To provide means for treating and preventing a wide variety of cancers and tumors, including cancer in which there is PI3K/Akt pathway activation or p53 deactivation, or tumors for which chemotherapy, radiation therapy, hormone therapy, and other such conventional treatment methods have low effectiveness, different molecularly targeted drugs such as OBP-801 and PI3K inhibitor-preferably LY294002, BKM120, GDC-0941, BEZ235, BYL719, or CH5132799-are used in combination. This makes it possible to simultaneously obtain a plurality of different marked pharmaceutical benefits which are synergistic, not being obtainable through use of a formulation with either of the respective molecularly targeted drugs alone, such as caspase pathway activation, enhanced expression of Bim, increased accumulation of intracellular reactive oxygen species, and suppressed expression of +survivin and XIAP protein, and makes it possible to provide new and clinically effective tumor treatment/prevention strategies in the form of effective therapeutic agents and prophylactic agents capable of application to a wide variety of tumors.
