PROCESS FOR THE PREPARATION OF BELUMOSUDIL MESYLATE AND ITS CRYSTALLINE FORM

1 . A process for the preparation of belumosudil, a compound of formula I, or a pharmaceutically acceptable salt thereof,

comprising the steps of:

a) reacting chloroacetyl chloride with isopropyl amine to obtain 2-chloro-N-(propan-2-yl)acetamide, a compound of formula II (the “compound II”);

b) reacting the compound II with an alkyl ester of 3-hydroxy benzoate (the “compound III”) in the presence of a base to obtain alkyl ester of 3-[2-(isopropylamino)-2-oxoethoxy]benzoate, a compound of formula IV (the “compound IV”);

wherein Alk refers to alkyl;

c) reacting the compound IV with an acid or a base to obtain 3-[2-(isopropylamino)-2-oxoethoxy]benzoic acid, the compound of formula V (the “compound V”);

d) reacting the compound V with 2-aminobenzamide (the “compound VI”) in the presence of a coupling agent to obtain N-[2-(aminocarbonyl)phenyl]-3-[2-(isopropylamino)-2-oxoethoxy]benzamide, a compound of formula VII (the “compound VII”);

e) reacting the compound VII with a base to obtain N-isopropyl-2-[3-(4-oxo-3,4-dihydroquinazolin-2-yl)phenoxy]acetamide, a compound of formula VIII (the “compound VIII”);

f) reacting the compound VIII with a chlorinating agent to obtain 2-[3-(4-chloroquinazolin-2-yl)phenoxy]-N-isopropylacetamide, a compound of formula IX (the “compound IX”);

g) reacting the compound IX with 5-amino indazole to obtain belumosudil, the compound I; and

h) optionally, converting belumosudil to its pharmaceutically acceptable salt.

2 . The process according to claim 1 , wherein the coupling agent used in the step d) is selected from the group consisting of N-Ethyl-N′-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC·HCl), N,N′-Dicyclohexylcarbodiimide (DCC), 1-Hydroxybenzotriazole (HOBT), 1-[Bis(dimethylamino)methylene]-1H-benzotriazolium 3-oxide tetrafluoroborate (TBTU), (2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU), and (1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU).

3 . The process according to claim 1 , wherein the chlorinating agent is selected from the group consisting of thionyl chloride, phosphorous oxychloride and phosphorous pentachloride.

4 . The process according to claim 1 , wherein in the step h) belumosudil is converted to its methane sulfonate salt.

5 . A one-pot process for the preparation of pharmaceutically acceptable salt of belumosudil, a compound of formula I-A (the “compound I-A”);

wherein HA is an acid selected from the group consisting of trifluoroacetic acid, methane sulfonic acid, hydrochloric acid, hydrobromic acid, oxalic acid, benzenesulfonic acid, p-toluenesulfonic acid, citric acid, tartaric acid, sulphuric acid, maleic acid, and fumaric acid;

comprising the steps of:

i) reacting the compound of formula IX (the “compound IX”) with 5-aminoindazole

to obtain a reaction mixture containing belumosudil free base, the compound I; and

(ii) reacting the reaction mixture containing the belumosudil free base obtained in step (i) with an acid HA to obtain the pharmaceutically acceptable salt of belumosudil, the compound I-A;

wherein belumosudil, the compound I, obtained in step i) is carried forward without isolation for reaction with an acid in step ii).

6 . The process according to claim 5 , wherein the acid HA used in step (ii) is methane sulfonic acid to obtain belumosudil methane sulfonate salt.

7 . A process for the preparation of crystalline belumosudil mesylate, the compound I-A, said process comprising the steps of:

(1-a) treating belumosudil mesylate with a mixture of water and a solvent to obtain a reaction mixture;

(1-b) heating the reaction mixture obtained in step (1-a);

(1-c) cooling the reaction mixture obtained in step (1-b); and

(1-d) isolating crystalline belumosudil mesylate from the reaction mixture of step (1-c); wherein the crystalline belumosudil mesylate is characterised by X-ray powder diffraction (XRPD) spectrum having peak reflections at about 7.1, 17.2, 20.3, 21.5, 22.1, 25.0 and 25.5±0.2° θ.

8 . The process as claimed in claim 7 , wherein the solvent is (C 1 -C 6 ) alcohol selected from the group consisting of methanol, ethanol, n-propanol, t-butanol, n-butanol, and isopropanol.

9 . (canceled)

10 . (canceled)

11 . (canceled)

12 . (canceled)

13 . (canceled)

14 . (canceled)

15 . The process according to claim 7 , wherein belumosudil methane sulfonate is substantially free of impurities represented by the following compounds of formulae XI to XXII;