WO2020023435A1

WO2020023435A1 - Venetoclax basic salts and processes for the purification of venetoclax

Info

Publication number: WO2020023435A1
Application number: PCT/US2019/042906
Authority: WO
Inventors: Brian Thomas GREGG; William Bert GEISS; Robert Jason Herr; Ravi R RAI
Original assignee: Albany Molecular Research, Inc.
Priority date: 2018-07-24
Filing date: 2019-07-23
Publication date: 2020-01-30

Abstract

The invention relates to basic salts of Venetoclax and processes for the purification of Venetoclax through said salts.

Description

VENETOCLAX BASIC SALTS AND PROCESSES FOR THE PURIFICATION OF

VENETOCLAX

Field of the Invention

The invention belongs to the field of drug synthesis, and more particularly relates to basic salts of Venetoclax and processes for the purification of Venetoclax through said salts.

Background of the Invention

Venetoclax (also known as ABT-199) is an orally active inhibitor of anti-apoptotic protein B-cell lymphoma-2 (Bcl-2) developed and marketed by AbbVie and Genentech for the treatment of chronic lymphocytic leukemia (CLL) under the tradename Venclexta in the U.S. and Venclyxto in Europe.

The chemical name of Venetoclax is 4-(4-{[2-(4-chlorophenyl)-4,4- dimethylcyclohex-1-en-1-yl]methyl}piperazin-1-yl)-N-({3-nitro-4-[(tetrahydro-2H-pyran- 4-ylmethyl)amino]phenyl}sulfonyl)-2-(1 H-pyrrolo[2,3-b]pyridin-5-yloxy)benzamide, corresponding to the molecular formula C₄₅H₅₀CIN₇O₇S and the following structure:

Venetoclax

Several methods have been disclosed in the state of the art for the synthesis of this compound.

Preparation of Venetoclax free-base was initially described in Example 5 of WO

2010/138588. The process disclosed in this document for the preparation of Venetoclax includes a first S_NAr at high temperature (1 15 °C, 24 h) to obtain intermediate (D) followed by coupling with the piperazine derivative (I) at high temperature (135 °C, 24 h) to afford intermediate (K). Further hydrolysis of the ester group followed by coupling of the resulting carboxylic acid with sulfonamide (N) gives rise to Venetoclax (Scheme 1).

Scheme 1

The same synthetic approach is disclosed in WO 2012/121758 and WO 2012/058392, which are patent applications drawn to solid dispersions comprising, in essentially non-crystalline form (e.g. amorphous), a Bcl-2 protein inhibitor of general Formula I such as Venetoclax.

WO 2012/071336 also shows the same synthetic route for the preparation of

Venetoclax, pointing out that the product of this process can be a solid that is amorphous in character. WO 2012/071336 further discloses various crystalline forms A to N of Venetoclax including solvated and non-solvated forms and salts of Venetoclax including hydrochloride, hydrochloride hydrate and sulfate (PXRD Patterns K, L, and M, respectively).

WO 2014/165044 discloses some improvements in relation to the previous synthesis (Scheme 2). In this new approach, the regioselectivity of the S_NAr is improved by carrying out the reaction over compound (C1), where the reactivity of ortho- and para- positions is differentiated by the presence of a F and Br atom, respectively. Further Palladium catalyzed C-N coupling reaction between compounds (D1) and (11), followed by hydrolysis of the ester group in intermediate (K1) gives rise to acid derivative (L). Due to the steric hindrance of the tert-butyl ester group, hydrolysis to the carboxylic acid (L) requires very specific reaction conditions.

Scheme 2

CN 104370905 A discloses a method for the synthesis of Venetoclax as shown in Scheme 3 below. S_NAr reaction of methyl 2-fluoro-4-nitrobenzoate with 5-hydroxy-7- azaindole gives rise to intermediate C, which is further hydrogenated to afford aniline D. The piperazine ring is introduced by reaction with dichloride E. Further coupling with intermediate H, hydrolysis of the ester group and coupling with sulfonamide K gives rise to Venetoclax.

Scheme 3

WO 2017/212431 relates to solid forms of Venetoclax and preparative processes thereof. The solid forms disclosed include amorphous and crystalline forms RT1 , RT2, RT3, RT4 and RT5 of the free-base compound and the following acid addition salts: trifluoro acetic acid (TFA), oxalic acid, maleic acid, Isethionic acid, ortho-phosphoric acid, citric acid, methanesulfonic acid and acetic acid. As in the previous patent applications, the final steps to Venetoclax according to examples 42 and 43 of WO 2017/212431 involve hydrolysis of the ester group followed by coupling with sulfonamide (Scheme 4).

Scheme 4

Further crystal forms of Venetoclax free-base are disclosed in WO 2017/063572 and WO 2017/156398.

Like any synthetic compound, Venetoclax can contain extraneous compounds or 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.

On the other hand, in the formulation of drug compositions, it is important for the drug substance to be in a form in which it can be conveniently handled and processed. This is of importance, not only from the point of view of obtaining a commercially-viable manufacturing process, but also from the point of view of subsequent manufacture of pharmaceutical formulations comprising the active compound. Further, the active compound should exhibit a good performance in the pharmaceutical formulation in terms of chemical stability, bioavailability (absorption, dissolution rate...), etc.

Drug products are generally produced as solid materials. Even when formulated as liquids, the API is still usually produced as a solid prior to the final dissolution. Thus, the discovery of new solid forms of new or existing APIs such as Venetoclax provides an opportunity to facilitate the manufacturing, handling and storage of the compound, and compositions containing it, and/or to improve the observed performance in the final dosage form. A constant need thus exists to develop processes suitable at commercial scale for the production of highly pure Venetoclax. There is also a need in the art for additional solid forms of Venetoclax that can act as intermediates during the manufacture process or that may provide in themselves a still better formulation of this API.

Summary of the Invention

The present invention solves the aforementioned needs by the provision of a process for the purification of Venetoclax via formation of a basic salt thereof. To the best knowledge of the inventors, there is no prior disclosure of a basic salt of Venetoclax.

After extensive research, the present inventors have identified two important dimeric impurities associated with the methods for preparing Venetoclax reported in the state of the art. The structure of said undesirable impurities, herein referred to as impurity I and impurity II, is depicted below:

Without being bound to any theory, it is believed that these impurities are generated in the final stage of the manufacturing process of the API since the last two reactions (hydrolysis of ester and coupling) are common in all the chemical routes.

The present inventors have conducted extensive experimentation with an intention to reduce such impurities and obtain highly pure Venetoclax. As a result of this research, the inventors have surprisingly found that the basic salts of Venetoclax (such as sodium or potassium salts), which are compounds not anticipated in the prior art, constitute suitable intermediates for obtaining highly pure Venetoclax forms. Attempts to reduce the amount of impurities I and II by other conventional methods failed or afforded unsatisfactory results. For instance, successive recrystallizations of either Venetoclax free-base or acid salts thereof (such as maleate, chlorhydrate or sulfate) do not allow achieving such a high degree of purification.

Thus, in a first aspect, the invention is directed to a basic salt of Venetoclax. In a particular embodiment, the basic salt of Venetoclax is selected from group consisting of sodium, potassium and lithium salt.

In another aspect, the invention is directed to a process for the preparation of a basic salt of Venetoclax, said process comprising the step of contacting Venetoclax or an acid salt thereof with a base so as to obtain a basic salt of Venetoclax.

In another aspect, the invention is directed to a process for the purification of Venetoclax, said process comprising:

(a) taking a sample comprising Venetoclax or an acid salt thereof and impurities I and/or II;

(b) treating said sample with a base so as to obtain a basic salt of Venetoclax;

(c) preferably, crystallizing said basic salt of Venetoclax from a suitable solvent system; and

(d) converting said basic salt of Venetoclax into Venetoclax or a different salt thereof.

In another aspect, the invention is directed to the compound Venetoclax or a salt thereof, said compound being obtainable according to the purification process disclosed herein.

In another aspect, the invention is directed to the compound Venetoclax or a salt thereof which is of a level of purity such that said compound contains less than 1 % of impurities I and II.

In another aspect, the invention is directed to the compound Venetoclax or a salt thereof obtainable according to the purification process disclosed herein and containing less than 1 % of impurities I and II.

In another aspect, the invention is directed to an impurity associated with the synthesis of Venetoclax, said impurity being selected from impurity I and impurity II. These aspects and preferred embodiments thereof are additionally also defined hereinafter in the detailed description and in the claims.

Brief Description of the Drawings

Figure 1 is an illustrative powder X-ray diffraction (PXRD) pattern of crystalline sodium salt of Venetoclax prepared by the method of Example No 1.

Figure 2 is an illustrative ¹H NMR (500 MHz, DMSO-cfe) of crystalline sodium salt of Venetoclax prepared by the method of Example No 1.

Figure 3 is an illustrative powder X-ray diffraction (PXRD) pattern of the sodium salt of Venetoclax in amorphous form.

Figure 4 is an illustrative ¹H NMR (500 MHz, DMSO-cfe) of impurity II.

Figure 5 is an illustrative direct inject mass spectrometry (ESI, + mode) data of impurity

Figure 6 is an illustrative direct inject mass spectrometry (ESI, - mode) data of impurity

Detailed Description of the Invention

The present inventors have developed a novel process for the purification of Venetoclax which is based on the formation of a basic salt thereof and neutralization to recover highly pure Venetoclax. The process of the present invention is simple, inexpensive, reproducible and is well suited for industrial scale.

Definitions

A solid state form, such as a crystal form or amorphous form, may be referred to herein as being characterized by graphical data "as depicted in" or "as substantially depicted in" a Figure. Such data include, for example, powder X-ray diffractograms and solid state NMR spectra. As is well-known in the art, the graphical data potentially provides additional technical information to further define the respective solid state form (a so-called "fingerprint") which cannot necessarily be described by reference to numerical values or peak positions alone. In any event, the skilled person will understand that such graphical representations of data may be subject to small variations, e.g., in peak relative intensities and peak positions due to certain factors such as, but not limited to, variations in instrument response and variations in sample concentration and purity, which are well known to the skilled person. Nonetheless, the skilled person would readily be capable of comparing the graphical data in the Figures herein with graphical data generated for an unknown crystal form and confirm whether the two sets of graphical data are characterizing the same crystal form or two different crystal forms. A crystal form of Venetoclax or a salt thereof referred to herein as being characterized by graphical data "as depicted in" or "as substantially depicted in" a Figure will thus be understood to include any crystal forms of Venetoclax or a salt thereof characterized with the graphical data having such small variations, as are well known to the skilled person, in comparison with the Figure.

A solid state form (or polymorph) may be referred to herein as polymorphically pure or as substantially free of any other solid state (or polymorphic) forms. As used herein in this context, the expression "substantially free of any other forms" will be understood to mean that the solid state form contains 20 % or less, 10 % or less, 5 % or less, 2 % or less, or 1 % or less of any other forms of the subject compound as measured, for example, by PXRD. Thus, solid state of Venetoclax or a salt thereof described herein as substantially free of any other solid state forms would be understood to contain greater than 80 % (w/w), greater than 90 % (w/w), greater than 95 % (w/w), greater than 98 % (w/w), or greater than 99 % (w/w) of the subject solid state form of Venetoclax or a salt thereof. Accordingly, in some embodiments of the invention, the described solid state forms of Venetoclax or a salt thereof may contain from 1 % to 20 % (w/w), from 5 % to 20 % (w/w), or from 5 % to 10 % (w/w) of one or more other solid state forms of the same compound.

As used herein, the term "about" means a slight variation of the value specified, preferably within 10 percent of the value specified. Nevertheless, the term "about" can mean a higher tolerance of variation depending on for instance the experimental technique used. Said variations of a specified value are understood by the skilled person and are within the context of the present invention. Further, to provide a more concise description, some of the quantitative expressions given herein are not qualified with the term“about”. It is understood that, whether the term“about” is used explicitly or not, every quantity given herein is meant to refer to the actual given value, and it is also meant to refer to the approximation to such given value that would reasonably be inferred based on the ordinary skill in the art, including equivalents and approximations due to the experimental and/or measurement conditions for such given value.

By“room temperature” or its abbreviation“rt” is meant herein that the reactions or processes are performed without heating or cooling. Generally, by room temperature may be understood as a temperature between about 15 °C and about 30 °C, or more particularly between about 20 °C and about 25 °C.

The term “solvent system” includes both a single solvent and a mixture of solvents. The solvent may be water, one or more organic solvents or any mixture thereof.

The term“organic solvent” includes for example cyclic and acyclic ethers (e.g. Et₂0, iPr₂0, tBu₂0, MeOtBu, 1 ,4-dioxane, tetrahydrofuran, methyltetrahydrofuran), hydrocarbon solvents (e.g. pentane, hexane, heptane), halogenated solvents (e.g. dichloromethane, chloroform), aromatic solvents (e.g. toluene, xylene), ketones (e.g. acetone, butanone, pentanone, methyl ethyl ketone, ethyl isopropyl ketone), esters (e.g. EtOAc, iPrOAc), nitriles (e.g. acetonitrile, benzonitrile), amides (e.g. DMF, DMA, HMPA), alcohols (e.g. methanol, ethanol, propanol, isopropanol, sec-butanol, t- butanol), sulfoxides (DMSO) and mixtures thereof.

As used herein, and unless indicated otherwise, the term "substantially amorphous" is intended to mean greater than about 70 %; or greater than about 75 %; or greater than about 80 %; or greater than about 85 %; or greater than about 90 %; or greater than about 95 %), or greater than about 99 % of the compound present in a composition is in amorphous form.

As used herein, and unless state indicated otherwise, the term "substantially crystalline" is intended to mean that greater than about 70 %; or greater than about 75 %; or greater than about 80 %; or greater than about 85 %; or greater than about 90 %; or greater than about 95 %), or greater than about 99 % of the compound is present in a composition is in crystalline form.

As used herein, the term "isolated" in reference to solid state forms of Venetoclax of the present disclosure corresponds to a solid state form of Venetoclax that is physically separated from the reaction mixture in which it is formed.

The amount of solvent employed in a chemical process, e.g., a reaction or crystallization, may be referred to herein as a number of "volumes" or "vol" or "V." For example, a material may be referred to as being suspended in 10 volumes (or 10 vol or 10V) of a solvent. In this context, this expression would be understood to mean milliliters of the solvent per gram of the material being suspended, such that suspending a 5 grams of a material in 10 volumes of a solvent means that the solvent is used in an amount of 10 milliliters of the solvent per gram of the material that is being suspended or, in this example, 50 mL of the solvent. Unless otherwise stated, references to purity may be understood as HPLC purity.

Venetoclax sodium salt

In a first aspect the invention is directed to a basic salt of Venetoclax. The basic salt of Venetoclax may be in crystalline or in amorphous form. The basic salt of Venetoclax may be also in substantially crystalline or in substantially amorphous form. The basic salts of Venetoclax herein disclosed may be characterized for instance by powder X-ray diffraction (PXRD), proton nuclear magnetic resonance (1 H-NMR), and differential scanning calorimetry (DSC).

In a particular embodiment, the basic salt of Venetoclax is selected from group consisting of Venetoclax sodium, Venetoclax potassium and Venetoclax lithium.

In a particular embodiment, is provided a crystalline form of Venetoclax sodium salt, designated as form 1. The crystalline form 1 of Venetoclax sodium salt may be characterized by having a PXRD pattern substantially as depicted in figure 1.

In one embodiment, the crystalline form of Venetoclax sodium salt is isolated. In another embodiment, the crystalline form 1 of Venetoclax sodium salt is polymorphically pure.

In another aspect, the present application provides a process for the preparation of a basic salt of Venetoclax comprising the step of contacting Venetoclax, either in free or acid-form, with a base so as to obtain a basic salt of Venetoclax. Said base includes, but is not limited to, sodium containing bases, potassium containing bases and lithium containing bases.

Suitable sodium containing bases include, but are not limited to, sodium hydride, sodium hydroxide, sodium carbonate and sodium alkoxides such as sodium methoxide, sodium ethoxide, sodium tert-butoxide and the like. In a particular embodiment, the sodium containing base is sodium hydroxide and more particularly aqueous sodium hydroxide.

Suitable potassium containing bases include, but are not limited to, potassium hydride, potassium hydroxide, potassium carbonate and potassium alkoxides such as potassium methoxide, potassium ethoxide, potassium tert-butoxide and the like. In a particular embodiment, the potassium containing base is potassium hydroxide and more particularly aqueous potassium hydroxide.

Suitable lithium containing bases include, but are not limited to, lithium hydroxide, lithium carbonate and lithium amides (such as lithium diisopropylamide (LDA) and lithium diethylamide).

In a particular embodiment, Venetoclax may be contacted with the base in a mole ratio of about 1 :2 to 1 :20, or 1 :4 to 1 :15, or 1 :8 to 1 :14.

In an embodiment, the base may be used either in concentrated or diluted form before contacting with Venetoclax.

Venetoclax may be contacted with the base in a heterogeneous or homogeneous phase. In a particular embodiment, the reaction is heterogeneous. More particularly, a solution or suspension of Venetoclax in a suitable organic solvent or mixture of organic solvents is contacted with an aqueous basic solution such as aqueous solution of sodium hydroxide.

Suitable solvent systems for preparing the basic salt of Venetoclax include but are not limited to a mixture of DCM/alcohol, MeTHF/alcohol, THF/alcohol or AcOEt/alcohol. The alcohol of said mixtures may be for instance methanol, ethanol, propanol, isopropanol, sec-butanol, or t-butanol, and more preferably methanol, ethanol, and isopropanol.

In an embodiment, Venetoclax may be contacted with the base at a suitable temperature at about 0 °C and above for time sufficient for salt formation. In an embodiment, the reaction mixture comprising Venetoclax and the base may be stirred for sufficient time and at suitable temperature for the completion of salt formation. In a more particular embodiment, the reaction mixture comprising Venetoclax and the base is stirred and heated at about 30-60 °C or more for about 4-18 h.

In an embodiment, after salt formation, the reaction mixture is cooled to suitable temperature (e.g. 30-35 °C) and / or subject to phase separation to obtain an organic phase comprising the basic salt of Venetoclax.

Isolation of the basic salt of Venetoclax may be carried out by any methods known in the art or procedures described in the present application. In an embodiment, the sodium salt of Venetoclax may be isolated by employing any of the techniques, but not limited to: decantation, filtration by gravity or suction, centrifugation, adding solvent to make slurry followed by filtration, or other techniques specific to the equipment used and the like, and optionally washing with a solvent and drying.

In an embodiment, the basic salt of Venetoclax is isolated by cooling the organic phase and precipitation followed by filtration. In another embodiment, the basic salt of Venetoclax is isolated by partial distillation of the organic phase and then cooling and precipitation followed by filtration. In another embodiment, the basic salt of Venetoclax is isolated by adding a non-polar solvent that acts as anti-solvent.

In a particular embodiment, an organic phase comprising Venetoclax sodium salt is concentrated by distillation for sufficient time and at suitable temperature (e.g. until a batch of 5-15 Vol) and then cooled so as to precipitate Venetoclax sodium salt. Typically, sodium Venetoclax is obtained as a bright yellow solid. Depending on the conditions, the solid obtained may be amorphous or crystalline.

In a particular embodiment, the precipitate Venetoclax sodium salt is collected and washed with a suitable solvent such as DCM or a mixture DCM/methanol (e.g. 90:10 v/v), one, two or more times, and then dried under vacuum for a period of from about 15 minutes to 3 hours or longer.

Unexpectedly, the formation of basic salts of Venetoclax (such as the sodium salt) as herein described allows increasing the degree of purity by reducing the amount of impurities, especially impurity II. For instance, starting from a crude reaction obtained when synthetizing Venetoclax (coupling with sulfonamide as shown in Scheme 4 above) comprising about 5% of impurity II, Venetoclax sodium salt may be obtained with a content of impurity II of about 0.3%

The basic salt of Venetoclax (such as the sodium salt) can be easily purified by crystallization in a suitable solvent system. Preferably, the solvent system is an alcohol e.g. methanol, ethanol, propanol, isopropanol, sec-butanol, t-butanol), preferably methanol, or a mixture of an alcohol (e.g. methanol) with DCM and optionally MTHF. After heating the corresponding suspension/solution of the basic salt of Venetoclax, normally to reflux, for a period of from about 15 minutes to 10-18 hours or longer and cooling the reactor, normally to room temperature or below, the solids may be collected, washed with a suitable organic solvent (e.g. methanol) and dried to give the basic salt of Venetoclax as a crystalline solid.

Regarding the solvent choice for an effective crystallization, it is preferred that the basic salt of Venetoclax has low solubility (i.e., almost sparingly soluble) at low temperature and high solubility at high temperature. Particular solvents systems useful for crystallizing Venetoclax sodium salt or other basic salts include, but are not limited to: MeOH/DCM (1-5/10-20 Vol), MeOH (15-30 Vol) MeTHF/MeOH (10/2-4 Vol), MeTHF/AcOEt, AcOEt, Acetone, DMF (2-4 Vol), ACN, etc. Drying may be carried out using standard techniques. In an embodiment, drying the basic salt of Venetoclax may be carried out at temperatures and times sufficient to achieve the desired quality of product such as from about 15 minutes to 1-3 hours or longer in a vacuum oven at a temperature above 35 °C (e.g. 50-60 °C).

Crystallisation may also be initiated and/or effected by way of standard techniques, for example with or without seeding with crystals of the appropriate crystalline compound of the invention. In order to ensure that a particular crystalline form is prepared in the absence of other crystalline forms, crystallizations are preferably carried out by seeding with nuclei and/or seed crystals of the desired crystalline form in substantially complete absence of nuclei and/or seed crystals of other crystalline forms. Seed crystals of appropriate crystalline form may be prepared, for example, by way of slow evaporation of solvent from a portion of solution of Venetoclax basic salt.

With only one crystallization the purity of Venetoclax sodium salt or other basic salts of Venetoclax may be increased to above 99% (e.g. about 99.5%). Further purification may be effected using additional recrystallizations.

In one embodiment, the process for converting Venetoclax to a sodium salt thereof comprises the following steps:

(i) providing an organic phase comprising Venetoclax and an alcohol;

(ii) adding an aqueous phase of sodium hydroxide;

(iii) stirring and heating the mixture so as to form Venetoclax sodium salt:

(iv) cooling and subjecting the mixture to phase separation to obtain an organic phase comprising Venetoclax sodium salt;

(v) cooling the organic phase so as to precipitate Venetoclax sodium salt;

(vi) optionally, purifying Venetoclax sodium salt by crystallization.

The process for converting Venetoclax to a basic salt other than sodium may be the same as described above but replacing the sodium hydroxide with the corresponding base (e.g. potassium or lithium hydroxide).

The basic salt of Venetoclax such as the sodium salt may be used to purify Venetoclax.

The basic salt of Venetoclax such as the sodium salt can be used to prepare other solid state forms of Venetoclax, Venetoclax salts, and solid state forms thereof.

The present disclosure provides Venetoclax basic salts for use in the preparation of pharmaceutical compositions.

The present disclosure also encompasses the use of Venetoclax basic salts for the preparation of pharmaceutical compositions.

The present disclosure comprises processes for preparing the above mentioned pharmaceutical compositions. The processes comprise combining a Venetoclax basic salt with at least one pharmaceutically acceptable excipient.

Venetoclax basic salts and the pharmaceutical compositions of Venetoclax basic salts of the present disclosure can be used as medicaments, particularly for the treatment of chronic lymphocytic leukemia.

The present disclosure also provides methods of treating of chronic lymphocytic leukemia comprising administering a therapeutically effective amount of a Venetoclax basic salt of the present disclosure, or at least one of the above pharmaceutical compositions, to a subject in need of the treatment.

Purification of Venetoclax

Almost all the synthetic schemes described for preparing Venetoclax have in common two final steps comprising a hydrolysis step given place to a carboxylic acid group and a final coupling reaction of this carboxylic group with the sulfonamide moiety:

Surprisingly, the inventors have found that there are some characteristic impurities, due to the Pyrrolo[2,3-b]pyridine group reactivity coming from the hydrolysis/coupling step or directly from the coupling step, as for example the dimeric impurities I and II, not described or characterized in any previous document.

The inventors have also found that these dimeric impurities of high molecular weight are also difficult to purify because of they are very insoluble in protic/aprotic solvents.

Therefore, to achieve highly pure API at commercial scale, a process was required to reduce/remove all these impurities.

In order to increase such solubility, some acid addition salts were tested, such as chlorhydrate salt, sulfate salt, maleate salt, etc., but it was unexpectedly found that basic addition salts such as the sodium salt proved to be more efficient and the API salt form easily crystallized in a variety of solvents.

The present invention describes such impurities and also provides an efficient process for the purification of Venetoclax through the formation of a basic salt thereof, preferably followed by crystallization, and finally neutralization to the free form or salt exchange to obtain a different salt of Venetoclax.

Starting from a sample of Venetoclax, or an acid salt thereof, that is contaminated with impurities I and/or II, a basic salt of Venetoclax such as Venetoclax sodium salt, preferably in crystal form, may be obtained as described hereinabove in the previous section. The basic salt may be converted into the free compound or into a different salt by conventional procedures.

In an embodiment, Venetoclax sodium salt or another basic salt may be converted into the free compound by neutralization with e.g. treatment with an acid, passing through an acid ion-exchange resin, etc.

In another embodiment, the sodium salt of Venetoclax or another basic salt may be converted to its free form by subjecting the salt to suitable conditions which may include, but not limited to: suspending or dissolving the basic salt of Venetoclax in a suitable solvent optionally in the presence of a suitable acid and optionally at elevated temperatures. Suitable acids include, but are not limited to: NH4CI, CIH, TFA, TsOH, MsOH, P04H3, maleic acid.

Since this product is an amino acid like product, care has to be taken with pH value, normally it can acidified until a pH balance between 5 to 7 is achieved.

Once neutralized the basic salt (e.g. sodium), Venetoclax free-base may be isolated in crystalline or amorphous form. For instance, Venetoclax free-base may be isolated in amorphous form by contacting a solution of Venetoclax free-base in an organic solvent with water. In a particular embodiment, once neutralized the sodium salt, the solvent was changed for instance to DMF, and the solution of Venetoclax was contacted with water so as to precipitate Venetoclax in amorphous form. In another particular embodiment, once neutralized the sodium salt, Venetoclax free-base was isolated, redissolved in an organic solvent such as DMF and then the solution of Venetoclax free-base was contacted with water so as to precipitate Venetoclax in amorphous form.

The basic salt of Venetoclax can be converted into a different salt by a salt exchange reaction. For example, using CIH, S04H2, TsOH, MsOH, maleic acid.

The transformation of a basic salt of Venetoclax into Venetoclax or a different salt does not affect the purity. Accordingly, the present disclosure allows obtaining Venetoclax with a content of impurities below 1 %. Specifically, the content of impurities I and II may be reduced below 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2% or even below 0.1 %, complying with the requirements normally imposed by Good Manufacturing Practices (GMP) for Pharmaceutical Products.

In one aspect, the invention is directed to the compound Venetoclax or a salt thereof (e.g. a basic salt), said compound being obtainable according to the purification process disclosed herein. In a particular embodiment, the invention relates to the compound Venetoclax free-base or Venetoclax sodium salt, said compound being obtainable according to the purification process disclosed herein. In another aspect, the invention is directed to the compound Venetoclax or a salt thereof (e.g. a basic salt) which is of a level of purity such that said compound contains less than 1 % of the sum of impurities I and II. In a particular embodiment, the invention relates to the compound Venetoclax free-base or Venetoclax sodium salt which is of a level of purity such that said compound contains less than 1 % of the sum of impurities I and II.

In a particular embodiment, the compound Venetoclax or a salt thereof (e.g. a basic salt) such as the sodium salt is obtainable according to a purification process as disclosed herein and contains less than 1 % of the sum of impurities I and II.

Preferably, the sum of the content of impurities I and II in the compound

Venetoclax or a salt thereof (e.g. a basic salt) such as the sodium salt is about 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1 % or less. Advantageously, the compound Venetoclax or a salt thereof (e.g. a basic salt) such as the sodium salt may be provided according to the invention at a level of purity of above 99% and preferably about 99.1 %, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or more.

Impurities I and II

In another aspect, the present invention relates to impurity I and impurity II as depicted below:

The ¹ H NMR (DMSO-d6) as well as direct inject mass spec (ESI, + and - mode) data of impurity II are as follows: ¹H NMR (500 MHz, DMSO-cfe) d 1 1 .59 (s, 1 H), 8.51 (brs, 1 H), 8.02-7.97 (m, 1 H), 7.81 (d, J = 4.1 Hz, 1 H), 7.80-7.75 (m, 1 H), 7.75-7.72 (m, 1 H), 7.65 (d, J = 2.6 Hz, 1 H), 7.53-7.40 (m, 2H), 7.43-7.41 (m, 1 H), 7.36-7.30 (m, 5H), 7.08-6.98 (m, 5H), 6.77-6.68 (dq, J = 6.7, 2.0 Hz, 2H),6.62 (d, J = 4.1 Hz, 1 H), 6.32-6.30 (m, 1 H), 6.28 (s, 1 H), 6.20- 6.17 (m, 1 H), 3.82 (dd, J = 1 1.3, 3.1 Hz, 2H), 3.29 (s, 6H), 3.32-3.15 (m, 5H), 3.15-3.00 (m, 7H), 2.85-2.75 (m, 3H), 2.30-2.04 (m, 1 1 H), 1.98-1.90 (m, 4H), 1.88-1.79 (m, 1 H), 1.41-1.33 (m, 4H), 1.29-1.17 (m, 2H), 0.92 (d, J = 12.5 Hz, 12H); m/z\ [M+H]⁺ = 1421 ; m/z\ [M-H]- = 1419

It should be understood that the scope of the present disclosure includes all the possible combinations of embodiments disclosed herein.

The following examples are merely illustrative of certain embodiments of the invention and cannot be considered as restricting it in any way.

EXAMPLES

The following equipment and procedures may be used in the characterization of Venetoclax, salts thereof and impurities

a) Powder X-ray Diffraction analysis (PXRD)

Approximately 20 mg of product samples may be prepared in standard sample holders using two foils of polyacetate.

Powder diffraction patterns may be acquired on a D8 Advance Series 2Theta/Theta powder diffraction system using Cu_Ka-radiation in transmission geometry (Wavelength: 1.54060). The system may be equipped with a VANTEC-1 single photon counting PSD, a Germanium monochromator, a ninety positions auto changer sample stage, fixed divergence slits and radial soller. Programs used: Data collection with DIFFRAC plus XRD Commander V.2.5.1 and evaluation with EVA V.12.0.

b) Proton Nuclear Magnetic Resonance (1 H NMR)

Proton nuclear magnetic resonance analyses may be recorded in deuterated chloroform (CDCI3) or dimethyl sulfoxide (DMSO-c/₆) in a Bruker Avance 400 Ultrashield NMR spectrometer, equipped with a z gradient 5 mm BBO (Broadband Observe) probe with ATM and an automatic BACS-120 autosampler. Spectra may be acquired solving 2-10 mg of sample in 0.6 mL of deuterated solvent.

c) Differential Scanning Calorimetry analysis (DSC)

Standard DSC analyses may be recorded in a Mettler Toledo DSC822e. Samples of 1-2 mg may be weighted into 40 mI_ aluminium crucibles with a pinhole lid, and may be heated, under nitrogen (50 mL/min), from 30 to 300 °C at 10 °C/min. Data collection and evaluation may be done with software STARe.

Example 1 : Preparation of Venetoclax sodium salt

a) Reaction process (preparation of Venetoclax):

A 3-L jacketed reactor (Kettle 1) equipped with a mechanical stirrer, nitrogen inlet/outlet, temperature control unit and reflux condenser was inerted with nitrogen and charged with 3-nitro-4-(((tetrahydro-2H-pyran-4-yl)methyl)amino)benzenesulfonamide (19.7 g, 0.95 equiv), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC, 22.1 g, 1.75 equiv), 4-dimethylaminopyridine (DMAP, 16.1 g, 2 equiv) and dichloromethane (DCM, 200 ml_, 5 vo I).

In a separate 1-L reactor (Kettle 2) equipped with a mechanical stirrer, nitrogen inlet/outlet was charged with 2-((1 H-pyrrolo[2,3-b]pyridin-5-yl)oxy)-4-(4-((4'-chloro-5,5- dimethyl-3, 4, 5, 6-tetrahydro-[1 ,1 '-biphenyl]-2-yl)methyl)piperazin-1-yl)benzoic acid hydrochloride salt (40.0 g, 65.8 mmol), and DCM (400 mL, 10 vol). Triethylamine (36.7 mL, 4.00 equiv) was added in one portion.

The solution in Kettle 2 was dosed into Kettle 1 using a transfer pump. The batch was stirred at room temperature for 5-25 h then acetic acid (10% v/v, 10 Vol, 400 mL) was added to the batch and stirred for 15 min.

After the acid washes, the purity of Venetoclax in two different batches was as follows:

b) Work up:

The stirring was stopped, phases allowed to separate and the aqueous phase was removed and discarded. The organic layer was charged back to the reactor and washed with acetic acid (10% v/v, 10 Vol, 400 mL) for 15 min, the phases allowed to separate, the aqueous layer was removed and discarded.

The organic layer was charged back to the reactor and methanol (240 mL, 6 Vol) was added. The reactor was set up with a reflux condenser and aqueous sodium hydroxide (2N, 400 mL, 10 vol) was added and the batch stirred and heated at 30-60 °C for 4-18 h after which time the temperature was lowered to 30-35 °C, the phases allowed to separate and the aqueous layer discarded.

The reactor was cleaned with methanol, the organic phase was charged back to the reactor and the batch was distilled to a total batch of 10 volumes. The batch was cooled to room temperature over 3-5 h then held up to 36 h. The solids were collected, washed with DCM/methanol (90:10 v/v, 2 x 2 Vol), conditioned under vacuum for 3 h until dry to give 46.2 g of sodium venetoclax as a bright yellow solid.

After filtration the purity of Venetoclax in the BTG-AO-19 batch is was as follows:

In this step, impurity II has lowered significantly.

c) Final crystallization:

The sodium venetoclax was charged back to the clean reactor and methanol (925 mL, 20 Vol) was added and the batch heated to reflux for 10-18 h. The batch was cooled to room temperature, the solids collected and washed with methanol (2 x 2 vol). The cake was conditioned for 1-3 h then dried to constant weight in a vacuum oven at 50-60 °C to give sodium venetoclax as a crystalline solid (42.6 g, 73%).

After cristalization the purity of Venetoclax in the BTG-AO-18 and 19 batches was as follows:

d) Venetoclax and Amorphous Form Preparation:

In a clean reactor (Kettle 3) was charged sodium venetoclax (40 g) and 2- methyltetrahydrofuran (400 mL, 10 Vol). The batch was warmed to 55-60 °C to give a homogeneous solution to which 10% ammonium chloride solution (400 mL, 10 vol) was added. The batch was stirred at 55-60 °C for a minimum of 15 min, the phases allowed to separate and the aqueous layer removed. A second 10% ammonium chloride wash was performed (400 mL, 10 vol) followed by a water wash (400 mL, 10 vol). N,N- Dimethylformamide (160 mL, 4 vol) was added and the batch was distilled to achieve a batch of 4 volumes.

In a separate reactor (Kettle 4) water (240 mL, 6 vol) was charged and set at room temperature. The batch Kettle 3 was dosed into Kettle 4 over a period of 5-15 min with moderate stirring. The batch was then warmed to 45 ± 5 °C for 60-90 min then cooled to 35 °C. The batch was filtered and the resulting cake washed with water (80 mL, 2 vol). After conditioning for 30-60 min, the cake was transferred back to the reactor (Kettle 4) and water (1.0 L, 25 vol) was added. The batch was heated to 70-90 °C for 30-60 min, cooled to 35 °C, and the batch was filtered and the cake washed with water (80 mL, 2 vol). The cake was conditioned for 2 h then dried to constant weight under vacuum until residual DMF achieved specifications. Yield 38.5 g (95 %) as a bright yellow amorphous solid.

This solid is as pure as the crystalized one.

Example 2: Preparation of Venetoclax maleate (comparative)

a) Reaction process:

A 50-L jacketed reactor equipped with a mechanical stirrer, nitrogen inlet/outlet, heating mantle and reflux condenser was inerted with flow through nitrogen and charged with 3-nitro-4-(((tetrahydro-2H-pyran-4-yl)methyl)amino)benzenesulfonamide (493 g, 0.95 equiv) EDCI (552 g, 1.75 equiv), DMAP (402 g, 2. equiv) and DCM (5 L, 5 vo I).

Separately a 20-L carboy was charged with 2-((1 /-/-Pyrrolo[2,3-b]pyridin-5-yl)oxy)- 4-(4-((4'-chloro-5,5-dimethyl-3,4,5,6-tetrahydro-[1 ,T-biphenyl]-2-yl)methyl)piperazin-1- yl)benzoic acid hydrochloride salt (1 kg, 1.64 moles), DCM (10 L, 10 vol) and stirred. Triethylamine (920 mL, 4.00 equiv.) was added and the batch was stirred at room temperature.

This solution was dosed into the jacketed reactor over 3 h. The batch was stirred at room temperature for 8-25 h indicated reaction was complete. Batch was distilled down to ~ 5 L and diluted with 2-MeTHF (15 L, 15 vol). The batch was then distilled from ~ 20 L to ~10 L.

b) Work up:

The batch temperature was adjusted to 40°C over 15 min and was washed with two 10% AcOH washes (10 L each) and then separating phases. The batch was then washed with 2 N NaOH (10 L, 10 vol) by heating to 40 ± 5 °C after addition, stirring for 15 min and then phase separation. Isopropyl alcohol (IPA, 15 L, 15 vol) was charged to the reactor and the batch was distilled down from 21 L to ~ 10 L.

Separately maleic acid (287 g, 1.5 equiv) was dissolved in water (1 L, 1 vol) and this solution was charged to the reactor. Upon addition of the maleic acid solution, it was heated to 70 °C over 20 min and aged.

The slurry was then filtered and rinsed with IPA (2.0 L). The cake was dried to constant weight to give crude maleate salt (1.525 kg).

c) Final crystallization:

The crude maleate salt was charged to the 50-L reactor and DCM (18 L, 18 vol), methanol (20 L, 20 vol) were charged and the batch was heated to 40 °C over 1.5 h. The batch was cooled to 15 ± 5 °C over 2 h and aged at that temperature for ~12 h. The slurry was then filtered. The cake was rinsed with 1 :1 DCM/heptanes (2.0 L). The cake was dried to constant weight to give maleate salt (1 kg).

Therefore, a new attempt was made using 1-PrOH instead of MeOH in order to get a solution before crystallization occurs:

As can be seen, the level of impurities in the crystals of the sodium salt was considerably lower than in the maleate salt. Purification with other acid salts (such as hydrochloride or sulfate) was even worse.

In the case of the sodium salt, in a single crystallization it is possible to reach levels of impurity about or below 0.1 % and the transformation from the salt into Venetoclax amorphous did not alter the good purity of the product. Accordingly, the present invention allows preparing Venetoclax with purity above 99% (e.g. about 99.5%).

Claims

1. A basic salt of Venetoclax.

2. The basic salt of Venetoclax according to claim 1 , which is selected from the sodium, potassium and lithium salt.

3. The basic salt of Venetoclax according to claim 2, which is Venetoclax sodium salt.

4. The basic salt of Venetoclax according to any one of claims 1 and 3 which is in crystalline or in amorphous form.

5. The basic salt of Venetoclax according to any one of claims 1 to 4 which is a Venetoclax sodium salt designated as crystalline form 1 and characterized by a PXRD pattern substantially as depicted in figure 1.

6. A process for the preparation of a basic salt of Venetoclax as defined in any one of claims 1 to 5, said process comprising the step of contacting Venetoclax or an acid salt thereof with a base so as to obtain a basic salt of Venetoclax.

7. The process according to claim 6, wherein the base is a sodium containing base selected from the group consisting of sodium hydride, sodium hydroxide and sodium alkoxides.

8. The process according to claim 7, wherein the sodium containing base is aqueous sodium hydroxide.

9. A process for the purification of Venetoclax, said process comprising:

(a) taking a sample of Venetoclax a salt of Venetoclax or an acid salt thereof containing impurities I and/or II;

(b) treating said sample with a base so as to obtain a basic salt of Venetoclax; (c) preferably, crystallizing said basic salt of Venetoclax from a suitable solvent system; and

10. The process for the purification of Venetoclax according to claim 9, wherein step (d) comprises treatment with an acid and isolation of Venetoclax free-base in crystalline or amorphous form.

1 1. The process for the purification of Venetoclax according to claim 10, wherein Venetoclax free-base is isolated in amorphous form by contacting a solution of Venetoclax free-base in an organic solvent with water.

12. A compound selected from impurities I and impurity II:

13. Venetoclax free-base containing less than 1 % of impurities I and II.

14. Venetoclax free-base obtainable according to the process of any one of claims 9 to 1 1 and containing less than 1 % of impurities I and II.

15. Venetoclax basic salt containing less than 1 % of impurities I and II.