Abstract: The invention provides a compound of the formula (I) for use in the prophylaxis or treatment of a disease state or condition mediated by a cyclin dependent kinase: wherein A is a group R2 or CH2—R2 where R2 is a carbocyclic or heterocyclic group having from 3 to 12 ring members; B is a bond or an acyclic linker group having a linking chain length of up to 3 atoms selected from C, N, S and O; R1 is hydrogen or a group selected from SO2Rb, SO2NR7R8, CONR7R8, NR7R9 and carbocyclic and heterocyclic groups having from 3 to 7 ring members; R3, R4, R5 and R6 are the same or different and are each selected from hydrogen, halogen, hydroxy, trifluoromethyl, cyano, nitro, carboxy, amino, carbocyclic and heterocyclic groups having from 3 to 12 ring members; a group Ra—Rb wherein Ra is a bond, O, CO, X1C(X2), C(X2)X1, X1C(X2)X1, S, SO, SO2, NRc, SO2NRc or NRcSO2; and Rb is selected from hydrogen, carbocyclic and heterocyclic groups having from 3 to 12 ring members, and a C1-8 hydrocarbyl group optionally substitu