Abstract: The imidazo[1,2-b]pyridazine compounds of the formula: ##STR1## wherein R.sub.1 is a hydrogen or halogen atom, or a lower alkyl group optionally having substituent(s), R.sub.2 and R.sub.3 are, independently, a hydrogen atom, a lower alkyl group optionally having substituent(s), a cycloalkyl group or a phenyl group optionally having substituent(s) or R.sub.2 and R.sub.3 together with the adjacent nitrogen atom to which they bond may form a heterocyclic ring optionally having substituent(s), X is an oxygen atom or S(O).sub.n (n=0 to 2), Alk is a straight or branched chain alkylene group containing 1-10 carbon atoms and optionally having substituent(s), or their pharmaceutically acceptable salts which possess antiallergic, anti-inflammatory and anti-PAF activities, and their production and use.

Abstract: The imidazo[1,2-b]pyridazine compounds of the formula: ##STR1## wherein R.sub.1 is a hydrogen or halogen atom, or a lower alkyl group optionally having substituent(s), R.sub.2 an R.sub.3 are, independently, a hydrogen atom, a lower alkyl group optionally having substituent(s), a cycloalkyl group or a phenyl group optionally having substituent(s) or R.sub.2 and R.sub.3 together with the adjacent nitrogen atom to which they bond may form a heterocyclic ring optionally having substituent(s), X is an oxygen atom or S(O)n (n=0 to 2), Alk is a straight or branched chain alkylene group containing 1-10 carbon atoms and optionally having substituent(s), or their pharmaceutically acceptable salts which possess antiallergic, anti-inflammatory and anti-PAF activities, and their production and use.