A compound of formula I, wherein: R 1 represents a cyclic group selected from phenyl, heteroaryl 1 and heterocyclyl 1; wherein each cyclic group is optionally substituted with from 1 to 3 substituents selected from halo, C 1-6 alkyl optionally substituted with 1-3 halogen atoms, phenyl, C 1-6 alkoxy optionally substituted with 1-3 halogen atoms, cyano, heteroaryl 1a and heterocyclyl 1a; 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 heterocyclyl 1 and heterocyclyl 1a may additionally be substituted with =O; X represents a bond or CH 2; R 2 represents H; R 3 represents H or CH 2 CH 3; Y represents a bond or C 1-2 alkylene; R 4 is selected from methoxyphenyl, chlorophenyl, pyridinyl, 2,3-dihydro-1H-indenyl, dichlorophenyl, 2,6-difluoro-3methyl phenyl, naphthyl and benzopyrrolidinyl Heteroaryl 1 and heteroaryl 1a represent a 5- or 6-membered heteroaryl group containing from 1 to 3 heteroatoms (selected from N, O and S); and heterocyclyl 1 and heterocyclyl 1a 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. R 1 represents a cyclic group selected from phenyl, heteroaryl 1 and heterocyclyl 1; wherein each cyclic group is optionally substituted with from 1 to 3 substituents selected from halo, C 1-6 alkyl optionally substituted with 1-3 halogen atoms, phenyl, C 1-6 alkoxy optionally substituted with 1-3 halogen atoms, cyano, heteroaryl 1a and heterocyclyl 1a; 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 heterocyclyl 1 and heterocyclyl 1a may additionally be substituted with =O; wherein each cyclic group is optionally substituted with from 1 to 3 substituents selected from halo, C 1-6 alkyl optionally substituted with 1-3 halogen atoms, phenyl, C 1-6 alkoxy optionally substituted with 1-3 halogen atoms, cyano, heteroaryl 1a and heterocyclyl 1a; 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 heterocyclyl 1 and heterocyclyl 1a may additionally be substituted with =O; X represents a bond or CH 2; R 2 represents H; R 3 represents H or CH 2 CH 3; Y represents a bond or C 1-2 alkylene; R 4 is selected from methoxyphenyl, chlorophenyl, pyridinyl, 2,3-dihydro-1H-indenyl, dichlorophenyl, 2,6-difluoro-3methyl phenyl, naphthyl and benzopyrrolidinyl Heteroaryl 1 and heteroaryl 1a represent a 5- or 6-membered heteroaryl group containing from 1 to 3 heteroatoms (selected from N, O and S); and heterocyclyl 1 and heterocyclyl 1a 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.