The invention provides a compound for use in the prophylaxis or treatment of a disease state or condition mediated by a cyclin dependent kinase, the compound having the formula (I): (I) and salts, tautomers, N-oxides or solvates thereof; wherein A is a bond, C=O, NR g (C=O) or O(C=O) wherein R g is hydrogen or C 1-4 hydrocarbyl optionally substituted by hydroxy or C 1-4 alkoxy; Y is a bond or an alkylene chain of 1, 2 or 3 carbon atoms in length; Q is S or CR 2 ; J is S or CH; provided that one of Q and J is S, and the other of Q and J is not S; when Q is S, there is a double bond between the ring carbon atoms “a” and “b” and a double bond between the ring nitrogen N and J; and when J is S, there is a double bond between Q and the ring carbon atom “a” and a double bond between the ring nitrogen N and the ring carbon atom “b”; and R 1 to R 4 are as defined in the claims.