A compound of formula (I) ##STR00001## where one of A.sup.1, A.sup.2 or A.sup.3 is N, and the others are independently selected from CH or N; ring B is a fused 5 or 6-membered carbocyclic or heterocyclic ring which is optionally substituted as defined in the specification, and R.sup.1, R.sup.2, R.sup.3, R.sup.4, and n are as defined in the specification.The compounds are inhibitors of EphB4 or EphA2 and therefore may be useful in pharmaceutical compositions for the treatment of conditions such as cancer.