IMMUMOASSAYS FOR DIDEMNINS

THE OVERALL GOAL OF THIS PROJECT IS TO DEVELOP IMMUNOASSAYS CAPABLE OF DETECTING DIDEMNINS AT THE NANOGRAM LEVEL. DIDEMNIN B IS THE MOST POTENT ANTITUMOR, ANTIVIRAL, AND CYTOTOXIC MEMBER OF A FAMILY OF FIVE CYCLIC DEPSIPEPTIDES ISOLATED FROM MARINE TUNICATES. THIS COMPOUND IS CURRENTLY IN CLINICAL TRIALS AS AN ANTITUMOR AGENT. AVAILABLE BIOASSAY AND HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY METHODS FOR DETECTING DIDEMNINS IN BIOLOGICAL MATRICES LACK THE PRECISION AND SENSITIVITY REQUIRED FOR PHARMACOKINETIC AND DRUG METABOLISM STUDIES. IT IS PLANNED TO SYNTHESIZE WELL-CHARACTERIZED DIDEMNIN A-DERIVED IMMUNOGENS THAT SHOULD ELICIT ANTIBODY RESPONSES. THIS WILL BE ACHIEVED BY COUPLING DIDEMNIN A TO IMMUNOGENIC CARRIERS VIA ITS N-METHYL-D-LEUCINE SIDE CHAIN TO EXPOSE THE MACROCYCLIC EPITOPE COMMON AMONG ALL DIDEMNINS. EARLIER ATTEMPTS FAILED TO DEVELOP A RADIOIMMUNOASSAY, POSSIBLY BECAUSE OF THE STRONG IMMUNOSUPPRESSIVE ACTION OF DIDEMNIN B. HOWEVER, BECAUSE DIDEMNIN A IS LESS POTENT THAN DIDEMNIN B, CAREFUL MANIPULATION OF IMMUNIZATION PARAMETERS SUCH AS CHOICE OF IMMUNOGENIC CARRIER, IMMUNIZINGDOSE, ROUTE OF IMMUNIZATION, ADJUVANT TYPE, AND PRIOR PRIMING WITH IMMUNOGENIC CARRIER IS EXPECTED TO EVOKE HUMORAL IMMUNE RESPONSES. PHASE I EFFORTS WILL FOCUS ON DEMONSTRATING THE FEASIBILITY OF DEVELOPING A GENERIC IMMUNOASSAY FOR ALL DIDEMNINS. PHASE II WILL FOCUS ON REFINING THE GENERIC ASSAY AND WILL DEVELOP SELECTIVE IMMUNOASSAYS FOR DIDEMNINS.