It is an object of the present invention to provide an antitumor agent, which is further excellent as a treatment agent used in the prevention and/or therapy of tumor associated with a bromodomain, and also to provide a bromodomain inhibitor, which is useful as a treatment agent for diseases or states associated with a bromodomain.An antitumor agent and a bromodomain inhibitor, comprising a compound represented by the following formula, have an excellent bromodomain inhibitory activity and are useful as treatment agents in the prevention and/or therapy of tumor associated with a bromodomain, and the like:wherein R1 represents a C1-6 alkyl group, etc.； R2 represents a hydrogen atom, etc.； R3 represents a halogen atom, etc.； Z1, Z2 and Z3 each represent CH, etc.； X1 represents CONH, etc.； Ring A represents a phenyl group, etc.； R4 represents a halogen atom, etc.； and m represents an integer from 0 to 5.
