Compounds of formula (I) are inhibitors of CD80 and useful in immunomodulation therapy:wherein R1 and R3 independently represent H； F； Cl； Br； —NO2； —CN； C1-C6 alkyl optionally substituted by F or Cl； or C1-C6 alkoxy optionally substituted by F； R4 represents a carboxylic acid group (—COOH) or an ester thereof, or —C(═O)NR6R7, —NR7C(═O)R6, —NR7C(═O)OR6, —NHC(═O)NR7R6 or —NHC(═S)NR7R6 wherein R6 represents H, or a radical of formula -(Alk)m-Q wherein m is 0 or 1, Alk is an optionally substituted divalent straight or branched C1-C12 alkylene, or C2-C12 alkenylene, or C2-C12 alkynylene radical or a divalent C3-C12 carbocyclic radical, any of which radicals may contain one or more —O—, —S— or —N(R8)— links wherein R8 represents H or C1-C4 alkyl, C3-C4 alkenyl, C3-C4 alkynyl, or C3-C6 cycloalkyl, and Q represents H； —NR9R10 wherein R9 and R10 independently represents H； C1-C4 alkyl； C3-C4 alkenyl； C3-C4 alkynyl； C3-C6 cycloalkyl； an ester group； an optionally substituted carbocyclic or heterocyclic group； or R9 and R10 form a ring when taken together with the nitrogen to which they are attached, which ring is optionally substituted； and R7 represents H or C1-C6 alkyl； or when taken together with the atom or atoms to which they are attached R6 and R7 form an optionally substituted monocyclic heterocyclic ring having 5, 6 or 7 ring atoms； and X represents a bond or a divalent radical of formula —(Z)n-(Alk)- or -(Alk)-(Z)n— wherein Z represents —O—, —S— or —NH—, Alk is as defined in relation to R6 and n is 0 or 1.
