The present invention relates to novel 2,6-disubstituted-9-cyclopentyl-9H-purines of general formula I, capable of inhibiting the activity of kinases such as FLT3, CDKs and PDGFRs in cancer and other related proliferative diseases. The invention further includes pharmaceutical compositions containing the 2,6-disubstituted-9-cyclopentyl-9H-purines. Compounds of the present invention can be used as active ingredients of a pharmaceutical compositions for treating acute myeloid leukemia (AML).