The invention provides compounds of formula I, wherein: R1 represents a cyclic group selected from phenyl, heteroaryl1, heterocyclyl1 and C3-6 cycloalkyl; wherein each cyclic group is optionally substituted with from 1 to 3 substituents selected from halo, C1-6 alkyl optionally substituted with 1-3 halogen atoms, phenyl, C1-6 alkoxy optionally substituted with 1-3 halogen atoms, cyano, heteroaryl1a and heterocyclyl1a; and wherein each cyclic group is optionally fused to a benzene ring or a 5- or 6-membered heteroaromatic or heterocyclic ring each containing from 1 to 3 heteroatoms (selected from N, O and S); and when the group is substituted the substitution may occur anywhere on the optionally fused ring system as a whole; and wherein heterocyclyl1 and heterocyclyl1a may additionally be substituted with ═O; X represents a bond or C1-6 alkylene (which may be straight or branched); R2 represents H or C1-6 alkyl; R3 represents H or C1-6 alkyl; Y represents a bond or C1-6 alkylene (which may be straight or branched, and optionally substituted with OH or CF3); R4 represents a cyclic group selected from phenyl, heteroaryl4, heterocyclyl4 and C3-6 cycloalkyl; wherein each cyclic group is optionally substituted with from 1 to 3 substituents selected from halo, C1-6 alkyl optionally substituted with 1-3 halogen atoms, phenyl, C1-6 alkyl substituted with phenyl, C1-6 alkoxy optionally substituted with 1-3 halogen atoms, cyano, heteroaryl4a and heterocyclyl4a; and wherein each cyclic group is optionally fused to benzene ring or a 5- or 6-membered heteroaromatic or heterocyclic ring each containing from 1 to 3 heteroatoms (selected from N, O and S); and when the group is substituted the substitution may occur anywhere on the optionally fused ring system as a whole; and wherein heterocyclyl4 and heterocyclyl4a may additionally be substituted with ═O; heteroaryl1, heteroaryl1a, heteroaryl4 and heteroaryl4a independently represent a 5- or 6-membered heteroaryl group containing from 1 to 3 heteroatoms (selected from N, O and S); and heterocyclyl1, heterocyclyl1a, heterocyclyl4 and heterocyclyl4a independently represent a 5- or 6-membered heterocyclyl group containing from 1 to 3 heteroatoms (selected from N, O and S); and pharmaceutically acceptable salts and solvates thereof. The compounds are useful as pharmaceuticals, particularly in the treatment of fibrotic diseases, cancer and pain.