Description:FORM 2

THE PATENT ACT, 1970
(39 of 1970)

COMPLETE SPECIFICATION
(See section 10, rule 13)

“A PROCESS FOR PURIFICATION OF VENETOCLAX OR ITS PHARMACEUTICALLY ACCEPTABLE SALT THEREOF”

Laurus Labs Limited, an Indian company of DS-1, IKP Knowledge Park, Genome valley, Turkapally, Shameerpet Mandal, Medchal-Malkajgiri district, Hyderabad –500 078, Telangana, INDIA

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

The present invention relates to a process for purification of venetoclax or its pharmaceutically acceptable salt thereof and pharmaceutical composition containing the same.

BACKGROUND OF THE INVENTION

Venetoclax, also known as 4-(4-{[2-(4-chlorophenyl)-4,4-dimethylcyclohex-1-en-1-yl]methyl}piperazin-1-yl)-N-({3-nitro-4-[(tetrahydro-2H-pyran-4yl-methyl)-amino]-phenyl}sulfonyl)-2-(1H-pyrrolo[2,3-b]pyridin-5-yloxy)benzamide):

Venetoclax

Venetoclax is marketed by Abbvie under the trade name Venclexta®in US and Venclyxto® in EP for the treatment of patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) or in combination with azacitidine/ decitabine/ or low-dose cytarabine for the treatment of newly diagnosed acute myeloid leukemia (AML).

U.S. Patent No. 8,546,399 (“the ‘399 patent”) discloses venetoclax and process for preparation by involving final acid-amine coupling in presence of EDC.HCl as a coupling agent. The ‘399 patent process involves purification of venetoclax by column chromatography using a mixture of ethyl acetate: hexanes and then with a mixture of methanol: ethyl acetate: acetic acid to obtain venetoclax as a white solid.

Venetoclax is very less soluble in most of the polar and aprotic solvents and this limits the solvent options for purification of final API; hence, purification of the venetoclax API is always a challenging task. Venetoclax prepared according to the ‘399 patent is always contaminate with the many processes impurities, these impurities may include unreacted starting materials, byproducts of the reaction, products of side reactions, and/or degradation products.

Impurities in venetoclax or any active pharmaceutical ingredient ("API") are undesirable and, in extreme cases, might even be harmful to a patient being treated with a dosage form of the API. Therefore, identifying impurities of an API produced in a manufacturing process and reducing/eliminating the presence of the same in the final product is crucial for commercialization.

Venetoclax is one of the important drug available in the market for the treatment of many types of leukemia. Hence, it is important to develop a simple and effective purification process for preparation of pure venetoclax API, which is readily amenable to large scale production and free from its impurities. Thus, the main objective of the present invention is to provide cost effective purification processes of venetoclax or a pharmaceutically acceptable salt thereof.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a process for purification of venetoclax or a pharmaceutically acceptable salt thereof.

In accordance with one embodiment, the present invention provides a process for purification of venetoclax or its pharmaceutically acceptable salts thereof, comprising:
a) suspending or dissolving venetoclax or a pharmaceutically acceptable salt thereof in a suitable solvent at a suitable temperature;
b) adding a suitable anti-solvent to the step a) reaction mass(or)addingstep a) reaction mass to a suitable anti-solvent; and
c) isolating the pure venetoclax or its pharmaceutically acceptable salts thereof.

In accordance with another embodiment, the present invention provides a process for purification of venetoclax or its pharmaceutically acceptable salts thereof, comprising:
a) suspending or dissolving venetoclax or a pharmaceutically acceptable salt thereof in a suitable solvent at a suitable temperature;
b) adding a suitable anti-solvent to the step a) reaction mass(or)addingstep a) reaction mass to a suitable anti-solvent; and
c) isolating the pure venetoclax or its pharmaceutically acceptable salts thereof; wherein the venetoclax or a pharmaceutically acceptable salt thereof as used in the step a) containing at least one related impurityby HPLC selected from the group comprising:

Formula I
Formula II Formula III

Formula IV
Formula V Formula VI

Formula VII
Formula VIII
Formula IX

Formula X
Formula XI
Formula XII

Formula XIII
Formula XIV
Formula XV

Formula XVI
Formula XVII
Impurity at 1.05 RRT
And
Impurity at 1.39 RRT

In accordance with another embodiment, the present invention provides a process for purification of venetoclax or its pharmaceutically acceptable salts thereof, comprising:
a) suspending or dissolving venetoclax or a pharmaceutically acceptable salt thereof in a suitable solvent at a suitable temperature;
b) adding a suitable anti-solvent to the step a) reaction mass(or)addingstep a) reaction mass to a suitable anti-solvent; and
c) isolating the pure venetoclax or its pharmaceutically acceptable salts thereof; wherein the suitable solvent is selected from the group comprising halogenated hydrocarbons, aromatic hydrocarbons, ketones, esters, nitriles, amides, sulfoxides, alkanoic acids and mixtures thereof; wherein the suitable anti-solvent is selected from the group comprising alcohols, ethers, aliphatic hydrocarbons, cyclic hydrocarbons and the like, and water and mixtures thereof.

In accordance with another embodiment, the present invention provides a process for purification of venetoclax or its pharmaceutically acceptable salts thereof, comprising:
a) suspending or dissolving venetoclax or a pharmaceutically acceptable salt thereof in a suitable solvent at a suitable temperature;
b) adding a suitable anti-solvent to the step a) reaction mass(or)addingstep a) reaction mass to a suitable anti-solvent; and
c) isolating the venetoclax or its pharmaceutically acceptable salts thereof;
wherein the suitable solvent is selected from the group comprising halogenated hydrocarbons, aromatic hydrocarbons, ketones, esters, nitriles, amides, sulfoxides, alkanoic acids and mixtures thereof;
wherein the suitable anti-solvent is selected from the group comprising alcohols, ethers, aliphatic hydrocarbons, cyclic hydrocarbons and the like, and water and mixtures thereof; and
wherein the venetoclax or a pharmaceutically acceptable salt thereof as used in the step a) containing at least one related impurity by HPLC selected from the group comprising:

Formula I
Formula II Formula III

Formula IV
Formula V Formula VI

Formula VII
Formula VIII
Formula IX

Formula X
Formula XI
Formula XII

Formula XIII
Formula XIV
Formula XV

Formula XVI
Formula XVII
Impurity at 1.05 RRT
And
Impurity at 1.39 RRT

In accordance with another embodiment, the present invention provides venetoclaxor a pharmaceutically acceptable salt thereofhaving less than 0.15% by HPLC of one or more of following impurities:

Formula I
Formula II Formula III

Formula IV
Formula V Formula VI

Formula VII
Formula VIII
Formula IX

Formula X
Formula XI
Formula XII

Formula XIII
Formula XIV
Formula XV

Formula XVI
Formula XVII
Impurity at 1.05 RRT
And
Impurity at 1.39 RRT

In accordance with another embodiment, the present invention provides a pharmaceutical composition comprising venetoclax or a pharmaceutically acceptable salt thereofobtained by the process of the invention and/or at least one pharmaceutically acceptable excipient.

DETAILED DESCRIPTION OF THE INVENTION

The present invention encompasses to a process for purification ofvenetoclax or a pharmaceutically acceptable salt thereof by simple solvent and anti-solvent method, which is readily amenable to large scale production and free from its impurities.
Venetoclax is very less soluble in most of the polar and aprotic solvents, which limited the solvent options for purification of final API. To date purification methods disclosed under the reported literature involves either silica-gel column chromatography or by solvent crystallization or by salt formation methods. By using theseknown purification methods present inventors observed that very difficult to eliminate the process impurities completely even after repeated purifications either by solvent crystallization methods and/or saltification and desaltification steps.

The present inventors have observed that, preparation of venetoclax as per the process disclosed in the ‘399 patent”involves formation of numerous process impurities.These impurities are very difficult to separate from venetoclax even after repeated purifications using either silica gel column chromatography or salt formation method or crystallization method. The impurities identified by the present inventors are listed as below:

Formula I
Formula II Formula III

Formula IV
Formula V Formula VI

Formula VII
Formula VIII
Formula IX

Formula X
Formula XI
Formula XII

Formula XIII
Formula XIV
Formula XV

Formula XVI
Formula XVII
Impurity at 1.05 RRT
And
Impurity at 1.39 RRT

Moreover the known purification methods are not enough to get required purity and the known methods are laborious and gives less yield.To overcome the difficulties associated with the art, the inventors of the present invention have surprisingly found that purification of venetoclaxor a pharmaceutically acceptable salt thereofusing simple solvent and anti-solvent method using a specific solvent system effectively eliminates the process and other impurities thereby getting pure product with higher yield without need of cumber some salt formation and silica-gel column purifications.

In accordance with one embodiment, the present invention provides a process for purification of venetoclax or its pharmaceutically acceptable salts thereof, comprising:
a) suspending or dissolving venetoclax or a pharmaceutically acceptable salt thereof in a suitable solvent at a suitable temperature;
b) adding a suitable anti-solvent to the step a) reaction mass(or)addingstep a) reaction mass to a suitable anti-solvent; and
c) isolating the pure venetoclax or its pharmaceutically acceptable salts thereof; wherein the venetoclax or a pharmaceutically acceptable salt thereof as used in the step a) containing at least one related impurity by HPLC selected from the group comprising:

Formula I
Formula II Formula III

Formula IV
Formula V Formula VI

Formula VII
Formula VIII
Formula IX

Formula X
Formula XI
Formula XII

Formula XIII
Formula XIV
Formula XV

Formula XVI
Formula XVII
Impurity at 1.05 RRT
And
Impurity at 1.39 RRT

The crude venetoclax or a pharmaceutically acceptable salt thereof may be prepared by any known processes; including process disclosed by US8546399 or can be prepared by following the process disclosed by present inventors, the content of which is incorporated herein by reference.

In another embodiment, the "venetoclax or a pharmaceutically acceptable salt thereof" in step a) refers to crude venetoclax or a pharmaceutically acceptable salt thereofwhich may be having content of total impurities about 20%, and/or having at least one or more of the impurities selected from Formula I to Formula XVII and Impurity at 1.05 RRT and Impurity at 1.39 RRT as identified by HPLC.

In a preferred embodiment, the "venetoclax or a pharmaceutically acceptable salt thereof" in step a) refers to crude venetoclax or a pharmaceutically acceptable salt thereof which may be having content of total impurities about 20%, preferably having about 15% and more preferably having about 10% and/or having at least one or more of the impurities selected from Formula I to Formula XVII and Impurity at 1.05 RRT and Impurity at 1.39 RRT as identified by HPLC.

The step a) of forgoing process involves, suspending or dissolving crude venetoclax or a pharmaceutically acceptable salt thereof in a suitable solvent at a temperature of about 0°C to about reflux temperature; preferably at about 25°C to about 60°C.

The suitable solvent used in aforementioned step a) is selected from the group comprisingof but not limited tohalogenated hydrocarbons, aromatic hydrocarbons, ketones, esters, nitriles, amides, sulfoxides, alkanoic acids and mixtures thereof. The halogenated hydrocarbons include, but are not limited tomethylene chloride, chloroform, chlorobenzene and the like; aromatic hydrocarbons include, but are not limited to toluene, xylene and the like; ketonesinclude, but are not limited toacetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone and the like; esters include, but are not limited toethyl acetate, propyl acetate, isopropyl acetate, butyl acetate and the like; nitriles include, but are not limited toacetonitrile, propionitrile and the like; amides include, but are not limited toN,N-dimethylformamide, N,N-dimethylacetamide and the like; sulfoxidesinclude, but are not limited todimethylsulfoxideand the like; alkanoic acids include, but are not limited toformic acid, acetic acid, propionic acid, butyric acid, palmitic acid and the likeand mixture thereof; preferably toluene, methylene chloride, acetone, ethyl acetate, acetonitrile, N,N-dimethylformamide, dimethylsulfoxide, formic acid, acetic acidand mixtures thereof; more preferablymethylene chloride, formic acidand mixture thereof.
The step b) of the aforementioned process involves, adding a suitable anti-solvent to the step a) reaction mass (or) adding step a) reaction mass to a suitable anti-solvent at a temperature of about 0°C to about reflux temperature; preferably at about 25°C to about 65°C.

The suitable anti-solvent used in aforementioned step b) is selected from the group comprising of but not limited to alcohols, ethers, aliphatic hydrocarbons, cyclic hydrocarbons and the like, and water and mixtures thereof. The alcohols include, but are not limited tomethanol, ethanol, butanol, propanol,tert-butanol and the like; ethers include, but are not limited totetrahydrofuran, dimethyl ether, isopropyl ether, methyl tertiary butyl ether, 1,4-dioxane and the like; aliphatic hydrocarbonsinclude, but are not limited to hexane, heptane, octane and the like; cyclic hydrocarbonsinclude, but are not limited to cyclopropane, cyclobutane, cyclopentane, cyclohexane, methyl cyclohexane, cycloheptane, cyclooctane and the like; and water and mixtures thereof; preferably methanol, ethanol, tetrahydrofuran, cyclohexane and mixtures thereof; more preferably methanol.

Then the resultant pure venetoclax can be isolated by conventional techniques such as precipitation by cooling the reaction mass, isolated by solvent precipitation, crystallization, concentrated by subjecting the solution to heating, decantation or filtration; preferably precipitation by cooling the reaction mass to below 35°C. The resultant product may optionally be further dried at a temperature of about 35°C to about 85°C for sufficient period of time.

In another embodiment, the present invention provides,as one of skilled in the art would appreciate, one or more purifications may be involved to get the pure venetoclax free from its impurities.

In another embodiment, the present invention provides venetoclax, obtained by the purification process described herein, having a purity of at least about 97%, as measured by HPLC, preferably at least about 99%, and more preferably at least about 99.5%; having total impurities less than 0.5%, as measured by HPLC, preferably less than 0.2%, more preferably less than 0.1%; substantially free of one or more of impurities from Formula I to XVII and Impurity at 1.05 RRT and Impurity at 1.39 RRT; where in the word “substantially free” refers to said impurities are less than 0.10% as measured by HPLC, preferably less than 0.05% as measured by HPLC, more preferably less than the detectable value by HPLC.

Venetoclax is very less soluble in most of the polar and aprotic solvents, which limited the solvent options for purification of final API.The known purification methods described for purification of venetoclax in the art are involved either by silica-gel column chromatography or by solvent crystallization or by saltification and followed by desaltification methods, which methods are not effective in either decreasing the process impurities or obtaining the desired pure API. The present invention provides a process for purification of venetoclax or a pharmaceutically acceptable salt thereofusing simple solvent and anti-solvent method using a specific solvent system, preferably by dissolving crude venetoclax in a mixture of methylene chloride and formic acid and followed by precipitating by adding methanol, which involves mainly eliminating process and other impurities thereby getting product with more pure and more yield. Therefore, cumbersome salt formation and silica-gel column purifications are avoided.

The present invention provides venetoclax, obtained by the above process, as analyzed using high performance liquid chromatography (“HPLC”) with the conditions are tabulated below:

Column XBridge phenyl column
Mobile phase A: Buffer and Acetonitrile
B: Acetonitrile and Methanol
Flow rate 1.0 mL/min
Elution Gradient
Detection By UV at 220 nm
Injection volume 20 µL
Run time 100 min
Mode Time in min Mobile phase A
(% v/v) Mobile phase B
(% v/v)
0 95 5
20 70 30
60 40 60
80 25 75
100 95 5

EXAMPLES

The following non limiting examples illustrate specific embodiments of the present invention. They are not intended to be limiting the scope of the present invention in any way.

EXAMPLE-1: Preparation of crude venetoclax

Acid intermediate (100 gm), methylene chloride (1.4 lit) and triethylamine (35.4 g) were added in to a round bottom flask and stirred for 1 hr at 25-35°C.Sulfonamide intermediate (52.5 g), methylene chloride (1.5lit), EDC.HCl (43.8 g) and 4-Dimethylaminopyridine (42.8 g) were added in to another round bottom flask and stirred for 1 hr at 25-35°C. To the reaction mass the above acid intermediate solution was added in 3-4 hr at 25-35°C. Reaction mass was stirred for 10 hr at 25-35°C. After completion of the reaction, to the reaction mass aq. acetic acid (2×500 mL) was added and stirred for 20-40 min at 25-35°C. Then the product containing organic layer and aqueous layers were separated and the organic layer was washed with aq. sodium bicarbonate solution (500 mL) and followed by aq sodium chloride solution (500 mL). The product containing organic layer was separated and concentrated under vacuum at below 45°C and dry the wet material to obtain title compound. Wt.: 173 g.

Purity and Impurity % by HPLC:

venetoclax Formula I Formula II Formula III Formula IV Formula V Formula VI
91.2% 0.1% 0.05% 0.05% 0.05% 0.02% 4.8%
Formula VII Formula VIII Formula IX Formula XVII 1.05 RRT 1.39 RRT
0.1% 0.05% 1.04% 0.1% 0.1% 0.4%

EXAMPLE-2: Purification of venetoclax

Venetoclax (86.5 g from Ex-1),methylene chloride (100 mL)and Formic acid (100 mL) were added in to a round bottom flask at 25-35°C. Reaction mass was heated to 42-46°C and stirred for 30 min at same temperature. To the reaction mass methanol (500 mL) was added in 60 min at 42-46°C and stirred for 30-40 min at same temperature.Reaction mass was allowed to cool to 25-30°C and stirred for 15 hr at same temperature. Solid was filtered and washed with methanol (50 mL), suck dried the solid for 30 min to obtain the title compound. Wt: 60 g.
Purity and Impurity % by HPLC:
Venetoclax 99.9% Formula VIII ND Formula XVI ND
Formula I 0.01% Formula IX ND Formula XVII ND
Formula II ND Formula X ND 1.05 RRT 0.01%
Formula III ND Formula XI ND 1.39 RRT 0.04%
Formula IV ND Formula XII ND Formula VII 0.06%
Formula V 0.02% Formula XIII ND Formula XV ND
Formula VI ND Formula XIV ND
*ND: Not detected by HPLC

EXAMPLE-3: Purification of venetoclax

Purification of venetoclax (from Ex-1) is carried out by following the process same as described in Example-2by using the below solvent volumes (v) and the HPLC data is as follows:

Solvent system:

Methylene chloride:
Formic acid:
Methanol 2 v:
2 v:
10 v 1.5 v:
2v:
10 v 2.5 v:
2 v:
10 v 2 v:
1.5 v:
10 v 2 v:
2.5 v:
10 v 2 v:
2 v:
8 v 2 v:
2 v:
12 v

Purity and Impurity % by HPLC:

Venetoclax 99.94% 99.95% 99.86% 99.94% 99.95% 99.93% 99.9%
Formula I 0.01% 0.01% 0.01% ND ND ND 0.01%
Formula II ND ND 0.01% ND ND ND ND
Formula III ND ND ND ND ND ND ND
Formula IV 0.01% ND 0.01% ND ND ND ND
Formula V ND 0.04% 0.06% 0.03% ND ND 0.04%
Formula VI 0.02% 0.02% ND 0.02% 0.02% 0.01% 0.01%
Formula VII 0.05% 0.05% 0.03% 0.06% 0.05% ND 0.04%
Formula VIII ND ND 0.01% ND ND ND ND
Formula IX ND ND ND ND ND ND ND
Formula X ND ND ND ND ND ND ND
Formula XI ND ND ND ND ND ND ND
Formula XII ND ND ND ND ND ND ND
Formula XIII ND ND ND ND ND ND ND
Formula XIV ND ND ND ND ND ND ND
Formula XV ND ND ND ND ND ND ND
Formula XVI ND ND ND ND ND ND ND
Formula XVII ND ND ND ND ND ND ND
1.05 RRT ND ND ND ND ND ND ND
1.39 RRT 0.04% 0.03% ND 0.04% 0.01% 0.05% 0.05%
*ND: Not detected by HPLC

It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore the above description should not be constructed as limiting, but merely as exemplifications of preferred embodiments. For example, the functions described above and implemented as the best mode for operating the present invention are for illustration purposes only. Other arrangements and methods may be implemented by those skilled in the art without departing from the scope and spirit of this invention. Moreover, those skilled in the art will envision other modifications within the scope and spirit of the specification appended hereto.
, Claims:We Claim:

1. A process for purification of venetoclax or its pharmaceutically acceptable salts thereof, comprising:
a) suspending or dissolving venetoclax or a pharmaceutically acceptable salt thereof in a suitable solvent at a suitable temperature;
b) adding a suitable anti-solvent to the step a) reaction mass(or)addingstep a) reaction mass to a suitable anti-solvent; and
c) isolating the pure venetoclax or its pharmaceutically acceptable salts thereof;
wherein in the suitable solvent is selected from the group comprising of halogenated hydrocarbons, aromatic hydrocarbons, ketones, esters, nitriles, amides, sulfoxides, alkanoic acids and mixtures thereof; and wherein theanti-solventis selected from the group comprising of alcohols, ethers, aliphatic hydrocarbons, cyclic hydrocarbons and water and mixtures thereof.

2. The process as claimed in claim 1, wherein in thesuitable solventis selected from the group comprising of methylene chloride, chloroform, chlorobenzene, toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, acetonitrile, propionitrile, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide,formic acid, acetic acid, propionic acid, butyric acid, palmitic acid and mixture thereof.

3. The process as claimed in claim 1, wherein the step a) is carried out at a temperature of about 25°C to about 60°C.

4. The process as claimed in claim 1, wherein theanti-solventis selected from the group comprising ofmethanol, ethanol, butanol, propanol,tert-butanol, tetrahydrofuran, dimethyl ether, isopropyl ether, methyl tertiary butyl ether, 1,4-dioxane, hexane, heptane, octane, cyclopropane, cyclobutane, cyclopentane, cyclohexane, methyl cyclohexane, cycloheptane, cyclooctane and water and mixtures thereof.

5. The process as claimed in claim 1, wherein thesolvent is methylene chlorideand formic acid and the anti-solventis methanol.

6. The process as claimed in claim 1, wherein the step b) is carried out at a temperature of about 25°C to about 65°C.

7. The process as claimed in claim 1, wherein the venetoclax or a pharmaceutically acceptable salt thereof of step a) comprises at least one related impurity by HPLC from the following impurities:

Formula I
Formula II Formula III

Formula IV
Formula V Formula VI

Formula VII
Formula VIII
Formula IX

Formula X
Formula XI
Formula XII

Formula XIII
Formula XIV
Formula XV

Formula XVI
Formula XVII

Impurity at 1.05 RRT
And
Impurity at 1.39 RRT

8. The process as claimed in claim 1, wherein the venetoclax or a pharmaceutically acceptable salt obtained is having less than 0.15% by HPLC of one or more impurities of Formula I to XVII and Impurities at 1.05 RRT and1.39 RRT.

9. Venetoclax or a pharmaceutically acceptable salt thereof having less than 0.15% by HPLC of one or more of following impurities:

Formula I
Formula II Formula III

Formula IV
Formula V Formula VI

Formula VII
Formula VIII
Formula IX

Formula X
Formula XI
Formula XII

Formula XIII
Formula XIV
Formula XV

Formula XVI
Formula XVII

Impurity at 1.05 RRT
And
Impurity at 1.39 RRT

10. A pharmaceutical composition comprising venetoclax or a pharmaceutically acceptable salt thereof according to claims 1-9 and at least one pharmaceutically acceptable excipient.