There are disclosed compound of Formula (1): A1, A2, A3 and A4 which may be the same or different, represent N or CR1, X is a divalent group selected from O, S(O)n, C=W, NR4, NC(=O)R5 and CR6R7, W is O, S, NR20, Y is N or CR8, one of R4, R5, R6, R8, R9 and NR20 represents -L-R3, in which L is a single bond or a linker group, additionally, R1, R3-R9, which may be the same or different, independently represent hydrogen or a substituent and R20 represents hydrogen, hydroxyl, alkyl optionally substituted by aryl, alkoxy optionally substituted by aryl, aryl, CN, optionally substituted alkoxy, optionally substituted aryloxy, optionally substitute alkanoyl, optionally substituted aroyl, NO2, NR30R31, in which R30 and R31, which may be the same or different, represent hydrogen, optionally substituted alkyl or optionally substituted aryl； additionally, one of R30 and R31 may represent optionally substituted alkanoyl or optionally substituted aroyl, n represents an integer from 0 to 2, in addition, when an adjacent pair of A1-A4 each represent CR1, then the adjacent carbon atoms, together with their substituents may form a ring B, when X is CR6R7, R6 and R7, together with the carbon atom to which they are attached may form a ring C, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the therapeutic and/or prophylactic treatment of Duchenne muscular dystrophy, Becker muscular dystrophy or cachexia.
