A compound which is an isoxazolyl imidazopyridine of formula (I): wherein: R0 and R, which are the same or different, are each H or C alkyl; R9′ and R9″, which are the same or different, are each H or F; X is -(alk)n-, -alk-C(═O)—NR—, -alk-NR—C(═O)— or -alk-C(═O)—; R1 is selected from —S(═O)2R′ and a 4- to 7-membered heterocyclic group which is unsubstituted or substituted; R2 and R2′, which are the same or different, are each H or C1-6 alkyl; or R2 and R2′ form, together with the C atom to which they are attached, a C3-6 cycloalkyl group; R3 and R3′, which are the same or different, are each H, C1-6 alkyl, OH or F; R4 is phenyl or a 5- to 12-membered N-containing heteroaryl group and is unsubstituted or substituted; alk is C1-6 alkylene; R′ is C1-6 alkyl; and n is 0 or 1; or a pharmaceutically acceptable salt thereof. The compound has activity in modulating the activity of p300 and/or CBP and is used to treat cancer.