The present invention relates to a compound represented by the formula: ##STR00001## wherein W is C(R.sup.1) or N, each A is an optionally substituted aryl group or a heteroaryl group, X.sup.1 is --NR.sup.3--Y.sup.1--, --O--, --S--, --SO--, --SO.sub.2-- or --CHR.sup.3-- wherein R.sup.3 is a hydrogen atom or an optionally substituted aliphatic hydrocarbon group, or R.sup.3 is optionally bonded to A to form an optionally substituted ring structure, R.sup.1 is a hydrogen atom or an optionally substituted group bonded via a carbon atom, a nitrogen atom or an oxygen atom, R.sup.2 is a hydrogen atom or optionally substituted group bonded via a carbon atom or a sulfur atom, or R.sup.1 and R.sup.2, or R.sup.2 and R.sup.3 are optionally bonded to form an optionally substituted ring structure, or a salt thereof, and a tyrosine kinase inhibitor or an agent for the prophylaxis or treatment of cancer, which contains this compound or a prodrug thereof.