Compounds of formula (I) are described in which Het is a five or six membered heteroaromatic ring of the formula ##STR00001## in which one of R.sup.1 and R.sup.2 is optionally substituted heteroaryl and the other is optionally substituted heteroaryl or optionally substituted aryl; X.sup.1 is a bond, X.sup.3 and X.sup.4 are each independently N or C and X.sup.2 and X.sup.5 are independently CH, N, NH, O or S; or X.sup.3 and X.sup.4 are C, one of X.sup.1, X.sup.2 and X.sup.5 is N and the others are N or CH; but excluding compounds in which X.sup.1 is a bond, one of X.sup.2 and X.sup.5 is N and the other is NH and X.sup.3 and X.sup.4 are both C; R.sup.3 represents a group -L.sup.1-R.sup.6; R.sup.4 represents hydrogen, alkyl or hydroxyalkyl; or R.sup.3 and R.sup.4, when attached to the same carbon atom, may form with the said carbon atom a cycloalkyl, cycloalkenyl or heterocycloalkyl ring or a group C.dbd.CH.sub.2; R.sup.5 represents hydrogen or alkyl; and m is zero or an integer 1 or 2; and N-oxides thereof, and their prodrugs; and pharmaceutically acceptable salts and solvates of compounds of formula (I) and N-oxides thereof, and their prodrugs.The compounds are TNF inhibitors and are useful as pharmaceuticals. ##STR00002##