Phenylalanine derivatives of formula (1) are described:
in which:
Ar1 is an aromatic or heteroaromatic group;
L1 is a linker atom or group;
R is a carboxylic acid or a derivative thereof;
Ar2 is an optionally substituted aromatic or heteroaromatic group;
and the salts, solvates, hydrates and N-oxides thereof.
The compounds are able to inhibit the binding of &agr;4 integrins to their ligands and are of use in the prophylaxis and treatment of immune or inflammatory disorders.