Pharmaceutical composition for treating flt3 mutation-positive cancer, flt3 mutant inhibitor, and use of said pharmaceutical composition and said inhibitor

The present invention addresses the problem of providing: a pharmaceutical composition for treating FLT3 mutation-positive cancer; an FLT3 mutant inhibitor; and a use of the pharmaceutical composition and the inhibitor. Provided are: a pharmaceutical composition for treating FLT3 mutation-positive cancer, which contains, as an active ingredient, a compound represented by general formula [1] or a salt thereof; an FLT3 mutant inhibitor; an anti-cancer agent; a method for predicting the therapeutic effect of the administration of a pharmaceutical composition containing a compound represented by general formula [1] or a salt thereof in a subject, said method comprising a step of detecting the presence or absence of an FLT3 mutation; a method for selecting a subject to whom a pharmaceutical composition containing a compound represented by general formula [1] or a salt thereof can be applied, said method comprising a step of detecting the presence or absence of an FLT3 mutation; and a method for determining whether or not a pharmaceutical composition containing a compound represented by general formula [1] or a salt thereof can be administered to a subject, said method comprising a step of detecting the presence or absence of an FLT3 mutation.