A radioimmunoassay procedure for tallysomycin S10b in human plasma and urine

A simple and sensitive radioimmunoassay (RIA) procedure was developed and validated for the analysis of tallysomycin S10b in human plasma and urine. The assay utilized antisera developed in rabbits, 125I-tallysomycin as the radioligand, and dextran-coated charcoal to separate free and bound antigen. The antibody was specific in that it did not cross-react with either tallysomycin A or bleomycin. The lower limit of quantification was 5 ng per ml plasma or urine, and the linear range of the assay was 5-320 ng tallysomycin S10b base per ml plasma or urine. The within-day assay variability (%RSD) for plasma and urine was 11% at a concentration of 50 ng per ml, and 3% and 7% for plasma and urine, respectively at 200 ng per ml. Within-day accuracy ranged from 100% to 108% of the theoretical value. Tallysomycin S10b was stable in human plasma and urine at concentrations of 20 and 160 ng per ml for at least 7 months when stored at -20 degrees C. The method was applied to the analysis of plasma and urine samples from a patient given tallysomycin S10b as part of a phase I study.