Phenylalanine enamide derivatives of formula (1) are described: ##STR00001## wherein R.sup.1 is a group Ar.sup.1L.sup.2Ar.sup.2Alk- in which: Ar.sup.1 is an optionally substituted aromatic or heteroaromatic group; L.sup.2 is a covalent bond or a linker atom or group; Ar.sup.2 is an optionally substituted arylene or heteroarylene group; and Alk is a chain --CH.sub.2--CH(R)--, --CH.dbd.C(R)-- or ##STR00002## in which R is a carboxylic acid (--CO.sub.2H) or a derivative or biostere thereof; X is an --O-- or --S-- atom or --N(R.sup.2)-- group in which: R.sup.x, R.sup.y and R.sup.z which may be the same or different is each a hydrogen atom or an optional substituent; or R.sup.z is an atom or group as previously defined and R.sup.x and R.sup.y are joined together to form an optionally substituted spiro linked cycloaliphatic or heterocycloaliphatic group; and the salts, solvates, hydrates and N-oxides thereof.The compounds are able to inhibit the binding of integrins to their ligands and are of use in the prophylaxis and treatment of immuno or inflammatory disorders or disorders involving the inappropriate growth or migration of cells.