NEW MATERIAL: Imidazopyridazine derivative of formula I (R1 is carbocyclic aryl having a 6-10 ring member, wherein at least one aromatic ring is contained, heterocyclic aryl having a 5-10 ring member, 1-10C alkyl, 2-10C alkenyl, 3-10C cycloalkyl or 3-10C cycloalkenyl; R2 is R1, 2-10C alkynyl or aryl 1-4C alkyl(aryl portion is as defined above); R3 is H or 1-4C alkyl; X is O, S, CH or NR4(R4 is R3); Y is CH2 or CH2CH2; X and Y together form CH=CH).

EXAMPLE: Methyl N-[6(3,4,5trimethoxybenzyloxy)imidazo[1,2-b]pyridazine2- yl]carbamate.

USE: The compound has cytotoxic activity and is useful especially as an anti- tumor agent.

PROCESS: A compound of formula I is obtained, for example, by allowing pyridazine derivative of formula II to react with the compound of formula III(Z is halogen).