Provided is a
combination therapy for an antitumor agent that exhibits a high antitumor effect using a pyridone
carboxylic acid derivative. An antitumor agent characterized by being administered in combination with other antitumor agents, and comprising, as an
active ingredient, a compound represented by the formula (1) (in the formula, the wavy line represents the steric configuration being the R configuration or the S configuration) or a salt thereof, wherein the other antitumor agents are one or more types selected from
cytarabine,
venetoclax,
azacitidine, gilteritinib, birabresib,
vorinostat, GSK126, MK-8776, AZD7762, rabusertib, dabrafenib, vemurafenib,
olaparib, adavosertib, alisertib,
decitabine, midostaurin, and AZD5991.