The invention relates to 7H-pyrrolo[2,3-d]pyrimidine derivatives of formula (I), wherein the symbols and substituents are as defined in the description, to processes for the preparation thereof, to pharmaceutical compositions comprising such derivatives and to the use of such derivatives - alone or in combination with one or more other pharmaceutically active compounds - for the preparation of pharmaceutical compositions for the treatment especially of a proliferative disease, such as a tumour.