The invention is directed to physiologically active compounds of general formula (I): R1Z1—Het—L1—Ar1—L2—Y  (I) wherein Het is an optionally substituted, saturated, partially saturated or fully unsaturated 8 to 10 membered bicyclic ring containing at least one heteroatom selected from O, S or N; R1 is optionally substituted aryl, heteroaryl, alkyl, alkenyl, alkynyl, cycloalkyl or heterocycloalkyl; Z1 represents a direct bond, an alkylene chain, NR4, O or S(O)n; L1 is an a —R5—R6— linkage where R5 is alkylene, alkenylene or alkynylene and R6 is a direct bond, cycloalkylene, heterocycloalkylene, arylene, heteroaryldiyl, —C(═Z3)—NR4—, —NR4—C(═Z3)—, —Z3—, —C(═O)—, —C(═NOR4)—, —NR4—, —NR4—C(═Z3)—NR4—, —SO2—NR4—, —NR4—SO2—, —O—C(═O)—, —C(═O)—O—, —NR4—C(═O)—O— or —O—C(═O)—NR4—; L2 is a direct bond; an optionally substituted alkylene, alkenylene, alkynylene, cycloalkenylene, cycloalkylene, heteroaryldiyl, heterocycloalkylene or arylene linkage; a —[C(═O)—N(R9)—C(R4)(R10)]p— linkage; a —Z4—R11— linkage; a —C(═O)—CH2—C(═O)— linkage; a —R11—Z4—R11— linkage; or a —L3—L4—L5— linkage; and Y is carboxy or an acid bioisostere; and the corresponding N-oxides, and their prodrugs; and pharmaceutically acceptable salts and solvates (e.g. hydrates) of such compounds and their N-oxides and prodrugs. Such compounds have valuable pharmaceutical properties, in particular the ability to regulate the interaction of VCAM-1 and fibronectin with the integrin VLA-4 (&agr;4&bgr;1).