A compound of the formula (I): a pharmaceutically acceptable salt or solvate thereof, where R1 is optionally substituted lower alkyl, Y is —S(O)2—, R2 is hydrogen or optionally substituted lower alkyl, R7 is hydrogen or optionally substituted lower alkyl, X is a group of the formula: where R5 and R6 are each independently hydrogen, a group of the formula: is optionally substituted cycloalkylene, p is 0, and q is 1 or 2, Z is optionally substituted carbocyclyl or optionally substituted heterocyclyl, and provided that a compound wherein Z is fused heterocyclyl consisting of three rings or optionally substituted pyrimidinyl is excluded.