A compound of the formula : or a salt thereof, wherein q is 1; r is 1 or 2; s is 0 or 1, where the total of r and s is 1 or 2; Q is NR 5 R 6 ; R 3 is hydrogen; R 4 is hydrogen or a C 1-6 non-aromatic hydrocarbon group which is optionally substituted with one to six fluorine atoms; R 5 is selected from hydroxy; OR 7 ; COR 7 ; COOR 7 ; CH 2 COR 7 ; CH 2 COOR 7 ; a C 1-6 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 oxidized forms thereof; and a group W or CH 2 W where W is 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; R 6 is selected from hydroxy; OR 7 ; COR 7 ; COOR 7 ; CH 2 COR 7 ; CH 2 COOR 7 ; a C 1-6 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 oxidized forms thereof; and a group W or CH 2 W where W is 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; and R 7 is selected from hydrogen a C 1-6 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 oxidized forms thereof; and a group W or CH 2 W where W is 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; and the dotted line is absent indicating a single bond. q is 1; r is 1 or 2; s is 0 or 1, where the total of r and s is 1 or 2; Q is NR 5 R 6 ; R 3 is hydrogen; R 4 is hydrogen or a C 1-6 non-aromatic hydrocarbon group which is optionally substituted with one to six fluorine atoms; R 5 is selected from hydroxy; OR 7 ; COR 7 ; COOR 7 ; CH 2 COR 7 ; CH 2 COOR 7 ; a C 1-6 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 oxidized forms thereof; and a group W or CH 2 W where W is 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; R 6 is selected from hydroxy; OR 7 ; COR 7 ; COOR 7 ; CH 2 COR 7 ; CH 2 COOR 7 ; a C 1-6 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 oxidized forms thereof; and a group W or CH 2 W where W is 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; and R 7 is selected from hydrogen a C 1-6 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 oxidized forms thereof; and a group W or CH 2 W where W is 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; and the dotted line is absent indicating a single bond. <EOS>