The invention relates to thienopyrimidinediones of formula (1) wherein R.sup.1 and R.sup.2 each independently represent a C.sub.1-6alkyl, C.sub.3-6alkyl, C.sub.3-6alkenyl, C.sub.3-5cycloalkylC.sub.1-3alkyl or C.sub.3-6cycloalkyl; each of which may be optionally substituted by 1 to 3 halogen atoms R.sup.3 is a group CO-G or SO.sub.2-G where G is a 5- or 6-membered ring containing a nitrogen atom and a second heteroatom selected from oxygen and sulphur adjacent to the nitrogen; the ring being substituted by at least one group as defined in the specification, Q is CR.sup.4R.sup.5 where R.sup.4 is hydrogen, fluorine or C.sub.1-6 alkyl and R.sup.5 is hydrogen, fluorine or hydroxy; and Ar is a 5-10-membered aromatic ring system wherein up to 4 ring atoms may be heteroatoms independently selected from nitrogen, oxygen and sulphur, the ring system being optionally substituted by one or more groups defined in the specification; as well as pharmaccutically acceptable salts and solvates thereof. Processes for their preparation of the compounds, pharmaceutical compositions containing them and their use in therapy, in particular in immunosuppressive therapy are also described ##STR00001##