The present invention relates to compounds of formula (I): wherein R1 is NH2 or NHMe R2 is halo and one of R3 or R4 is hydrogen and the other is selected from &mdashSO2NH2, &mdashSO2NHMe or &mdashSO2NMe2, &mdashSO2NHEt, or &mdashSO2NEt2 or a pharmaceutically acceptable salt or solvate thereof. The compounds of formula (I) are inhibitors of protein kinases, especially cyclic dependent kinases (CDKs) such as CDK9. The present invention also relates to processes for the preparation of these compounds, to pharmaceutical compositions comprising them, and to their use in the treatment of proliferative disorders, such as cancer, as well as other diseases or conditions in which protein kinase/CDK activity is implicated.
