with water and a coordinating
co-solvent. Non-limiting examples of low water miscible ether solvents identified in the US '159
application for use in the process include tert-butyl methyl ether, tert-butyl ethyl ether, tert-amyl methyl ether, and isopropyl ether.
Further, the US '159 application discloses a process for the preparation of Bortezomib which
comprises:

(i) Providing a biphasic mixture comprising the intermediate boronic ester compound of formula-IX, an organic boronic acid acceptor, a lower alkanol, a C5.8 hydrocarbon solvent, and aqueous
mineral acid;

(ii) stirring the biphasic mixture to afford Bortezomib;

(iii) separating the solvent layers; and

(iv) extracting Bortezomib or a boronic acid anhydride thereof into an organic solvent.

To enhance the purity of the product, the aqueous layer obtained after step (iii) is washed to remove neutral organic impurities prior to the extracting step (iv). Such process comprises the following steps:

1) separating the solvent layers;

2) adjusting the aqueous layer to basic pH;

3) washing the aqueous layer with an organic solvent; and

4) adjusting the aqueous layer to a pH of less than about 6.

Thus, the process described in the US '159 comprises multiple organic solvent washings under acidic and basic conditions, followed by extracting the compound into an organic solvent, isolating the product and further recrystallization to obtain Bortezomib of enhanced purity.

It has been found that exposure of Bortezomib to an aqueous basic solution decrease the purity of Bortezomib. Particularly, when such process is performed on a large scale, exposure of Bortezomib to aqueous basic conditions for longer hours is difficult to avoid and hence this process may not be amenable for use on an industrial scale.

WO2008075376A1 discloses crystalline forms I and II of Bortezomib and process for their preparation. Form-I of Bortezomib is prepared by using solvents such as acetone, CHCI3, CH2CI2 or nitriles and diluents such as Diisopropyl ether, Tertiary butyl methyl ether, n-hexane and n- heptane. Form-II of Bortezomib is prepared from hot solution of ethyl acetate. The application
also discloses that form-I and form-II are inter-changeable by using the above described
solvents.

Palle et al in US2010/0226597 disclose a process for the preparation of Bortezomib, its
intermediates and process for crystalline forms designated as Forms A and B of Bortezomib.
Being Bortezomib as an important anticancer therapeutic agent, additional and improved ways of preparing Bortezomib and its new solid crystalline form may be of immense value to
pharmaceutical science and the healthcare of cancer patients. Hence, there exists a need in the development of new stable Bortezomib form and economically viable processes, which may be
commercially up-scalable, viable, safer for handling, less time consuming and with better and
consistent quality parameters.

The present inventors have found Bortezomib (la) as its stable crystalline form as monohydrate designated as Form-SB and process for preparation thereof.

SUMMARY OF INVENTION

Particular aspects of the present application relates to the process/es for preparation of Crystalline Bortezomib (la).

The application relates to process for preparation of Bortezomib (la) and its stable crystalline polymorphic form designated as Form-SB, which is substantially free from process related impurities. The crystalline polymorphic form of Bortezomib (la) obtained by the processes according to the present invention are useful as active pharmaceutical ingredient in pharmaceutical compositions for treatment of cancer particularly multiple myeloma, relapsed multiple myeloma, and mantle cell lymphoma, by administering the compound in a composition. Different aspects of the present application are summarized herein below individually.

In one aspect of the present application, it relates to Bortezomib monohydrate (la) crystalline Form-SB characterized by having water content ranging between 5.5- 8.0 % w/w and X-ray powder diffraction pattern comprising characteristic 29°peaks selected from the XRPD peak set of 5.6, 7.5, 9.8, 10.2, 11.3,15.1,18.0, 20.5, 21.5 and 23.6 ± 0.20 29°.

Said Bortezomib (la) Crystalline form -SB is further characterized by DSC isotherm comprising two endothermic peaks ranging between-

a. Peak -1 - Between 45 to 60°C

b. Peak-2- Between 175-185 °C
Bortezomib (la) according to present invention has an IR absorption spectrum having characteristic peaks expressed in cm"1 approximately at 3387 cm"1, 3304 cm"1, 2953 cm"1, 2927 cm'1, 2868 cm"1, 1627 cm"1, 1455 cm"1, 1400 cm'1, 1201cm'1, 1150cm'1, 1020 cm'1, 747 cm"1 and 702 cm"1 and Raman absorption spectrum having characteristic peaks expressed in cm"1 approximately 3066 cm"1, 1583 cm"1, 1528 cm"1, 1281cm"1, 1213 cm"1, 1035 cm"1, 1022cm"1 and 1004 cm"1.

In another aspect of the present invention, Bortezomib (la) crystalline Form-SB is further characterized by X-ray powder diffraction pattern substantially according to Fig-1, DSC isothermal pattern substantially according to Fig-2 , IR absorption spectrum substantially according to Fig-3 and Raman spectrum substantially according to Fig-4. .

In yet another aspect of the present invention, it relates to a process for preparing Bortezomib (la) crystalline Form-SB characterized by X-ray powder diffraction pattern comprising the characteristic 29°peaks of 5.6, 7.5, 9.8, 10.2, 11.3, 15.1, 18.0, 20.5, 21.5 and 23.6 ± 0.20 29°, DSC isotherm comprising the endothermic peaks ranging between 45 to 60 °C (Peak -1) and 175 to 185°C (Peak -2) and IR absorption characteristic peaks approximately at 3387 cm"1, 3304 cm'1, 2953 cm'1, 2927 cm"1, 2868 cm"1, 1627 cm"1, 1455 cm'1, 1400 cm"1, 1201cm"1, 1150cm"1,1020 cm", 747 cm" and 702 cm" and Raman absorption having characteristic peaks at approximately at 3066 cm"1, 1583 cm"1, 1528 cm"1, 1281cm"1, 1213 cm'1, 1035 cm"1, 1022cm" 1 and 1004 cm'1, which process comprising the steps of-

a. Combining the crude bortezomib with an aliphatic ester (C3 to C8 ) solvent or a
mixture of aliphatic ester (C3 to C8 ) solvent and water

b. raise the temperature upto about 40- 70°C

c. Stir the solution at same temperature up to a time between 15 to 60 minutes.

d. combine aliphatic C6 to C7 hydrocarbon solvent
e. optionally maintain the mixture for 10-60 minutes

f. cooling the mixture upto about 10-40°C

g. isolating the crystalline material
Individual steps of the present invention shall be detailed in the further text of detailed description and with non-limiting examples represented in the relevant locations in the specification.

In a further aspect, the Crystalline Form SB of Bortezomib monohydrate (la) obtained by the process/es according to the present application may be formulated as compositions for injectable or oral administration in the form of powders, solutions, capsules, tablets, pills, or granules useful in the treatment of hyper-proliferative disorders, such as cancer. Further aspects of the present invention are demonstrated in detailed description section as well as examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is Illustration of X-ray powder diffraction (XRPD) pattern of Bortezomib monohydrate -Form SB, prepared according to Example-3

Fig. 2 is an Illustration of a differential scanning calorimetric ("DSC") curve of Bortezomib monohydrate -Form SB, prepared according to Example-3

Fig. 3 is an Illustration of a IR spectrum of Bortezomib monohydrate -Form SB, prepared according to Example-3

Fig.4 is an Illustration of a Raman spectrum of Bortezomib monohydrate -Form SB, prepared according to Example-3

DETAILED DESCRIPTION

In our endeavor for embodiments of the present invention as set forth herein, the present invention provides crystalline polymorphic Form SB of Bortezomib monohydrate (la), processes for preparation thereof and pharmaceutical compositions of Form- SB useful in the treatment of hyper-proliferative disorders, such as cancer.
Individual embodiments of the present invention are detailed herein below separately.

In one embodiment of the present application, it provides Bortezomib monohydrate (la) crystalline
Form-SB characterized by having water content ranging between 5.5- 8.0 % w/w and X-ray powder diffraction pattern comprising characteristic 26°peaks selected from the XRPD peak set of 5.6, 7.5, 9.8, 10.2, 11.3, 15.1, 18.0, 20.5,21.5 and 23.6 ± 0.20 26°.

Said Bortezomib (la) Crystalline form -SB is further characterized by DSC isotherm comprising two endothermic peaks ranging between-

a. Peak -1 - Between 45 to 60°C

b. Peak-2- Between 175-185 °C

The characteristic and main peaks and their d spacing values of the new crystalline Form-SB are summarized tabulated in the Table-1.

Table-1: Characteristic XRPD Peaks of Crystalline Form-SB A few minor variations in the observed 2 9° angles values may be expected based on the analyst person, the specific XRPD diffractometer employed and the sample preparation technique. Further possible variations may also be expected for the relative peak intensities, which may be largely affected by the non-uniformity of the particle size of the sample. Hence, identification of the exact crystalline form of a compound should be based primarily on observed 2 theta angles with lesser importance attributed to relative peak intensities. The 2 theta diffraction angles and corresponding d-spacing values account for positions of various peaks in the X-ray powder diffraction pattern. D-spacing values are calculated with observed 2 theta angles and copper K a wavelength using the Bragg equation well known to those of having skill in the art of XRPD diffractometry science.

In view of possibility of marginal error in the assigning 2 theta angles and d-spacings, the
preferred method of comparing X-ray powder diffraction patterns in order to identify a particular crystalline form is to overlay the X-ray powder diffraction pattern of the unknown form over the X-ray powder diffraction pattern of a known form. For example, one skilled in the art can overlay an X-ray powder diffraction pattern of an unidentified crystalline form of Bortezomib over FIG. 1 and readily determine whether the X-ray diffraction pattern of the unidentified form is substantially the same as the X-ray powder diffraction pattern of the crystalline form of this invention. If the X-ray powder diffraction pattern is substantially the same as FIG. 1, the previously unknown crystalline form of Bortezomib can be readily and accurately identified as the crystalline Form SB of thisinvention.

The crystalline Form-SB of Bortezomib appears to be monohydrate, which may be evident from the KF moisture determination (in pyridine) resulted in water content in the range of 5.5 to ~8 %w/w. A sample of the crystalline Form SB prepared by the inventors had moisture content up to ~ 7.5%w/w by KF method, which also confirmed the monohydrate nature of the compound. While the invention is not limited to any specific theory, it should be understood however that the crystalline form SB of Bortezomib monohydrate may contain additional residual or unbound moisture corresponding to slightly more than stoichiometric water content without losing its monohydrate character and/or its monohydrate crystalline form-SB characteristics.

Nevertheless, person having skill in the art should be able to determine whether they are same crystalline forms or not, by looking at the overall shape of the X-ray powder diffraction pattern optionally with help of other thermal data like DSC or IR/ Raman.

Further, Bortezomib crystalline form-SB according to present invention has an IR absorption spectrum having characteristic peaks expressed in cm"1 approximately at 3387 cm", 3304 cm", 2953 cm"1, 2927 cm"1, 2868 cm"1, 1627 cm"1, 1455 cm"1, 1400 cm"1, 1201cm"1, 1150cm"1, 1020 cm'1, 747 cm"1 and 702 cm"1 and Raman absorption spectrum having characteristic peaks expressed in cm'1 approximately 3066 cm"1, 1583 cm"1 , 1528 cm"1 , 1281cm"1 , 1213 cm"1 , 1035 cm"1, 1022cm"1 and 1004 cm"1.

An in-depth review of the Raman spectra along with general literature for Boronic acid compounds provides that series of Raman absorption bands at 1213, 1245 and 1281 cm-1 are apparently ascribed to OH groups of boronic acid in-plane bending modes. Further, multiple Raman bands in the OH stretching region are also observed at 3206 and 3249 cm"1 lead to a belief about nature of the Crystalline Form-SB as [(li?)-3-methyl-l-({(25)-3-phenyl-2-[(pyrazin-2-ylcarbonyl)amino] propanoyl} amino)butyl] boronic acid monohydrate, which may be coordinated with electron lone pair/s residing on oxygen atom of water molecule. Embodiments of the present invention encompass Bortezomib (la) crystalline Form-SB, which is in particular is characterized by X-ray powder diffraction pattern substantially according to Fig-1, DSC isothermal pattern substantially according to Fig-2 , IR absorption spectrum substantially according to Fig-3 and Raman spectrum substantially according to Fig-4. .

In further embodiment of the present invention, it provides process for preparing Bortezomib (la) crystalline Form-SB characterized by X-ray powder diffraction pattern comprising the characteristic 29°peaks of 5.6, 7.5, 9.8, 10.2, 11.3, 15.1, 18.0, 20.5, 21.5 and 23.6 ± 0.20 20°, DSC isotherm comprising the endothermic peaks ranging between 45 to 60 °C (Peak -1) and 175 to 185°C (Peak -2) and IR absorption characteristic peaks approximately at 3387 cm"1, 3304 cm"1, 2953 cm"1, 2927 cm"1, 2868 cm"1, 1627 cm"1, 1455 cm"1, 1400 cm"1, 1201cm"1, 1150cm", 1020 cm", 747 cm"1 and 702 cm'1 and Raman absorption having characteristic peaks at approximately at 3066 cm"1, 1583 cm"1, 1528 cm"1, 1281cm"1,1213 cm'1, 1035 cm"1, 1022cm" 1 and 1004 cm"1, which process comprising the steps of-

a. Combining the crude bortezomib with an aliphatic ester (C3 to C8) solvent or a
mixture of aliphatic ester (C3 to C8 ) solvent and water

b. raise the temperature upto about 40- 70°C

c. Stir the solution at same temperature up to a time between 15 to 60 minutes.

d. combine aliphatic C6 to C7 hydrocarbon solvent

e. optionally maintain the mixture for 10-60 minutes

f. cooling the mixture upto about 10-40°C

g. isolating the crystalline material
Step of combining the Bortezomib with an aliphatic ester (C3 to C8 ) solvent or a mixture of aliphatic ester (C3 to C8 ) solvent and water comprise either mixing or suspending or making solution with Bortezomib obtained by any process /any form with an aliphatic ester (C3 to C8 ) solvent or a mixture of aliphatic ester (C3 to C8 ) solvent and water having a water content in the range between 1-10 % w/w. In this embodiment, it may be understood that representing mixture of aliphatic ester solvent and water having ratio between 90:10 to 99:1 v/v means the same purpose for the present invention. The temperature of combining the solvent and Bortezomib may range between 20-40 deg C.

In this embodiment, aliphatic ester (C3 to C8 ) solvent used may be selected from methyl
acetate, ethyl acetate, propyl acetate or the like.

In a particular embodiment, aliphatic ester as ethyl acetate was used for preparing form SB.
Any form of Crude or Pure Bortezomib obtained by known processes may be used for preparing
Form-SB.

In the present embodiment, process represented in the Scheme-I was utilized to obtain the
Bortezomib.

Scheme-I: Process for preparation of Bortezomib
The specifics of the process are detailed and clearly understood from the examples represented
below in the example section for a person skilled in the art.

A material obtained directly by the process may directly be processed to stage of resulting
Crystalline Form-SB of the present invention.
In the step of raising the temperature in the range about 40- 70°C, it preferred to raise the
heating gradually followed by continued stir the solution at same temperature up to a time
ranging between 15 to 60 minutes.

The step of combining aliphatic C6 to C7 hydrocarbon solvent is an important step, wherein
crystalline form-SB gets isolated.

The solution may optionally be maintain under stirring for a time ranging between 10-60 minutes
in order to retain the maximum isolation of the crystalline material.

The step of cooling the mixture may be carried out for the mixture upto about 10-40°C as per
need to attain the crystalline material precipitated out with no or minimal possible degradation if any. Simultaneously, it is also essentially required to cool the solution in the successive lower

rate of cooling in order to retain the characteristics of Form-SB, while achieving the pure crystal
formation.

The process related impurities, including unreacted intermediates, side products, degradation products and other medium dependent impurities, that appears in the impurity profile of the Bortezomib monohydrate can substantially be removed by the process of the present invention resulting in the formation crystalline form-SB. A substantially pure product having purities more than 99.5% (by HPLC) can be obtained by the process of the present invention. In view of maintaining the equilibrium to the impurity profile compliance, the process requires frequent quality checks, while raising the temperature especially in step b) upto 40-70°C.

The product may be isolated from the reaction mass by conventional processes including filtering and optional drying, which may be carried out at room temperature for the suitable durations to retain the crystalline polymorphic form characteristics.

Crystalline Form-SB can be recovered by conventional processes, which are not limited to scrapping, breaking, triturating and if required conventional drying.

Bortezomib monohydrate crystalline Form-SB obtained according to present invention shall be dried under vacuum, however, water content corresponding to monohydrate may get retained in the range between 5.5 to 8.0 % w/w (including residual/channel water if any) The Crystalline Form-SB of Bortezomib monohydrate described herein characterized by X-ray powder diffraction pattern (XRPD) and IR absorption spectra and Thermal techniques such as differential scanning calorimetric (DSC) Analysis, TGA. The samples of Bortezomib monohydrate Crystalline Form-SB were analyzed by XRPD on a Bruker AXS D8 Advance Diffractometer using X-ray source - Cu Ka radiation using the wavelength 1.5418 A, however, DSC analysis were carried out on a Perkin Elmer Jade instrument and RAMAN spectra was carried out on Perkin Elmer Raman Station 400 instrument. Illustrative examples of analytical data for the Crystalline Form-SB of Bortezomib monohydrate obtained in the Examples are set forth in the Figs. 1-4.

In a further embodiments of the present invention, the Crystalline Form SB of Bortezomib monohydrate (la) obtained by the process/es according to the present application may be formulated as compositions for injectable or oral administration in the form of powders, solutions, capsules, tablets, pills, or granules useful in the treatment of hyper-proliferative disorders, such as cancer.

Crystalline Form-SB of Bortezomib monohydrate of the present invention may have one or more advantageous and desirable properties compared to the known Bortezomib as anhydrate or trimeric form, which are not limited to better stability, solubility and quality parameter (improved purity ; > 99.5%) in leading to improved shelve life storage and distribution.

In Bortezomib monohydrate Crystalline Form-SB compositions, the active product is mixed with one or more pharmaceutically acceptable excipients. The drug substance can be formulated as lyophilized or ready to use compositions for injectable or solid / liquid compositions for oral administration including solutions, suspensions, syrups, elixirs and emulsions, containing solvents or vehicles such as water, sorbitol, glycerine, propylene glycol or liquid paraffin.

The compositions for parenteral administration can be solutions, suspensions, emulsions or aqueous or non-aqueous sterile solutions. As a solvent or vehicle, propylene glycol, polyethylene glycol, vegetable oils, especially olive oil, and injectable organic esters, e.g. ethyl oleate, may be employed. These compositions can contain adjuvants, especially wetting, emulsifying and dispersing agents. The sterilization may be carried out in several ways, e.g. using a bacteriological filter, by incorporating sterilizing agents in the composition, by irradiation or by heating. They may be prepared in the form of sterile compositions, which can be dissolved at the time of use in sterile water or any other sterile injectable medium.

Pharmaceutically acceptable excipients used in the compositions comprising Crystalline Form-SB of Bortezomib monohydrate of the present application include, but are but not limited to diluents such as starch, pregelatinized starch, lactose, powdered cellulose, microcrystalline cellulose, dicalcium phosphate, tricalcium phosphate, mannitol, sorbitol, sugar and the like; binders such as acacia, guar gum, tragacanth, gelatin, pre-gelatinized starch and the like; disintegrants such as starch, sodium starch glycolate, pregelatinized starch, Croscarmellose sodium, colloidal silicon dioxide and the like; lubricants such as stearic acid, magnesium stearate, zinc stearate and the like; glidants such as colloidal silicon dioxide and the like; solubility or wetting enhancers such as anionic or cationic or neutral surfactants, waxes and the like. Other pharmaceutically acceptable excipients that are of use include but not limited to film formers, plasticizers, colorants, flavoring agents, sweeteners, viscosity enhancers, preservatives, antioxidants and the like.

Pharmaceutically acceptable excipients used in the compositions derived from Crystalline Form-SB of Bortezomib monohydrate of the present application may also comprise to include the pharmaceutically acceptable carrier used for the preparation of solid dispersion, wherever utilized in the desired dosage form preparation.

Certain specific aspects and embodiments of the present application will be explained in more detail with reference to the following examples, which are provided by way of illustration only and should not be construed as limiting the scope of the invention in any manner.

EXPERIMENTAL DETAILS

The process for preparation according to the present invention of crystalline Bortezomib Form-SB may be demonstrated by examples as given below.

EXAMPLE 1: Preparation of Bortezomib

Preparation of Bortezomib comprise of three main stages-Stage-1: Preparation of N-((2S)-1 -(Y3-methyl-1 -((3aRV3a.5.5-trimethvlhexahvdro-4,6-methanobenzo f d] |" 1,3.21 dioxaborol-2- vDbutvOamino)-1 -oxo-3 -phenylpropan-2-vl)pvrazine-2-carboxamide (Intermediate, which is used without isolation for the next stage')
Take 98 ml MDC under nitrogen and add 7 gm of (S)-3-phenyl-2-(pyrazine-2-carboxamido) propanoic acid, 3.3 gm of N-Hydroxy succinimide and 6.0 gm of N,N-Diyclohexylcarbodimide.

Stir the reaction solution for 20 min at room temperature andunder continuous N2 purging.

Charge (R) Boroleu pinanediol trifluoro acetic acid 9.8 gm and 7.0 ml triethylamine and
continue stirring for about 4 hrs at room temperature and under continuous N2 purging.

Filter the mass and wash the cake with 20 ml methylene dichloride (MDC).

Collect MDC layer and wash with IN HC1200 ml followed by 200 ml of saturated solution of sodium bicarbonate.

Dry the MDC layer with dried sodium sulphate.

Distill out MDC under vacuum below 40 deg C and add 98 ml methanol and redistill.

Again add 98 ml methanol and redistill under vacuum at 45 deg C to get Stage 1-Intermediate material as residue.

Stage 2: Converting Stage-1 residue insitu into Crude Bortezomib ((3 -methyl- l-((S)-3-phenvl-2-(pyrazine-2-carboxamido) propanamido) butyl) boronic acid Take 255 ml methanol to the stage I -Intermediate residue (Insitu material) and add about 255 ml n- Heptane at room temperature.

Charge 3.0 gm iso butyl boronic acid and 255 ml
of freshly prepared 1 N HC1 aq. solution. Stir the mass at room temperature (20-30 deg C) for about 90 min.

Separate n -Heptane Organic layer.

Again charge 255 ml n -Heptane, stir for 60 min at RT and separate n Heptane layer.

Repeat the same process once again.
Distill of methanol from aq layer until the mass is turbid under vacuum below 45 deg C.

Cool the solution to RT and extract the product with 255 ml x 3 times with MDC.

Colect the the MDC layers and wash the MDC layer with 128 ml of saturated solution of sodium bicarbonate, followed by 128 ml of brine solution.

Dry with said MDC layer with sodium sulphate and distill of MDC completely under vacuum at below 45 deg C. Add 128 ml x 2 times ethyl acetate and distill out under vacuum below 45 deg C.

Charge 25 ml ethyl acetate at 45 deg C and slowly cool the solution to about 20-25 deg
C.

Start adding slowly up to about 95 ml toluene and continue stir for about 2 hrs at RT for material crystallization. Filter the mass by suck dry, wash the material with 5% of 128 ml ethyl acetate in toluene followed by dry at RT under vacuum. Yield = 4.2 gm Purity=98.8 % (by HPLC)

Stage 3: Preparing pure ((3-methvl-l-((SV3-phenvl-2-("pvrazine-2-carboxamido)propanamido) butyl) boronic acid monohydrate

1. Charge 12 ml methanol at RT in a RB flask and add Stage 2 material (4.0 gm) at RT.

2. Stir the solution at RT for complete dissolution.

3. Charge 12 ml water slowly in about 30-60 min and stir for 2 hrs at RT.

4. Filter the mass and wash with 6 methanol + 6 ml water mixture followed by suck drying and unloading.

5. Dry the unloaded material at 40-45 deg C under vacuum. Dry wt. (Yield) = 3.5 gm.

Purity= 99.65 % (By HPLC) Individual Impurity 0.11 & 0.14% EXAMPLE 2: Preparation of Crystalline Bortezomib monohydrate (Form-SB)
3.5 gms Stage 3 material (of example 1) is dissolved in 87.5 volumes of ethyl acetate at 40
deg to 45 deg C and filtered.
Start addition of 87.5 ml n-Heptane slowly at 40-45 deg C.

Slowly cool the solution mass to 25-30 deg C.
Stop stirring and maintain for about 4 hrs.

Filter and dry under vacuum at 40 deg C to get Bortezomib.

Dry wt. (Yield = 3:0-3.2 gm)Purity = 99.7% (By HPLC); Individual impurity=0.07% EXAMPLE 3: Preparation of Crystalline Bortezomib monohydrate (Form-SB) Batch No. #473/p32/09/12

a) In a clean RB flask, 50 ml mixture of ethyl acetate: water (95:5) is charged.

b) Add 2.0 gm Bortezomib-Pharma and stir the solution for 10-15 minutes at 25-30 °C

c) Slowly raise the temperature of the mixture to 40-45 °C to get the clear solution.

d) Filter the clear solution obtained in the above step through membrane paper.

e) Into the clear filtrate, was added 50 ml n-Heptane drop wise in 30 minutes at 40-45 °C.

f) Slowly cool the reaction mixture to 10-15 °C and maintain this mixture at same temperature for about 2 hours.

g) Filter the separated solid and washed with 4ml n-Heptane (Chilled).

h) Dry the material at below 40 °C under vacuum for 12 hours Yield =1.45 g Chromatographic purity (By HPLC) = 99.91% ; H. Indi=0.05% ; Total impurities=0.09%; Water content= ~7.5%w/w (in pyridine) XRPD as per Fig-1; DSC as per Fig.-2; IR spectra as per Fig.-3 and Raman Spectra as per Fig-4.

The abovementioned examples, which are provided by way of illustration, should not be construed as limiting the scope of the invention with respect to parameter/s, ingredient/s and quantities used in any manner.

Claims:

1). Bortezomib (la) as monohydrate crystalline Form-SB characterized by having water
content 5.5- 8.0 % w/w; X-ray powder diffraction pattern comprising characteristic 20°peaks selected from the XRPD peak set of 5.6, 7.5, 9.8, 10.2, 11.3, 15.1, 18.0, 20.5, 21.5 and 23.6 ±0.20 29°.

2). Bortezomib (la) according to claim-1, which is further characterized by DSC isotherm comprising two endothermic peaks ranging between-

c. Peak -1 - Between 45 to 60°C

d. Peak-2- Between 175-185 °C

3). Bortezomib (la) according to claim-1, which has an IR absorption spectrum having characteristic peaks expressed in cm"1 approximately at 3387 cm'1, 3304 cm'1, 2953 cm' \ 2927 cm'1, 2868 cm"1, 1627 cm"1,1455 cm"1, 1400 cm"1, 1201cm"1,1150cm"1, 1020 cm" ', 747 cm"1 and 702 cm"1

4). Bortezomib (la) according to claim-1, which has an Raman absorption spectrum having characteristic peaks expressed in cm'1 approximately 3066 cm"1, 1583 cm"1, 1528 cm" , 1281cm"1, 1213 cm"1,1035 cm"1, 1022cm"1 and 1004 cm"1.

5). Bortezomib (la) crystalline Form-SB characterized by X-ray powder diffraction pattern comprising the characteristic 28°peaks of 5.6, 7.5, 9.8, 10.2, 11.3, 15.1, 18.0, 20.5, 21.5 and 23.6 ± 0.20 29° , DSC isotherm comprising the endothermic peaks ranging between 45 to 60 °C (Peak -1) and 175 to 185°C (Peak -2) and IR absorption characteristic peaks at approximately at 3387 cm'1, 3304 cm*1, 2953 cm"1, 2927 cm"1, 2868 cm'1, 1627 cm"1, 1455 cm'1,1400 cm"1, 1201cm"1,1150cm"1,1020 cm"1, 747 cm"1 and 702 cm"1.

6). Bortezomib (la) crystalline Form-SB according to claim -3, characterized by X-ray powder diffraction pattern substantially according to Fig-1, DSC isothermal pattern substantially according to Fig-2 , IR absorption spectrum substantially according to Fig-3 and Raman spectrum substantially according to Fig-4. .

7). A process for preparing Bortezomib (la) crystalline Form-SB characterized by X-ray powder diffraction pattern comprising the characteristic 20°peaks of 5.6, 7.5, 9.8, 10.2, 11.3, 15.1, 18.0, 20.5, 21.5 and 23.6 ± 0.20 26°, DSC isotherm comprising the endothermic peaks ranging between 45 to 60 °C (Peak -1) and 175 to 185°C (Peak -2) and IR absorption characteristic peaks approximately at 3387 cm"1, 3304 cm"1, 2953 cm" \ 2927 cm"1, 2868 cm"1, 1627 cm"1, 1455 cm"1, 1400 cm"1, 1201cm"1, 1150cm"1, 1020 cm" , 747 cm" and 702 cm"1 and Raman absorption having characteristic peaks at approximately at 3066 cm"1, 1583 cm"1, 1528 cm"1, 1281cm'1,1213 cm"1,1035 cm"1, 1022cm"1 and 1004 cm"1 comprising the steps of-

a. Combining the crude bortezomib with an aliphatic ester solvent or a mixture of
aliphatic ester solvent and water

b. raise the temperature upto about 40- 70°C

c. Stir the solution at same temperature up to a time between 15 to 60 minutes.

d. combine aliphatic C6 to C7 hydrocarbon solvent

e. optionally maintain the mixture for 10-60 minutes

f. cooling the mixture upto about 10-40°C

g. isolating the crystalline material

8). A process for preparing Bortezomib (la) crystalline Form-SB according to claim 7,
wherein aliphatic ester solvent is selected from C3 to C8 aliphatic ester solvent.

9). A process for preparing Bortezomib (la) crystalline Form-SB according to claim 6,
wherein mixture of aliphatic ester solvent and water having ratio between 90:10 to 99:1
v/v.

10). Bortezomib (la) crystalline Form-SB according to any of the preceding claims having
water content in the range between 5.5 to 8.0 % w/w