DESC:FIELD OF THE INVENTION
The present application relates to crystalline solid form of Siponimod, its preparative method and pharmaceutical compositions thereof.

BACKGROUND OF THE INVENTION
The drug compound having the adopted name Siponimod, has a chemical name (E)-1-(4-(1-(((4-cyclohexyl-3-(trifluoromethyl)benzyl)oxy)-imino)ethyl)-2-ethylbenzyl)-azetidine-3-carboxylic acid, and is represented by the structure of formula I.

Siponimod is a selective sphingosine-1-phosphate receptor modulator drug approved in USA for the treatment of secondary progressive multiple sclerosis.
Siponimod base, its synthetic process and its pharmaceutical compositions are described in US patent No. 7,939,519 B2 (US ‘519). Siponimod hemifumarate and its pharmaceutical compositions are described in US patent application No. 20150175536 A1 (US ‘536).
The US ‘536 also describes crystalline forms of Siponimod hemifumarate salt and their pharmaceutical compositions.
International patent application, WO 2019/064184 A1, published on 4 April 2019 describes crystalline solid state forms of Siponimod hemifumarate and siponimod monofumarate.
Polymorphism, the occurrence of different crystal forms, is a phenomenon of some molecules and molecular complexes. A single molecule may give rise to a variety of polymorphs having distinct crystal structures and physical properties. Polymorphs in general will have different melting points, thermal behaviors (e.g. measured by thermogravimetric analysis - "TGA", or differential scanning calorimetry - "DSC"), X-ray powder diffraction (XRPD or powder XRD) pattern, infrared absorption fingerprint, and solid state nuclear magnetic resonance (NMR) spectrum. One or more of these techniques may be used to distinguish different polymorphic forms of a compound.
Discovering new polymorphic forms, hydrates, solvates and co-crystals of a pharmaceutical product can provide materials having desirable processing properties, such as ease of handling, ease of processing, storage stability, and ease of purification or as desirable intermediate crystal forms that facilitate conversion to other polymorphic forms. New polymorphic forms and solvates of a pharmaceutically useful compound or salts thereof can also provide an opportunity to improve the performance characteristics of a pharmaceutical product. It enlarges the repertoire of materials that a formulation scientist has available for formulation optimization, for example by providing a product with different properties, e.g., better processing or handling characteristics, improved dissolution profile, or improved shelf-life. For at least these reasons, there is a need for additional solid forms of Siponimod.

SUMMARY OF THE INVENTION
Aspects of the present application relate to novel crystalline form of Siponimod, its preparative process and pharmaceutical compositions thereof.
In one aspect, the present application provides a crystalline Form SFF1 of Siponimod, characterized by a PXRD pattern comprising the peaks at about 6.46, 13.08, 16.68, and 18.74 ± 0.2° 2?.
In another aspect, the present application provides a process for the preparation of crystalline Form SFF1 of Siponimod, comprising,
(a) dissolving Siponimod hemifumarate and maleic acid in methanol,
(b) evaporating the solution of step (a), and
(c) isolating the crystalline Form SFF1 of Siponimod.
In another aspect, the present application provides use of the crystalline forms of Siponimod to improve the purity of Siponimod, its co-crystals and its salts.
In another aspect, the present application provides a pharmaceutical composition comprising the crystalline form of Siponimod and at least one pharmaceutically acceptable carrier.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is powder X-ray diffraction ("PXRD") pattern of crystalline form SFF1 of Siponimod prepared according to Example 1.

DETAILED DESCRITPION
Aspects of the present application relate to novel crystalline solid forms of Siponimod, their preparative processes and pharmaceutical compositions thereof. The present application also encompasses the use of novel crystalline solid forms of Siponimod provided herein, for the preparation of other solid forms of Siponimod, its co-crystals and its salts, for the purification of Siponimod hemifumarate and for the preparation of pharmaceutical dosage forms.
In one aspect, the present application provides a crystalline Form SFF1 of Siponimod, characterized by a PXRD pattern comprising the peaks at about 6.46, 13.08, 16.68, and 18.74 ± 0.2° 2?.
In another aspect, the present application provides a process for the preparation of crystalline Form SFM1 of Siponimod, comprising,
(a) dissolving Siponimod hemifumarate and maleic acid in methanol,
(b) evaporating the solution of step (a), and
(c) isolating the crystalline Form SFF1 of Siponimod.
The step (a) involves providing a solution of Siponimod hemifumarate, maleic acid and methanol. Methanol may be taken in the ratio of 1:5 to 1:50 w/v with respect to siponimod hemifumarate. Any physical form of Siponimod hemifumarate may be used as starting material. Siponimod hemifumarate, maleic acid and methanol are mixed and sonicated the mixture to obtain a solution. The solution formed may be filtered through a filter paper to remove any undissolved material. The step (b) involves evaporation of the solution obtained in step (a). The evaporation is slow evaporation and is carried at room temperature.
The step (c) involves isolation of the solid from the vial or flask. The isolated solid is characterized by PXRD.
In another aspect, the crystalline Form SFF1 of Siponimod is further characterized by a PXRD pattern comprising the peaks at about 10.73, 15.55, 18.12, 19.75, 23.10 and 23.80 ± 0.2° 2?.
In another aspect, the crystalline Form SFF1 of Siponimod is characterized by the PXRD pattern of Figure 1.
In another aspect, the present application provides use of the crystalline form of Siponimod of the present invention in the purification of Siponimod or its co-crystals or its salts and in the preparation of other crystalline forms of Siponimod.
In another aspect, the present application provides pharmaceutical composition comprising crystalline form of Siponimod described in this application and one or more pharmaceutically acceptable excipients.
In another aspect, the present application provides a method of treating multiple sclerosis, comprising administering to a subject in need thereof an effective amount of the crystalline form of Siponimod of the present application, or a pharmaceutical composition comprising crystalline form of Siponimod of the present invention.
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 following definitions are used in connection with the present invention unless the context indicates otherwise. The term “amorphous” refers to a solid lacking any long-range translational orientation symmetry that characterizes crystalline structures although; it may have short range molecular order similar to a crystalline solid.
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.
All percentages and ratios used herein are by weight of the total composition and all measurements made are at about 25°C and about atmospheric pressure, unless otherwise designated. All temperatures are in degrees Celsius unless specified otherwise. As used herein, “comprising” means the elements recited, or their equivalents in structure or function, plus any other element or elements which are not recited. The terms “having” and “including” are also to be construed as open ended. All ranges recited herein include the endpoints, including those that recite a range “between” two values. Whether so indicated or not, all values recited herein are approximate as defined by the circumstances, including the degree of expected experimental error, technique error, and instrument error for a given technique used to measure a value.
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. Reasonable variations of the described procedures are intended to be within the scope of the present invention. While particular aspects of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
EXAMPLES
Example-1: Preparation of crystalline Form SFF1 of Siponimod
Siponimod hemifumarate (2 g), Maleic acid (0.22 g) and methanol (20 mL) were charged into a glass vial. The mixture was sonicated to get clear solution and the clear solution was filtered through a whatman filter paper. The solution was then kept at room temperature for slow evaporation of the solvent. After 2 days the solid formed was filtered to obtain crystalline Form SFF1 of Siponimod. PXRD as shown in Figure 1.
,CLAIMS:We claim:
1. Crystalline Form SFF1 of Siponimod, characterized by a PXRD pattern comprising the peaks at about 6.46, 13.08, 16.68, and 18.74 ± 0.2° 2?.
2. The crystalline Form SFF1 of Siponimod of claim 1 is characterized by the PXRD pattern of Figure 1.
3. The crystalline Form SFF1 of Siponimod of claim 1 is further characterized by a PXRD pattern comprising peaks at about 10.73, 15.55, 18.12, 19.75, 23.10 and 23.80 ± 0.2° 2?.
4. A process for the preparation of crystalline Form SFF1 of Siponimod, comprising,
(a) dissolving Siponimod hemifumarate and maleic acid in methanol,
(b) evaporating the solution of step (a), and
(c) isolating the crystalline Form SFF1 of Siponimod.
5. A pharmaceutical composition comprising crystalline Form SFF1 of Siponimod and one or more pharmaceutically acceptable excipients.