Process for the preparation of crystalline form of rabeximod

Abstract

The present invention relates to a process for the preparation of a crystalline form of 9-chloro-2, 3-dimethyl-6-(N, N-dimethylaminoethylamino-2-oxoethyl)-6H-indolo-[2, 3-b] quinoxaline (rabeximod) wherein the process is suitable for large scale synthesis, and to a process for the preparation of a crystalline form of 9-chloro-2, 3-dimethyl-6-(N, N-dimethylaminoethylamino-2-oxoethyl)-6H-indolo-[2, 3-b] quinoxaline (rabeximod).

Description

[0001] This application is a divisional application of a Chinese patent application titled "Method for Preparing Crystalline Form of Rabeximod" with an application date of June 10, 2021 and an application number of 202180041778.5. Technical Field

[0002] The present invention relates to a method for preparing 9-chloro-2,3-dimethyl-6-(N,N-dimethylaminoethylamino-2-oxoethyl)-6H-indolo-[2,3-b]quinoxaline (rabeximod), wherein the process is suitable for large-scale synthesis. The parameters of the method are stable, and the method is suitable for GMP. Background Art

[0003] The compound rabeximod has been described in European Patent Application Publication EP1756111A1, which was later granted as EP1756111B1. The preparation of rabeximod as compound E was specifically described in EP1756111A1 as a small-scale method, but there is no description on how to develop a method applicable to GMP and scale-up. Rabeximod was prepared in a small-scale laboratory method with a yield of 58%, but the parameters for scale-up were not disclosed.

[0004] The object of the present invention is to provide a method suitable for large-scale synthesis, with high yield, stable method parameters and suitable for GMP production. Summary of the Invention

[0005] The present invention relates to a new method for preparing 9-chloro-2,3-dimethyl-6-(N,N-dimethylaminoethylamino-2-oxoethyl)-6H-indolo-[2,3-b]quinoxaline (also known as rabeximod), which can be scaled up to large-scale and / or industrial scale, such as 10 kg or higher. The method can also be used for smaller scales, such as 200 g to 10 kg.

[0006] More objectives and advantages of the present invention will become apparent from the following description and claims.

[0007] Description of the Invention

[0008] The compound known under the INN as "rabeximod" has the IUPAC name 9-chloro-2,3-dimethyl-6-(N,N-dimethylaminoethylamino-2-oxoethyl)-6H-indolo-[2,3b]quinoxaline and has the following molecular structure.

[0009]

[0010] Throughout the present application, the terms "Rabeximod", "rabeximod", or "9-chloro-2,3-dimethyl-6-(N,N-dimethylaminoethylamino-2-oxoethyl)-6H-indolo[2,3b]quinoxaline" are used interchangeably and mean the compound in any solid or liquid form, unless otherwise stated or implied in a given context.

[0011] In a first aspect, the present invention relates to a process for preparing 9-chloro-2,3-dimethyl-6-(N,N-dimethylaminoethylamino-2-oxoethyl)-6H-indolo[2,3-b]quinoxaline (Rabeximod) or a salt thereof, which process is suitable for large-scale production / synthesis, and which process comprises the following steps:

[0012] - Reacting a solution or suspension of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline with 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof in the presence of an aqueous solution of a base sufficient to deprotonate the indole N-H and optionally a catalyst to obtain Rabeximod or a salt thereof.

[0013] In one embodiment, a catalyst is present. When present, the catalyst is generally a catalyst based on an alkali metal halide, such as KI (potassium iodide).

[0014] In a further embodiment, 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline or a salt thereof is dissolved in an organic solvent. Generally, such solvents are water-miscible organic solvents, such as polar water-miscible organic solvents, such as polar aprotic water-miscible organic solvents, such as cyclic ethers, such as THF. Typical embodiments are selected from one or more of acetonitrile, isopropyl acetate, ethyl acetate, THF, and toluene, optionally mixed with water.

[0015] In a still further embodiment, 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof is dissolved in an organic solvent, such as a water-miscible organic solvent, such as a polar water-miscible organic solvent. Generally, such as a polar aprotic water-miscible organic solvent, such as a cyclic ether, such as THF.

[0016] During the process of the method, 2-chloro-N-(2-dimethylaminoethyl)acetamide can be used in the form of the free base or a salt. In a further embodiment, 2-chloro-N-(2-dimethylaminoethyl)acetamide is a salt, preferably the hydrochloride salt. In another embodiment, 2-chloro-N-(2-dimethylaminoethyl)acetamide is used in the form of the free base.

[0017] As described above, the method involves using an aqueous alkali solution, and generally the aqueous alkali solution is an alkali based on an alkali metal, such as an aqueous solution of KOH or NaOH. Preferably, the alkali is an aqueous solution of NaOH, such as a 50% aqueous solution of NaOH.

[0018] In a further embodiment, the reaction occurs at atmospheric pressure under an inert gas such as nitrogen or argon. Preferably, the inert gas is nitrogen.

[0019] In a still further embodiment, about 1 molar equivalent of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline is deprotonated with at least about 2 volumes of the aqueous alkali solution. Generally, about 8 equivalents (relative to 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline) of the aqueous alkali solution are used. Preferably, 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline and the aqueous alkali solution are mixed at a suitable temperature such as about 50 - 65 °C until a clear solution is formed, for example up to about 1 hour or longer. It is preferred that a solvent such as THF dissolves all of the 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline, as the yield increases.

[0020] Preferably, a catalyst is present. In one embodiment, a suitable amount of the catalyst is added under vigorous stirring and mixed at a suitable temperature such as about 50 - 65 °C for about 10 to 60 minutes. A suitable amount of the catalyst should be sufficient to exert a catalytic effect and can be about 0.5 to 1.5 molar equivalents. For example, KI is generally used in an amount of about 0.7 - 0.9 molar equivalents.

[0021] In a still further embodiment, 2-chloro-N-(2-dimethylaminoethyl)acetamide or its salt is added to a solution of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline in an aqueous alkali solution, such as a THF solution, and mixed at a suitable temperature such as about 50 - 65 °C for at least about 1 hour, for example at least about 2 hours. Preferably, the amount of 2-chloro-N-(2-dimethylaminoethyl)acetamide added is about 1 - 3 molar equivalents, such as about 2 molar equivalents.

[0022] The Rabeximod compound can be purified according to known techniques or as described later herein and / or in the experimental section. In a preferred embodiment, Rabeximod is purified and isolated as the free base, such as the crystalline free base.

[0023] In another aspect, the present invention relates to the crystalline free base of Rabeximod. Preferably, the crystalline free base of Rabeximod has a melting point of 259 - 261 °C. Also by Figure 1 and Figure 2The XRPD diffraction pattern, DSC and X-rays shown in identified the crystalline free base of Rabeximod. The crystalline free base of Rabeximod was isolated with high purity, such as being higher than 98% as measured by HPLC. Therefore, in a further embodiment, the crystalline free base of Rabeximod is an isolated free base with a purity higher than 98%.

[0024] The crystalline rabeximod free base compound is suitable for further processing into solid oral dosage compositions for the treatment of autoimmune diseases such as rheumatoid arthritis and / or multiple sclerosis.

[0025] In a further embodiment, the method includes the following prior steps:

[0026] - Reacting a solution or suspension of 4,5-dimethyl-1,2-benzenediamine with 5-chloroindirubin under acidic conditions at an elevated temperature up to reflux to obtain 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline or a salt thereof.

[0027] In a still further embodiment, the method includes the following prior steps:

[0028] - Reacting a solution or suspension of chloroacetyl chloride with N,N-dimethylethylenediamine to obtain 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof.

[0029] Preferably, the method for preparing Rabeximod according to the present invention includes the following two prior steps:

[0030] - Reacting a solution or suspension of 4,5-dimethyl-1,2-benzenediamine with 5-chloroindirubin under acidic conditions at an elevated temperature up to reflux to obtain 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline or a salt thereof, and

[0031] - Reacting a solution or suspension of chloroacetyl chloride with N,N-dimethylethylenediamine to obtain 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof.

[0032] In yet another aspect, the present invention relates to a method for preparing 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline, which method is suitable for large-scale production / synthesis, and wherein the method includes the following steps:

[0033] - Reacting a solution or suspension of 4,5-dimethyl-1,2-benzenediamine with 5-chloroindirubin under acidic conditions at an elevated temperature up to reflux to obtain 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline.

[0034] The embodiments described below are independently embodiments of a method for preparing Rabeximod or a salt thereof and a method for preparing 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline or a salt thereof.

[0035] In a further embodiment, the acidic condition is an organic acid, such as a C2-C5 carboxylic acid, typically acetic acid.

[0036] In a still further embodiment, both 4,5-dimethyl-1,2-phenylenediamine and 5-chloroindirubin are dissolved in the acid before the reaction.

[0037] In a further embodiment, the acid is in excess, for example at least 2 volumes, such as at least 4 volumes. Generally, the acid is in an excess of at least 4 volumes with respect to 4,5-dimethyl-1,2-phenylenediamine and in an excess of at least 10 volumes with respect to 5-chloroindirubin.

[0038] In a still further embodiment, the elevated temperature is the reflux temperature.

[0039] In a further embodiment, 4,5-dimethyl-1,2-phenylenediamine or a salt thereof is dissolved in the acid before reacting with 5-chloroindirubin, and 5-chloroindirubin or a salt thereof is dissolved in the acid before reacting with 4,5-dimethyl-1,2-phenylenediamine.

[0040] In a still further embodiment, the addition amount of 4,5-dimethyl-1,2-phenylenediamine is about 1-3 molar equivalents, such as about 1-2 molar equivalents, for example about 1.1 molar equivalents.

[0041] In a further embodiment, the addition amount of 5-chloroindirubin is about 1-3 molar equivalents, such as about 1-2 molar equivalents, for example about 1 molar equivalent.

[0042] In a still further embodiment, the dissolved 4,5-dimethyl-1,2-phenylenediamine is added to the dissolved 5-chloroindirubin at the reflux temperature. Generally, the 4,5-dimethyl-1,2-phenylenediamine is added to the 5-chloroindirubin at the reflux temperature for at least about 2 hours, such as 2-4 hours.

[0043] In a further embodiment, the acid is distilled off from the reaction mixture, and additional acid is added at a similar rate during the distillation. Generally, the reaction mixture is stirred at the reflux temperature for at least about 1 hour, such as about 2 hours, after the distillation.

[0044] In a still further embodiment, 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline is purified and isolated as the free base.

[0045] On the other hand, the present invention relates to 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline in solid form, such as the crystalline free base.

[0046] In another aspect, the present invention relates to a process for preparing 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof, which process is suitable for large-scale production / synthesis, and which process comprises the steps of:

[0047] - Reacting a solution or suspension of chloroacetyl chloride with N,N-dimethylethylenediamine to obtain 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof.

[0048] The embodiments described below are independently embodiments of a process for preparing Rabeximod or a salt thereof and a process for preparing 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof.

[0049] In one embodiment, chloroacetyl chloride is dissolved in an organic solvent, such as an organic ester, such as a C4 to C6 ester, such as ethyl acetate.

[0050] In a further embodiment, N,N-dimethylethylenediamine is dissolved in an organic solvent, such as an organic ester, such as a C4 to C6 ester, such as ethyl acetate.

[0051] In a still further embodiment, both chloroacetyl chloride and N,N-dimethylethylenediamine are dissolved before the reaction.

[0052] In a further embodiment, N,N-dimethylethylenediamine in solution form is added to chloroacetyl chloride in solution form at a rate such that the temperature in the solution is maintained below about 30 °C.

[0053] In a still further embodiment, N,N-dimethylethylenediamine or a salt thereof is dissolved in a solvent before reacting with chloroacetyl chloride, and 5-chloroacetyl chloride or a salt thereof is dissolved in a solvent before reacting with N,N-dimethylethylenediamine.

[0054] In a further embodiment, the solvent is in excess relative to chloroacetyl chloride, such as at least about 2 volumes, such as at least about 4 volumes.

[0055] In a still further embodiment, the solvent is in equivalent or volume excess relative to N,N-dimethylethylenediamine, such as in an equivalent ratio.

[0056] In a further embodiment, the amount of chloroacetyl chloride added is about 1 - 3 molar equivalents, such as about 1 - 2 molar equivalents, such as about 1 molar equivalent.

[0057] In a further embodiment, the amount of N,N-dimethylethylenediamine added is about 1-3 molar equivalents, such as about 1-2 molar equivalents, such as about 1 molar equivalent.

[0058] In a further embodiment, 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof is purified and isolated as its salt, such as the HCl salt.

[0059] In a preferred embodiment, rabeximod obtained by the method described herein is purified by the following consecutive steps: dissolving the crude reaction product in a mixture of a water-miscible organic solvent (such as a polar water-miscible organic solvent, such as a polar aprotic water-miscible organic solvent, such as a cyclic ether, usually tetrahydrofuran), water, and an acid (such as a hydrohalide, usually HCl); filtering and heating to above 35 °C, preferably to about 50 °C; adjusting the pH to at least 9, usually to a value in the range of 10-12 by adding an aqueous base solution (usually NaOH); cooling to a temperature between 18 and 25 °C and diluting with water; stirring for at least 10 hours, usually at least 12 hours; filtering usually at 20-25 °C; and washing on the filter with a mixture of a water-miscible organic solvent (such as a polar water-miscible organic solvent, such as a polar aprotic water-miscible organic solvent, such as a cyclic ether, usually tetrahydrofuran) and water to provide the purified rabeximod crystalline free base. If desired, a pharmaceutically acceptable salt can be made from a solution of the rabeximod crystalline free base.

[0060] In a particular embodiment, there is provided a method for preparing 9-chloro-2,3-dimethyl-6-(N,N-dimethylaminoethylamino-2-oxoethyl)-6H-indolo-[2,3-b]quinoxaline (Rabeximod) or a salt thereof as defined herein, the method comprising the following steps:

[0061] a) Reacting a solution or suspension of 4,5-dimethyl-1,2-phenylenediamine with 5-chloroindirubin under acidic conditions at an elevated temperature up to reflux to obtain 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline or a salt thereof;

[0062] b) Reacting a solution or suspension of chloroacetyl chloride with N,N-dimethylethylenediamine to obtain 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof;

[0063] c) React the solution or suspension of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline obtained in step a) with 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof obtained in step b) in the presence of an aqueous base solution strong enough to deprotonate the indole N-H and an optional catalyst to obtain rabeximod or a salt thereof;

[0064] d) Subject the rabeximod or a salt thereof obtained in step c) to one or more purification steps, preferably to a purification procedure as defined above.

[0065] Based on the present disclosure, it will be apparent to those skilled in the art that steps a) and b) in the above method can (and usually are) carried out independently and in any order or sequence, including simultaneously.

[0066] Another aspect of the present invention relates to rabeximod compounds obtainable by any of the methods defined herein.

[0067] Other embodiments of the method are described in the experimental section herein, and each individual method and each starting material constitute embodiments that can form part of an embodiment.

[0068] The term "and / or" as used herein is intended to mean both alternative options and each of the individual alternative options. For example, the expression "xxx and / or yyy" means "xxx and yyy"; "xxx"; or "yyy", all three alternative options being subject to the individual embodiments.

[0069] The above embodiments should be considered to refer to any one aspect described herein (e.g., "crystalline free base of Rabeximod" and / or "method suitable for large-scale synthesis for preparing rabeximod") and any one embodiment described herein, unless the embodiment is specified to relate to a particular aspect or aspects of the present invention.

[0070] All references cited herein, including publications, patent applications, and patents, are incorporated herein by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in full herein.

[0071] All headings and subheadings used herein are for convenience only and should not be construed as limiting the present invention in any way.

[0072] Unless otherwise stated herein or clearly contradicted by the context, the present invention encompasses any combination of all possible variations of the above elements.

[0073] The terms "a", "an", and "the" and similar referents used in the context of describing the present invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by the context.

[0074] Unless otherwise indicated herein, the recitation of numerical ranges herein is merely intended to serve as a shorthand method for referring individually to each separate value falling within the range, and each separate value is incorporated into the specification as if it were individually recited herein.

[0075] Unless otherwise indicated, all exact values provided herein represent corresponding approximate values (e.g., all exact exemplary values provided for a particular factor or measurement can be considered to also provide the corresponding approximate values, modified by "about" where appropriate).

[0076] Unless otherwise indicated herein or clearly contradicted by the context, all methods described herein can be performed in any suitable order.

[0077] Unless otherwise indicated, the use of any and all examples or exemplary language (e.g., "such as") provided herein is merely intended to better illustrate the present invention and does not limit the scope of the present invention. No language in the specification should be construed as indicating that any element is essential for the practice of the present invention unless explicitly stated.

[0078] The patent documents cited and incorporated herein are for convenience only and do not reflect any opinion as to the validity, patentability, and / or enforceability of such patent documents.

[0079] The description of any aspect or embodiment of the present invention using terms such as "comprising", "having", "including", or "containing" when referring to one or more elements is intended to support similar aspects or embodiments of the present invention "consisting of", "consisting essentially of", or "substantially containing" such particular one or more elements, unless otherwise indicated or clearly contradicted by the context (e.g., a composition described herein as containing a particular element should be understood to also describe a composition consisting of that element, unless otherwise indicated or clearly contradicted by the context).

[0080] The present invention includes all modifications and equivalents of the subject matter recited in the aspects or claims presented herein to the maximum extent permitted by applicable law.

[0081] The present invention is further illustrated by the following examples, which, however, should not be construed as limiting the scope of protection. The features disclosed in the foregoing description and the following examples, either individually or in any combination thereof, may be critical for implementing the present invention in different forms.

[0082] Numbered Embodiments of the Invention

[0083] 1. A process for preparing 9-chloro-2,3-dimethyl-6-(N,N-dimethylaminoethyl-amino-2-oxoethyl)-6H-indolo-[2,3-b]quinoxaline (Rabeximod) or a salt thereof, wherein the process comprises the steps of:

[0084] - Reacting a solution or suspension of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline with 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof in an aqueous solution of a base strong enough to deprotonate the indole N-H and in the presence of an optional catalyst to obtain Rabeximod or a salt thereof.

[0085] 2. The process according to embodiment 1, wherein a catalyst is present.

[0086] 3. The process according to any one of embodiments 1-2, wherein 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline or a salt thereof is dissolved in an organic solvent.

[0087] 4. The process according to any one of embodiments 1-3, wherein 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof is dissolved in an organic solvent.

[0088] 5. The process according to any one of embodiments 1-4, wherein 2-chloro-N-(2-dimethylaminoethyl)acetamide is a salt.

[0089] 6. The process according to any one of embodiments 1-5, wherein the aqueous solution of the base is NaOH.

[0090] 7. The process according to any one of embodiments 1-6, wherein the reaction takes place under an inert gas.

[0091] 8. The process according to any one of embodiments 1-7, wherein 1 molar equivalent of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline is deprotonated with at least 2 volumes of the aqueous solution of the base.

[0092] 9. The process according to embodiment 8, wherein 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline and the aqueous solution of the base are mixed at a suitable temperature until a clear solution is formed.

[0093] 10. The process according to any one of embodiments 2-9, wherein a suitable amount of the catalyst is added with vigorous stirring and mixed at a suitable temperature for 10 to 60 minutes.

[0094] 11. The method according to any one of embodiments 1-10, wherein 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof is added to a solution of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline in an aqueous alkali solution, and the mixture is stirred at a suitable temperature for at least 1 hour.

[0095] 12. The method according to embodiment 11, wherein 2-chloro-N-(2-dimethylaminoethyl)acetamide is added in an amount of 1-3 times.

[0096] 13. The method according to any one of embodiments 1-12, wherein Rabeximod is purified and isolated as a free base.

[0097] 14. The method according to embodiment 13, wherein Rabeximod is purified and isolated as a crystalline free base.

[0098] 15. The method according to any one of embodiments 1-14, wherein the method comprises the following prior steps:

[0099] - Reacting a solution or suspension of 4,5-dimethyl-1,2-phenylenediamine with 5-chloroindirubin under acidic conditions at an elevated temperature up to reflux to obtain 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline or a salt thereof.

[0100] 16. The method according to any one of embodiments 1-14, wherein the method comprises the following prior steps:

[0101] - Reacting a solution or suspension of chloroacetyl chloride with N,N-dimethylethylenediamine to obtain 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof.

[0102] 17. The method according to any one of embodiments 1-14, wherein the method comprises the prior step of embodiment 15 and the prior step of embodiment 16.

[0103] 18. A method for preparing 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline, wherein the method comprises the following steps:

[0104] - Reacting a solution or suspension of 4,5-dimethyl-1,2-phenylenediamine with 5-chloroindirubin under acidic conditions at an elevated temperature up to reflux to obtain 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline.

[0105] 19. The method according to embodiment 15 or 18, wherein the acidic condition is an organic acid.

[0106] The method according to any one of embodiments 15, 18, and 19, wherein both 4,5-dimethyl-1,2-phenylenediamine and 5-chloroindirubin are dissolved in an acid before the reaction.

[0107] The method according to any one of embodiments 15 and 18 - 20, wherein the acid is in excess.

[0108] The method according to embodiment 15 or 21, wherein the acid is at least 4 - fold in volume excess with respect to 4,5-dimethyl-1,2-phenylenediamine and at least 10 - fold in volume excess with respect to 5-chloroindirubin.

[0109] The method according to any one of embodiments 15 and 18 - 22, wherein the elevated temperature is the reflux temperature.

[0110] The method according to any one of embodiments 15 and 18 - 23, wherein 4,5-dimethyl-1,2-phenylenediamine or its salt is dissolved in an acid before reacting with 5-chloroindirubin, and 5-chloroindirubin or its salt is dissolved in an acid before reacting with 4,5-dimethyl-1,2-phenylenediamine.

[0111] The method according to any one of embodiments 15 and 18 - 24, wherein the addition amount of 4,5-dimethyl-1,2-phenylenediamine is 1 - 3 molar equivalents.

[0112] The method according to any one of embodiments 15 and 18 - 25, wherein the addition amount of 5-chloroindirubin is 1 - 3 molar equivalents.

[0113] The method according to any one of embodiments 15 and 23 - 26, wherein the dissolved 4,5-dimethyl-1,2-phenylenediamine is added to the dissolved 5-chloroindirubin at the reflux temperature.

[0114] The method according to embodiment 15 or 27, wherein 4,5-dimethyl-1,2-phenylenediamine is added to 5-chloroindirubin at the reflux temperature for at least 2 hours.

[0115] The method according to any one of embodiments 15 and 27 - 28, wherein the acid is distilled from the reaction mixture, and additional acid is added at a similar rate during the distillation.

[0116] The method according to embodiment 15 or 29, wherein the reaction mixture is stirred at the reflux temperature for at least 1 hour after distillation.

[0117] The method according to any one of embodiments 15 and 18 - 30, wherein 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline is purified and isolated as the free base.

[0118] 32. A method for preparing 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof, wherein the method comprises the following steps:

[0119] - Reacting a solution or suspension of chloroacetyl chloride with N,N-dimethylethylenediamine to obtain 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof.

[0120] 33. The method according to embodiment 16 or 32, wherein chloroacetyl chloride is dissolved in an organic solvent.

[0121] 34. The method according to any one of embodiments 16 and 32-33, wherein N,N-dimethylethylenediamine is dissolved in an organic solvent.

[0122] 35. The method according to any one of embodiments 16 and 32-34, wherein both chloroacetyl chloride and N,N-dimethylethylenediamine are dissolved before the reaction.

[0123] 36. The method according to any one of embodiments 16 and 32-34, wherein N,N-dimethylethylenediamine in solution form is added to chloroacetyl chloride in solution form at a rate that maintains the temperature in the solution below 30 °C.

[0124] 37. The method according to any one of embodiments 16 and 32-36, wherein N,N-dimethylethylenediamine or a salt thereof is dissolved in a solvent before reacting with chloroacetyl chloride, and chloroacetyl chloride or a salt thereof is dissolved in a solvent before reacting with N,N-dimethylethylenediamine.

[0125] 38. The method according to any one of embodiments 16 and 32-37, wherein the solvent is in excess relative to chloroacetyl chloride, for example at least about 2 volumes.

[0126] 39. The method according to any one of embodiments 16 and 32-38, wherein the solvent is in an equivalent or molar excess relative to N,N-dimethylethylenediamine, for example in an equivalent ratio.

[0127] 40. The method according to any one of embodiments 16 and 32-39, wherein chloroacetyl chloride is added in an amount of 1-3 molar equivalents.

[0128] 41. The method according to any one of embodiments 16 and 32-40, wherein N,N-dimethylethylenediamine is added in an amount of 1-3 molar equivalents.

[0129] 42. The method according to any one of embodiments 16 and 32-41, wherein 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof is purified and isolated as its salt.

[0130] 43. The crystalline free base of Rabeximod, having a melting point of 259 - 261 °C.

[0131] 44. The crystalline free base of Rabeximod obtainable by the method as defined in any one of Embodiments 1 - 17, 19 - 31 and 33 - 42. Brief Description of the Drawings

[0133] Figure 1 Shows the differential scanning calorimetry (DSC) thermogram and thermogravimetric analysis (TGA) curve of Rabeximod.

[0134] Figure 2 Shows the X - ray powder pattern of Rabeximod.

[0135] Experiments

[0136] As shown in the following reaction scheme and described in detail below, the current method for manufacturing Rabeximod involves several method steps.

[0137]

[0138] Method for Manufacturing the OXY001 - 01 Intermediate

[0139]

[0140] Starting Materials: 5 - Chloroindirubin (CIDO) and 4,5 - Dimethyl - 1,2 - phenylenediamine (DAX)

[0141] Table 1: Overview of the raw materials and amounts required for Step 1

[0142] Project description MW Mol Required amount Eq. 5-Chloroindirubin (CIDO) 181.58 66.1 12.0 kg 1.0 4,5-Dimethyl-1,2-phenylenediamine (DAX) 136.19 72.7 9.9 kg <![CDATA[1.1 a > Acetic acid, AcOH - - 282L <![CDATA[23.5 c > Ethanol, EtOH - - 150L <![CDATA[12.5 c > Drinking water - - 50 <![CDATA[4.2 c >

[0143] a) mol / mol of CIDO; b) kg / kg of CIDO; c) L / kg of CIDO

[0144] Table 2: Specifications of the raw materials for Step 1

[0145]

[0146] Product Obtained (Intermediate): OXY001 - 01

[0147] Batch Size: 13.03 kg of OXY001 - 01

[0148] Method description: 4,5-Dimethyl-1,2-phenylenediamine (1.1 equivalents) was added to acetic acid (4.7 volumes) in a reactor (the reactor operates under nitrogen and atmospheric pressure) and stirred at a moderate rate at +20 to +25 °C for up to 3 hours until a clear dark brown solution was formed. The solution of 4,5-dimethyl-1,2-phenylenediamine in acetic acid solution was transferred to an intermediate feed container. 5-Chloroindigo (1.0 equivalent) was added to acetic acid (14.3 volumes) in the reactor and stirred while the jacket temperature of the reactor was adjusted to approximately +150 °C to reach the reflux temperature for active reflux of the solvent. When the reflux temperature was reached, the acetic acid solution of 4,5-dimethyl-1,2-phenylenediamine was slowly added over 2 - 3 hours while acetic acid (4.7 volumes) was distilled from the reaction mixture. Fresh acetic acid portion (4.7 volumes) was added to the reactor at approximately the same rate as the distillation (4.7 volumes) occurred. After distillation, the reaction mixture was stirred at the reflux temperature for at least 2 hours. The expected appearance of the contents in the reactor was a dark yellow to orange slurry. The reaction mixture was cooled to +65 to +70 °C and filtered using a Nutsche filter with a polyester filter cloth (27 μm) or the like as the filter medium. The filter cake was washed 3 times with fresh ethanol (3 × 4.2 volumes) and 1 time with water (1 × 4.2 volumes). After washing, the filter cake was dried at +40 to +45 °C for 12 hours and additionally dried in a vacuum tray dryer at +40 °C for 12 hours to obtain a yellow to orange / brown solid. Take control samples during the process and analyze the loss on drying (LOD). The LOD should be <2% (w / w). If the LOD is >2%, repeat the vacuum tray dryer step.

[0149] Theoretical yield: 18.62 kg

[0150] Yield: 70 ± 5% (13.03 ± 0.96 kg)

[0151] Maximum volume: 216 LOXY001 - 03 Method for manufacturing HCl intermediate

[0152]

[0153] Starting materials: chloroacetyl chloride (CAC) and N,N-dimethylethylenediamine (DMEN)

[0154] Table 3: Overview of raw materials and amounts required for Step 2

[0155] Project description MW Mol Required amount Eq. N,N-Dimethylethylenediamine (DMEN) 88.15 124.8 11.0 kg 1.0 Chloroacetyl chloride (CAC) 112.94 128.5 14.5 kg <![CDATA[1.03 a > Ethyl acetate, EtOAc - - 341L <![CDATA[31 c >

[0156] a) mol / mol of DMEN; b) kg / kg of DMEN; c) L / kg of DMEN

[0157] Table 4: Specifications of raw materials for Step 2

[0158]

[0159]

[0160] Product obtained (intermediate): OXY001-03 HCl

[0161] Batch size: 22.6 kg of OXY001-03 HCl

[0162] Method description: At +20 °C, chloroacetyl chloride (1.03 equivalents) was dissolved in ethyl acetate (15 volumes) in a reactor (the reactor was operated under nitrogen and atmospheric pressure). The solution was stirred and cooled to +10 °C. When the temperature reached the range of +10 to +25 °C, a solution of N,N-dimethylethylenediamine (1.00 equivalent) in ethyl acetate (1.0 volume) was slowly added to the reactor at a rate such that the internal temperature did not exceed +25 °C over 1 - 2 hours. The slurry was stirred at +20 to +25 °C for 5 to 30 minutes and filtered using a Nutch filter with a polyamide filter cloth (25 μm) or the like as the filtering medium. The product was washed 3 times (3 × 5 volumes) with ethyl acetate on the filter and dried on the filter for at least 16 hours, and additionally dried in a vacuum tray dryer at +40 °C for 12 hours to obtain an off-white to beige solid.

[0163] Theoretical yield: 25.09 kg

[0164] Yield: 90 ± 5% (22.6 ± 1.25 kg)

[0165] Maximum volume: 202 LMethod for manufacturing OXY001 crude product

[0166]

[0167] Starting materials: OXY001-01 and OXY001-03 HCl

[0168] Table 5: Overview of raw materials and amounts required for step 3

[0169] Project description MW Mol Required amount Eq. OXY001-01 281.74 46.3 13.0 kg 1.0 OXY001-03HCl 201.09 92.5 18.6 kg <![CDATA[2.0 a > 50% Aqueous NaOH 40.00 370.1 29.6 kg <![CDATA[8.0 a > Potassium iodide, KI 166.00 37.5 6.2 kg <![CDATA[0.81 a > Tetrahydrofuran, THF - - 705L <![CDATA[54.2 c > Drinking water - - 395L <![CDATA[30.4 c >

[0170] a) mol / mol of OXY001-01; b) kg / kg of OXY001-01; c) L / kg of OXY001-01

[0171] Table 6: Specifications of raw materials / intermediate materials for step 3

[0172]

[0173] Product obtained: Crude OXY001 (crude rabeximod)

[0174] Batch size: 11.38 kg of crude OXY001

[0175] Method description: Dissolve OXY001-01 (1.0 equivalent) in tetrahydrofuran (15.4 volumes) and 50% aqueous NaOH solution (8.0 equivalents relative to OXY001-01) in a reactor (the reactor operates under nitrogen and atmospheric pressure), and mix at +55 to +60 °C for about 1 hour until a clear dark red solution is formed. Add potassium iodide (0.81 equivalent) with vigorous stirring and mix at +55 to +60 °C for 10 to 30 minutes. Add OXY001-03 HCl (2.0 equivalents) to the solution and mix at +55 to +60 °C for at least 2 hours. After the reaction is complete, quench the mixture with water (15.4 volumes) and remove tetrahydrofuran (15.4 volumes) by evaporation under reduced pressure. Cool the slurry to +20 to +25 °C and stir for 1 hour, and filter using a Nutch filter with a polyamide filter cloth (25 μm) or the like as the filter medium. Wash the resulting filter cake with water 3 times (3 × 5 volumes) until the pH of the filtrate is between 8 - 7, then dry on the filter by air suction at +40 to +45 °C for at least 12 hours and additionally dry in a vacuum tray dryer at +40 °C for 12 hours. Then suspend the resulting material in tetrahydrofuran (25 volumes) at +45 to +50 °C for at least 1 hour. Separate the crude OXY001 by filtering using a Nutch filter with a polyamide filter cloth (25 μm) or the like as the filter medium, and wash it with tetrahydrofuran 2 times (2 × 7 volumes) on the filter. Dry the resulting filter cake on the filter at +40 to +45 °C for at least 12 hours and additionally dry in a vacuum tray dryer at +40 °C for 12 hours.

[0176] Theoretical yield: 18.96 kg

[0177] Yield: 60 ± 5% (11.38 ± 0.95 kg)

[0178] Maximum volume: 500 L

[0179] Purification of crude rabeximod:

[0180] Dissolve crude OXY001 (1.0 equivalent) in a mixture of tetrahydrofuran (10 volumes), water (3 volumes) and 2M HCl (1.4 volumes). Filter the solution to clarify and heat to +50 °C. Adjust the pH of the mixture to 10 - 12 by adding 2M NaOH (1.3 volumes). Cool the resulting slurry to +20 to +25 °C and dilute with water (12 volumes).

[0181] After stirring for at least 12 hours, the slurry was filtered at +20 to +25 °C and washed on the filter with a mixture of tetrahydrofuran:water (5:2) (2 × 3 volumes). Rabeximod has a molecular weight of 409.92 g / mol and was isolated as a crystalline free base with a melting point of 259 - 261 °C.

[0182] The batch release results for the Phase 2 and Phase 1 clinical studies are provided in Table 7.

[0183] The purity was equal to or higher than 98% as measured by HPLC.

[0184] Table 7: Batch release results of Rabeximod API used in Phase 1 and Phase 2 clinical studies

[0185]

Claims

1. A method for preparing 9-chloro-2,3-dimethyl-6-(N,N-dimethylaminoethyl-amino-2-oxoethyl)-6H-indolo-[2,3-b]quinoxaline (Rabeximod) or a salt thereof, wherein the method comprises the following steps: - In the presence of an aqueous solution of a base strong enough to deprotonate the indole N-H and an optional catalyst, reacting a solution or suspension of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline with 2-chloro - N-(2-dimethylaminoethyl)acetamide or a salt thereof to obtain Rabeximod or a salt thereof.

2. The method according to claim 1, wherein the catalyst is present.

3. The method according to any one of claims 1-2, wherein 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline or a salt thereof is dissolved in an organic solvent, and wherein 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof is dissolved in an organic solvent.

4. The method according to any one of claims 1-3, wherein the aqueous solution of the base is NaOH.

5. The method according to any one of claims 1-4, wherein 1 molar equivalent of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline is deprotonated with at least 2 volumes of the aqueous solution of the base, and wherein 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline and the aqueous solution of the base are mixed at a suitable temperature until a clear solution is formed.

6. The method according to any one of claims 2-5, wherein an appropriate amount of the catalyst is added under vigorous stirring and mixed at a suitable temperature for 10-60 minutes.

7. The method according to any one of claims 1-6, wherein 2-chloro-N-(2-dimethylaminoethyl)acetamide or a salt thereof is added to the solution of 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline in the aqueous solution of the base and mixed at a suitable temperature for at least 1 hour.

8. The method according to any one of claims 1-7, wherein Rabeximod is purified and isolated as a crystalline free base.

9. The method according to any one of claims 1-8, wherein the method comprises the following steps: - Reacting a solution or suspension of 4,5-dimethyl-1,2-phenylenediamine with 5-chloroindirubin under acidic conditions at an elevated temperature up to reflux to obtain 9-chloro-2,3-dimethyl-6H-indolo[2,3-b]quinoxaline or a salt thereof.

10. The method according to any one of claims 1-9, wherein the method comprises the following prior steps: - Reacting a solution or suspension of chloroacetyl chloride with N,N-dimethylethylenediamine to obtain 2-chloro - N-(2-dimethylaminoethyl)acetamide or a salt thereof.

11. The method according to any one of claims 1-10, wherein the method comprises the prior step according to claim 9 and the prior step according to claim 10.

12. The method according to claim 9, wherein the acidic condition is an organic acid.

13. The method according to any one of claims 9 and 12, wherein 4,5-dimethyl-1,2-phenylenediamine and 5-chloroindirubin are both dissolved in an acid before the reaction.

14. The method according to any one of claims 9 and 12-13, wherein the elevated temperature is the reflux temperature.

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