Enzyme-Linked Immunosorbent Assay for LY163502, a Potent Dopamine Agonist

A rapid and sensitive enzyme-linked immunosorbent assay (ELISA) for the potent selective dopaminergic receptor (D2) agonist, LY163502, is described. The ELISA is a competitive assay in which peroxidase-labeled LY163502 competes with unlabeled LY163502 for binding to solid-phase antibodies specific for LY163502. The limit of detection is 8pg/mL; intra- and interassay coefficients of variation are 7.2 and 12.3%, respectively, for human plasma determinations. Recovery of LY163502 from plasma and urine is quantitative. We found two potential metabolites of LY163502, despropyl-LY163502 and N-oxide LY163502, to be 44 and 0.5% cross-reactive at the ED50 level, respectively. However, LY163502 levels measured by the ELISA and by a specific gas-liquid chromatography (GLC) assay are highly correlated [Pearson's correlation coefficient, r=0.964]. This suggests that the ELISA assay of biological fluids is not affected by cross-reactivity due to LY163502 metabolites. Application of the ELISA to the measurement of LY163502 in biological fluids is demonstrated.