DESC:Field of the Invention:
The present invention provides polymorphic forms of Lesinurad. Specifically the present invention relates to the novel crystalline solvates of lesinurad. The present invention also provides process for preparation of an amorphous form of lesinurad.
Background of the Invention:
Lesinurad is chemically known as 2-((5-bromo-4-(4- cyclopropylnaphthalen-l-yl)-4H-l,2,4-triazol-3-yl)thio)acetic acid, having the structural formula:

Lesinurad is a urate transporter inhibitor for treating hyperuricemia associated with gout in patients who have not achieved target serum uric acid levels with a xanthine oxidase inhibitor alone. It has been approved by FDA on December 22, 2015. Lesinurad is marketed in USA and Europe under the trade name of Zurampic®.
Lesinurad is used for decreasing uric acid levels in one or more tissues or organs, blood, serum, urine, or combinations thereof. It is also used for reducing uric acid production, increasing uric acid excretion or both in an individual and for treating an individual suffering from a condition characterized by abnormal tissue levels of uric acid.
Literature survey reveals that lesinurad can exist in different polymorphic forms, which differ from each other in terms of stability, physical properties and pharmacokinetics. The reported polymorphs of lesinurad are incorporated here by the way of reference.
PCT publication WO2012092395 describes crystalline Form I and II of lesinurad with their XPRD.
PCT publication WO 2015075561 describes crystalline forms III, IV, V and VI of lesinurad with their XPRD.
Polymorphs often improve physical and biological characteristics of mother compounds without modifying primary pharmacological activity, based on mechanism of action. Thus there is a continuing need to obtain new polymorphs of lesinurad having improved physical and/or chemical properties.

Summary of the Invention:
In one aspect, the invention provides crystalline methanol solvate of lesinurad depicted as Form L1 and process for preparation thereof.
In another aspect, the invention provides crystalline methanol solvate of lesinurad depicted as Form L2 and process for preparation thereof.
In another aspect, the invention provides crystalline methanol solvate of lesinurad depicted as Form L3 and process for preparation thereof.
In another aspect, the invention provides crystalline ethanol solvate of lesinurad depicted as Form L4 and process for preparation thereof.
In another aspect, the invention provides process for preparation of an amorphous form of lesinurad.
In another aspect, the invention provides for pharmaceutical compositions comprising any one of the Form L1, L2, L3 and L4 of lesinurad or mixture thereof.

Description of the drawings:
Figure 1: Illustrates X-ray powder diffraction pattern of Methanol solvate of Lesinurad (Form L1).
Figure 2: Illustrates Differential Scanning Calorimetry thermogram of Form L1 of Lesinurad.
Figure 3: Illustrates Thermogravimetric analysis curve of Form L1 of Lesinurad.
Figure 4: Illustrates X-ray powder diffraction pattern of Methanol solvate of Lesinurad (Form L2).
Figure 5: Illustrates Differential Scanning Calorimetry thermogram of Form L2 of Lesinurad.
Figure 6: Illustrates Thermogravimetric analysis curve of Form L2 of Lesinurad.
Figure 7: Illustrates X-ray powder diffraction pattern of Methanol solvate of Lesinurad (Form L3).
Figure 8: Illustrates Differential Scanning Calorimetry thermogram of Form L3 of Lesinurad.
Figure 9: Illustrates Thermogravimetric analysis curve of Form L3 of Lesinurad.
Figure 10: Illustrates calculated powder XRD pattern of Form L3 of Lesinurad.
Figure 10A: Illustrates Oak Ridge Thermal Ellipsoid Plot (ORTEP) view of Form L3 of Lesinurad.
Figure 11: Illustrates X-ray powder diffraction pattern of ethanol solvate of Lesinurad (Form L4).
Figure 12: Illustrates Differential Scanning Calorimetry thermogram of Form L4 of Lesinurad.
Figure 13: Illustrates Thermogravimetric analysis curve of Form L4 of Lesinurad.
Figure 14: Illustrates X-ray powder diffraction pattern of amorphous form of lesinurad.
Figure 15: Illustrates calculated powder XRD pattern of Form L4 of Lesinurad.
Figure 16: Illustrates Oak Ridge Thermal Ellipsoid Plot (ORTEP) view of Form L4 of Lesinurad.

Detail Description of the Invention:
The present invention provides novel polymorphic forms of Lesinurad. These solid state forms includes crystalline and crystalline solvate forms of lesinurad. These solid state forms can be used to prepare any formulations of lesinurad.
The crystals of the present invention can be solvates, i.e. crystals wherein solvent molecules from part of the crystal structure. The solvate may be formed from water, in which case the solvates are often referred to as hydrates. Alternatively, the solvates may be formed from other solvents, such as e.g. methanol, ethanol, acetone, or ethyl acetate. The exact amount of solvate often depends on the conditions. For instance, hydrates will typically loose water as the temperature is increased or as the relative humidity is decreased.
It has been found that, depending on the choice of the conditions which may be used during the purification of the crude product obtained after industrial production, lesinurad may be obtained in different crystalline modifications.
It has been found that these different modifications can be decisively obtained by the choice of solvents used for the crystallization and by the choice of the operating conditions like heating, cooling, isolation etc. selected during the crystallization process. The volume of the solvent taken for dissolution also plays important role in crystallization process.
In one embodiment, the invention provides a crystalline methanol solvate of lesinurad (Form L1), which is characterized by XRPD (X-ray powder diffractogram) which comprises of peaks expressed as 2? at 7.80, 8.20, 8.81, 11.50, 14.21, 16.97, 19.97, 22.06, 26.80, 32.96 ± 0.2 degrees. The XRPD of lesinurad Form L1 is depicted in figure 1.
The present invention further provides a process for preparation of lesinurad Form L1, which comprises the steps of:
a) dissolving lesinurad in a methanol solvent;
b) optionally cooling the solution obtained in step (a); and
c) isolating lesinurad Form L1.
The dissolution of lesinurad is carried out at a temperature of 35 to 60°C, more preferably 45 to 50°C.
The isolation of lesinurad Form L1 of step (c) could be done by conventional techniques known in prior art such as concentration, filtration, centrifugation and drying etc. Combination of more than one conventional technique can be used for the isolation of desired product.
In another embodiment, the invention provides a crystalline methanol solvate of lesinurad (Form L2), which is characterized by XRPD (X-ray powder diffractogram) which comprises of peaks expressed as 2? at 8.17, 8.76, 15.07, 17.60, 19.93, 22.13, 25.89, 29.33, 31.10 ± 0.2 degrees. The XRPD of crystalline lesinurad Form L2 is depicted in figure 4.
The present invention further provides a process for preparation of lesinurad Form L2, which comprises the steps of:
a) dissolving lesinurad in a methanol solvent;
b) distillation of solution obtained in step (a); and
c) isolating lesinurad Form L2.
The dissolution of lesinurad is carried out at a temperature of 35 to 60°C, more preferably 45 to 50°C.
The distillation of the solvent of step (b) is done at 500C in 30-45 mins.
The isolation of lesinurad Form L2 of step (c) could be done by conventional techniques known in prior art such as filtration, centrifugation and drying etc. Combination of more than one conventional technique can be used for the isolation of desired product.
Isolation of Form L2 in step (c) is done by drying under vacuum at 45°C for 3-4 h.
In another embodiment, the invention provides a crystalline methanol solvate of lesinurad (Form L3), which is characterized by XRPD (X-ray powder diffractogram) which comprises of peaks expressed as 2? at 7.72, 9.66, 11.49, 14.20, 16.97, 19.91, 21.06, 24.27, 26.81, 31.34, 32.83 ± 0.2 degrees. The XRPD of crystalline lesinurad Form L3 is depicted in figure 7.
The crystalline methanol solvate of lesinurad (Form L3) also characterized by a triclinic elementary cell with the parameters a=9.017 (7) Å, b=9.213(7) Å, c=11.692(9) Å, and cell volume=943.9(12) Å3 determined by single crystal X-ray structural analysis.
The crystalline methanol solvate of lesinurad (Form L3) crystallizes in a triclinic crystallographic system (see Table 1).
Table 1
Chemical formula C17H14BrN3O2S. CH4O
Formula Weight 478.52
Temperature (K) 296(2)
Wavelength (Å) 0.71075
Crystal lattice triclinic
Space group P-1
a, b, c [Å] 9.017(7), 9.213(7), 11.692(9)
a, ß, ? [°] 80.87(2), 79.827(19), 88.01(3)
V [Å3] 943.9(12)
Z 2
D(calc) [g/cm3] 1.535
µ/mm?1 2.311
R1 [I > 2 F(I)] 0.0549
wR2 (all) 0.1722
GOF 1.106
Diffractometer OXFORD CCD

The present invention further provides a process for preparation of crystalline lesinurad Form L3, which comprises the steps of:
a) dissolving lesinurad in a methanol solvent;
b) gradual cooling of the solution obtained in step (a) up to 100C; and
c) isolating lesinurad Form L3.
The dissolution of lesinurad is carried out at a temperature of 35 to 60°C, more preferably 45 to 50°C.
The gradual cooling of the step (b) is done in 35-40 min.
The isolation of lesinurad Form L3 of step (c) could be done by conventional techniques known in prior art such as filtration, centrifugation, concentration, dying and evaporation etc. Combination of more than one conventional technique can be used for the isolation of desired product.
Isolation of Form L3 in step (c) is done by filtration and drying under vacuum at 45°C for 8-9 h then drying is continued at room temperature for another 8-9 h.
In another embodiment, the invention provides a crystalline ethanol solvate of lesinurad (Form L4), which is characterized by XRPD (X-ray powder diffractogram) which comprises of peaks expressed as 2? at 7.76, 8.14, 8.74, 14.27, 15.03, 19.68, 21.89, 22.64, 25.34, 28.76, 31.22, 32.77 ± 0.2 degrees. The XRPD of crystalline lesinurad Form L4 is depicted in figure 11.
The crystalline ethanol solvate of lesinurad (Form L4) also characterized by a triclinic elementary cell with the parameters a=13.292 (6) Å, b=7.366 (3) Å, c=20.193 (9) Å, and cell volume=9474.5(15) Å3 determined by single crystal X-ray structural analysis.
The crystalline ethanol solvate of lesinurad (Form L4) crystallizes in a triclinic crystallographic system (see Table 2).
Table 2
Chemical formula C17H14BrN3O2S. C2H6O
Formula Weight 450.35
Temperature (K) 296(2)
Wavelength (Å) 0.71075
Crystal lattice Monoclinic
Space group P-21/n
a, b, c [Å] 13.292(6), 7.366(3), 20.193(9)
a, ß, ? [°] 90, 92.857(6), 90
V [Å3] 1974.5(15)
Z 4
D(calc) [g/cm3] 1.515
µ/mm?1 2.212
R1 [I > 2 F(I)] 0.0461
wR2 (all) 0.1488
GOF 1.236
Diffractometer Rigaku CCD

The present invention further provides a process for preparation of lesinurad Form L4, which comprises the steps of:
a) dissolving lesinurad in an ethanol solvent;
b) cooling the solution obtained in step (a); and
c) isolating lesinurad Form L4.
The dissolution of lesinurad is carried out at a temperature of 40 to 70°C, more preferably 50 to 60°C.
The cooling temperature of the step (b) is 0-100C, more preferably 2-50C.
The crystalline solid which precipitates out could be isolated by conventional techniques known in prior art such as filtration, centrifugation, concentration and evaporation etc. Combination of more than one conventional technique can be used for the isolation of desired product.
Isolation of polymorph in step (c) is done by filtration and drying under vacuum at 45°C for 6 h then drying is continued at room temperature for another 9-10 h.
In another embodiment of the present invention, provided process for the preparation of a stable and substantially pure amorphous form of lesinurad, which comprises:
a) suspending or dissolving lesinurad in a solvent;
b) adding base to the step (a);
c) heating the reaction mixture of step (b);
d) adding acid to the step (c); and
e) isolating amorphous form of lesinurad.
Suitable solvents in all process may include but are not limited to water; alcohols such as methanol, ethanol, isopropanol, 2-propanol, 1-butanol, t-butyl alcohol, 1-pentanol, 2- pentanol, amyl alcohol, ethylene glycol, glycerol and the like; ketones such as acetone, butanone, 2-pentanone, 3-pentanone, methyl butyl ketone, methyl isobutyl ketone, and the like; esters such as ethyl formate, methyl acetate, ethyl acetate, propyl acetate, t-butyl acetate, isobutyl acetate, hydrocarbons like toluene, xylene, methylene dichloride, cyclohexane, ethylene dichloride, chlorobenzene, and the like, nitriles like acetonitrile, ethers like diethyl ether, diisopropyl ether, t-butyl methyl ether, dibutyl ether, tetrahydrofuran, 1,4-dioxane, 2-methoxyethanol. Polar aprotic solvents like N,N-dimethylformamide, ?,?-dimethylacetamide, N-methylpyrrolidone, pyridine, dimethylsulfoxide, sulfolane, formamide, acetamide, propanamide, formic acid, acetic acid, propionic acid, methane sulphonic acid and the like; and mixtures thereof.
The base used in step (b) could be organic or inorganic bases which includes but not limited to alkali metal carbonates, bicarbonates, hydrides and hydroxides; triethylamine, ammonia, methylamine, pyridine, ?,?-diethylamine, and lithium diisopropylamine.
The pH range of the solution of step (b) could be maintained basic, more preferably at 9 - 10.
The heating of step (c) is carried out at 30-550C, more preferably at 40-450C.
The acid used in step (d) could be organic or inorganic acid which includes but not limited to sulfuric acid, p-tolunesulfonic acid, methane sulfonic acid, hydrochloric acid, nitric acid, and phosphoric acid.
The pH range of the solution of step (d) could be maintained acidic, more preferably at 2 - 3.
Removal of solvent in step-(e) is accomplished by, for example, filtering the solid under inert atmosphere. Alternatively, the solvent may also be removed by evaporation. Evaporation can be achieved at sub-zero temperatures by the lyophilisation or freeze- drying technique. The solution may also be completely evaporated in, for example, a pilot plant Rota vapor, a Vacuum Paddle Dryer or in a conventional reactor under vacuum above about 720 mm Hg by flash evaporation techniques by using an agitated thin film dryer ("ATFD"), or evaporated by spray drying.
The process can produce amorphous lesinurad in substantially pure form. The term "substantially pure amorphous form of lesinurad" refers to the amorphous form of lesinurad having purity greater than about 98%, specifically greater than about 99%, more specifically greater than about 99.5% and still more specifically greater than about 99.9% (measured by HPLC).
The amorphous lesinurad obtained by the process disclosed herein is consistently reproducible and has good flow properties, and which is particularly suitable for bulk preparation and handling.
Alternately amorphous form of lesinurad can be prepared by using solvent-antisolvent method.
The amorphous lesinurad obtained by the above process is characterized by X-ray diffraction pattern as depicted in Figure 14.
In another embodiment, the invention provides pharmaceutical compositions comprising an effective amount of any one of the Form L1, L2, L3 and L4 of lesinurad or mixture thereof.
Pharmaceutical formulations novel polymorphs of lesinurad according to the present invention comprises of one or more pharmaceutically acceptable carriers or excipients such as diluents, binders, stabilizers, glidants, disintegrants, surfactants, lubricants or combinations thereof and optionally other therapeutic agents. Pharmaceutical formulations containing the active ingredient may be in any form suitable for the intended method of administration. When used for oral use for example, tablets, troches, lozenges, aqueous or oil suspensions, dispersible powders or granules, emulsions, hard or soft capsules, syrups or elixirs may be prepared.
The diluents, binders, stabilizers, lubricants, glidants, disintegrating agents, surfactants, and other additives that are commonly used in solid pharmaceutical dosage form preparations includes
Diluents:
Various useful fillers or diluents include but are not limited to starches, lactose, mannitol (PearlitolTM SD200), cellulose derivatives, confectioner's sugar and the like. Different grades of lactose include but are not limited to lactose monohydrate, lactose DT (direct tableting), lactose anhydrous, FlowlacTM, PharmatoseTM and others. Different starches include but are not limited to maize starch, potato starch, rice starch, wheat starch, pregelatinized starch and starch 1500, starch 1500 LM grade (low moisture content grade) from Colorcon, fully pregelatinized starch and others. Different cellulose compounds that can be used include crystalline celluloses and powdered celluloses. Examples of crystalline cellulose products include but are not limited to CEOLUSTM KG801, AvicelTM PH101, PH102, PH301, PH302 and PH-F20, PH112 microcrystalline cellulose 114, and microcrystalline cellulose 112. Other useful diluents include but are not limited to carmellose, sugar alcohols such as mannitol (PearlitolTM SD200), sorbitol and xylitol, calcium carbonate, magnesium carbonate, dibasic calcium phosphate, and tribasic calcium phosphate.
Binders:
Various useful binders include but are not limited to hydroxypropylcelluloses, also called HPC (KlucelTM LF, Klucel EXF) and useful in various grades, hydroxypropyl methylcelluloses, also called hypromelloses or HPMC (MethocelTM) and useful in various grades, polyvinylpyrrolidones or povidones (such as grades PVP-K25, PVP-K29, PVP-K30, and PVP-K90), PlasdoneTM S-630 (copovidone), powdered acacia, gelatin, guar gum, carbomers (CarbopolTM), methylcelluloses, polymethacrylates, and starches.
Disintegrants:
Various useful disintegrants include but are not limited to carmellose calcium, carboxymethylstarch sodium, croscarmellose sodium, crospovidones, examples of commercially available crospovidone products including but not limited to crosslinked povidone, KollidonTM CL, PolyplasdoneTM XL, XI-10, and INF-10 and low-substituted hydroxypropylcelluloses. Examples of low-substituted hydroxypropylcelluloses include but are not limited to low-substituted hydroxypropylcellulose LH11, LH21, LH31, LH22, LH32, LH20, LH30, LH32 and LH33. Other useful disintegrants include sodium starch glycolate, colloidal silicon dioxide, and starches.
Stabilizers:
Various useful stabilizers include basic inorganic salts, such as but not limited to basic inorganic salts of sodium, potassium, magnesium and calcium. Examples of basic inorganic salts of sodium are sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, and the like. Examples of basic inorganic salts of potassium are potassium carbonate, potassium hydrogen carbonate, potassium hydroxide, and the like. Examples of basic inorganic salts of magnesium are heavy magnesium carbonate, magnesium carbonate, magnesium oxide, magnesium hydroxide, magnesium metasilicate aluminate, magnesium silicate, magnesium aluminate, synthetic hydrotalcite [Mg6Al2(OH)16.CO3.4H2O], aluminum hydroxide-magnesium [2.5MgO.Al2O3.xH2O], and the like. Examples of basic inorganic salts of calcium include precipitated calcium carbonate, calcium hydroxide, and the like.
Surface-Active Agents:
Useful surface-active agents include non-ionic, cationic and anionic surface-active agents. Useful non-ionic surface-active agents include ethylene glycol stearates, propylene glycol stearates, diethylene glycol stearates, glycerol stearates, sorbitan esters (SPANTM) and polyhydroxyethylenically treated sorbitan esters (TWEENTM), aliphatic alcohols and PEG ethers, phenol and PEG ethers. Useful cationic surface-active agents include quaternary ammonium salts (e.g. cetyltrimethylammonium bromide) and amine salts (e.g. octadecylamine hydrochloride). Useful anionic surface-active agents include sodium stearate, potassium stearate, ammonium stearate, and calcium stearate, triethenolamine stearate, sodium lauryl sulphate, sodium dioctylsulphosuccinate, and sodium dodecylbenzenesulphonate. Natural surface-active agents may also be used, such as for example phospholipids, e.g. diacylphosphatidyl glycerols, diaceylphosphatidyl cholines, and diaceylphosphatidic acids, the precursors and derivatives thereof, such as for example soybean lecithin and egg yolk.
Lubricants:
An effective amount of any pharmaceutically acceptable tableting lubricant can be added to assist with compressing tablets. Useful tablet lubricants include magnesium stearate, glyceryl monostearates, palmitic acid, talc, carnauba wax, calcium stearate sodium, sodium or magnesium lauryl sulfate, calcium soaps, zinc stearate, polyoxyethylene monostearates, calcium silicate, silicon dioxide, hydrogenated vegetable oils and fats, stearic acid and combinations thereof.
Glidants:
One or more glidant materials, which improve the flow of powder blends and minimize dosage form weight variations can be used. Useful glidants include but are not limited to silicone dioxide, talc and combinations thereof.
Coloring Agents:
Coloring agents can be used to color code the compositions, for example, to indicate the type and dosage of the therapeutic agent therein. Suitable coloring agents include, without limitation, natural and/or artificial compounds such as FD&C coloring agents, natural juice concentrates, pigments such as titanium oxide, silicon dioxide, iron oxides, zinc oxide, combinations thereof, and the like.
Useful additives for coatings include but are not limited to plasticizers, antiadherents, opacifiers, solvents, and optionally colorants, lubricants, pigments, antifoam agents, and polishing agents.

Various useful plasticizers include but are not limited to substances such as castor oil, diacetylated monoglycerides, dibutyl sebacate, diethyl phthalate, glycerin, polyethylene glycol, propylene glycol, triacetin, and triethyl citrate. Also, mixtures of plasticizers may be utilized. The type of plasticizer depends upon the type of coating agent. An opacifier like titianium dioxide may also be present, typically in an amount ranging from about 10% to about 20% based on the total weight of the coating.
The present invention will now be further illustrated by reference to the following examples, which do not limit the scope of the invention any way.

Examples:
Single Crystal XRD Method for Analysis of crystalline lesinurad form L3 and L4:
Data were collected on a Rigaku Mercury 375/M CCD (XtaLAB mini) diffractometer using graphite monochromated Mo K_radiation at 296 K. The data were processed with CrystalClear software (Rigaku, 2009). Structure solution and refinements were executed using SHELX97 (Sheldrick, 2008) and the WinGX (Farrugia, 1999) suite of programs. All non-hydrogen atoms were refined with the full-matrix least-squares method. The hydrogen atoms were located from fourier maps or using a riding model.

Example 1:
Preparation of Crystalline Form L1 of Lesinurad
5.0 g of Lesinurad was dissolved in methanol (28.0 ml, 5.6v) at 45-50°C, followed by concentration of reaction mixture to 22.0 ml. The solid obtained was filtered and dried at 45°C for 15-16 h to give 3.4 g of desired product.

Example 2:
Preparation of Crystalline Form L2 of Lesinurad
6.6 g of Lesinurad was dissolved in methanol (20 ml, 11v) at 45-50°C, followed by distillation of reaction mixture over a period of 30-40 minutes. The solid obtained was dried to give 6.5 g of desired product.

Example 3:
Preparation of Crystalline Form L3 of Lesinurad
3.0 g of Lesinurad was dissolved in methanol (29 ml, 6.7v) at 45-50°C, followed by cooling slowly in steps between 25 to 10°C. The solid obtained was filtered and dried under vacuum to give 2.5 g of desired product.

Example 4:
Preparation of Crystalline Form L4 of Lesinurad
3.6 g of Lesinurad was dissolved in methanol (66 ml, 9.7v) at 45-50°C, followed by cooling slowly in steps between 25 to 5°C. The solid obtained was filtered and dried under vacuum to give 3.5 g of desired product.

Example 5:
Preparation of Amorphous Form of Lesinurad
2.1 g of Lesinurad was dissolved in distilled water (42 ml) and added trimethylamine (0.8 ml) in cooling. After addition reaction mixture was heated at 40-50°C, followed by cooling and filtration. Methane sulphonic acid was added slowly to the filtrate to obtain slurry, followed by filtration. The solid obtained was dried under vacuum to give 1.8 g of desired product.

Example 6:
Preparation of Amorphous Form of Lesinurad
Cyclohexane (20 ml) comprising lesinurad (1 g) was heated at 600C and added 2-propanol (12 ml) dropwise. Heating of reaction mixture at 700C was continued for another 20 mins followed by hot filtration. Filtrate was cooled to room temperature, stirred for 1 h followed by distillation. The solid obtained was dried under vacuum to give 0.7 g of desired product.
,CLAIMS:1) A process for preparation of crystalline Form L2 characterized by powder x-ray diffraction pattern peaks expressed in terms of 2? values 8.17, 8.76, 15.07, 17.60, 19.93, and 25.89 ± 0.2 degrees of lesinurad comprising steps of:
i) dissolving lesinurad in methanol;
ii) partially removing methanol from reaction mixture thereof; and
iii) isolating crystalline Form L2 of lesinurad.
2) A process for preparation of crystalline Form L3 characterized by powder x-ray diffraction pattern peaks expressed in terms of 2? values 7.72, 9.66, 11.49, 16.97, 19.91, 21.06, 24.27 and 26.81 ± 0.2 degrees of lesinurad comprising steps of:
i) dissolving lesinurad in methanol;
ii) cooling the solution; and
iii) isolating crystalline Form L3 of lesinurad.
3) The process according to claim 2, wherein the cooling temperature of step (ii) is between 10-200C.
4) A process for preparation of crystalline Form L4 characterized by powder x-ray diffraction pattern peaks expressed in terms of 2? values 7.76, 8.14, 14.27, 19.68, 21.89, 25.34 and 28.76 ± 0.2 degrees of lesinurad comprising steps of:
i) dissolving lesinurad in ethanol;
ii) cooling the solution; and
iii) isolating crystalline Form L4 of lesinurad.
5) The process according to claim 4, wherein the cooling temperature of step (ii) is between 0-100C.
6) A process for preparation of pure amorphous form of lesinurad comprising steps of:
a) dissolving lesinurad in a solvent;
b) adding base to the step (a);
c) heating the reaction mixture of step (b);
d) adding acid to the step (c); and
e) isolating amorphous form of lesinurad.
7) The process according to claim 6, wherein the base is added to adjust pH in range of 9-10 in step (b).
8) The process according to claim 6, the step (c) is carried out at 40-500C.
9) The process according to claim 6, wherein the acid is added to adjust the pH in range of 2-3 in step (d).
10) The process according to claim 1, 2, 4 and 6, the isolation step is carried out by one of the techniques selected from filtration, concentration, evaporation, ATFD, spray drying, lyophilisation or freeze- drying.