Chemical compounds

A compound of formula (I):

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is a ‘C-linked’ 5- or 6-membered heteroaryl comprising one or two nitrogen atoms, wherein said heteroaryl is optionally substituted on a ring carbon atom by F or CI;
• or
• R1 is a ‘C-linked’ 5-membered heteroaryl comprising one or two nitrogen atoms and one sulphur atom, wherein said heteroaryl is optionally substituted on a ring carbon atom by F or CI;
• R2, R3 and R4 are independently H, F, CI or —OCH3;
• R5 is CN, F, CI or R6;
• Ra is phenyl optionally substituted by one to three substituents that are independently F, CI, CN, H2N(C1-C4)alkylene-, (C1-C4)alkylNH(C1-C4)alkylene-, (C3-C8)cycloalkyl or R6;
• or
• Ra is a ‘C-linked’ 5- or 6-membered heteroaryl comprising one or two nitrogen atoms, wherein said heteroaryl is optionally substituted by R7 or R8, or both R7 and R8;
• Rb is H, F, CI, CN or R6;
• R6 is (C1-C4)alkyl or (C1-C4)alkyloxy, each optionally substituted by one to eight F;
• Z1 is phenyl optionally substituted by one to three substituents that are independently F, CI or R6;
• or
• Z1 is a ‘C-linked’ 5- or 6-membered heteroaryl comprising one or two nitrogen atoms, wherein said heteroaryl is optionally substituted by R7 or R8, or both R7 and R8;
• R7 is attached to a Z1 ring carbon and is F, CI, NR9R10, R6, (C3-C8)cycloalkyl or Het';
• R8 is attached to a Z1 ring nitrogen and is (C1-C4)alkyl or (C3-C8)cycloalkyl, each optionally substituted by, one to three F;
• or
• R8 is attached to a Z1 ring nitrogen and is a ‘C-linked’ Het1;
• Het1 ‘is a 3- to 8-membered saturated monoheterocycloalkyl comprising one or two ring members selected from —N(R11)— and —O—, wherein said monoheterocycloalkyl is optionally substituted on a ring carbon atom by one to three substituents that are independently F, (C1-C6)alkyl, (C1-C4)alkyloxy(Co-C4)alkylene or (C3-C8)cycloalky;
• and .
• R9, R10 and R11 are independently H, (C1-C6)alkyl or (C3-C8)cycloalkyl;
• or, when Het1 is ‘N-linked’, R11 is absent from that nitrogen atom.