A pharmaceutical composition comprising a compound represented by the formula (I) or pharmaceutically acceptable salt thereof or solvate thereof and a basic substance is excellent in dissolution, is stable even after a long term storage, and is useful as a preventive or therapeutic agent against a tumor: wherein, R1 is a hydrogen atom,a c-1-6 alkyl group or a c3-8 cycloalkyl group and R2 is a hyfrogen atom or a methoxy group.
