Oxadiazole derivative

A compound of formula (1):

• or a pharmaceutically acceptable salt thereof, wherein
• Q1 is fluorine or chlorine,
• Q2 is hydrogen,
• X, Y, and Z are the same or different and are nitrogen atom or oxygen atom, provided that the ring containing X, Y, and Z is a heteroaryl wherein any two of X, Y, and Z are nitrogen atom and the other is oxygen atom,
• R1 is the following formula (2) or (3):
• R2 and R3 are taken together with the carbon atom to which they are attached to form C3-6 cycloalkyl which may be substituted with 1 to 3 substituents selected independently from the group consisting of halogen, hydroxy, C1-3 alkyl, and C1-3 alkoxy, or C4-6 saturated hetero ring containing one or two heteroatoms selected independently from nitrogen atom and oxygen atom, said saturated hetero ring may be substituted with 1 to 3 substituents selected independently from the group consisting of halogen, hydroxy, C1-3 alkyl, and C1-3 alkoxy.