Imidazopyridazines, their production and use

Claim 1

An imidazo [1,2-b]pyridazine compound of the formula (I): ##STR15## or a pharmaceutically acceptable salt thereof, wherein: R 1 is halogen or a lower alkyl group optionally substituted with one to four substituents selected from the group consisting of hydroxy, amino, mono-lower alkylamino, lower alkoxy and halogen; R 2 and R 3 are independently selected from the group consisting of hydrogen; a lower alkyl group optionally substituted with one to four substituents selected from the group consisting of hydroxy, amino, mono-lower alkylamino, lower alkoxy and halogen; a cycloalkyl group; and a phenyl group optionally substituted with one to five substituents selected from the group consisting of amino, mono-lower alkylamino, di-lower alkylamino, lower alkoxy and halogen; or R 2 and R 3 together with the adjacent nitrogen atom to which they are bonded form a four to seven membered heterocyclic ring having carbon atoms, at least one nitrogen atom and optionally oxygen or sulfur atoms as constituent atoms of the heterocyclic ring, said heterocyclic ring being unsubstituted or substituted with one to five substituents selected from the group consisting of hydroxy, amino, mono-lower alkylamino, di-lower alkylamino, lower alkoxy and halogen; X is an oxygen atom or S(O) k wherein k is 0 to 2; group --○-- is a bivalent three to seven membered carbocyclic or heterocyclic group, said heterocyclic group having carbon atoms and at least one oxygen, sulfur or nitrogen atoms as constituent atoms of the ring, wherein said carbocyclic or heterocyclic group is unsubstituted or substituted with one to five substituents selected from the group consisting of a lower alkyl group optionally substituted with one to four substituents selected from the group consisting of hydroxy, an amino group, mono-lower alkylamino, lower alkoxy and halogen; an amino group; a mono-C 1-4 alkylamino group; a di-C 1-4 alkylamino group; a five- to seven-membered cyclic amino group having carbon atoms and at least one nitrogen atom as constituent ring atoms; an amido group; a C 1-4 acylamido group; hydroxy; a lower alkoxy group; and halogen; m 1 and m 2 are independently an integer of 0 to 4; and n is 0 or 1.