Preparation method of ridinilazole and its crystalline form

Abstract

Methods for preparing 2,2'-di(pyridin-4-yl)-1H,1'H-5,5'-bibenzo[d]imidazole (which may also be known as 5,5'-bis[2-(4-pyridinyl)-1H-benzimidazole]) (referred to herein by the INN name ridinilazole), and pharmaceutically acceptable derivatives, salts, hydrates, solvates, complexes, bioisosteres, metabolites, or prodrugs thereof, are described. The invention also relates to various compositions of purified ridinilazole, various crystalline forms of ridinilazole, methods for their preparation, and related pharmaceutical products and their uses, including their medical uses and use in the efficient large-scale synthesis of ridinilazole.

Description

[Technical Field]

[0001] 1. Field of the Invention The present invention relates to a process for the preparation of 2,2'-di(pyridin-4-yl)-1H,1'H-5,5'-bibenzo[d]imidazole (which may also be known as 5,5'-bis[2-(4-pyridinyl)-1H-benzimidazole], 2,2'-bis(4-pyridyl)-3H,3'H-5,5'-bibenzimidazole or 2-pyridin-4-yl-6-(2-pyridin-4-yl-3H-benzimidazol-5-yl)-1H-benzimidazole), referred to herein by the INN name ridinilazole, and pharmaceutically acceptable derivatives, salts, hydrates, solvates, complexes, bioisosteres, metabolites or prodrugs thereof. The present invention also relates to various crystalline forms (crystalline forms) of ridinilazole, methods for their preparation, and related pharmaceutical products and their uses, including their medical uses and use in the efficient large-scale synthesis of ridinilazole. [Background technology]

[0002] 2. Background of the invention Infection with Clostridioides difficile (formerly known as Clostridium difficile) (CDI) leads to Clostridioides difficile-associated disease (CDAD). In the United States, more than 450,000 cases of CDI occur annually, with over 80,000 first recurrences and approximately 29,000 deaths. The most common contributing factor is antibiotic use, which can lead to the development of a species-poor microbiota that is susceptible to pathogen invasion over a prolonged period, resulting in a loss of colonization resistance. Oral vancomycin and oral metronidazole treatment are associated with a high recurrence rate of CDI, likely due to adverse effects on the resident colonic microbiota. Recurrences are costly in terms of both clinical burden and healthcare resource utilization. In one study, approximately one-third of recurrences required hospital readmission.

[0003] Both the biomass of the gut microbiota and the composition of the gut-bacterial interface may influence the colonization niche of C. difficile (Clostridioides difficile). Colonization resistance is associated with specific taxa, but different and diverse microbial community structures may confer protection. Consistent characteristics of CDI-susceptible communities include lower levels of diversity, reduced metabolic function, a relative decrease in members of the Bacteroidetes and Firmicutes phyla, and an increase in members of the Proteobacteria phyla. Fecal microbial transplantation (FMT) normalizes these characteristics and interrupts the recurrent cycle of CDI.

[0004] Overall, these data support the role of CDI medications to reduce the risk of recurrence while minimizing the impact on the resident microbiota.

[0005] Ridinilazole (also known as SMT19969 and may be variously referred to in the literature as 2,2'-di(pyridin-4-yl)-1H,1'H-5,5'-bibenzo[d]imidazole or 5,5'-bis[2-(4-pyridinyl)-1H-benzimidazole]) is a narrow-spectrum, poorly absorbed, potent antibacterial agent that targets C. difficile (Clostridioides difficile). Ridinilazole is represented by the following formula:

[0006] [ka]

[0007] In a recent phase 2 randomized, controlled, double-blind clinical trial, ridinilazole compared efficacy with vancomycin, significantly reducing the incidence of recurrent disease (14.3% vs. 34.8%). Ridinilazole exhibits robust preservation of the human gut microbiota compared with vancomycin, which may contribute to the reduction in CDI recurrence observed in the phase 2 study.

[0008] Therefore, there is a need for an efficient synthesis of ridinilazole.

[0009] The control of genotoxic and potentially genotoxic impurities (PGIs) in drug manufacturing is a major concern, and acceptable levels should not exceed those justified by safety data. There is a need in the art for methods that allow for the effective removal of PGIs to prepare drug candidates.

[0010] The present inventors have now developed an efficient method for producing ridinilazole and its pharmaceutically acceptable salts, hydrates, solvates, complexes, bioisosteres, metabolites, or prodrugs, which (a) are suitable for large-scale synthesis under GMP conditions, and (b) reduce the PGI to a level acceptable for commercial manufacturing of the formulation.

[0011] The inventors have now also discovered three different crystalline forms (polymorphs) of ridinilazole, which are particularly useful in the above method and find application in the efficient large-scale synthesis of ridinilazole for medical uses (and in the medical field in general).

[0012] 3. Prior art WO 2010 / 063996 describes various benzimidazoles, including ridinilazole, and their use as antibacterial agents, including for the treatment of CDAD.

[0013] WO 2011 / 151621 describes various benzimidazoles and their use as antibacterial agents, including for the treatment of CDAD.

[0014] WO2007056330, WO2003105846 and WO2002060879 disclose various 2-aminobenzimidazoles as antibacterial agents.

[0015] WO2007148093 discloses various 2-aminobenzothiazoles as antibacterial agents.

[0016] WO 2006076009, WO 200 / 041209, and Bowser et al. (Bioorg.Med.Chem.Lett., 2007, 17, 5652-5655) disclose various substituted benzimidazole compounds useful as anti-infective agents that reduce microbial resistance, virulence, or growth. The compounds are said to exhibit no intrinsic antibacterial activity in vitro.

[0017] U.S. Patent No. 5,824,698 discloses various dibenzimidazoles as broad-spectrum antibiotics, and discloses activity against both Gram-negative and Gram-positive bacteria, including Staphylococcus and Enterococcus. However, this document does not disclose activity against anaerobic spore-forming bacteria, and in particular, does not disclose activity against any Clostridioides bacteria (including C. difficile).

[0018] U.S. Patent Application Publication No. 2007 / 0112048 discloses various biarylimidazolidines and triarylimidazolidines, biarylamidines, and triarylamidines as broad-spectrum antibiotics, and discloses activity against both Gram-negative and Gram-positive bacteria, including Staphylococcus, Enterococcus, and Clostridioides. However, this document does not disclose the compound of formula (I) described herein.

[0019] Chaudhuri et al. (2007) J. Org. Chem. 72, 1912-1923 describes various bis-2-(pyridyl)-1H-benzimidazoles (including the compound of formula I described herein) as DNA binding agents. The document is silent on potential antibacterial activity.

[0020] Singh et al. (2000) Synthesis 10: 1380-1390 describes a condensation reaction to prepare 2,2'-di(pyridin-4-yl)-1H,1'H-5,5'-bibenzo[d]imidazole using 4-pyridinecarboxaldehyde, FeCl3, O2 in DMF at 120°C.

[0021] Bhattacharya and Chaudhuri (2007) Chemistry-An Asian Journal 2: 648-655 describe a condensation reaction to prepare 2,2'-di(pyridin-4-yl)-1H,1'H-5,5'-bibenzo[d]imidazole using 4-pyridinecarboxaldehyde and nitrobenzene at 120°C.

[0022] WO 2019 / 068383 describes the synthesis of ridinilazole by metal ion-catalyzed coupling of 3,4,3′,4′-tetraaminobiphenyl with 4-pyridinecarboxaldehyde in the presence of oxygen, followed by the addition of a complexing agent. Summary of the Invention

[0023] 4. Summary of the Invention According to a first aspect of the present invention, there is provided a composition comprising a mixture of compounds, said mixture comprising ridinilazole and a compound represented by formula (II) and formula (IV):

[0024] [ka] wherein the total amount of impurities E and F in the mixture is less than 100 ppm.

[0025] In a preferred embodiment, ridinilazole is present as a crystalline form of ridinilazole tetrahydrate (Form A) characterized by an X-ray powder diffraction diagram (XRPD) containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°.

[0026] In a second aspect of the present invention, there is provided a method for preparing a composition according to the first aspect of the present invention, comprising the steps of: (a) providing a crude ridinilazole composition comprising a mixture of compounds, said mixture comprising ridinilazole and compounds of formula (II) and formula (IV):

[0027] [ka] and The total amount of impurities E and F in the mixture is greater than 100 ppm; and then (b) removing impurities E and F from the mixture to produce a purified ridinilazole composition, wherein the total amount of impurities E and F present in the mixture is less than 100 ppm; The present invention provides a method comprising:

[0028] In a third aspect, the present invention provides a composition according to the first aspect of the invention obtainable (or produced) by a method of the present invention.

[0029] In another aspect, the present invention provides a pharmaceutical composition comprising an effective amount of a composition of the present invention and a pharmaceutically acceptable excipient.

[0030] In another aspect, the present invention provides a composition of the present invention for use in therapy or prophylaxis.

[0031] In another aspect, the present invention provides a composition of the present invention for use in the treatment or prevention of CDI or CDAD.

[0032] In another aspect, the present invention provides use of a composition of the present invention for the manufacture of a medicament for the treatment, therapy, or prevention of CDI or CDAD.

[0033] In another aspect, the present invention provides a crystalline form of ridinilazole tetrahydrate (Form A) characterized by a powder X-ray diffraction pattern comprising characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°.

[0034] In another aspect, the present invention provides a crystalline form of ridinilazole anhydrate (Form D), characterized by a powder X-ray diffraction pattern comprising characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, and (27.82±0.2)°, and optionally comprising characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, (27.82±0.2)°, (19.5±0.2)°, and (22.22±0.2)°.

[0035] Other aspects and embodiments of the present invention are set out in the claims appended hereto. [Brief explanation of the drawings]

[0036] 6. Brief description of the drawings [Figure 1] 1 is a graph showing a representative X-ray powder diffraction pattern of lysinyl azole tetrahydrate Form A. [Figure 2] 1 is a graph showing a representative X-ray powder diffraction pattern of lysinyl azole tetrahydrate Form N. [Figure 3] 1 is a graph showing a representative X-ray powder diffraction pattern of lysinyl azole anhydrate Form D. [Figure 4] FIG. 1 is a phase diagram of lysinyl azole in MeOH / HO. [Figure 5] FIG. 1 shows the asymmetric unit content of lysinyl azole tetrahydrate form N. [Figure 6] FIG. 1 shows the hydrogen bonding pattern of lysinylazole tetrahydrate form N. [Figure 7] FIG. 1 shows an ORTEP plot of lysinyl azole and water molecules in the Form A structure. [Figure 8] FIG. 1 is a packing diagram of the ridinilazole form A structure along each crystallographic axis. [Figure 9] FIG. 1 is a packing diagram of the ridinilazole form A structure along each crystallographic axis. [Figure 10] FIG. 1 is a packing diagram of the ridinilazole form A structure along each crystallographic axis. [Figure 11] FIG. 1 is an ORTEP plot of the lysinyl azole molecule in Form D structure. [Figure 12] FIG. 16 is a packing diagram of the ridinilazole form D structure along each crystallographic axis. [Figure 13] FIG. 16 is a packing diagram of the ridinilazole form D structure along each crystallographic axis. [Figure 14] FIG. 16 is a packing diagram of the ridinilazole form D structure along each crystallographic axis. [Figure 15] FIG. 1 shows hydrogen bonding between ridinilazole form D molecules that form a two-dimensional network along the a-b plane (i.e., viewed along the c-axis). [Figure 16] FIG. 1 shows the conformations of the ridinilazole molecule in form A (syn conformation), form N (anti conformation) and form D (anti conformation). [Figure 17] Figure 1 shows ridinidazole Form N (top) and Form A (bottom) viewed along the axis, both to show the water channels. Circled are the water channels containing two independent water molecules and the water channels containing four independent water molecules. [Figure 18] 1 is a graph showing an overlay of XRPD of ridinilazole tablets (top trace), placebo (middle trace), and Form A (bottom trace) between about 10° 2-theta angles and about 25° 2-theta angles. [Figure 19] 1 is a graph showing a representative powder X-ray diffraction pattern of ridinilazole lithium salt. DETAILED DESCRIPTION OF THE INVENTION

[0037] 5. Detailed Description and Examples of the Invention All publications, patents, patent applications and other references mentioned herein are incorporated herein by reference in their entirety and for all purposes to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference and its contents fully set forth.

[0038] 5.1 Definitions and General Precedence As used herein, and unless otherwise indicated, the following terms are intended to have the following meanings in addition to any broader (narrower) meaning that such terms may enjoy in the art. Unless the context requires otherwise, the use of the singular herein shall be read to include the plural, and vice versa. The term "a" or "an," in reference to a term referring to an entity, shall be read to refer to one or more of that entity. Thus, the terms "a" (or "an"), "one or more," and "at least one" are used interchangeably herein.

[0039] As used herein, the term "comprise," or variations thereof, such as "comprises" and "comprising," should be read to indicate the inclusion of any stated component (e.g., feature, element, characteristic, property, method / process step, limitation) or group of components (e.g., feature, element, characteristic, property, method / process step, or limitation), but not any other component or group of components. Thus, as used herein, the term "comprising" is inclusive or open-ended and does not exclude additional, unrecited components or method / process steps.

[0040] As used herein, the phrase "consisting essentially of" requires certain components or steps as well as those that do not materially affect the characteristics or functionality of the claimed invention.

[0041] As used herein, the term "consisting of" is used to indicate only the presence of a stated component (e.g., feature, element, characteristic, property, method / process step, or limitation) or group of components (e.g., feature, element, characteristic, property, method / process step, or limitation).

[0042] The pharmaceutical compositions of the present invention are included in pharmaceutical kits, packs, or patient packs.

[0043] As used herein, the term "pharmaceutical kit" defines a configuration of a unit dose or multiple unit doses of a pharmaceutical composition together with a dosing means (e.g., a measuring device) and / or a delivery means (e.g., an inhaler or syringe). The unit doses and dosing means may optionally all be contained in a common outer box. The unit doses may be contained in a blister pack. The pharmaceutical kit may optionally further include instructions for use.

[0044] As used herein, the term "pharmaceutical pack" defines an arrangement of single or multiple unit doses of a pharmaceutical composition, optionally contained in a common outer box. The unit doses may also be contained in a blister pack. The pharmaceutical pack may optionally further include instructions for use.

[0045] As used herein, the term "patient pack" defines a package prescribed to a patient that contains pharmaceutical compositions for a full course of treatment. Patient packs typically contain one or more blister packs. Patient packs have the advantage over traditional prescriptions in which a pharmacist portions out a patient's supply of medication from a bulk supply, and patients always have access to the package insert included in the patient pack, which is typically lost with patient prescriptions. The inclusion of the package insert has been shown to improve patient compliance with physician instructions.

[0046] As used herein, the term ridinilazole is used to define the compound 2,2'-di(pyridin-4-yl)-1H,1'H-5,5'-bibenzo[d]imidazole (which may also be known as 5,5'-bis[2-(4-pyridinyl)-1H-benzimidazole], 2,2'-bis(4-pyridyl)-3H,3'H-5,5'-bibenzimidazole, or 2-pyridin-4-yl-6-(2-pyridin-4-yl-3H-benzimidazol-5-yl)-1H-benzimidazole). This term also includes pharmaceutically acceptable derivatives, salts, hydrates, solvates, complexes, bioisosteres, metabolites, or prodrugs of ridinilazole, as defined herein.

[0047] The term "pharmaceutically acceptable derivative" as applied to ridinilazole defines a compound obtained (or obtainable) by chemical derivatization of the parent compound of the present invention. Thus, a pharmaceutically acceptable derivative is suitable for administration to or contact with mammalian tissue without undue toxicity, irritation, or allergic response (i.e., commensurate with a reasonable benefit / risk ratio). Preferred derivatives are those obtained (or obtainable) by alkylation, esterification, or acylation of the parent compound of the present invention. The derivatives may be active per se or may be inactive until processed in vivo. In the latter case, the derivatives of the present invention act as prodrugs. Particularly preferred prodrugs are ester derivatives esterified at one or more free hydroxyls and activated by in vivo hydrolysis. Other preferred prodrugs are covalently bonded compounds that release the active parent drug of Formula (I) after cleavage of the covalent bond in vivo.

[0048] The pharmaceutically acceptable derivatives of the present invention retain some or all of the activity of the parent compound. In some cases, derivatization increases activity. Derivatization can also enhance other biological activities of the compound, such as bioavailability.

[0049] The term "pharmaceutically acceptable salts" as applied to ridinilazole defines any non-toxic organic or inorganic acid addition salt of the free base compound that is suitable for use in contact with mammalian tissues without undue toxicity, irritation, or allergic response, and that is commensurate with a reasonable benefit / risk ratio. Suitable pharmaceutically acceptable salts are well known in the art. Examples are salts with inorganic acids (e.g., hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid), organic carboxylic acids (e.g., acetic acid, propionic acid, glycolic acid, lactic acid, pyruvic acid, malonic acid, succinic acid, fumaric acid, malic acid, tartaric acid, citric acid, ascorbic acid, maleic acid, hydroxymaleic acid, dihydroxymaleic acid, benzoic acid, phenylacetic acid, 4-aminobenzoic acid, 4-hydroxybenzoic acid, anthranilic acid, cinnamic acid, salicylic acid, 2-phenoxybenzoic acid, 2-acetoxybenzoic acid, and mandelic acid), and organic sulfonic acids (e.g., methanesulfonic acid and p-toluenesulfonic acid). The compounds of the present invention may be converted into their (mono- or di-)salts by reaction with a suitable base, such as an alkali metal hydroxide, methoxide, ethoxide or tert-butoxide, or an alkyl lithium, such as selected from NaOH, NaOMe, KOH, KOtBu, LiOH and BuLi, and pharmaceutically acceptable salts of ridinilazole may also be prepared in this manner.

[0050] These salts and free base compounds can exist in either hydrated or substantially anhydrous form.Crystalline forms of the compounds of the present invention are also contemplated, and generally, acid addition salts of the compounds of the present invention are crystalline materials that are soluble in water and various hydrophilic organic solvents and demonstrate higher melting points and increased solubility compared to their free base forms.For example, the sodium salt of ridinilazole is sufficiently soluble in methanol that the methanol solution can pass through activated carbon.

[0051] The term "pharmaceutically acceptable solvate," as applied to ridinilazole, defines any pharmaceutically acceptable solvate form of a particular compound that retains the biological effectiveness of such compound. Examples of solvates include compounds of the invention in combination with water (hydrates), short chain alcohols (including isopropanol, ethanol, and methanol), dimethyl sulfoxide, ethyl acetate, acetic acid, ethanolamine, acetone, dimethylformamide (DMF), dimethylacetamide (DMAc), pyrrolidones (such as N-methyl-2-pyrrolidone (NMP)), tetrahydrofuran (THF), and ethers (such as tertiary butyl methyl ether (TBME)).

[0052] Also included are miscible preparations of solvated mixtures, such as a compound of the present invention in a mixture of acetone and ethanol. In a preferred embodiment, the solvate comprises a compound of the present invention in combination with about 20% ethanol and about 80% acetone. Thus, the structural formulas include compounds having the indicated structure, including hydrated and non-hydrated forms.

[0053] The term pharmaceutically acceptable prodrug, as applied to ridinilazole, defines any pharmaceutically acceptable compound that can be converted under physiological conditions or by solvolysis in vivo to ridinilazole, to a pharmaceutically acceptable salt of such compound, or to a compound that shares at least some of the antibacterial activity of the specified compound (e.g., exhibits activity against Clostridioides difficile).

[0054] The term pharmaceutically acceptable metabolite as applied to ridinilazole defines a pharmacologically active product produced by metabolism in the body of ridinilazole or a salt thereof.

[0055] Prodrugs and active metabolites of the compounds of the invention can be identified using routine techniques known in the art (see, for example, Bertolini et al., J. Med. Chem., 1997, 40, 2011-2016).

[0056] The term "pharmaceutically acceptable complex" as applied to ridinilazole defines a compound or composition in which a compound of the invention forms a constituent moiety. Thus, complexes of the invention include derivatives in which a compound of the invention is physically associated (e.g., by covalent or non-covalent bonding) with another moiety or moieties. Thus, the term includes multimeric forms of compounds of the invention. Such multimers can be prepared by linking or placing multiple copies of a compound of the invention in close proximity to one another (e.g., via a scaffold or carrier moiety). The term includes cyclodextrin complexes.

[0057] The term bioisostere (or simply bioisostere) is used in the art to define drug analogs in which one or more atoms (or groups of atoms) have been replaced by a replacement atom (or groups of atoms) with similar steric and / or electronic characteristics to the replaced atoms. Replacing hydrogen atoms or hydroxyl groups with fluorine atoms is a commonly used bioisostere replacement. Silasubstitution (C / Si exchange) is a relatively recent technique for producing isoisosteres. This technique involves the replacement of one or more specific carbon atoms in a compound with silicon (for a review, see the article by Tacke and Zilch in Endeavour, New Series, 1986, 10, 191-197). Silasubstitution equivalents (silicon equivalents) may exhibit improved pharmacological properties, such as better tolerability, longer half-life, or increased potency (see the article by Englebienne in Med. Chem., 2005, 1(3), 215-226). Similarly, substitution of a single atom by an isotope, e.g., replacement of hydrogen with deuterium, may also lead to improved pharmacological properties, e.g., longer half-life (see, e.g., Kushner et al (1999) Can J Physiol Pharmacol. 77(2): 79-88). In its broadest aspect, the present invention contemplates all bioisosteres (and specifically all silicon bioisosteres) of the compounds of the present invention.

[0058] In its broadest aspect, the present invention contemplates all tautomers, optical isomers, racemates, and diastereoisomers of the compounds described herein. Those skilled in the art will understand that due to the asymmetrically substituted carbon atoms present in the compounds of the present invention, the compounds can be produced in optically active and racemic forms. When chiral or other isomeric centers are present in the compounds of the present invention, all forms of such isomer(s), including enantiomers and diastereoisomers, are intended to be encompassed herein. Compounds of the present invention containing a chiral center (or multiple chiral centers) can be used as racemic mixtures, enantiomerically enriched mixtures, or racemic mixtures can be separated using well-known techniques and the individual enantiomers used alone. Thus, reference to a compound of the present invention encompasses the product as a mixture of diastereoisomers, as individual diastereoisomers, as a mixture of enantiomers, and in the form of individual enantiomers.

[0059] Thus, the present invention contemplates all optical isomers of the compounds of the present invention as well as their racemic forms, and unless otherwise indicated (e.g., by the use of dash-wedge structural formulas), the compounds depicted herein are intended to encompass all possible optical isomers of the depicted compound. Where the stereochemical form of the compound is important to pharmaceutical utility, the present invention contemplates the use of isolated eutomers.

[0060] As used herein, the term condensation reaction refers to a reaction of two or more reactants that results in a single major product and is accompanied by the formation of small molecules such as water, ammonia, ethanol, acetic acid, or hydrogen sulfide, such as in the case of 3,3'-diaminobenzidine (DAB) to yield ridinilazole and an intermediate by-product of formula (II), and is therefore used herein as a broad technical term.

[0061] The abbreviation "XRPD" stands for X-ray powder diffraction (or X-ray powder diffractogram, where the context allows).

[0062] As used herein, the term "room temperature" (RT) relates to a temperature between 15 and 25°C.

[0063] The term "substantially identical" with respect to XRPD diffraction patterns is intended to take into account variations in peak positions and relative intensities. The ability to determine the substantial identity of X-ray diffraction patterns is within the skill of the art. For example, typical accuracy of 2-theta values ​​is within ±0.2° 2-theta. Thus, a diffraction peak that normally appears at 14.9° 2-theta may appear between 14.7° and 15.1° 2-theta on most X-ray diffractometers under standard conditions. Furthermore, variability may arise from the specific instrument used, as well as sample crystallinity, orientation, sample preparation, and other factors. XRPD measurements are typically performed at room temperature, e.g., 20°C, preferably at 40% relative humidity.

[0064] As used herein, "Form A" of ridinilazole refers to a crystalline form of ridinilazole tetrahydrate characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°.

[0065] As used herein, "Form N" of ridinilazole refers to a crystalline form of ridinilazole tetrahydrate characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (10.82±0.2)°, (13.35±0.2)°, and (19.15±0.2)°, and optionally containing characteristic peaks at 2-theta angles of (10.82±0.2)°, (13.35±0.2)°, (19.15±0.2)°, (8.15±0.2)°, and (21.74±0.2)°.

[0066] As used herein, "Form D" of ridinilazole refers to a crystalline form of ridinilazole anhydrate characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, and (27.82±0.2)°, and optionally containing characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, (27.82±0.2)°, (19.5±0.2)°, and (22.22±0.2)°.

[0067] Those skilled in the art will understand that XRPD patterns can be obtained with measurement errors that depend on the measurement conditions used. In particular, it is generally known that the intensities of XRPD patterns may vary depending on the measurement conditions used. Relative intensities may also vary depending on experimental conditions, so they should not be considered determinative. Furthermore, since the measurement error of the diffraction angles in conventional XRPD patterns is typically about 5% or less, the degree of such measurement error must be taken into account when considering the diffraction angles described. It will be understood that the various crystalline forms described herein are not limited to crystalline forms that produce X-ray diffraction patterns that are completely identical to the X-ray diffraction patterns shown in the accompanying figures. Rather, crystalline forms of ridinilazole that exhibit X-ray diffraction patterns (as defined above) that substantially match the X-ray diffraction patterns shown in the figures are within the scope of the present invention.

[0068] As used herein, the term "substantially pure" with respect to a particular crystalline (polymorphic) form of ridinilazole is used to define one that contains less than 10% by weight, preferably less than 5% by weight, more preferably less than 3% by weight, and most preferably 1% by weight of any other physical form of ridinilazole.

[0069] As used herein, the term "impurity E" refers to an impurity of formula (II):

[0070] [ka] means a compound of the formula:

[0071] As used herein, the term "impurity F" refers to an impurity of formula (IV):

[0072] [ka] Define the compound.

[0073] 5.2 Synthesis of crude ridinilazole by imidate-DAB condensation The inventors have determined that crude ridinilazole composition can be conveniently synthesized by subjecting 3,3'-diaminobenzidine (DAB) to a condensation reaction to produce said ridinilazole. In a preferred embodiment, the condensation reaction comprises reacting DAB with an imidate (which may be referred to herein as "imidate-DAB condensation"). The imidate is preferably represented by formula (V):

[0074] [ka] It is methyl isonicotinimidate.

[0075] In a preferred embodiment, the condensation reaction is as follows: (a) adding sodium methoxide to 4-cyanopyridine to produce a compound of formula (V); and (b) reacting the compound of formula (V) of step (a) with said DAB Includes:

[0076] The imidate-DAB condensation reaction may involve two chemical steps: Step 1a: Reaction of 4-cyanopyridine with methanol, catalyzed by sodium methoxide, to form methyl isonicotinimidate; and Step 1b: Coupling of methyl isonicotinimidate with 3,3′-diaminobenzidine (DAB) to form crude ridinilazole.

[0077] The condensation reaction (Step 1b) can be carried out at a temperature between 10°C and 160°C. The reaction can be carried out at the reflux temperature of the solvent (e.g., 152°C to 154°C for DMF) at atmospheric pressure. The reaction can be carried out in any suitable solvent that does not interfere with the reaction. Suitable solvents include methanol (as shown in exemplary Reaction Scheme 1 below). Others include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc).

[0078] Therefore, the imidate-DAB condensation is (a) adding sodium methoxide to 4-cyanopyridine in methanol to produce a compound of formula (V); and (b) adding the compound of formula (V) of step (a) to a mixture of DAB and acetic acid in methanol; or (c) adding a mixture of DAB and acetic acid in methanol to the compound of formula (V) of step (a); Includes.

[0079] [ka]

[0080] By using different alkoxide / alcohol combinations in step 1a, other imidates can be prepared and used in the condensation reaction, for example, sodium ethoxide / ethanol can be used instead of sodium methoxide / methanol, while other cations (preferably alkali metals such as lithium or potassium) can be substituted for sodium.

[0081] In Step 1b, the amount of acetic acid is preferably less than 3.5 equivalents, for example, 2.5 to 3.0 equivalents. Instead of acetic acid, other acids (such as TFA) can also be used.

[0082] There is a wide range of scope for manipulating the exact conditions for the imidate-DAB condensation reaction, and all such manipulations are within the scope of the present invention. Resources that may be helpful to those skilled in the art in practicing the present invention include Vogel's Textbook 5 of Practical Organic Chemistry, Fifth Edition, B.S. Furniss et al., Pearson Education Limited, 1988, which discusses general practical procedures. Additionally, synthetic methods are discussed in Comprehensive Heterocyclic Chemistry, Vol. 1 (Eds.: A.R. Katritzky, C.W. Rees), Pergamon Press, Oxford, 1984, and Comprehensive Heterocyclic Chemistry II: A Review of the Literature 1982-1995 The Structure, Reactions, Synthesis, and Uses of Heterocyclic Compounds, Alan R. Katritzky (Editor), Charles W. Rees (Editor), EFV. Scriven (Editor), Pergamon Press, June 1996. Other general resources to assist the skilled practitioner include March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, Wiley-Interscience; 5th edition (January 15, 2001).

[0083] A preferred imidate-DAB reaction is shown schematically below.

[0084] [ka]

[0085] In exemplary Reaction Scheme 1 shown above, the condensation reaction begins with a slurry of DAB in methanol, and at approximately three-quarters of the imidate charge, the reaction mixture briefly goes into solution, after which the crude ridinilazole product precipitates from solution (and can be recovered as a wet filter cake).

[0086] The inventors have discovered that the dynamics of this crystallization method are volatile and depend, among other things, on stochastic nucleation events. Without wishing to be bound by any theory, it is believed that impurities E and F are entrained within the ridinilazole crystals (and / or within their amorphous regions). For example, during the precipitation process, it is believed that some unreacted impurity E is trapped in the product crystals and cannot further react with the imidate (even when the imidate is present in large excess).

[0087] Thus, the recovered crude ridinilazole product contains a mixture of impurities E and F, along with anhydrous crystalline form D of ridinilazole, characterized by an XRPD pattern substantially consistent with FIG.

[0088] 5.3 Impurities E and F in crude ridinilazole In the synthesis of crude ridinilazole described in Section 5.2 (above), the reaction of DAB with an imidate requires two equivalents of imidate to complete the reaction. The inventors have discovered that an intermediate impurity, a compound of formula (II) (also referred to herein as "impurity E"), is formed when DAB reacts with only one equivalent of imidate, as shown below.

[0089] [ka]

[0090] The present inventors have also discovered that monoaminobenzidine (MAB, referred to herein as the compound of formula (III)) is present as an impurity in commercial sources of DAB. The present inventors have discovered that MAB also reacts with imidates to form a second (process) impurity, which is a compound of formula (IV) (also referred to herein as "impurity F"), as shown below:

[0091] [ka]

[0092] Thus, crude ridinilazole produced as described above comprises a mixture of compounds, said mixture comprising ridinilazole, formula (II), and formula (IV):

[0093] [ka] (impurities E and F, respectively).

[0094] The present inventors have surprisingly discovered that despite the use of highly toxic DAB and the production of impurities E and F (both compounds of formula (II) and (IV) are potentially genotoxic impurities (PGIs)), an efficient, large-scale GMP synthesis of ridinilazole suitable for use in the formulation of pharmaceutical compositions for administration at levels for the treatment of CDI and CDAD in humans can be achieved by ensuring that the combined amount of impurities E and F is less than 100 ppm, as described in more detail below.

[0095] Accordingly, the present invention provides a composition comprising a mixture of compounds, said mixture comprising ridinilazole and compounds represented by formulas (II) and (IV):

[0096] [ka] and A composition is provided, wherein the total amount of impurity E and impurity F in the mixture is less than 100 ppm.

[0097] In a preferred embodiment, ridinilazole is present in the crystalline form of ridinilazole tetrahydrate (Form A) characterized by an X-ray powder diffraction diagram (XRPD) containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°.

[0098] 5.4 Determination of Impurities E and F by HPLC-MS material Water, extra-high quality (e.g., MilliQ) or equivalent Formic Acid, 99% MS Grade Methanesulfonic acid (MSA), 99% ultra pure Methanol, HPLC grade Impurity E Impurity F

[0099] Device Balance: Minimum 5 balance points

[0100] System parameters HPLC / MS system: Agilent LC1200, MSD 61508 Column: ACE 3 C18, 100 x 4.6 mm, Cat. No. ACE-111-1046 Mobile phase A: 0.1% v / v formic acid in ion-exchange water Mobile phase B: 0.1% v / v formic acid in methanol Diluent: 98:2:2 v / v / v (water:MeOH:methanesulfonic acid) Injection volume: 2μL Detection: MSD / SIM m / z 302.1 for impurity E m / z 287.1 for impurity F Column temperature: 45℃ Flow rate: 1.0mL / min Autosampler temperature: 5℃ Needle Cleaning: Diluent

[0101] Gradient

[0102] [Table 1]

[0103] Post run: 3 minutes

[0104] MSD parameters Spray chamber setup Drying gas flow rate 12.0 L / min Nebulizer pressure 60psi Drying gas temperature 350℃ Capillary voltage 3000V

[0105] MSD signal settings Ion source API-ES positive Fragmenter 70 Gain 1.0 SIM ion of impurity E m / z 302.1 at 5.00 min SIM ion of impurity F m / z 287.1 at 5.00 min

[0106] Injector Program

[0107] [Table 2]

[0108] Preparation of solutions

[0109] [Table 3]

[0110] Injection procedure

[0111] [Table 4]

[0112] component: SMT 19969 Impurity E: Retention time approximately 6.1 minutes SMT 19969 Impurity F: Retention time approximately 6.6 minutes

[0113] System Compatibility The signal to noise ratio of each impurity peak in the working standard solution should be less than 10. The retention time window is within ±1 minute of the expected retention time of each component listed above.

[0114] 5.5 Removal of Impurities E and F from Crude Ridinilazole By reference to the various dosing regimens indicated for the treatment of CDI or CDAD in human patients, the inventors have determined that the crude ridinilazole product of the above process is advantageously further purified to such an extent that the combined amount of compounds of formula (II) and (IV) (i.e., impurities E and F, respectively) present in the mixture is less than 100 ppm.

[0115] Any suitable purification method or combination of methods can be used, provided that it results in a purified ridinilazole composition having less than 100 ppm of the total amount of impurities E and F present in the mixture.

[0116] Accordingly, the present invention provides a method for producing a composition comprising a mixture of compounds, said mixture comprising ridinilazole and impurities E and F, wherein the total amount of impurities E and F in the mixture is less than 100 ppm, the method comprising: (a) providing a crude ridinilazole composition comprising a mixture of compounds, said mixture comprising ridinilazole and compounds of formula (II) and (IV):

[0117] [ka] and the total amount of impurities E and F in the mixture exceeds 100 ppm; and then (b) removing impurities E and F from the mixture to produce a purified ridinilazole composition having a total amount of impurities E and F in the mixture of less than 100 ppm; The present invention provides a method comprising:

[0118] It will be appreciated that the purification methods described herein may also be useful in removing or reducing the concentration of other impurities, such as impurities present in the starting materials, reactants, and process reagents (such as DAB and MAB), as well as other process impurities that may occur.

[0119] Preferred purification methods for use as removal step (b) can be used alone or in any combination and are described in more detail below.

[0120] 5.5.1 Treatment of Crude Ridinilazole with Imidate to Purge Impurity E The crude ridinilazole product of the imidate-DAB condensation reaction described in Section 5.2 (above) can be treated with an imidate solution to react with impurity E, thereby purging it from the mixture.

[0121] For example, an imidate solution was prepared using 0.7 equivalents of 4-cyanopyridine, 0.5 equivalents of sodium methoxide and 7.2 volumes of methanol and stirred at ambient temperature for 2 hours.

[0122] To this solution was added 5.5 equivalents of acetic acid and heated at 40°C for 30 minutes. Crude ridinilazole, prepared by the imidate-DAB condensation reaction described in Section 5.2 (above), was dissolved in 9.8 volumes of methanol and 4 equivalents of sodium methoxide. The ridinilazole solution was added to the imidate solution over 5 hours at 40°C and stirred for 10 hours. The mixture was cooled to ambient temperature over 1 hour and stirred for 1 hour. The slurry was filtered and washed with methanol (2 x 4.5 volumes).

[0123] The wet cake was slurried in 12 volumes of methanol at ambient temperature for 2 hours. The slurry was filtered and washed with methanol (2 x 4.5 volumes). The wet cake was dried at 40°C, giving a recovery of 86%.

[0124] The table below summarizes the LCMS results and shows that the imidate treatment is effective in significantly reducing impurity E.

[0125] [Table 5]

[0126] Imidate-related impurities introduced by the imidate purge step can be easily removed by carbon treatment (e.g., as described in Section 5.5.6 below). For example, the product from the imidate reworking was dissolved in MeOH upon treatment with NaOMe, and the solution was treated with carbon to remove imidate-related impurities, and the impurity-purged ridinilazole product was precipitated by adding HOAc.

[0127] 5.5.2 Reprecipitation The levels of these entrained impurities E and F can be reduced by dissolving the crude ridinilazole (thus liberating the entrained impurities E and F) and then reprecipitating the ridinilazole. This reprecipitation can conveniently be carried out by forming a salt solution (preferably an alkali metal salt solution, for example, in methanol) and then reprecipitating the ridinilazole (e.g., by neutralization, e.g., by adding acetic acid).

[0128] Suitable alkali metal salts include sodium, potassium, and lithium salts.

[0129] Preferably, crude ridinilazole and sodium methoxide are dissolved in methanol and then precipitated with acetic acid.

[0130] Another preferred method is DMSO / acetic acid reprecipitation / reslurry (described in more detail below).

[0131] This reprecipitation step can also be used after imidate treatment (described above in Section 5.5.1).

[0132] Exemplary reprecipitation process using NaOMe / HOAc A crude ridinilazole wetcake produced by the imidate-DAB condensation reaction described in Section 5.2 (above) was analyzed as described herein and found to contain impurity E (17576 ppm) and impurity F (901 ppm).

[0133] NaOMe / HOAc precipitation (based on 200 g of DAB) can be carried out as follows. 1) Place the wet cake into the reactor. 2) To the same reactor, add methanol (21.5 volumes). 3) Stabilize the temperature of the slurry at 20-25°C. 4) Add 30% NaOMe / MeOH (4.0 equiv.) solution over at least 30 minutes while maintaining the temperature between 20-30°C. 5) Stir the mixture at 20-25°C for at least 30 minutes or until all solids are dissolved. 6) Add water (critical fill, 0.9 vol) to the reactor and stir for at least 30 minutes. 7) While maintaining the temperature between 20-25°C, add glacial acetic acid to adjust the pH to 5-7 over at least 2 hours. 8) Stir the slurry for at least 6 hours. 9) Filter the slurry. 10) Wash the cake with methanol (18.0 vol) and dry under vacuum at 40° C. for at least 24 hours.

[0134] This procedure yielded anhydrous crystalline Form D of ridinilazole characterized by an XRPD pattern substantially in accordance with Figure 3. It also reduced the levels of impurities E and F to 4195 ppm and 303 ppm, respectively.

[0135] In the exemplary reprecipitation process described above, crude ridinilazole is treated with 4 equivalents of sodium methoxide and dissolved in methanol. Because ridinilazole has two acidic protons, theoretically, only 2 equivalents of sodium methoxide are required. Using 2 equivalents of NaOMe instead of 4 equivalents in the above example resulted in better purging of impurities E and F. Therefore, the reduction in the levels of impurities E and F by the reprecipitation step can be increased by using a stoichiometric amount of salt-forming agent (here, sodium methoxide).

[0136] In the exemplary reprecipitation process described above, the reduction in the levels of impurities E and F can be further improved by adding acetic acid in an amount needed to adjust the pH to between 6 and 7 (rather than adding a fixed amount).

[0137] Exemplary reprecipitation process using DMSO / HOAc A crude ridinilazole wetcake produced by the imidate-DAB condensation reaction described in Section 5.2 (above) was analyzed as described herein and found to contain impurity E (17576 ppm) and impurity F (901 ppm).

[0138] A 5 g sample of this crude ridinilazole composition was slurried in 50 mL DMSO and the pH of the mixture was adjusted from 11.7 to 6.9 using 25.43 g of HOAc. The mixture was heated to 100° C. and cooled to ambient temperature.

[0139] This procedure yielded anhydrous crystalline Form D of ridinilazole, characterized by an XRPD pattern substantially in accordance with Figure 3. It also reduced the levels of impurities E and F to 248 ppm and 81 ppm, respectively.

[0140] 5.5.3 Recrystallization The difference in solubility between ridinilazole and impurities E and F can be exploited in a recrystallization procedure to crystallize ridinilazole from a solution containing dissolved impurities E and F. This allows separation of ridinilazole from the dissolved impurities.

[0141] Thus, the removing step (b) may comprise dissolving the crude ridinilazole composition in a high boiling aprotic solvent followed by recrystallization of the ridinilazole.

[0142] In a preferred embodiment, the high boiling aprotic solvent is DMSO.

[0143] In other preferred embodiments, the removing step (b) further comprises slow cooling and / or temperature cycling of the solution.

[0144] Thus, the present invention contemplates the use of a ridinilazole recrystallization step to reduce the levels of impurities E and / or F, in which a composition comprising a mixture of ridinilazole and impurities E and F is heated in DMSO such that ridinilazole goes into solution and subsequently comes out of solution.

[0145] The purging effectiveness of this method for impurities E and F can be improved by slow cooling and temperature cycling, and one skilled in the art can easily optimize these parameters by reference to the levels of impurities E and F present in the starting material (see below) and the ridinilazole mixture.

[0146] Such a recrystallization step can be used after the imidate treatment (as described above in Section 5.5.1).

[0147] Alternatively (or in addition), it can be used after a reprecipitation step (as described above in Section 5.5.2), for example, it can be used after an imidate treatment followed by a reprecipitation step (see Sections 5.5.1 and 5.5.2 above).

[0148] Exemplary Recrystallization Methods The crude ridinilazole product from the imidate-DAB condensation reaction described in Section 5.2 (above) was analyzed and found to contain impurity E (474 ​​ppm) and impurity F (65 ppm). Dry cake (225 g) was added to a reactor, followed by 20 volumes of DMSO (4950 g) and water (112.5 g, 0.5 volumes). The mixture was heated to 100°C with stirring.

[0149] The resulting solution was then cooled to 25°C over 2 hours and stirred for at least 2 hours. The resulting slurry was filtered and the cake washed with DMSO (990 g, 4 vol) and MTBE (2 x 666 g, 2 x 4 vol). The solid was dried under vacuum at 40°C for at least 24 hours.

[0150] Analysis of the recovered solids revealed that the recrystallization process reduced the levels of impurities E and F to 5 ppm and 20 ppm, respectively.

[0151] In a further experiment, the above procedure was applied to a composition prepared according to Example 12 (below) containing ridinilazole hydrate form A and a mixture of impurities E (36 ppm) and F (318 ppm). Analysis of the recovered solids revealed that the recrystallization process reduced the levels of impurities E and F to 3 ppm and 159 ppm, respectively.

[0152] In yet further experiments, the above procedure was applied to a composition prepared according to Example 12 (below) comprising a mixture of ridinilazole hydrate Form A spiked with impurity E (up to 2036 ppm) and containing impurity F (318 ppm). Analysis of the recovered solids revealed that the recrystallization process reduced the levels of impurities E and F to 111 ppm and 124 ppm, respectively.

[0153] Purging of impurities can be improved by slow cooling and temperature cycling. A composition prepared according to Example 12 (below) containing a mixture of ridinilazole hydrate Form A spiked with impurity E (up to 2036 ppm) and containing impurity F (318 ppm) was used as the starting material.

[0154] In a slow cooling experiment, a mixture of this ridinilazole composition and DMSO was heated to 100°C, held for 4 hours, and then cooled to ambient temperature over 8 hours. Impurities E and F were found to be reduced to 306 and 89 ppm, respectively.

[0155] In a temperature cycling experiment, the same mixture was heated to 100°C and held for 1 hour, then cooled to ambient temperature over 3 hours and held for 1 hour. The mixture was then heated to 100°C over 3 hours and cooled three times, followed by a 7-hour hold at ambient temperature. Impurities E and F were found to be reduced to 117 and 124 ppm, respectively.

[0156] 5.5.4 Solvent exchange and / or crystallization with ridinilazole alkali metal salts The difference in solubility of alkali metal salts of ridinilazole (such as sodium, lithium, and potassium salts) in various solvents can be used to remove trapped impurities E and F. For example, the difference in solubility of the sodium salt of ridinilazole in various solvents can be used to remove trapped impurities E and F.

[0157] Thus, the present invention contemplates the use of a ridinilazole sodium salt solvent exchange step to reduce the levels of impurities E and / or F. In this step, a composition comprising a solution of ridinilazole sodium salt mixed with impurities E and F in a first solvent (e.g., MeOH) is exchanged with a second solvent (e.g., isopropyl alcohol (IPA)) in which ridinilazole sodium salt has a lower solubility.

[0158] For example, dissolving crude ridinilazole and sodium methoxide in methanol releases any trapped impurities E and F into solution. Solvent exchange to IPA slowly precipitates ridinilazole sodium salt out of solution while retaining the impurities in the mother liquor.

[0159] When the above process was applied to a composition prepared according to Example 12 (below) containing a mixture of ridinilazole hydrate form A and impurities E and F, analysis of the recovered solids revealed that the solvent exchange method reduced the levels of impurities E and F by 46% and 59%, respectively.

[0160] The sodium salt is also very soluble in DMSO and insoluble in MTBE, and therefore a crystallization technique can be applied whereby the sodium salt is dissolved in a suitable solvent (e.g., methanol or DMSO) and then induced to crystallize by adding a solvent in which the salt is less soluble (e.g., MTBE).

[0161] The purified ridinilazole salt can then be dissolved and the anhydrous ridinilazole precipitated (e.g., by adding acetic acid, as described above in Section 5.5.2) to obtain purified anhydrous crystalline Form D of ridinilazole, characterized by an XRPD pattern substantially consistent with Figure 3.

[0162] 5.5.5 Solvent exchange with ridinilazole lithium salt The difference in solubility of the lithium salt of ridinilazole in various solvents can also be used to remove the trapped impurities E and F.

[0163] Thus, the present invention contemplates the use of a ridinilazole lithium salt solvent exchange step to reduce the levels of impurities E and / or F. In this step, a composition comprising a solution of ridinilazole lithium salt mixed with impurities E and F in a first solvent is exchanged with a second solvent in which ridinilazole lithium salt has a lower solubility.

[0164] Ridinilazole lithium salt can be prepared from crude ridinilazole Form D and LiOH in THF / DMSO at 20° C. using a 1:2 ridinilazole:base stoichiometry. The diffractogram is shown in Figure 19 and shows crystalline material. The elevated baseline of the diffractogram may indicate some amorphous content and / or may contain DMSO solvate.

[0165] 5.5.6 Carbon Treatment Impurities E and F can be removed from the crude ridinilazole composition by carbon treatment. Carbon treatment is preferably applied to a solution of the crude ridinilazole mixture and may involve contacting such a solution with activated carbon. Suitable solutions include alkali metal ridinilazole salt solutions, such as sodium, potassium, or lithium ridinilazole salt solutions.

[0166] Treatment with activated carbon preferably further comprises removing said activated carbon by filtration. Alternatively, or in addition, carbon treatment may comprise recirculating the solution through an activated carbon filter cartridge.

[0167] In a preferred embodiment, prior to carbon treatment, an alkali metal salt solution (e.g., in methanol) is formed. After carbon treatment of this solution, ridinilazole can be precipitated (e.g., by adding acetic acid, as described above in Section 5.5.2). Suitable alkali metal salts include sodium, potassium, and lithium salts. Preferably, crude ridinilazole and sodium methoxide are dissolved in methanol, followed by carbon treatment and subsequent precipitation with acetic acid.

[0168] Any suitable solution and any form of activated carbon can be used, such as stirring with Norit® SX Plus and recirculating the solution through an activated carbon filter cartridge (e.g., a Zetacarbon R53SP™ cartridge), in which case a carbon load corresponding to 0.086 weight percent can be used and recirculated through the filter for at least 2.5 hours.

[0169] The carbon treatment cycle can be repeated while monitoring the levels of impurities E and F until the levels are reduced to the target levels.

[0170] The purified ridinilazole can then be precipitated (e.g., by adding acetic acid, as described above in Section 5.5.2) to obtain purified ridinilazole anhydrous crystalline Form D, characterized by an XRPD pattern substantially in accordance with FIG. 3.

[0171] Exemplary Methods Involving Carbon Treatment According to a first example, there is provided a process for preparing ridinilazole, or a pharmaceutically acceptable derivative, salt, hydrate, solvate, complex, bioisostere, metabolite or prodrug thereof, comprising: (a) subjecting 3,3'-diaminobenzidine (DAB) to a condensation reaction to obtain the ridinilazole and a compound of formula (II):

[0172] [ka] and then (b) after dissolving the ridinilazole, removing or reducing the level of residual DAB and / or intermediate of formula (II) by treating the ridinilazole solution with activated carbon to obtain a purified form of ridinilazole; A method is provided, comprising:

[0173] In some embodiments of this example, the DAB in step (a) has the formula:

[0174] [ka] Contains contaminant aminobenzidine compounds (MAB).

[0175] Contaminating MAB may be present at about 0.5% or greater, and when subjected to the condensation reaction of step (a), form compounds of formula (IV):

[0176] [ka] intermediate by-products are produced.

[0177] Thus, the DAB in step (a) is of formula (III):

[0178] [ka] In embodiments where the aminobenzidine contaminant is present in the condensation reaction along with The condensation reaction is represented by formula (IV):

[0179] [ka] to produce further by-products of The method preferably further comprises the step of removing or reducing the levels of compounds of formula (III) and / or (IV).

[0180] The treatment with activated carbon in step (b) may include forming a salt solution of ridinilazole and then treating the solution with activated carbon. Suitable salts include sodium, potassium, and lithium salts. The sodium salt is preferred.

[0181] There is wide scope for manipulating the exact conditions of the imidate-DAB condensation reaction, and all such manipulations are within the scope of the present invention (as explained in Section 5.2 above).

[0182] The condensation reaction can be carried out at a temperature of from 10° C. to 100° C. Generally, the reaction can be carried out at the reflux temperature of the solvent at atmospheric pressure.

[0183] The reaction can be carried out in any suitable solvent that does not interfere with the reaction, such as methanol.

[0184] Condensation is (a) adding sodium methoxide to 4-cyanopyridine in methanol to produce an imidate compound of formula (V); and then (b) adding the compound of formula (V) of step (a) to a mixture of DAB and acetic acid in methanol; may also include:

[0185] [ka]

[0186] By using different alkoxide / alcohol combinations in step (a), other imidates can be prepared and used in the condensation reaction, for example, sodium ethoxide / ethanol can be used instead of sodium methoxide / methanol, while other cations (preferably alkali metals) can be substituted for sodium.

[0187] In step (b), other acids such as TFA can be used in place of acetic acid.

[0188] The present inventors have surprisingly discovered that despite the use of highly toxic 3,3'-diaminobenzidine (DAB) and the potentially toxic intermediate by-product of formula (II), large-scale GMP synthesis of 2,2'-di(pyridin-4-yl)-1H,1'H-5,5'-bibenzo[d]imidazole suitable for use in the formulation of pharmaceutical compositions can be achieved by using activated carbon to reduce the aforementioned toxic compounds to acceptable levels.

[0189] Other exemplary embodiments are as defined in the following numbered paragraphs:

[0190] 1. A process for producing ridinilazole, or a pharmaceutically acceptable derivative, salt, hydrate, solvate, complex, bioisostere, metabolite or prodrug thereof, comprising: (a) subjecting 3,3'-diaminobenzidine (DAB) to a condensation reaction to obtain the ridinilazole and a compound of formula (II):

[0191] [ka] and then (b) after dissolving the ridinilazole, treating the ridinilazole solution with activated carbon to remove or reduce the level of residual DAB and / or intermediates of formula (II) to obtain a purified form of ridinilazole; A method comprising:

[0192] 2. The DAB of step (a) is of formula (III):

[0193] [ka] present in the condensation reaction along with the aminobenzidine contaminant of The condensation reaction is represented by formula (IV):

[0194] [ka] to produce further by-products of 10. The method of paragraph 1, further comprising removing or reducing the level of compounds of formula (III) and / or (IV).

[0195] 3. The method of paragraph 1 or 2, wherein the treatment with activated carbon in step (b) forms a solution of a salt of ridinilazole, e.g., a sodium, potassium, or lithium salt, followed by treating the solution with activated carbon.

[0196] 4. The method of paragraph 3, wherein the salt solution of ridinilazole is the sodium salt dissolved in methanol.

[0197] 5. The method of paragraph 4, wherein the sodium salt of ridinilazole is formed by treatment with sodium methoxide.

[0198] 6. The method of any one of the preceding paragraphs, wherein treating with activated carbon in step (b) further comprises removing the activated carbon by filtration.

[0199] 7. The method of any one of paragraphs 1 to 5, wherein the treatment with activated carbon in step (b) comprises recirculating the solution through an activated carbon filter cartridge.

[0200] 8. The method of any one of the preceding paragraphs, wherein the treatment with activated carbon in step (b) further comprises an acidifying step to obtain ridinilazole in purified form.

[0201] 9. The treatment with activated carbon in step (b) (i) forming the sodium salt of ridinilazole in methanol, for example by treatment with sodium methoxide; (ii) treating the solution obtained in step (i) with activated carbon; (iii) acidifying to obtain ridinilazole in purified form; The method of any one of the preceding paragraphs, including:

[0202] 10. The method of any one of the preceding paragraphs, wherein treatment with activated carbon in step (b) reduces the level of the intermediate by-product of formula (II) to less than 100 ppm.

[0203] 11. The method of any one of paragraphs 2 to 10, wherein the treatment with activated carbon in step (b) reduces the level of the compound of formula (IV) to less than 50 ppm.

[0204] 12. In step (a), the condensation comprises converting DAB to a compound of formula (V):

[0205] [ka] The method of any one of the preceding paragraphs, comprising reacting with a compound of

[0206] 13. In step (a), the condensation (a) adding sodium methoxide to 4-cyanopyridine to produce a compound of formula (V); and (b) adding the compound of formula (V) of step (a) to DAB; 13. The method of paragraph 12, comprising:

[0207] 14. In step (a), the condensation (a) adding sodium methoxide to 4-cyanopyridine in methanol to produce a compound of formula (V); and (b) adding the compound of formula (V) of step (a) to a mixture of DAB and acetic acid in methanol; or (c) adding a mixture of DAB and acetic acid in methanol to the compound of formula (V) of step (a); 14. The method of paragraph 13, comprising:

[0208] 15. (a) Mixing purified ridinilazole in methanol / water to obtain a solid; (b) separating the solids; (c) drying the solids; The method of any one of the preceding paragraphs, further comprising isolating ridinilazole by

[0209] 16. The method of paragraph 15, wherein in step (a) the ratio of methanol:water is 1:2 to 1:4, for example about 1:3.

[0210] 17. The method of paragraph 15 or 16, wherein in step (a), purified ridinilazole is stirred in methanol / water.

[0211] 18. The method of any one of paragraphs 15 to 17, wherein in step (a), purified ridinilazole is mixed with 10 to 40, for example about 20, volumes of methanol / water.

[0212] 19. The method of any one of paragraphs 15 to 18, wherein in step (b), the solids are separated by filtration.

[0213] 20. The method of any one of paragraphs 15 to 19, wherein in step (c), the solids are dried in a filter dryer, and optionally the level of water and / or methanol is monitored.

[0214] 21. The method of any one of the preceding paragraphs, wherein the condensation is carried out at a temperature of 30 to 80°C.

[0215] 22. The method of paragraph 21, wherein the condensation is carried out at a temperature of about 60°C.

[0216] 23. The method of any one of the preceding paragraphs, further comprising forming a pharmaceutically acceptable derivative, salt, hydrate, solvate, complex, bioisostere, metabolite, or prodrug of said ridinilazole.

[0217] 24. The method of paragraph 23, further comprising forming a solvate of said ridinilazole, for example with DMSO.

[0218] 25. The method of any one of the preceding paragraphs, further comprising formulating the purified ridinilazole in a pharmaceutically acceptable excipient to produce a pharmaceutical composition.

[0219] 26. The method of paragraph 25, further comprising the step of configuring the pharmaceutical formulation into a pharmaceutical kit, pharmaceutical pack or patient pack.

[0220] 5.5.7 Polymorphic Transformations In a preferred embodiment, ridinilazole is present in the crude ridinilazole composition as anhydrous crystalline Form D characterized by an XRPD pattern substantially in accordance with FIG. 3, and removing step (b) comprises polymorphic conversion of Form D to Form A.

[0221] In such embodiments, the polymorphic conversion can be effected by slurrying the crude ridinilazole composition in an aqueous solvent at a water activity (A ) that favors crystallization of ridinilazole Form A. w ) and temperature, seeding the slurry with crystals of ridinilazole form A.

[0222] The Form A seeds used in the seeding step can be in any physical form, such that they are (a) micronized, (b) in the form of a dry powder, or (c) in the form of a slurry.

[0223] A w is preferably 0.4 or more, and / or the temperature is 2 to 60°C, and more preferably, A w is 0.4 to 0.5, and the temperature is greater than 2°C and less than 30°C, and even more preferably, A w is 0.4 to 0.5 and the temperature is room temperature.

[0224] Any suitable aqueous solvent can be used. In a preferred embodiment, the solvent is MeOH / H2O.

[0225] For example, a crude ridinilazole product characterized by an XRPD pattern substantially consistent with FIG. 3 and containing a mixture of impurities E and F along with anhydrous crystalline ridinilazole Form D, prepared according to Reaction Scheme 1 (above), can be prepared by slurrying the crude ridinilazole composition in an aqueous solvent and then adjusting the water activity (A) to favor crystallization of ridinilazole Form A. w ) and temperature, ridinilazole form A was converted to ridinilazole form A by seeding the slurry with crystals of ridinilazole form A (crystals may be micronized, added as a dry powder, or added in the form of a slurry).

[0226] The exemplary Form D to Form A polymorphic conversion procedure described above was found to reduce the level of impurity F by approximately 60%.

[0227] Exemplary Ridinilazole D to A Polymorphic Conversion Process The conversion can be performed as follows: 1) Add Form D. 2) Add MeOH. 3) Heat to 60°C. Stir at 300 rpm. 4) Hold for 15 minutes. 5) Add water over 30 minutes, a w Approximately 0.47 6) Cool to 40°C over 2 hours. 7) Seed with 2 wt% Form A (or seed a slurry with 2 wt% Form A prepared in MeOH / HO (80 vol / 20 vol) and slurried for 2.5 hours before addition) 8) Wait 1 hour. Thick slurry, limited mobility. 9) Cool to 20°C over 2 hours. 10) Heat to 40°C for 4 hours. 11) Cool to 20°C over 10 hours. 12) Wait 2.5 hours. You will have a thick, mobile slurry. 13) Vacuum filtration. Filtration time: 15 seconds. 14) Wash the reactor with 1 volume MeOH / H2O (80 vol / 20 vol), 3 times, 3 ml each. Wash the wet cake with 1 volume MeOH / H2O (80 vol / 20 vol), 3 ml each.

[0228] In the event that the polymorphic conversion is not complete, or if form N is produced (perhaps due to local variations in water activity), a reslurry process can be performed. Thus, the polymorphic conversion process is preferably preceded by a hot methanol reslurry step that converts all forms present (including form N, if present) to form D.

[0229] A preferred methanol reslurry process is as follows: Methanol (7.4 vol) is added to the reactor. Crude ridinilazole is added to the reactor as a wet cake. Heat the slurry to 55-60°C for at least 3 hours. Cool to 20-25°C and stir for at least 3 hours. Filter the slurry. · Wash the cake with methanol (2.8 vol) and dry under vacuum. Vacuum dry at 40°C for at least 24 hours.

[0230] 5.6 Crystalline forms of ridinilazole As mentioned above, the present inventors have discovered three distinct crystalline forms (polymorphs) of lysinyl azole that are particularly useful in the above process and are applied to the efficient large-scale synthesis of lysinyl azole for medical use.

[0231] Described herein is a crystalline form of ridinilazole tetrahydrate (Form A), characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°.

[0232] Also described herein is a crystalline form of ridinilazole tetrahydrate (Form N), characterized by a powder X-ray diffraction pattern comprising characteristic peaks at 2-theta angles of (10.82±0.2)°, (13.35±0.2)°, and (19.15±0.2)°, and optionally comprising characteristic peaks at 2-theta angles of (10.82±0.2)°, (13.35±0.2)°, (19.15±0.2)°, (8.15±0.2)°, and (21.74±0.2)°.

[0233] Also described herein is a crystalline form of ridinilazole anhydrate, Form D, characterized by a powder X-ray diffraction pattern comprising characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, and (27.82±0.2)°, and optionally comprising characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, (27.82±0.2)°, (19.5±0.2)°, and (22.22±0.2)°.

[0234] Other embodiments and aspects of this aspect of the invention are as defined in the following numbered paragraphs:

[0235] 1. A crystalline form of ridinilazole tetrahydrate (Form A) characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°.

[0236] 2. Crystalline Form A, as described in paragraph 1, characterized by an XRPD pattern substantially in accordance with Figure 1.

[0237] 3. The crystalline form A of paragraph 1 or 2, which is substantially pure.

[0238] 4. A composition comprising at least 80%, 90%, 95% or 99% by weight of crystalline form A according to any one of paragraphs 1 to 3.

[0239] 5. A crystalline form of ridinilazole tetrahydrate (Form N) characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (10.82±0.2)°, (13.35±0.2)° and (19.15±0.2)°, and optionally containing characteristic peaks at 2-theta angles of (10.82±0.2)°, (13.35±0.2)°, (19.15±0.2)°, (8.15±0.2)° and (21.74±0.2)°.

[0240] 6. Crystalline form N, as described in paragraph 5, characterized by an XRPD pattern substantially in accordance with Figure 2.

[0241] 7. The crystalline form N according to paragraph 5 or 6, which is substantially pure.

[0242] 8. A composition comprising at least 80%, 90%, 95% or 99% by weight of crystalline form N described in any one of paragraphs 5 to 7.

[0243] 9. A crystalline form of ridinilazole anhydrate (Form D), characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)° and (27.82±0.2)°, and optionally containing characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, (27.82±0.2)°, (19.5±0.2)° and (22.22±0.2)°.

[0244] 10. Crystalline form D, as described in paragraph 9, characterized by an XRPD pattern substantially in accordance with Figure 3.

[0245] 11. Crystalline form D according to paragraph 9 or 10, which is substantially pure.

[0246] 12. A composition comprising at least 80%, 90%, 95% or 99% by weight of crystalline form D according to any one of paragraphs 9 to 11.

[0247] 13. The crystalline form or composition of any one of the preceding paragraphs, wherein XRPD is measured with Cu-K alpha radiation having a wavelength of 0.15419 nm.

[0248] 14. The crystalline form or composition of paragraph 13, wherein the XRPD is measured at room temperature.

[0249] 15. A method of producing a crystalline form or composition as defined in any one of paragraphs 1 to 4, comprising the steps of: (a) providing a slurry of ridinilazole form D in an aqueous solvent; and (b) providing a slurry of ridinilazole form D in an aqueous solvent at a water activity that favors crystallization of ridinilazole form A (A w) and temperature. and seeding the slurry with crystals of ridinilazole form A or form N.

[0250] 16.A w is 0.4 or more, and / or the temperature is 2 to 60°C, and optionally, A w is 0.4 to 0.5, and the temperature is greater than 2°C and less than 30°C, for example, A w 16. The method of paragraph 15, wherein is 0.4 to 0.5 and the temperature is room temperature.

[0251] 17. A method of producing a crystalline form or composition as defined in any one of paragraphs 5 to 8, comprising the steps of: (a) providing a slurry of ridinilazole form D in an aqueous solvent; and (b) providing a slurry of ridinilazole form N at a water activity (A) that favors crystallization of ridinilazole form N. w ) and temperature. and seeding the slurry with crystals of ridinilazole form A or form N.

[0252] 18.A w is 0.5 or more, and / or the temperature is 2 to 60°C, and optionally, A w is greater than 0.5, and the temperature is greater than 2°C and less than 60°C, e.g., A w 18. The method of paragraph 17, wherein is greater than 0.55 and the temperature is room temperature.

[0253] 19. The method of any one of paragraphs 15 to 18, wherein the solvent is MeOH / H2O.

[0254] 20. A crystalline form of ridinilazole tetrahydrate obtained or produced by the process of any one of paragraphs 15 to 19.

[0255] 21. A pharmaceutical composition comprising an effective amount of the crystalline form or composition of any one of paragraphs 1 to 14 or 20 and a pharmaceutically acceptable excipient.

[0256] 22. The crystalline form or composition of any one of paragraphs 1 to 14 or 20 for use in therapy or prophylaxis.

[0257] 23. A crystalline form or composition according to any one of paragraphs 1 to 14 or 20, or a pharmaceutical composition according to paragraph 21, for use in the treatment or prevention of CDI or CDAD.

[0258] 24. Use of a crystalline form or composition according to any one of paragraphs 1 to 14 or 20 in the manufacture of a pharmaceutical composition.

[0259] 5.7 Medical uses Clostridioides difficile-associated disease (CDAD) defines a set of symptoms associated with Clostridioides difficile (C difficile) infection (CDI). CDAD includes diarrhea, abdominal distension, flu-like symptoms, fever, loss of appetite, abdominal pain, nausea, dehydration, and intestinal inflammation (colitis). The most severe symptom of CDAD is pseudomembranous colitis (PMC), which histologically manifests as colitis with mucosal patches and clinically manifests as severe diarrhea, abdominal cramps, and systemic toxic symptoms. The ridinilazole polymorphic / crystalline forms and pharmaceutical compositions of the present invention are applicable to the treatment of all forms of CDAD, including diarrhea, abdominal distension, flu-like symptoms, fever, loss of appetite, abdominal pain, nausea, dehydration, colitis, and pseudomembranous colitis.

[0260] 5.8 Pharmacology The pharmaceutical compositions of the present invention can be administered orally or parenterally, including intravenous, intramuscular, intraperitoneal, subcutaneous, transdermal, respiratory (aerosol), rectal, vaginal, topical (including buccal and sublingual) administration.

[0261] The amount of pharmaceutical composition administered will vary widely depending on the particular dosage unit used, the duration of treatment, the age and sex of the patient being treated, and the nature and severity of the disorder being treated.

[0262] In general, the effective amount of the pharmaceutical composition administered will generally be in the range of about 0.01 mg / kg to 10,000 mg / kg per day. A unit dose may contain 0.05 to 500 mg of ridinilazole and may be taken one or more times per day.

[0263] The preferred route of administration is oral. Generally, suitable dosages range from 0.01 to 500 mg per kilogram of recipient body weight per day.

[0264] The desired dose is preferably presented as a single dose for daily administration. However, two, three, four, five, six or more subdoses administered at appropriate intervals throughout the day may be used. These subdoses may be administered in unit dosage forms, for example, containing 0.001 to 100 mg, preferably 0.01 to 10 mg, and most preferably 0.5 to 1.0 mg of active ingredient per unit dosage form.

[0265] In determining the effective amount or dose, several factors will be considered by the attending physician, including, but not limited to, the potency and duration of action of the compound used, the nature and severity of the disease being treated, and the sex, age, weight, general health, individual response, and other relevant circumstances of the patient being treated. Those skilled in the art will appreciate that dosages can also be determined by guidance from Goodman & Goldman's *The Pharmacological Basis of Therapeutics*, Ninth Edition (1996), Appendix II, pp. 1707-1711.

[0266] The effectiveness of a particular dosage of a pharmaceutical composition of the present invention can be determined by monitoring the effect of a given dosage on the progression of CDI and / or CDAD.

[0267] 5.9 Formulations Pharmaceutical compositions may contain stabilizers, antioxidants, colorants, and diluents. Pharmaceutically acceptable carriers and excipients are selected to minimize side effects from the pharmaceutical compound and not to impair the compound's performance to the extent that they render the treatment ineffective.

[0268] Oral (intragastric) is a typical route of administration. Pharmaceutically acceptable carriers can be solid dosage forms, including tablets, capsules, pills, and granules, which can be prepared with coatings and shells, such as enteric coatings and others known in the art. Liquid dosage forms for oral administration include pharmaceutically acceptable emulsions, solutions, suspensions, syrups, and elixirs.

[0269] When administered, the pharmaceutical composition may be at or near body temperature.

[0270] Compositions intended for oral use can be prepared according to any method known in the art for the manufacture of pharmaceutical compositions, and such compositions can contain one or more agents selected from the group consisting of sweeteners, flavoring agents, coloring agents, and preservatives to provide a pharmaceutically smooth and palatable preparation. Tablets contain the active ingredient mixed with non-toxic, pharmaceutically acceptable excipients suitable for the manufacture of tablets. These excipients can be, for example, inert diluents such as calcium carbonate, sodium carbonate, lactose, calcium phosphate, or sodium phosphate; granulating and disintegrating agents such as corn starch or alginic acid; binders such as starch, gelatin, or gum arabic; and lubricants such as magnesium stearate, stearic acid, or talc. Tablets can be uncoated or coated by known techniques, for example, to delay disintegration and absorption in the gastrointestinal tract, thereby providing a sustained action over a longer period. For example, time-delay materials such as glyceryl monostearate or glyceryl distearate can be used.

[0271] Formulations for oral use may be presented as hard gelatin capsules in which the active ingredient is mixed with an inert solid diluent, such as calcium carbonate, calcium phosphate, or kaolin, or as soft gelatin capsules in which the active ingredient is present by itself or mixed with water or an oil medium, such as peanut oil, liquid paraffin, or olive oil.

[0272] Aqueous suspensions can be prepared containing the active material in admixture with excipients suitable for the manufacture of aqueous suspensions. Such excipients include suspending agents, for example, sodium carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanth, and gum acacia, and the dispersing or wetting agent can be a naturally occurring phosphatide, for example, lecithin, or a condensation product of an alkylene oxide with a fatty acid, for example, polyoxyethylene stearate, or a condensation product of ethylene oxide with a long-chain aliphatic alcohol, for example, heptadecaethyleneoxycetanol, or a condensation product of ethylene oxide with a partial ester derived from a fatty acid and a hexitol, such as polyoxyethylene sorbitol monooleate, or a condensation product of ethylene oxide with a partial ester derived from a fatty acid and a hexitol anhydride, for example, polyoxyethylene sorbitan monooleate.

[0273] The aqueous suspensions may also contain one or more preservatives, for example, ethyl or n-propyl p-hydroxybenzoate, one or more coloring agents, one or more flavoring agents, or one or more sweetening agents, such as sucrose or saccharin.

[0274] Oily suspensions can be formulated by suspending the active ingredient in an omega-3 fatty acid, a vegetable oil such as arachis oil, olive oil, sesame oil or coconut oil, or a mineral oil such as liquid paraffin. Oily suspensions may contain a thickening agent such as beeswax, hard paraffin or cetyl alcohol.

[0275] Sweetening agents such as those set forth above, and flavoring agents may be added to provide a palatable oral preparation.These compositions may be preserved by the addition of an antioxidant such as ascorbic acid.

[0276] Dispersible powders and granules suitable for preparing aqueous suspensions by adding water are provided by mixing the active ingredient with a dispersing or wetting agent, a suspending agent, and one or more preservatives.Suitable dispersing or wetting agents and suspending agents are exemplified by those mentioned above.Additional excipients, such as sweeteners, flavoring agents, and coloring agents, may also be present.

[0277] Syrups and elixirs containing ridinilazole can be formulated with sweetening agents, for example, glycerol, sorbitol, or sucrose. Such formulations may also contain a demulcent, a preservative, a flavoring, and a coloring agent.

[0278] The compositions of the present invention can optionally be supplemented with additional agents, such as viscosity enhancers, preservatives, surfactants, and penetration enhancers. Viscosity enhancers include, for example, polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, or other agents known to those skilled in the art. Such agents are typically used at levels of about 0.01% to about 2% by weight of the pharmaceutical composition.

[0279] Preservatives are optionally used to prevent the growth of microorganisms before or during use. Suitable preservatives include polyquaternium-1, benzalkonium chloride, thimerosal, chlorobutanol, methylparaben, propylparaben, phenylethyl alcohol, edetate disodium, sorbic acid, or other agents known to those skilled in the art. Typically, such preservatives are used at a level of about 0.001% to about 1.0% by weight of the pharmaceutical composition.

[0280] The solubility of the components of the compositions of the present invention can be enhanced by the addition of surfactants or other suitable cosolvents to the compositions. Such cosolvents include polysorbates 20, 60, and 80, polyoxyethylene / polyoxypropylene surfactants (e.g., Pluronic F-68, F-84, and P-103), cyclodextrins, or other agents known to those skilled in the art. Typically, such cosolvents are used at a level of about 0.01% to about 2% by weight of the pharmaceutical composition.

[0281] Pharmaceutically acceptable excipients and carriers include all of the above and similar.The above considerations regarding effective formulation and administration procedures are well known in the art and are described in standard textbooks.See, for example, Remington: The Science and Practice of Pharmacy, 20th Edition (Lippincott, Williams and Wilkins), 2000; Lieberman et al., ed., Pharmaceutical Dosage Forms, Marcel Decker, New York, NY (1980) and Kibbe et al., ed., Handbook of Pharmaceutical Excipients (3rd Edition), American Pharmaceutical Association, Washington (1999).

[0282] Therefore, in the embodiment in which the compound of the present invention is formulated with a pharmaceutically acceptable excipient, any suitable excipient can be used, including, for example, inert diluents, disintegrants, binders, lubricants, sweeteners, flavorings, colorings, and preservatives.Suitable inert diluents include sodium and calcium carbonate, sodium and calcium phosphate, and lactose, while corn starch and alginic acid are suitable disintegrants.Binders include starch and gelatin, while lubricants, if present, are generally magnesium stearate, stearic acid, or talc.The pharmaceutical composition can take any suitable form, including, for example, tablets, elixirs, capsules, solutions, suspensions, powders, granules, nail lacquers, varnishes, and veneers, skin patches, and aerosols.

[0283] The pharmaceutical composition may be in the form of a kit of parts, which may comprise a composition of the invention together with instructions for use, and / or a number of different ingredients in unit dosage form.

[0284] For oral administration, the pharmaceutical compositions of the present invention can be formulated into solid or liquid preparations such as capsules, pills, tablets, troches, lozenges, dissolution agents, powders, granules, solutions, suspensions, dispersions, and emulsions (these solutions, suspensions, dispersions, or emulsions may be aqueous or non-aqueous). Solid unit dosage forms may be ordinary hard- or soft-shell gelatin capsules containing, for example, surfactants, lubricants, and inert fillers such as lactose, sucrose, calcium phosphate, and corn starch. Tablets for oral use may contain pharmaceutically acceptable excipients such as inert diluents, disintegrants, binders, lubricants, sweeteners, flavoring agents, coloring agents, and preservatives. Suitable inert diluents include sodium and calcium carbonate, sodium and calcium phosphate, and lactose, while corn starch and alginic acid are suitable disintegrating agents. Binders include starch and gelatin, while lubricants, if present, are generally magnesium stearate, stearic acid or talc.If necessary, tablets can be coated with materials such as glycerin monostearate or glyceryl distearate to delay absorption in the gastrointestinal tract.Capsules for oral use include hard gelatin capsules in which the compound of the present invention is mixed with a solid diluent, and soft gelatin capsules in which the active ingredient is mixed with water or oil such as peanut oil, liquid paraffin or olive oil.

[0285] Suitable aqueous vehicles include Ringer's solution and isotonic sodium chloride. Aqueous suspensions according to the present invention may contain suspending agents such as cellulose derivatives, sodium alginate, polyvinylpyrrolidone and tragacanth gum, and wetting agents such as lecithin. Suitable preservatives for aqueous suspensions include ethyl and n-propyl p-hydroxybenzoates.

[0286] The compounds of the present invention may also be presented in liposomal formulations.

[0287] The pharmaceutical compositions of the present invention may be tableted using conventional tablet bases such as lactose, sucrose, and corn starch in combination with binders such as gum arabic, corn starch, and gelatin; disintegrants such as potato starch, alginic acid, corn starch, and guar gum that aid in disintegration and dissolution of the tablet after administration; lubricants such as talc, stearic acid, magnesium stearate, calcium stearate, or zinc stearate that improve the flowability of tablet granules and prevent tablet material from adhering to the surfaces of the tablet dies and punches; and dyes, coloring agents, and flavoring agents to improve the aesthetic appeal and patient acceptance of the tablets.

[0288] Excipients suitable for use in oral liquid formulations include water and alcoholic diluents, such as ethanol, benzyl alcohol, and polyethylene alcohol, with or without pharmaceutically acceptable surfactants, suspending agents, or emulsifying agents. [Example]

[0289] 7. Example The present invention will now be described with reference to specific examples, which are merely exemplary and for illustrative purposes only, and are not intended to limit in any way the scope of the claimed monopoly or the invention described.

[0290] method Water activity (A w ) Water activity coefficient and water activity were calculated using the UNIFAC Activity Coefficient Calculator (Choy, B.; Reible, D. (1996). UNIFAC Activity Coefficient Calculator (Version 3.0, 1996) [Software]. University of Sydney, Australia and Louisiana State University, USA).

[0291] X-ray powder diffraction (XRPD) XRPD analysis was performed using a Panalytical Xpert Pro diffractometer equipped with a Cu X-ray tube and a Pixcel detector system. Isothermal samples were analyzed in transmission mode and held between low-density polyethylene films. The XRPD program used had a 2θ range of 3–40°, a step size of 0.013°, a count time of 99 seconds, and a runtime of approximately 22 minutes. XRPD patterns were classified using HighScore Plus 2.2c software.

[0292] Carbon (Norit®) Treatment: Crude ridinilazole is dissolved in methanol and 30% sodium methoxide, and the resulting solution is treated with Norit® SX Plus (0-0.5 wt.), and the mixture is stirred. The Norit® is then removed by filtration through a filter aid. Water is then added to the filtrate, followed by acetic acid, to precipitate the purified ridinilazole.

[0293] [Example 1] Preparation of Ridinilazole Form A Reaction: A reaction flask was charged with 4-cyano-pyridine (0.85 kg) and charged with MeOH (5.4 kg) and NAM-30 (NaOMe as a 30 wt% solution in MeOH; 0.5 equivalents; 0.15 kg). The resulting mixture was heated at 60°C for 10 minutes and then cooled. This solution was added to a mixture of 3,3'-diaminobenzidine (DAB) (0.35 kg) and acetic acid (0.25 kg) in MeOH (1 L) at 60°C for 1 hour. The mixture was then heated for 2 hours. The reaction mixture was allowed to cool to ambient temperature overnight. The crystalline mass was filtered, washed with MeOH (1.4 L), and sucked dry on the filter.

[0294] Purification: Norit treatment was carried out four times.

[0295] Polymorph Formation: The desired polymorph was obtained by reslurrying in 20 volumes of 1:3 water for injection:MeOH and drying was carried out in a vacuum drying oven at ambient temperature and nitrogen purge for 6 days.

[0296] XRPD analysis showed that this method yielded hydrated ridinilazole Form A (see Figure 1). The reflections are shown in the table below.

[0297] [Table 6-1]

[0298] [Table 6-2]

[0299] [Example 2] Preparation of Ridinilazole Form N Pattern N material was isolated from a crystallization experiment performed in methyl acetate / water (15 vol, 95.3% vol:4.7% vol). Ridinilazole (5.0 g) was heated to 50° C. in methyl acetate. Water was added and the mixture was held at 50° C. for 1 hour before being cooled to ambient temperature at 0.2° C. / min.

[0300] XRPD analysis showed that this method yielded hydrated ridinilazole Form N (see Figure 2). The reflections are shown in the table below.

[0301] [Table 7]

[0302] [Example 3] Preparation of Ridinilazole Form D Reaction: A reaction flask was charged with 4-cyano-pyridine (0.85 kg) and charged with MeOH (5.4 kg) and 0.5 equivalents of NaOMe as a 30 wt% solution in MeOH (NAM-30). The resulting mixture was heated at 60° C. for 10 minutes and then cooled. This solution was added to a mixture of DAB (0.35 kg) and acetic acid (0.25 kg) in methanol (1 L) at 60° C. over 1 hour. The mixture was then heated for 2 hours. The reaction mixture was allowed to cool to ambient temperature overnight. The crystalline mass was filtered, washed with MeOH (1.4 L), and sucked dry on the filter.

[0303] Purification: Norit treatment was carried out four times.

[0304] XRPD analysis showed that this method yielded anhydrous ridinilazole form D (see Figure 3). The reflections are shown in the table below.

[0305] [Table 8]

[0306] [Example 4] Conversion of ridinilazole form D to form A Ridinilazole Form D is prepared as described in Example 3. Ridinilazole Form A is prepared as described in Example 1. Seed crystals were prepared by hand grinding and sieving. The conversion was carried out as follows: 1) Add Form D. 2) Add MeOH. 3) Heat to 60°C. Stir at 300 rpm. 4) Hold for 15 minutes. 5) Add water over 30 minutes, aw is about 0.47 6) Cool to 40°C over 2 hours. 7) Seeded with 2 wt% Form A (or prepared in MeOH / HO (80 vol / 20 vol) and slurried for 2.5 hours before addition, seeded with 2 wt% Form A)

[0307] 8) Wait 1 hour. Thick slurry, limited mobility. 9) Cool to 20°C over 2 hours. 10) Heat to 40°C for 4 hours. 11) Cool to 20°C over 10 hours. 12) Wait 2.5 hours. You will have a thick, mobile slurry. 13) Vacuum filtration. Filtration time is 15 seconds. 14) Wash the reactor with 1 volume MeOH / H2O (80 vol / 20 vol), 3 times, 3 ml each. Wash the wet cake with 1 volume MeOH / H2O (80 vol / 20 vol), 3 ml each.

[0308] [Example 5] Conversion of ridinilazole form D to form N Ridinilazole Form D is prepared as described in Example 3. Ridinilazole Form A is prepared as described in Example 1. Seed crystals were prepared by hand grinding and sieving. After about 20 minutes, microscopic images showed mostly smaller aggregates (about 20 μm), although some larger aggregates were still present (about 80 μm). XRPD analysis showed the material was still composed of Form A.

[0309] Conversions were carried out on a 3 g scale as shown in the table below.

[0310] [Table 9]

[0311] This slurry was relatively thin compared to that formed in Example 4 and remained mobile throughout. No discoloration (indicative of the presence of Form D, which is brown) was observed.

[0312] The above data indicate that lysinyl azole Form N exhibits improved rheology under seed slurry processing conditions, which may lead to faster filtration and improved drainage at larger scales.

[0313] [Example 6] Crystal structure of lysinylazole tetrahydrate form N Single crystals of ridinilazole form N of suitable quality for full structure determination were purified by dioxane / water (82% by volume:18% by volume, A) using MEK as the antisolvent. wwas grown by vapor diffusion from a solution of ridinilazole in approximately 0.83% DMSO at 5°C. The crystal structure was determined to be monoclinic and the P21 / C space group.

[0314] Form N of dilinilazole tetrahydrate has been fully resolved. The crystal structure is a tetrahydrate containing half a molecule of dilinilazole and two independent water molecules per asymmetric unit. Figures 5 and 6 show the asymmetric unit contents and hydrogen bonding pattern of the determined crystal structure, respectively.

[0315] [Example 7] Crystal structure of ridinilazole tetrahydrate form A Single crystals of ridinilazole form A were grown via liquid diffusion at room temperature from a solution of ridinilazole in NMP / dioxane using chloroform as the antisolvent. A needle-shaped crystal specimen with approximate dimensions of 0.380 mm × 0.015 mm × 0.010 mm was used for X-ray crystallography at Beamline 119 of Diamond Light Source.

[0316] The atomic numbering arrangement of ridinilazole and water molecules is shown as an ORTEP plot in Figure 7. Packing diagrams of the ridinilazole form A structure are shown in Figures 8 through 10 along each crystallographic axis. Hydrogen bonds between ridinilazole molecules cannot be described because only one hydrogen bond, between N24-H24···N51, can be clearly identified. Other hydrogen bonds occurring in the structure are formed between water molecules, imidazole hydrogens, and pyridine nitrogen atoms. However, due to the significant disorder of the water molecules and their hydrogen atoms, the hydrogen-bonding network cannot be fully resolved.

[0317] [Example 8] Crystal structure of ridinilazole anhydrate form D Single crystals of ridinilazole form D were grown via vapor diffusion at room temperature from a solution of ridinilazole in ethanol using water as the antisolvent and submitted for single crystal structure determination. A prismatic crystal specimen with approximate dimensions of 0.3 mm x 0.2 mm x 0.1 mm was used for X-ray crystallography.

[0318] The structure was solved by predefined automated direct methods, and all uniquely measured F2 values ​​were refined by least-squares refinement. The numbering arrangement used for refinement is shown in Figure 11. The atom numbering arrangement of the ridinilazole molecule is shown as an ORTEP plot in Figure 11. Packing diagrams for the ridinilazole form D structure are shown in Figures 12-14 along each crystallographic axis. Hydrogen bonds between ridinilazole molecules form a two-dimensional network along the ab plane (see Figure 15). Hydrogen bonds are formed between the hydrogen-donating imidazole nitrogen atoms and the accepting pyridine nitrogen atoms. This network is extended in the third direction by weaker interactions between hydrogen atoms and the π electrons of the aromatic carbons.

[0319] [Example 9] Comparison of the crystal structures of ridinilazole forms A, N and D The main difference observed in the three crystal structures is that the molecular conformation of ridinilazole is syn conformation in form A, whereas it is anti conformation in forms N and D (see Figure 16).

[0320] Another difference lies in the arrangement of hydrogen bonds: Form A shows hydrogen bonds between ridinilazole molecules, whereas in Form N, ridinilazole molecules interact only with water molecules. In Form A, larger water channels containing four independent water molecules are observed, whereas, as in Form N, all channels contain two independent water molecules. In Form D, there are no water molecules present, so only hydrogen bonds form between ridinilazole molecules (see Figure 17).

[0321] There are also significant differences between the torsion angles made in the three structures between the phenyl rings: for forms N and D, the torsion angle is equal to 180°, so the ridinilazole molecule is planar (center of symmetry between the phenyl rings), while for form A, the torsion angles are 43.0 and 43.3° (two independent molecules).

[0322] A further major difference between the two structures is that both are different tautomers of ridinilazole, with the hydrogen attached to N11 in form N, whereas in form D the hydrogen is attached to N8 of the imidazole ring. These are hydrogen bond donor groups in both structures, so the packing between both structures is very different.

[0323] [Example 10] Ridinilazole tablet dosage form with Form A Ridinilazole tablets (200 mg) were prepared as follows.

[0324] Wet granulation After sieving into the bowl of a high shear granulator, the batch quantities of ridinilazole (Form A), lactose monohydrate, microcrystalline cellulose, hydroxypropyl cellulose, and croscarmellose sodium for the intragranular phase of the wet granulation are first subjected to a brief premixing at 80 revolutions per minute (rpm) for approximately 1 minute.

[0325] Purified water is added while mixing continues. When 12% by weight of water has been added and when 24% by weight of water has been added, the wet mass is manually transferred through a 2000 μm sieve to improve water distribution and returned to the granulator bowl each time, and granulation continues. When approximately 35% by weight of water has been added, the wet granules are transferred to a fluid bed dryer.

[0326] Drying The wet granules are dried in a fluid bed dryer at an inlet air temperature of approximately 60° C. until the limit of detection (LOD) (initial dry formula +0.5%) is reached. Once drying is complete, the dried granules are transferred to an appropriately sized blender bin through a Cormill equipped with an 1143 μm screen.

[0327] Final Mixture Once the five (or six) dried granules are complete, combine them and manually transfer the calculated batch amounts of lactose monohydrate, microcrystalline cellulose, and croscarmellose sodium for the extra granular phase through a 1000 micrometer sieve into the 20 L bin containing the dried granules. Blending is performed by turning the 20 L bin upside down in a blender at 30 rpm for 2 minutes.

[0328] Smooth The calculated batch amount of magnesium stearate is manually transferred through a 250 micrometer sieve into the 20 L bottle containing the final formulation. Lubrication is performed by turning the 20 L bottle upside down in a compounder at 30 rpm for 2 minutes.

[0329] Tablet compression Tablets are compressed using oval tooling. Dust removal and metal checking are performed in the line post compression.

[0330] coating Tablet cores are coated in a pan coater using Opadry® II Brown with a target weight gain of 3-4% for the coated tablets.

[0331] XRPD analysis XRPD analysis was performed on ridinilazole tablets to confirm that no morphological changes occurred after tableting. One tablet was crushed in a pestle and mortar and analyzed by transmission XRPD. It was not possible to completely separate the small amount of sample coating from the crushed sample.

[0332] The XRPD traces showed that the sample had a small amount of peak shift compared to Form A, while extra peaks were present at approximately 12.5°2-theta and approximately 19-24°2-theta. XRPD analysis of ridinilazole tablets, ridinilazole Form A, and the placebo mixture confirmed that these extra peaks were due to the placebo mixture (Figure 18). That is, the extra peaks were present in the placebo mixture (Figure 18) and therefore due to the excipients.

[0333] [Example 11] Method for producing purified ridinilazole Reaction: A reaction flask was charged with 4-cyano-pyridine (0.85 kg) and charged with MeOH (5.4 kg) and NaOMe (as a 30 wt% solution in MeOH; 0.5 equiv.) (0.15 kg). The resulting mixture was heated at 60° C. for 10 min and then cooled.

[0334] The resulting solution was poured into a mixture of DAB (0.35 kg) and acetic acid (0.25 kg) in MeOH (1 L) at 60° C. over 1 hour and heated for 2 hours.

[0335] The reaction mixture was allowed to cool to ambient temperature overnight, then the cake was filtered, washed with MeOH (1.4 L) and sucked dry on the filter.

[0336] Purification: The crude product, Norit® SX Plus (260 g) and MeOH (6 kg) were placed in a vessel and NaOMe (as a 30 wt % solution in MeOH (600 g)) was added. Purification can also be achieved by recirculating the sodium salt solution through an activated carbon filter cartridge (e.g., an R53SP™ cartridge).

[0337] The resulting solution was stirred at ambient temperature and filtered through dicalite, then washed with MeOH (2 x 500 ml). Water (118 g; 4 equivalents) was added to the mixture, followed by acetic acid (206 g). The resulting slurry was stirred at ambient temperature for 2 days. The suspension was filtered, washed with MeOH (1.4 L) and dried. This treatment afforded the product of formula (II):

[0338] [ka] The process was repeated four times to reduce the intermediate by-products, and the concentration was reduced to less than 100 ppm.

[0339] Polymorph Formation: Reslurrying in 20 volumes of 1:3 water:MeOH gave pure ridinilazole. Drying in a vacuum drying oven at ambient temperature with a nitrogen purge for 6 days gave the solid hydrate.

[0340] X-ray powder diffraction: X-ray powder diffraction (XRPD) studies were performed on a Bruker AXS D2PHASER in Bragg-Brentano configuration. A Cu anode was used at 30 kV and 10 mA. Sample stage standard rotation; monochromatization with a Kα filter (0.5% Ni). Slits: fixed divergence slit 1.0 mm (=0.61°), primary axial Soller slit 2.5°, secondary axial Soller slit 2.5°. Detector: linear detector LYNXEYE with a receiving slit 5° detector aperture. Measurement conditions: scan range 5–45° 2q, sample rotation 5 rpm, 0.5 s / step, 0.010° / step, 3.0 mm detector slit. No background correction or smoothing was applied to the patterns. The Cu-Kα2 contribution was removed using Bruker software.

[0341] XRPD analysis showed that this method yielded ridinilazole hydrate form A (see Figure 1).

[0342] equivalent The foregoing description details presently preferred embodiments of the invention. Numerous modifications and variations in practice are expected to occur to those skilled in the art in light of these descriptions. These modifications and variations are intended to be encompassed within the scope of the claims appended hereto. The inventions described in the original claims of this application are set forth below. [1] A composition comprising a mixture of compounds, the mixture comprising ridinilazole and a compound of formula (II) and formula (IV): [ka] and The composition, wherein the total amount of impurity E and impurity F in the mixture is less than 100 ppm. [2] The composition of [1], wherein the ridinilazole is a crystalline form of ridinilazole tetrahydrate (Form A) characterized by an X-ray powder diffraction pattern (XRPD) containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°. [3] The composition of [2], wherein said crystalline form A is characterized by an XRPD pattern substantially in accordance with Figure 1. [4] The composition of [2] or [3], wherein the ridinilazole crystalline form A is substantially pure. [5] The composition of any one of [1] to [4], wherein the mixture comprises at least 80%, 90%, 95%, or 99% by weight of crystalline form A of any one of [2] to [4]. [6] The composition according to any one of [2] to [5], wherein the XRPD is measured using Cu-K alpha radiation having a wavelength of 0.15419 nm. [7] The composition according to [6], wherein the XRPD is measured at room temperature. [8] The composition according to any one of [1] to [7], wherein the amount of impurity E present in the mixture is less than 50 ppm. [9] The composition according to any one of [1] to [8], wherein the amount of impurity F present in the mixture is less than 50 ppm.

[10] The composition of any of [1] to [9], wherein (a) the amount of impurity E present in the mixture is less than 50 ppm, and (b) the amount of impurity F present in the mixture is less than 50 ppm.

[11] The composition of any one of [1] to [9], wherein the amount of impurity E or the amount of impurity F in the mixture is greater than 50 ppm but less than 100 ppm.

[12] A method for producing the composition of any of [1] to

[11] , comprising: (a) providing a crude ridinilazole composition comprising a mixture of compounds, the mixture comprising ridinilazole and compounds of formula (II) and (IV):

change

[13] The method of

[12] , further comprising the steps of determining the total amount of impurities E and F in the purified ridinilazole composition in step (b), and optionally determining the total amount of impurities E and F in the crude ridinilazole composition in step (a).

[14] The method of

[13] , wherein the determining step comprises HPLC-MS.

[15] The method according to any one of

[12] to

[14] , wherein the crude ridinilazole composition in step (a) is provided by subjecting 3,3'-diaminobenzidine (DAB) to a condensation reaction to produce the ridinilazole.

[16] The method according to

[15] , wherein the condensation reaction comprises reacting DAB with an imidate.

[17] The imidate is represented by formula (V):

change

[16] , wherein the compound is methyl isonicotinimidate.

[18] In step (a), the condensation reaction (a) adding sodium methoxide to 4-cyanopyridine to produce a compound of formula (V); and (b) reacting the compound of formula (V) of step (a) with said DAB; The method according to any one of

[15] to

[17] , comprising:

[19] In step (a), the condensation (a) adding sodium methoxide to 4-cyanopyridine in methanol to produce a compound of formula (V); and (b) adding the compound of formula (V) of step (a) to a mixture of DAB and acetic acid in methanol; or (c) adding a mixture of DAB and acetic acid in methanol to the compound of formula (V) of step (a); The method according to

[18] , comprising:

[20] The method according to any one of

[15] to

[19] , wherein the condensation reaction is carried out at a temperature of 20 to 90°C, for example, 30 to 80°C, for example, about 60°C.

[21] The crude ridinilazole composition of step (a) is prepared by the reaction scheme shown below:

change

[12] to

[20] , which is made as shown in

[22] The method of any of

[16] to

[21] , wherein a compound of formula (II) is formed when DAB reacts with only one equivalent of imidate, as shown below.

change

[23] The method according to any one of

[17] to

[22] , wherein the compound of formula (IV) is produced by reacting methyl isonicotinimidate of formula (V) with monoaminobenzidine (MAB).

[24] The compound of formula (IV) can be reacted with a compound represented by the following reaction scheme:

change

[23] is made as shown in FIG.

[25] The method according to any one of

[12] to

[24] , wherein the removal step (b) results in a purified ridinilazole composition in which the amount of impurity E present in the mixture is less than 50 ppm.

[26] The method according to any one of

[12] to

[25] , wherein the removal step (b) results in a purified ridinilazole composition in which the amount of impurity F present in the mixture is less than 50 ppm.

[27] The method according to any one of

[12] to

[26] , wherein the removal step (b) results in a purified ridinilazole composition in which (a) the amount of impurity E present in the mixture is less than 50 ppm, and (b) the amount of impurity F present in the mixture is less than 50 ppm.

[28] The method according to any of

[12] to

[26] , wherein the removal step (b) results in a purified ridinilazole composition in which the amount of impurity E or the amount of impurity F present in the mixture is greater than 50 ppm but less than 100 ppm.

[29] The method of any of

[12] to

[28] , wherein the removing step (b) comprises treating the crude ridinilazole composition with an imidate solution, optionally reacting the imidate solution with impurity E and / or impurity F and purging it / them from the mixture.

[30] The method of any of

[12] to

[29] , wherein the removing step (b) comprises dissolving the crude ridinilazole composition and then reprecipitating ridinilazole.

[31] The method of

[30] , wherein the removing step (b) comprises forming a dissolved metal salt of ridinilazole present in the crude ridinilazole composition, followed by precipitation of the ridinilazole, optionally by neutralization.

[32] The method of

[31] , wherein the metal salt is an alkali metal salt, optionally selected from sodium, potassium, and lithium salts of ridinilazole.

[33] The method of any of

[30] to

[32] , wherein the crude ridinilazole composition is dissolved in sodium methoxide in methanol, and then ridinilazole is precipitated with acetic acid.

[34] The method of any of

[12] to

[33] , wherein the removing step (b) comprises dissolving the crude ridinilazole composition in a high-boiling aprotic solvent followed by recrystallization of ridinilazole.

[35] The method according to

[34] , wherein the high-boiling aprotic solvent is DMSO.

[36] The method of

[34] or

[35] , wherein the removing step (b) further comprises slow cooling and / or temperature cycling of the solution.

[37] The method of any of

[12] to

[36] , wherein the removing step (b) optionally comprises a solvent exchange with an alkali metal salt of ridinilazole selected from the sodium, potassium and lithium salts of ridinilazole.

[38] The method of any of

[12] to

[37] , wherein the removing step (b) comprises carbon treatment.

[39] The method of

[38] , wherein the carbon treatment is applied to a crude ridinilazole mixture solution, optionally an alkali metal ridinilazole salt solution, such as a sodium, potassium or lithium ridinilazole salt solution.

[40] The method of

[39] , wherein the carbon treatment comprises contacting the solution with activated carbon.

[41] The method of

[40] , wherein the treatment with activated carbon further comprises removing the activated carbon by filtration.

[42] The method of any of

[38] to

[41] , wherein the carbon treatment comprises recirculating the solution through an activated carbon filter cartridge.

[43] Ridinilazole (i) exists as anhydrous crystalline form D, and said process comprises polymorphic conversion of form D to form A; or (ii) exists as crystalline form N of ridinilazole tetrahydrate, and said process comprises polymorphic conversion of form N to form D; or (iii) Ridinilazole exists as crystalline form N of tetrahydrate, said process comprising polymorphic conversion of form N to form D and then form D to form A; A method according to any one of

[12] to

[42] .

[44] The polymorphic conversion can be achieved by slurrying the crude ridinilazole composition in an aqueous solvent and then adjusting the water activity (A) to favor crystallization of ridinilazole Form A. w ) and temperature, and seeding the slurry with crystals of ridinilazole form A.

[45] A. w is 0.4 or more, and / or the temperature is 2 to 60°C.

[46] A. w

[45] The method according to

[45] , wherein the value is 0.4 to 0.5, and the temperature is greater than 2°C and less than 30°C.

[47] A. w is 0.4 to 0.5, and the temperature is room temperature.

[48] ​​The solvent is MeOH / H 2 The method according to any one of

[44] to

[47] , wherein O.

[49] The method of any of

[44] to

[48] , wherein the Form A seeds are (a) micronized, (b) in the form of a dry powder, or (c) in the form of a slurry.

[50] The removing step (b) (i) dissolving the crude ridinilazole composition and then reprecipitating ridinilazole as described in any one of

[30] to

[33] ; (ii) dissolving the reprecipitated ridinilazole from step (i) and then recrystallizing ridinilazole as described in any of

[34] to

[36] ; (iii) subjecting the recrystallized ridinilazole from step (ii) to carbon treatment as described in any of

[38] to

[42] to obtain ridinilazole anhydrous crystalline Form D, characterized by an XRPD pattern substantially in accordance with Figure 3; (iv) converting form D ridinilazole to form A by polymorphic transformation as described in any of

[43] to

[49] ; The method according to any one of

[12] to

[49] , comprising:

[51] The composition according to any one of [1] to

[11] , obtainable (or produced) by the method according to any one of

[12] to

[50] .

[52] A pharmaceutical composition comprising an effective amount of the composition according to any one of [1] to

[11] or

[51] and a pharmaceutically acceptable excipient.

[53] The composition according to any one of [1] to

[11] and

[51] or

[52] for use in treatment or prevention.

[54] The composition according to any one of [1] to

[11] and

[51] to

[53] for use in the treatment or prevention of CDI or CDAD.

[55] Use of a composition according to any one of [1] to

[11] and

[51] to

[54] for the manufacture of a medicament for the treatment, therapy or prevention of CDI or CDAD.

[56] A crystalline form of ridinilazole tetrahydrate (Form A) characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°.

[57] Crystalline form A described in

[56] , characterized by an XRPD pattern substantially in accordance with Figure 1.

[58] The crystalline form A of

[56] or

[57] , which is substantially pure.

[59] A composition comprising at least 80%, 90%, 95% or 99% by weight of crystalline form A according to any one of

[56] to

[58] .

[60] Crystalline form A according to any one of

[56] to

[58] or the composition according to

[59] , in the form of micronized seeds.

[61] Crystalline form A or composition according to any of

[56] to

[60] for use in the polymorphic conversion of ridinilazole form D to ridinilazole form A in a method according to any of

[12] to

[50] , for example as described in any of

[43] to

[49] .

[62] Use of crystalline form A or the composition according to any one of

[56] to

[60] in the manufacture of a composition according to any one of [1] to

[11] and

[51] to

[54] .

[63] A crystalline form of ridinilazole anhydrate (Form D) characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)° and (27.82±0.2)°, and optionally containing characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, (27.82±0.2)°, (19.5±0.2)° and (22.22±0.2)°.

[64] Crystalline form D described in

[63] , characterized by an XRPD pattern substantially in accordance with Figure 3.

[65] Crystalline form D according to

[63] or

[64] , which is substantially pure.

[66] A composition comprising at least 80%, 90%, 95% or 99% by weight of crystalline form D according to any of

[63] to

[65] .

[67] Crystalline form D or composition according to any of

[63] to

[66] for use in the step of polymorphic conversion of ridinilazole form D to form A in the method according to any of

[12] to

[50] , for example as described in any of

[43] to

[49] .

[68] Use of crystalline form D or the composition according to any one of

[63] to

[66] in the manufacture of a composition according to any one of [1] to

[11] and

[51] to

[54] .

[69] Use of crystalline form D or the composition according to any one of

[63] to

[66] as an intermediate in the manufacture of a composition according to any one of [1] to

[11] and

[51] to

[54] .

[70] A crystalline form of ridinilazole tetrahydrate (Form N) characterized by a powder X-ray diffraction pattern containing characteristic peaks at 2-theta angles of (10.82±0.2)°, (13.35±0.2)° and (19.15±0.2)°, and optionally containing characteristic peaks at 2-theta angles of (10.82±0.2)°, (13.35±0.2)°, (19.15±0.2)°, (8.15±0.2)° and (21.74±0.2)°.

[71] Crystalline form N described in

[70] , characterized by an XRPD pattern substantially in accordance with Figure 2.

[72] The crystalline form N according to

[70] or

[71] , which is substantially pure.

[73] A composition comprising at least 80%, 90%, 95% or 99% by weight of crystalline form N according to any one of

[70] to

[72] .

[74] Crystalline form N or a composition according to any one of

[70] to

[73] for use in the ridinilazole polymorphic conversion step in the method according to any one of

[12] to

[50] , for example as described in

[43] to

[49] .

[75] Use of crystalline form N or the composition according to any one of

[70] to

[73] in the manufacture of a composition according to any one of [1] to

[11] and

[51] to

[54] .

[76] Use of crystalline form N or the composition according to any one of

[70] to

[73] as an intermediate in the manufacture of a composition according to any one of [1] to

[11] and

[51] to

[54] .

[77] The crystalline form, composition, or use according to any of

[56] to

[76] , wherein the XRPD is measured with Cu-K alpha radiation having a wavelength of 0.15419 nm.

[78] The crystalline form or composition of

[77] , wherein the XRPD is measured at room temperature.

[79] Alkali metal salts of ridinilazole.

[80] The alkali metal salt according to

[79] , selected from sodium, lithium and potassium salts of ridinilazole.

[81] The alkali metal salt according to

[79] or

[80] for use as an intermediate in the preparation of the composition according to any one of [1] to

[11] and

[51] to

[54] .

[82] Use of an alkali metal salt according to any one of

[79] to

[81] as an intermediate in the production of a composition according to any one of [1] to

[11] and

[51] to

[54] .

Claims

1. Crystals of ridinilazole tetrahydrate characterized by an X-ray powder diffraction pattern (XRPD) containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°.

2. A composition comprising the crystalline ridinilazole tetrahydrate of claim 1, wherein the composition comprises at least 80%, 90%, 95%, or 99% by weight of the crystalline ridinilazole tetrahydrate.

3. 10. A method for producing a composition comprising a mixture of compounds, the mixture comprising the crystalline ridinilazole tetrahydrate of claim 1 and compounds represented by formulas (II) and (IV): 【Chemical 1】 and the total amount of compounds of formula (II) and (IV) in the mixture is less than 100 ppm; The method comprises: (a) providing a crude ridinilazole composition comprising a mixture of compounds, wherein the mixture in the crude ridinilazole composition comprises ridinilazole and compounds of formulae (II) and (IV), the total amount of the compounds of formulae (II) and (IV) in the mixture in the crude ridinilazole composition being greater than 100 ppm, and the crude ridinilazole composition is provided by subjecting 3,3'-diaminobenzidine (DAB) to a condensation reaction; (b) reducing the compounds of formulae (II) and (IV) in the mixture in the crude ridinilazole composition to produce a purified ridinilazole composition containing a mixture of compounds, wherein the mixture in the purified ridinilazole composition contains the crystalline ridinilazole tetrahydrate of claim 1 and the compounds of formulae (II) and (IV), and the total amount of the compounds of formulae (II) and (IV) present in the mixture in the purified ridinilazole composition is less than 100 ppm; Including, The method, wherein step (b) comprises at least one of the following steps (b)(i) and (b)(ii), and the following step (b)(iv): (b)(i) dissolving the crude ridinilazole composition in a high boiling point aprotic solvent to obtain a solution, and then recrystallizing ridinilazole; (b)(ii) dissolving the crude ridinilazole composition under basic conditions followed by reprecipitation of ridinilazole by neutralization; (b)(iv) The ridinilazole composition obtained in step (b)(i) and / or step (b)(ii) is slurried in an aqueous solvent containing water, and then the ridinilazole composition is slurried in an aqueous solvent containing water to a water activity (A) of 0.4 or more. ｗ ) and seeding the slurry with crystals of ridinilazole tetrahydrate characterized by an X-ray powder diffraction pattern (XRPD) containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)° at a temperature of 2 to 60°C.

4. In the step (b)(iv), ｗ 4. The method of claim 3, wherein the temperature is greater than 2°C and less than 30°C.

5. The above A ｗ The method according to claim 3 or 4, wherein the value is 0.4 to 0.5 and the temperature is 15 to 25°C.

6. The aqueous solvent in step (b)(iv) is MeOH and H ２ The method according to any one of claims 3 to 5, wherein O is O.

7. 7. The method of any one of claims 3 to 6, wherein the crystals of ridinilazole tetrahydrate seeded into the slurry in step (b)(iv), characterized by an X-ray powder diffraction pattern (XRPD) comprising characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°, are (a') micronized, (b') in the form of a dry powder, or (c') in the form of a slurry.

8. 8. The method of any one of claims 3 to 7, wherein the condensation reaction of step (a) comprises reacting DAB with an imidate.

9. The imidate has the formula (V): 【Chemistry 2】 9. The method of claim 8, wherein the compound is methyl isonicotinimidate.

10. In the step (a), the condensation reaction is (1) adding sodium methoxide to 4-cyanopyridine to produce a compound of formula (V); 【Chemistry 3】 Next (2) reacting the compound of formula (V) of step (a) with DAB; The method according to any one of claims 3 to 9, comprising:

11. In the step (a), the condensation reaction is (1') adding sodium methoxide to 4-cyanopyridine in methanol to produce a compound of formula (V); 【Chemistry 4】 Next (2') adding the compound of formula (V) of step (1') to a mixture of DAB and acetic acid in methanol; or (3') adding a mixture of DAB and acetic acid in methanol to the compound of formula (V) of step (1'); The method according to any one of claims 3 to 10, comprising:

12. 12. The method of any one of claims 3 to 11, wherein the condensation reaction of step (a) is carried out at a temperature of 20 to 90°C.

13. 13. The method of claim 12, wherein the condensation reaction of step (a) is carried out at a temperature of 30 to 80°C.

14. 14. The method according to any one of claims 3 to 13, wherein the high boiling aprotic solvent is DMSO.

15. 15. The method of any one of claims 3 to 14, wherein step (b)(i) further comprises slow cooling and / or temperature cycling of the solution.

16. 16. The method of any one of claims 3 to 15, wherein step (b)(ii) comprises forming a dissolved metal salt of ridinilazole present in the crude ridinilazole composition followed by precipitating ridinilazole by neutralization.

17. 17. The method of claim 16, wherein the metal salt is an alkali metal salt.

18. 18. The method of claim 16 or 17, wherein the metal salt is selected from the sodium, potassium and lithium salts of ridinilazole.

19. 19. The method of any one of claims 16 to 18, wherein the crude ridinilazole composition is dissolved in sodium methoxide in methanol, and then ridinilazole is precipitated with acetic acid.

20. The method of any one of claims 3 to 19, wherein step (b) further comprises a carbon treatment.

21. 21. The method of claim 20, wherein the carbon treatment is applied to a crude ridinilazole mixture solution.

22. 22. The method of claim 21, wherein the carbon treatment comprises contacting the crude ridinilazole mixture solution with activated carbon.

23. 23. The method of claim 22, wherein the treatment with activated carbon further comprises removing the activated carbon by filtration.

24. 24. The method of any one of claims 20 to 23, wherein the carbon treatment comprises recirculating the solution through an activated carbon filter cartridge.

25. A method for producing the crystals of ridinilazole tetrahydrate according to claim 1, comprising: (a) providing a slurry of crystals of ridinilazole anhydrate in an aqueous solvent comprising water, wherein the crystals are characterized by a powder X-ray diffraction pattern comprising characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, and (27.82±0.2)°, and optionally comprising characteristic peaks at 2-theta angles of (12.7±0.2)°, (23.18±0.2)°, (27.82±0.2)°, (19.5±0.2)°, and (22.22±0.2)°; (b) a water activity (A) of 0.4 or more ｗ ) and at a temperature of 2 to 60°C, seeding the slurry with crystals of ridinilazole tetrahydrate characterized by an X-ray powder diffraction pattern (XRPD) containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°; A method comprising:

26. A pharmaceutical composition comprising an effective amount of the crystalline ridinilazole tetrahydrate of claim 1 or the composition of claim 2, and a pharmaceutically acceptable excipient.

27. 27. The pharmaceutical composition of claim 26 for use in the treatment or prevention of Clostridioides difficile infection or Clostridioides difficile-associated disease.

28. 1. A composition comprising a mixture of compounds, said mixture comprising ridinilazole and a compound represented by formula (II) and formula (IV): 【Chemistry 5】 and A composition wherein the total amount of the compounds of formula (II) and formula (IV) in the mixture is less than 100 ppm, and the ridinilazole is a crystal of ridinilazole tetrahydrate characterized by an X-ray powder diffraction pattern (XRPD) containing characteristic peaks at 2-theta angles of (11.02±0.2)°, (16.53±0.2)°, and (13.0±0.2)°.

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