The crystalline Polymorph B of N-(2-aminophenyl)-4-[N-(pyridine-3-yl)methoxy-carbonyaminomethyl]benzamide (MS-275) of formula Iis described, as well as the process for the production of said compound, and its use as a medicament for the treatment of selected diseases.本發明係關於一種式I之N-(2-胺基苯基)-4-[N-(吡啶-3-基)-甲氧羰基-胺基甲基]-苯甲醯胺(MS-275)之多晶形B及製備該化合物之方法,及其作為治療特定疾病的醫藥品之用途。