The invention provides compounds of the formula (I): and salts, tautomers, solvates and N-oxides thereof; wherein Q is CH or N; X is N, N+—O− or CR3; Y is N, N+—O− or CR3a; R1 and R2 are independently selected from hydrogen and various substituents as defined in the claims; or R1 and R2 together with the atoms to which they are attached, link to form an optionally substituted carbocyclic or heterocyclic aromatic or non-aromatic ring of 4 to 7 members; R3 is selected from hydrogen and various substituents; and R3a is selected from hydrogen and various substituents as defined in the claims. Also provided are pharmaceutical compositions containing the compounds of formula (I), processes for making the compounds and the medical uses of the compounds. The compounds of formula (I) have activity as inhibitors of CDK kinases and are useful in the treatment of inter alia proliferative diseases such as cancers.