A COMPOUND OF FORMULA (I) OR A PHARMACEUTICALLY ACCEPTABLE SALT THEREOF: IN WHICH: X IS HALOGEN, CYANO, NITRO, OR C₁-₄ALKYL WHICH IS SUBSTITUTED BY ONE OR MORE HALOGEN ATOMS； Y IS SELECTED FROM HYDROGEN, HALOGEN, OR C₁-₆ALKYL； Z IS PHENYL, NAPHTHYL OR A RING A, WHERE A IS A SIX MEMBERED HETEROCYCLIC AROMATIC RING CONTAINING ONE OR TWO NITROGEN ATOMS OR MAY BE A 6,6 OR 6,5 FUSED BICYCLE CONTAINING ONE O, N OR S ATOMS OR MAY BE A 6,5-FUSED BICYCLE CONTAINING TWO O ATOMS, THE PHENYL, NAPHTHYL OR A RINGS ALL BEING OPTIONALLY SUBSTITUTED BY ONE OR MORE SUBSTITUENTS INDEPENDENTLY SELECTED FROM HALOGEN, CN, OH, NITRO, COR⁹, CO₂R⁶, S0₂R⁹, OR⁹, SR⁹, S0₂NR¹º0R¹¹, CONR¹ºR¹¹, NR¹º-R¹¹, NHSO₂R⁹, NR⁹SO₂R⁹, NR⁶CO₂R⁶, NR⁹COR⁹, NR⁶CONR⁴R⁵, NR⁶SO₂NR⁴R⁵, PHENYL, OR C₁-₆ALKYL, THE LATTER GROUP BEING OPTIONALLY SUBSTITUTED BY ONE OR MORE SUBSTITUENTS INDEPENDENTLY SELECTED FROM HALOGEN； R¹ AND R² INDEPENDENTLY REPRESENT A HYDROGEN ATOM, OR A C₁-₆ALKYL GROUP R⁴ AND R⁵ INDEPENDENTLY REPRESENT HYDROGEN, C₃-C₇ CYCLOALKYL OR C₁-₆ALKYL； R⁶ INDEPENDENTLY REPRESENTS A HYDROGEN ATOM OR C₁-C₆ALKYL； R⁸ IS C₁-₄ ALKYL； R⁹ REPRESENTS C₁-₆ALKYL, OPTIONALLY SUBSTITUTED BY ONE OR MORE SUBSTITUENTS INDEPENDENTLY SELECTED FROM HALOGEN OR PHENYL； R¹º AND R¹¹ INDEPENDENTLY REPRESENT PHENYL, A 5 MEMBERED AROMATIC RING CONTAINING TWO HETEROATOMS SELECTED FROM N OR S, HYDROGEN, C₃-C₇ CYCLOALKYL OR C₁-₆ALKYL, THE LATTER TWO GROUPS BEING OPTIONALLY SUBSTITUTED BY ONE OR MORE SUBSTITUENTS INDEPENDENTLY SELECTED FROM HALOGEN OR PHENYL ； OR R¹° AND R¹¹ TOGETHER WITH THE NITROGEN ATOM TO WHICH THEY ARE ATTACHED CAN FORM A 3-8 MEMBERED SATURATED HETEROCYLIC RING OPTIONALLY CONTAINING ONE OR MORE ATOMS SELECTED FROM O, S(O)n (WHERE n = 0, 1 OR 2), NR⁸； PROVIDED THAT THE COMPOUND IS NOT [(5-CYANOBIPHENYL-2-YL)OXY]ACETIC ACID； [(5-NITROLBIPHENYL-2-YL)OXY]ACETIC ACID； [(2',4',5'-TRICHLORO)-4,5-(DICHLORO)-[1,1'-BIPHENYL]-2-YL]OXY]ACETIC ACID；[(3,5- DICHLORO[1,1'–BIPHENYL]-2-YL)OXY]-ACETIC ACID； [(5-CHLOROBIPHENYL-2-YL)OXY
