[Bovine serum albumin conjugates of the new progestagen dienogest, synthesis and immunogenic properties].

In order to develop a radioimmunoassay for the new progestagen dienogest (STS 557, 17 alpha-cyanomethyl-17 beta-hydroxy-estra-4,9-dien-3-one), bovine serum albumin (BSA) conjugates of STS 557-3-carboxymethyloxime and of STS 557-11-hemisuccinate were synthesized as antigens for the production of antisera. It was proved that an excess of isobutylchlorocarbonate in the coupling reaction using the "mixed anhydride method" results in an acylation of free NH2-groups in the BSA. By the immunization of rabbits with the STS 557-antigen-antisera of high specificity and affinity to STS 557 were produced. Endogenous steroids show no cross reaction with the STS 557-antisera. Steroids with a 17 alpha-CH2CN-group, being obtained by chemical synthesis or microbial transformation, compete with STS 557 for the binding positions of the antibodies to a different extent.