The present invention relates to the crystalline mono mesylate monohydrate salt of N-[5 -(aminosulfonyl)-4-methyl-1,3-thiazol-2-yl]-N-methyl-2-[4-(2-pyridinyl)phenyl]acetamide in a definite particle size range, particle size distribution and a specific surface area range, which has demonstrated increased long term stability and release kinetics from pharmaceutical compositions, as well as to pharmaceutical compositions containing said crystalline N-[5-(amino sulfonyl)-4-methyl-1,3-thiazol-2-yl]-N-methyl-2-[4-(2 -pyridinyl)phenyl]acetamide mono mesylate monohydrate having the afore-mentioned particle size range, particle size distribution and specific surface area range. Moreover, the present invention relates to the pharmacokinetic and pharmacodynamic in vivo profiles of the resultant free base of N-[5-(aminosulfonyl)-4-methyl-1,3-thiazol-2-yl]-N-methyl-2-[4 -(2-pyridinyl)phenyl]-acetamide after administration of the afore-mentioned crystalline N-[5-(aminosulfonyl)-4-methyl-1,3-thiazol-2-yl]-N-methyl-2-[4-(2-pyridinyl)phenyl]-acetamide mono mesylate monohydrate salt to a subject in need thereof.