The invention discloses a compound selected from the group N*2*,N*4*-Bis-(2-methyl-1H-indol-5-yl)-pyrimidine-2,4-diamine, N*2*-(4-Diethylamino-1-methyl-butyl)-5-methyl-N*4*-(2-methyl-1H-indol-5-yl)-pyrimidine-2,4-diamine, N*2*,N*4*-Bis-(1H-indol-5-yl)-pyrimidine-2,4-diamine and N*2*-(1H-Indol-6-yl)-N*4*-(1H-indol-5-ylmethyl)-pyrimidine-2,4-diamine, preferably N*2*,N*4*-Bis-(2-methyl-1H-indol-5-yl)-pyrimidine-2,4-diamine,and any of its stereoisomeric forms or a mixture thereofor a salt or solvate of a compound of these compounds, especially for use in the treatment of malignant diseases.