Patent ID: 7829705

Claim:
A compound of formula I or salt thereof, where: Het is an optionally substituted pyridazine radical; A is O, S, NH, N(C 1-6 alkyl), CH 2 O, a direct bond or a bivalent heterocyclic radical of the formula: where one or more of the carbon atoms within the radicals (b-1) to (b-4) may be optionally substituted with C 1-6 alkyl or two carbon atoms in the radicals (b-1) to (b-4) may be bridged with a C 2-4 alkylene radical, m and n are each independently integers of 1 to 4 inclusive with the proviso that the sum of m and n in radicals (b-1) to (b-4) is 3, 4 or 5; Z is N or CR 6 where R 6 is hydrogen, hydroxy, C 1-6 alkyl, C 1-6 alkoxy or amino; Z′ is O, S, CHR 7 or NR 8 where R 7 is hydrogen, hydroxy, C 1-6 alkyl, C 1-6 alkoxy or amino and R 8 is hydrogen or C 1-6 alkyl; R 4 is hydrogen or C 1-6 alkyl; R 5 is hydrogen, hydroxy, C 1-6 alkyl or C 1-6 alkoxy; Alk is C 1-7 alkylene or a direct bond; W is O; X 1 , X 2 and X 3 are each independently selected from N and CR where R is hydrogen, halogen, hydroxy, C 1-6 alkyl or C 1-6 alkoxy; and B is a five or six membered unsaturated heterocyclic ring, substituted with at least one substituent selected from R 10 , OR 10 , SR 10 and NR 9 R 10 , where R 9 is hydrogen or C 1-6 alkyl and R 10 is C 1-6 alkyl, haloC 1-6 alkyl, C 1-6 alkenyl, haloC 1-6 alkenyl, C 1-6 alkynyl or haloC 1-6 alkynyl, with the proviso that the ring bearing B is not benzothiazole, benzimidazole, benzoxazole, benzofused isothiazole, benzofused pyrazole or benzofused isooxazole, and with the proviso that when Alk is a direct bond, then A is not O, S, CH 2 O or a direct bond.