A compound of formula (I) ##STR00001## wherein R is methyl, ethyl, n-propyl, iso-propyl, n-butyl or allyl; R' is hydrogen, C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.3 alkoxy; halogen, trifluoromethyl or OCH.sub.xF.sub.y, R'' is hydrogen, fluoro or chloro, that R'' being fluoro or chloro only when R' is fluoro or chloro; R.sub.3 is hydrogen or C.sub.1-C.sub.5 alkyl R.sub.4 is hydrogen, CH.sub.2OCOC(CH.sub.3).sub.3, pharmaceutically acceptable inorganic or organic cations, or COR.sub.4' wherein R.sub.4' is C.sub.1-C.sub.5 alkyl, phenyl, benzyl or phenethyl; R.sub.7 is methyl or ethyl; one of A and B is sulphur and the other is C-R.sub.2; when A is S, R.sub.2 is selected from hydrogen and methyl, with the proviso that R.sub.2 is methyl only when R.sub.3 is not hydrogen; and when B is S, R.sub.2 is hydrogen; and any tautomer thereof.A pharmaceutical composition comprising a compound of formula (I), a method of treating malignant tumours or diseases resulting from autoimmunity or pathologic inflammation.
