Pharmaceutical compounds

A compound of the formula (1):

• or a salt thereof, wherein:
• R1 is selected from NR5R6;
• CONR8R9;
• an optionally substituted 5- or 6-membered ring containing 0, 1, 2 or 3 heteroatoms selected from O, N and S and oxidized forms thereof;
• or
• R1 is linked to R2 to form an optionally substituted spirocyclic group;
• R2 is selected from hydrogen;
• fluorine;
• cyano;
• hydroxy;
• amino;
• and a C1-3 non-aromatic hydrocarbon group which is optionally substituted with one to six fluorine atoms and wherein one of the carbon atoms of the hydrocarbon group may optionally be replaced by a heteroatom selected from O, N and S and oxidized forms thereof, or R2 is linked to R1 to form an optionally substituted spirocyclic group;
• R4 is H or a C1-6 non-aromatic hydrocarbon group which is optionally substituted with one to six fluorine atoms and wherein one or two, but not all, carbon atoms of the hydrocarbon group may optionally be replaced by a heteroatom selected from O, N and S and oxidised forms thereof;
• R5 is COR7, a non-aromatic C1-6 hydrocarbon group optionally substituted with one or more fluorine atoms or optionally substituted with a 5- or 6-membered ring containing 0, 1, 2 or 3 heteroatoms selected from O, N and S and oxidized forms thereof, or R5 can be joined together with R6 to form an optionally substituted monocyclic or bicyclic ring containing 0, 1, 2 or 3 heteroatoms selected from O, N and S and oxidized forms thereof,
• R6 is hydrogen, a non-aromatic C1-6 hydrocarbon group optionally substituted with one or more fluorine atoms or optionally substituted with a 5- or 6-membered optionally substituted ring containing 0, 1, 2 or 3 heteroatoms selected from O, N and S and oxidized forms thereof, or R6 can be joined together with R5 or R7 to form an optionally substituted monocyclic or bicyclic ring containing 0, 1, 2 or 3 heteroatoms selected from O, N and S and oxidized forms thereof,
• R7 is a non-aromatic C1-6 hydrocarbon group optionally substituted with one or more fluorine atoms, or R7 can be joined together with R6 to form an optionally substituted monocyclic or bicyclic ring containing 0, 1, 2 or 3 heteroatoms selected from O, N and S and oxidized forms thereof,
• R8 is hydrogen, a non-aromatic C1-6 hydrocarbon group optionally substituted with one or more fluorine atoms, or R8 can be joined together with R9 to form an optionally substituted monocyclic or bicyclic ring containing 0, 1, 2 or 3 heteroatoms selected from O, N and S and oxidized forms thereof, and
• R9 is a non-aromatic C1-6 hydrocarbon group optionally substituted with one or more fluorine atoms, or R9 can be joined together with R8 to form an optionally substituted monocyclic or bicyclic ring containing 0, 1, 2 or 3 heteroatoms selected from O, N and S and oxidized forms thereof.