Solid State Form Of Abrocitinib And Processes For Its Preparation

DESC:The following specification describes particularly the invention and in the manner in which it is to be performed: 2 INTRODUCTION Aspects of the present application relate to solid forms of abrocitinib and pharmaceutical compositions thereof. Specific aspects relate to the crystalline form, amorphous form and amorphous solid dispersion of abrocitinib and processes for their preparation. The drug compound having the adopted name “Abrocitinib” is a Janus kinase (JAK) inhibitor having a chemical name N-((1s,3s)-3-(methyl(7Hpyrrolo[ 2,3-d]pyrimidin-4-yl)amino)cyclobutyl)propane-1-sulfonamide and the structure as below. Abrocitinib” is a Janus kinase (JAK) inhibitor indicated for the treatment of adults with refractory, moderate-to-severe atopic dermatitis whose disease is not adequately controlled with other systemic drug products, including biologics, or when use of those therapies is inadvisable. US 9035074 B2 discloses abrocitinib, its pharmaceutically acceptable salts and pharmaceutical formulations. Further, WO2020008391A1discloses crystalline form of abrocitinib and process for its preparation. WO2020261041 A1 discloses crystalline form of abrocitinib and process for its preparation. Also covers amorphous solid dispersion of abrocitinib. WO 2021218948 A1 discloses crystalline forms of abrocitinib and processes for their preparation. The existence and possible numbers of polymorphic forms for a given compound cannot be predicted, and there are no “standard” procedures that can be used to prepare polymorphic forms of a substance. However, new forms of a 3 pharmaceutically useful compound may provide an opportunity to improve the performance characteristics of pharmaceutical products. Further, discovery of additional polymorphic forms, including solvate polymorphs, may help in the identification of the polymorphic content of a batch of an active pharmaceutical ingredient. For example, in some cases, different forms of the same drug can exhibit very different solubility and different dissolution rates. The discovery of new polymorphic forms enlarges selection of materials with which formulation scientists can design a pharmaceutically acceptable dosage form of a drug with a targeted release profile or other desired characteristics. Therefore, there remains a need for preparing new and stable polymorphic forms of abrocitinib which can overcome the disadvantages of the prior art and their preparation in a more cost effective and industrially viable manner. Amorphous solid dispersions of drugs are generally known to improve the stability and solubility of drug products. However, such dispersions are generally unstable over time. Amorphous solid dispersions of drugs tend to convert to crystalline forms over time, which can lead to improper dosing due to differences of the solubility of crystalline drug material compared to amorphous drug material. The present invention, however provides stable amorphous solid dispersions of abrocitinib. Moreover, the present invention provides solid dispersions of abrocitinib which may be reproduced easily and is amenable for processing into a dosage form. SUMMARY In an aspect, the present application provides a crystalline form RT-1 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 13.7, 16.9, 21.0 and 23.5 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-1 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 9.9, 11.4, 22.3 and 27.7 ± 0.2° 2?. In an aspect, the present application provides a crystalline form RT-2 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 7.4, 13.8, 20.1 and 27.9 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-2 4 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 10.3, 17.1, 22.7 and 23.9 ± 0.2° 2?. In an aspect, the present application provides a crystalline form RT-3 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 9.4, 10.4, 31.0 and 38.3 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-3 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 17.0, and 23.7 ± 0.2° 2?. In an aspect, the present application provides a crystalline form RT-4 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 6.0, 8.0, 9.2 and 12.1 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-4 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 24.6, and 26.3 ± 0.2° 2?. In an aspect, the present application provides a crystalline form RT-5 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 5.0, 8.1 and 19.8 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-5 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 27.9, and 31.3 ± 0.2° 2?. In an aspect, the present application provides a pharmaceutical composition comprising amorphous form of abrocitinib and one or more pharmaceutically acceptable excipients. In an aspect, the present application provides a solid dispersion comprising amorphous form of abrocitinib and one or more pharmaceutically acceptable carriers. In another aspect, the present application provides a process for the preparation of crystalline Form RT-1 of abrocitinib, comprising a) suspending abrocitinib in ethyl acetoacetate; b) optionally heating the slurry obtained in step (a); and c) isolating the crystalline form RT-1 of abrocitinib. In another aspect, the present application provides pharmaceutical 5 compositions comprising crystalline form RT-1 of abrocitinib and at least one pharmaceutically acceptable excipient. In another aspect, the present application provides a process for the preparation of crystalline Form RT-2 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in acetone; b) Adding acid followed by base to the slurry obtained in step (a); and c) isolating the crystalline form RT-2 of abrocitinib. In another aspect, the present application provides a process for the preparation of crystalline Form RT-2 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in acetone; b) optionally adding acid followed by base to the slurry obtained in step (a); and c) isolating the crystalline form RT-2 of abrocitinib. In another aspect, the present application provides a process for the preparation of crystalline Form RT-3 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in formic acid; b) adding solution or suspension obtained in step (a) to methyl tertbutyl ether or adding methyl tert-butyl ether to solution or suspension obtained in step (a); and c) isolating the crystalline form RT-3 of abrocitinib. In another aspect, the present application provides a process for the preparation of crystalline Form RT-4 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in hexanoic acid; b) adding solution or suspension obtained in step (a) to methyl tertbutyl ether or adding methyl tert-butyl ether to solution or suspension obtained in step (a); and c) isolating the crystalline form RT-4 of abrocitinib. In another aspect, the present application provides a process for the preparation of crystalline Form RT-5 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in propionic acid; b) adding solution or suspension obtained in step (a) to methyl tert6 butyl ether or adding methyl tert-butyl ether to solution or suspension obtained in step (a); and c) isolating the crystalline form RT-5 of abrocitinib. In an aspect, the present application provides a method for preparing a solid dispersion comprising amorphous abrocitinib and one or more pharmaceutically acceptable carriers comprising the steps of: a) providing a mixture of abrocitinib and one or more pharmaceutically acceptable carriers in a solvent; and b) isolating solid dispersion comprising amorphous abrocitinib and one or more pharmaceutically acceptable carriers. BRIEF DESCRIPTION OF THE DRAWING Figure 1 is an illustrative X-ray powder diffraction pattern of crystalline form RT-1 of abrocitinib, prepared by the method of Example-1. Figure 2 is an illustrative X-ray powder diffraction pattern of crystalline form RT-2 of abrocitinib, prepared by the method of Example-2 and 3 Figure 3 is an illustrative X-ray powder diffraction pattern of crystalline form RT-3 of abrocitinib, prepared by the method of Example-4 Figure 4 is an illustrative X-ray powder diffraction pattern of crystalline form RT-4 of abrocitinib, prepared by the method of Example-5 Figure 5 is an illustrative X-ray powder diffraction pattern of crystalline form RT-5 of abrocitinib, prepared by the method of Example-6 Figure 6 is an illustrative X-ray powder diffraction pattern of Abrocitinib present in amorphous solid dispersion according to example 7. Figure 7 is an illustrative X-ray powder diffraction pattern of Abrocitinib present in amorphous solid dispersion according to example 8. Figure 8 is an illustrative X-ray powder diffraction pattern of Abrocitinib present in amorphous solid dispersion according to example 9. Figure 9 is an illustrative X-ray powder diffraction pattern of Abrocitinib present in amorphous solid dispersion according to example 10 Figure 10 is an illustrative X-ray powder diffraction pattern of Abrocitinib present in amorphous solid dispersion according to example 11 7 Figure 11 is an illustrative X-ray powder diffraction pattern of Abrocitinib present in amorphous solid dispersion according to example 12 DETAILED DESCRIPTION In an aspect, the present application provides a crystalline form RT-1 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 13.7, 16.9, 21.0 and 23.5 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-1 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 9.9, 11.4, 22.3 and 27.7 ± 0.2° 2?. In an aspect, the present application provides a crystalline form RT-2 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 7.4, 13.8, 20.1 and 27.9 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-2 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 10.3, 17.1, 22.7 and 23.9 ± 0.2° 2?. In an aspect, the present application provides a crystalline form RT-3 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 9.4, 10.4, 31.0 and 38.3 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-3 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 17.0, and 23.7 ± 0.2° 2?. In an aspect, the present application provides a crystalline form RT-4 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 6.0, 8.0, 9.2 and 12.1 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-4 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 24.6, and 26.3 ± 0.2° 2?. In an aspect, the present application provides a crystalline form RT-5 of abrocitinib, characterized by a PXRD pattern comprising the peaks at about 5.0, 8.1 and 19.8 ± 0.2° 2?. In another aspect, the present application provides a crystalline form RT-5 8 of abrocitinib, further characterized by a PXRD pattern comprising the peaks at about 27.9, and 31.3 ± 0.2° 2?. In an aspect, the present application provides a pharmaceutical composition comprising amorphous form of abrocitinib and one or more pharmaceutically acceptable excipients. In an aspect, the present application provides a solid dispersion comprising amorphous form of abrocitinib and one or more pharmaceutically acceptable carriers. Solid dispersion as used herein refers to the dispersion of one or more active ingredients in an inert excipient or polymer or carrier, where the active ingredients could exist in finely crystalline, solubilized or amorphous state (Sareen et al., 2012 and Kapoor et al., 2012). Solid dispersion consists of two or more components, generally a polymer or carrier and drug optionally along with stabilizing agent (and/or surfactant or other additives). The most important role of the added polymer or carrier or excipient in solid dispersion is to reduce the molecular mobility of the drug to avoid the phase separation and re-crystallization of drug during storage. The resulting solid dispersions may have increased solubility. The increase in solubility of the drug in solid dispersion is mainly because drug remains in amorphous form which is associated with a higher energy state as compared to crystalline counterpart and due to that it requires very less external energy to dissolve. A solid dispersion is a molecular dispersion of a compound, particularly a drug substance within a polymer or carrier. Formation of a molecular dispersion provides a means of reducing the particle size to nearly molecular levels (i.e. there are no particles). As the carrier dissolves, the drug is exposed to the dissolution media as fine particles that are amorphous, which can dissolve and be absorbed more rapidly than larger particles. In general, the term "solid dispersion" refers to a system in a solid state comprising at least two components, wherein one component is dispersed throughout the other component or components. The term "solid dispersion" as used herein, refers to stable solid dispersions comprising amorphous drug substance and one or more polymers or carriers. Further the term "solid dispersion" as used herein also refers to stable solid dispersions comprising amorphous drug substance and one or 9 more polymers or carriers with or without adsorbent/absorbent. By "amorphous drug substance," it is meant that the amorphous solid contains drug substance in a substantially amorphous solid state form i.e. at least about 80% of the drug substance in the dispersion is in an amorphous form. More preferably at least about 90% and most preferably at least about 95% of the drug substance in the dispersion is in amorphous form. The solid dispersion of abrocitinib of the present invention can be made by any of the numerous methods that result in a solid dispersion comprising amorphous abrocitinib. Several approaches can be used for the preparation of solid dispersion which includes spray drying, lyophilization, fusion method, solvent evaporation, hotmelt extrusion, ball milling, particle size reduction, supercritical fluid (SCF) processes, kneading, inclusion complexes, electrostatic spinning method, melt crystallization and surface-active carriers. Abrocitinib can be incorporated in the dispersion in amorphous state. The dispersing agent is typically composed of a pharmaceutically acceptable substance that does not substantially interfere with the pharmaceutical action of Abrocitinib. The phrase "pharmaceutically acceptable" is employed herein to refer to those substances which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. In some embodiments, the carrier is a solid at room temperature. Non-limiting examples of suitable polymers or excipients or pharmaceutically acceptable carriers are celluloses (e.g., carboxymethylcelluloses, methylcelluloses, hydroxypropylcelluloses, hydroxypropylmethylcelluloses); polysaccharides, heteropolysaccharides (pectins); poloxamers; poloxamines; ethylene vinyl acetates; polyethylene glycols; dextrans; polyvinylpyrrolidones; chitosans; polyvinylalcohols; propylene glycols; polyvinylacetates; phosphatidylcholines (lecithins); miglyols; polylactic acid; polyhydroxybutyric acid; mixtures of two or more thereof, copolymers thereof, derivatives thereof, and the like. Further examples of carriers include copolymer systems such as polyethylene 10 glycol-polylactic acid (PEG-PLA), polyethylene glycol-polyhydroxybutyric acid (PEG-PHB), polyvinylpyrrolidone-polyvinylalcohol (PVP-PVA), and derivatized copolymers such as copolymers of N-vinyl purine (or pyrimidine) derivatives and Nvinylpyrrolidone. An enteric coating polymer can also be used according to the present invention. Specific examples of the enteric coating polymers include cellulose acetate phthalate, cellulose acetate trimellitate, cellulose acetate succinate, hydroxymethylcellulose ethyl phthalate, hydroxypropylmethylcellulose phthalate, eudragit, hydroxypropylmethylcellulose acetate succinate, hydroxypropylmethyl acetate maleate, hydroxypropylmethyl trimellitate, carboxymethylethylcellulose, polyvinyl butyrate phthalate, polyvinyl alcohol acetate phthalate, methacrylic acid/ethyl acrylate copolymer, and methacrylic acid/methyl methacrylate copolymer, hydroxypropyl methylcellulose phthalate, hydroxypropylmethylcellulose acetate succinate (HPMCAS), hydroxypropylmethyl acetate maleate and hydroxypropylmethyl trimellitate. In another aspect, the present application provides a process for the preparation of crystalline Form RT-1 of abrocitinib, comprising a) suspending abrocitinib in ethyl acetoacetate; b) optionally heating the slurry obtained in step (a); and c) isolating the crystalline form RT-1 of abrocitinib. In another aspect, the present application provides a process for the preparation of crystalline Form RT-2 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in acetone; b) Adding acid followed by base to the slurry obtained in step (a); and c) isolating the crystalline form RT-2 of abrocitinib. In another aspect, the present application provides a process for the preparation of crystalline Form RT-2 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in acetone; b) optionally adding acid followed by base to the slurry obtained in step (a); and c) isolating the crystalline form RT-2 of abrocitinib. 11 In another aspect, the present application provides a process for the preparation of crystalline Form RT-3 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in formic acid; b) adding solution or suspension obtained in step (a) to methyl tertbutyl ether or adding methyl tert-butyl ether to solution or suspension obtained in step (a); and c) isolating the crystalline form RT-3 of abrocitinib. In another aspect, the present application provides a process for the preparation of crystalline Form RT-4 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in hexanoic acid; b) adding solution or suspension obtained in step (a) to methyl tertbutyl ether or adding methyl tert-butyl ether to solution or suspension obtained in step (a); and c) isolating the crystalline form RT-4 of abrocitinib. In another aspect, the present application provides a process for the preparation of crystalline Form RT-5 of abrocitinib, comprising a) providing a solution or suspension of abrocitinib in propionic acid; b) adding solution or suspension obtained in step (a) to methyl tertbutyl ether or adding methyl tert-butyl ether to solution or suspension obtained in step (a); and c) isolating the crystalline form RT-5 of abrocitinib. Providing a solution or suspension of abrocitinib includes: i) direct use of a reaction mixture containing abrocitinib that is obtained in the course of its synthesis; or ii) providing a solution suspension of abrocitinib in a solvent Any physical form of abrocitinib including solvates, hydrates, anhydrous or amorphous may be utilized for providing suspension of abrocitinib. In embodiments, abrocitinib can be suspended in a solvent or mixture of one or more solvents. The suspension temperatures may range from about 0°C to about the reflux temperature of the solvent, or less than about 90°C, less than about 70°C, less than about 40°C, less than about 30°C, less than about 20°C, less than 12 about 10°C, or any other suitable temperatures without affecting its quality. Isolation of crystalline form of abrocitinib may involve methods including cooling, concentrating the mass, adding an anti-solvent, adding seed crystals, or filtration at higher temperature or the like. Stirring or other alternate methods such as shaking, agitation, or the like, may also be employed for the isolation. The crystalline form of abrocitinib may be recovered by methods including decantation, centrifugation, gravity filtration, suction filtration, agitated nutsche filter & dryer or any other technique for the recovery of solid under pressure or under reduced pressure. The recovered solid may optionally be dried. Drying may be carried out in a tray dryer, vacuum oven, air oven, cone vacuum dryer, rotary vacuum dryer, fluidized bed dryer, spin flash dryer, flash dryer, agitated nutsche filter & dryer or the like. The drying may be carried out at temperatures less than about 100°C, less than about 80°C, less than about 60°C, less than about 50°C, less than about 30°C, or any other suitable temperatures, at atmospheric pressure or under a reduced pressure, as long as the abrocitinib is not degraded in quality. The drying may be carried out for any desired times until the required product quality is achieved. The dried product may optionally be subjected to a size reduction procedure to produce desired particle sizes. Milling or micronization may be performed before drying, or after the completion of drying of the product. Techniques that may be used for particle size reduction include, without limitation, ball, roller and hammer milling, and jet milling. In an aspect, the present application provides a method for preparing a solid dispersion comprising amorphous abrocitinib and one or more pharmaceutically acceptable carriers comprising the steps of: a) providing a mixture of abrocitinib and one or more pharmaceutically acceptable carriers in a solvent; and b) isolating solid dispersion comprising amorphous abrocitinib and one or more pharmaceutically acceptable carriers. Step (a) involves providing a mixture of abrocitinib and one or more 13 pharmaceutically acceptable carriers in a solvent; Any physical form of abrocitinib may be utilized for providing the mixture of Abrocitinib in step (a). Suitable solvent which can be used for preparing the solid dispersion of abrocitinib are the same as described in step (a) include water, alcohols or ketone solvents or mixture thereof. Any undissolved particles in the solution obtained in step (a) may be removed by suitable method as described herein above or any other technique known in the art. Step (b) involves isolation of solid dispersion comprising amorphous Abrocitinib and one or more pharmaceutically acceptable carriers. Isolation of solid dispersion in step (b) may be carried out by removing solvent from a solution or suspension or mixture obtained in step (a). Suitable techniques which can be used for the removal of solvent are the same as described in step (b) of third embodiment or any other technique known in the art. The solid dispersions of the present invention are prepared using conventional spray drying techniques, vacuum drying, fluid-bed drying, freezedrying, rotary evaporation, rotary vacuum paddle dryer, drum drying, or other solvent removal process known in the art. Another aspect of the invention involves preparation of solid dispersions of abrocitinib by melt processing, wherein the compound and a carrier are heated to a temperature above the melting point of both the carrier and compound, which results in the formation of a fine colloidal (as opposed to molecular) dispersion of compound particles, with some solubilization of the compound in the carrier matrix. Processing of such a molten mixture often includes rapid cooling, which results in the formation of a congealed mass which must be subsequently milled to produce a powder which can be filled into capsules or made into tablets. The resulting solid dispersion comprising an amorphous form of abrocitinib and one or more pharmaceutically acceptable polymers or carriers may be optionally further dried. Drying can be carried out by methods as described in step (b) of third embodiment herein above or any other technique known in the art. 14 The amount of Abrocitinib in the solid dispersions of the present invention ranges from about 0.1% to about 90% by weight of the solid dispersion; or from about 10% to about 70% by weight of the solid dispersion; or from about 20% to about 60% by weight of the solid dispersion; or from about 20% to about 40% by weight of the solid dispersion; or about 30% by weight of the solid dispersion. In some aspects, the weight ratio of abrocitinib to polymer or carrier is about 1:99 to about 99:1. In some aspects, the weight ratio of abrocitinib to polymer or carrier is about 1:99 to about 75:25 or about 1:99 to about 60: 40. In further aspects, the weight ratio of abrocitinib to polymer or carrier is about 1:99 to about 15:85; about 1:99 to about 10:90; or about 1:99 to about 5:95. In further aspects, the weight ratio of abrocitinib to polymer or carrier is about 25:75 to about 75:25, about 40:60 to about 60:40 or about 1:1 or about 2:1. Amorphous form or the solid dispersions of abrocitinib of the present application can be optionally subjected to particle size reduction procedures before or after the completion of drying of the product to produce desired particle sizes and distributions. Milling or micronization can be performed to achieve the desired particle sizes or distributions. Equipment that may be used for particle size reduction include, without limitation thereto, ball mills, roller mills, hammer mills, and jet mills. In an aspect, the present application provides pharmaceutical formulations comprising an amorphous form of abrocitinib or solid dispersion comprising amorphous form of Abrocitinib, together with one or more pharmaceutically acceptable carriers. Abrocitinib which may be used as the input in the process for preparation of the solid states of the present application can be prepared by any process known in the art. In another aspect, the present application provides crystalline form of abrocitinib or amorphous form or amorphous solid dispersion of Abrocitinib according to instant application and pharmaceutical compositions thereof, wherein the chemical purity of abrocitinib may be more than 99% by HPLC or more than 99.5% by HPLC or more than 99.9% by HPLC. 15 In another aspect, the present application provides pharmaceutical compositions comprising crystalline form RT-1, RT-2, RT-3, RT-4 and RT-5 of abrocitinib and at least one pharmaceutically acceptable excipient. Certain specific aspects and embodiments of the present application will be explained in greater detail with reference to the following examples, which are provided only for purposes of illustration and should not be construed as limiting the scope of the application in any manner. Variations of the described procedures, as will be apparent to those skilled in the art, are intended to be within the scope of the present application. Definitions The term "about" when used in the present application preceding a number and referring to it, is meant to designate any value which lies within the range of ±10%, preferably within a range of ±5%, more preferably within a range of ±2%, still more preferably within a range of ±1 % of its value. For example, "about 10" should be construed as meaning within the range of 9 to 11, preferably within the range of 9.5 to 10.5, more preferably within the range of 9.8 to 10.2, and still more preferably within the range of 9.9 to 10.1. EXAMPLES Example-1: Preparation of crystalline form RT-1 of abrocitinib Abrocitinib (2 g) and ethyl acetoacetate (40 mL) charged in to round bottom flask, heated to 60 ° C and the resulting slurry was stirred at 60° C for 24 hours. Solid was filtered and dried at 100 °C for 3 hours to afford the title compound. XRPD: Crystalline form RT-1, as depicted in Figure-1. Example-2: Preparation of crystalline form RT-2 of abrocitinib Abrocitinib (1 g) and acetone (20 mL) charged in to round bottom flask and stirred for 10 minutes. Con. Sulfuric acid solution (0.1 mL in 10 mL acetone) was slowly added to the reaction mass at 25 °C and stirred for 20 minutes. Triethylamine solution (0.3 mL in 10 mL acetone) was slowly added to the reaction mass and the resulting slurry was stirred at 25° C for 1 hour. Solid was filtered and dried at 100 °C for 3 hours to afford the title compound. 16 XRPD: Crystalline form RT-2, as depicted in Figure-2. Example-3: Preparation of crystalline form RT-2 of abrocitinib Abrocitinib (100 mg) and acetone (2 mL) charged in to round bottom flask and stirred for 10 minutes. Con. Sulfuric acid (32 µL) was slowly added to the reaction mass at 25 °C and stirred for 10 minutes. Conc. ammonia (50 µL) was slowly added to the reaction mass and the resulting slurry was stirred at 25° C for 1 hour 30 minutes. Solid was filtered and dried to afford the title compound. XRPD: Crystalline form RT-2, as depicted in Figure-2. Example-4: Preparation of crystalline form RT-3 of abrocitinib Abrocitinib (1 g) and formic acid (5 mL) charged in to round bottom flask and stirred for 10 minutes. The resultant clear solution was slowly added to precooled methyl tert-butyl ether solution (15 mL) at -50 °C and stirred for 2 hours. Solid was filtered and dried to afford the title compound. XRPD: Crystalline form RT-3, as depicted in Figure-3. Example-5: Preparation of crystalline form RT-4 of abrocitinib Abrocitinib (1 g) and hexanoic acid (5 mL) charged in to round bottom flask and stirred for 10 minutes. The resultant clear solution was slowly added to pre-cooled methyl tert-butyl ether solution (15 mL) at -50 °C and stirred for 2 hours. Solid was filtered and dried to afford the title compound. XRPD: Crystalline form RT-4, as depicted in Figure-4. Example-6: Preparation of crystalline form RT-5 of abrocitinib Abrocitinib (1 g) and propionic acid (4 mL) charged in to round bottom flask and stirred for 10 minutes. The resultant clear solution was slowly added to pre-cooled methyl tert-butyl ether solution (15 mL) at -50 °C and stirred for 2 hours. Solid was filtered and dried to afford the title compound. XRPD: Crystalline form RT-5, as depicted in Figure-5. Example-7: Preparation of abrocitinib solid dispersion with hydroxypropylmethylcellulose acetate succinate (HPMCAS) Abrocitinib (1.25 g), HPMCAS (3.75 g), mixture of methanol & acetone (200 mL; 1:1) and water (20 mL) charged into flask. Reaction mass was heated to 50 °C and stirred at 50 °C for 25 minutes. Filtered the reaction mass and the 17 filtrate was subjected to spray drying to afford title compound. (Spray dryer was operated at inlet temp of 70 °C, Flow rate of 8 gm/min, nozzle pressure of 2 Bar, Inlet pressure of 0.4 Bar). The Powder X-ray diffraction (PXRD) pattern of abrocitinib solid dispersion obtained in above example is in accordance with Figure 6. Example-8: Preparation of abrocitinib solid dispersion with hydroxypropylmethylcellulose acetate succinate (HPMCAS) Abrocitinib (1.67 g), HPMCAS (3.33 g), mixture of methanol & acetone (200 mL; 1:1) and water (20 mL) charged into flask. Reaction mass was heated to 50 °C and stirred at 50 °C for 20 minutes. Filtered the reaction mass and the filtrate was subjected to spray drying to afford title compound. (Spray dryer was operated at inlet temp of 70 °C, Flow rate of 8 gm/min, nozzle pressure of 2 Bar, Inlet pressure of 0.4 Bar). The Powder X-ray diffraction (PXRD) pattern of abrocitinib solid dispersion obtained in above example is in accordance with Figure 7. Example-9: Preparation of abrocitinib solid dispersion with hydroxypropylmethylcellulose acetate succinate (HPMCAS) Abrocitinib (2.5 g), HPMCAS (2.5 g), mixture of methanol & acetone (200 mL; 1:1) and water (20 mL) charged into flask. Reaction mass was heated to 50 °C and stirred at 50 °C for 20 minutes. Filtered the reaction mass and the filtrate was subjected to spray drying to afford title compound. (Spray dryer was operated at inlet temp of 70 °C, Flow rate of 8 gm/min, nozzle pressure of 2 Bar, Inlet pressure of 0.4 Bar). The Powder X-ray diffraction (PXRD) pattern of abrocitinib solid dispersion obtained in above example is in accordance with Figure 8. Example-10: Preparation of abrocitinib solid dispersion with Eudragit L100 Abrocitinib (1.25 g), Eudragit L100 (3.75 g), mixture of methanol & acetone (200 mL; 1:1) and water (20 mL) charged into flask. Reaction mass was heated to 50 °C and stirred at 50 °C for 25 minutes. Filtered the reaction mass and the filtrate was subjected to spray drying to afford title compound. (Spray dryer was operated at inlet temp of 70 °C, Flow rate of 8 gm/min, nozzle pressure of 2 18 Bar, Inlet pressure of 0.4 Bar). The Powder X-ray diffraction (PXRD) pattern of abrocitinib solid dispersion obtained in above example is in accordance with Figure 9. Example-11: Preparation of abrocitinib solid dispersion with Eudragit L100 Abrocitinib (1.67 g), Eudragit L100 (3.33 g), mixture of methanol & acetone (200 mL; 1:1) and water (20 mL) charged into flask. Reaction mass was heated to 50 °C and stirred at 50 °C for 25 minutes. Filtered the reaction mass and the filtrate was subjected to spray drying to afford title compound. (Spray dryer was operated at inlet temp of 70 °C, Flow rate of 8 gm/min, nozzle pressure of 2 Bar, Inlet pressure of 0.4 Bar). The Powder X-ray diffraction (PXRD) pattern of abrocitinib solid dispersion obtained in above example is in accordance with Figure 10. Example-12: Preparation of abrocitinib solid dispersion with Eudragit L100 Abrocitinib (2.5 g), Eudragit L100 (2.5 g), mixture of methanol & acetone (200 mL; 1:1) and water (20 mL) charged into flask. Reaction mass was heated to 50 °C and stirred at 50 °C for 20 minutes. Filtered the reaction mass and the filtrate was subjected to spray drying to afford title compound. (Spray dryer was operated at inlet temp of 70 °C, Flow rate of 8 gm/min, nozzle pressure of 2 Bar, Inlet pressure of 0.4 Bar). The Powder X-ray diffraction (PXRD) pattern of abrocitinib solid dispersion obtained in above example is in accordance with Figure 11. Dated: 10th of August 2023. Signature: _________________ Dr. B. Dinesh Kumar. Intellectual Property Management, Dr. Reddy’s Laboratories Limited. ,CLAIMS:1. A pharmaceutical composition comprising amorphous form of abrocitinib and one or more pharmaceutically acceptable excipients. 2. A solid dispersion comprising amorphous form of abrocitinib and one or more pharmaceutically acceptable carriers. 3. A solid dispersion according to claim 2, wherein the pharmaceutically acceptable carrier is hydroxypropylmethylcellulose acetate succinate (HPMCAS) or Eudragit L100 4. A method for preparing a solid dispersion comprising amorphous abrocitinib and one or more pharmaceutically acceptable carriers comprising the steps of: a) providing a mixture of abrocitinib and one or more pharmaceutically acceptable carriers in a solvent; and b) isolating solid dispersion comprising amorphous abrocitinib and one or more pharmaceutically acceptable carriers. 5. A method according to claim 3, wherein solvent is selected from water, alcohols or ketone solvents or mixture thereof