The invention provides compounds of the formula (3):






or a pharmaceutically acceptable salt or tautomer thereof, wherein:
Z is a 5-membered heteroaryl ring containing one or two nitrogen ring members and optionally one further heteroatom ring member selected from N and O;
ring X is a benzene or pyridine ring;
ring Y is a benzene, pyridine, thiophene or furan ring;
Ar1 is an optionally substituted benzene, pyridine, thiophene or furan ring;
m is 0, 1 or 2;
n is 0, 1 or 2;
R1 is selected from various substituents:
R2 is selected from hydrogen and a C1-4 hydrocarbon group;
R3 is selected from hydrogen and a C1-4 hydrocarbon group;
R4 is selected from various substituents;
R5 is selected from various substituents;
Ar2 is an optionally substituted phenyl, pyridyl or pyridone group;
R6 is a group Q1-Ra—Rb;
Q1 is absent or is a C1-3 saturated hydrocarbon linker;
Ra is selected from O; C(O); C(O)O; CONRc; N(Rc)CO; N(Rc)CONRc, NRc; and SO2NRc;
Rb is selected from hydrogen and various substituents;
and Rb is selected from R4.




The compounds are useful in the treatment of cancers.