IMMUNOMETRIC ASSAY OF BN-52080, A HEPTAPEPTIDE C-TERMINAL ANALOG OF SORBIN

A novel type of enzyme immunometric assay has been developed for a hep tapeptide, BN 52080. This compound is a short C-terminal analogue of s orbin and is under clinical evaluation for treatment of chronic diarrh ea. In this solid-phase immobilized epitope immunoassay (SPIE-IA), the peptide is first immunologically bound to polyclonal antibodies adsor bed to a solid phase and then, after covalent immobilization with glut araldehyde, is released from the antibody paratope by NaOH. The peptid e linked to the solid phase is further quantified with a tracer consis ting of the same antibodies purified by affinity chromatography and co upled to acetylcholinesterase. This assay has a detection limit of 10 pg/ml and is therefore five times more sensitive than competitive enzy me immunoassay using the same antibodies and BN 52080 coupled to acety lcholinesterase as tracer. The assay is specific and allows direct mea surement of peptide in human plasma after subcutaneous or intravenous administration of 200 mu g of BN 52080 to volunteers.