Radioimmunoassay of bleomycin

A radioimmunoassay for bleomycin has been produced using 125l-labeled bleomycin and antisera raised in rabbits against a carbodiimide-catalyzed bleomycin-bovine serum albumin conjugate. 125l-Labeled bleomycin was synthesized by direct iodination of the drug using the chloramine-T technique. The standard curve of the assay was linear on a logit-log plot and the lower limit of sensitivity was 250 pg bleomycin sulfate. A mean recovery of 102.6% (+/- 3.3% S.E.) was obtained using bleomycin added to normal sera. No significant decrease in bleomycin immunoreactivity was observed following 24 hr incubation of the drug in serum at 37 degrees. The radioimmunoassay was also suitable for measuring bleomycin in the presence of other drugs since the assay was not significantly affected by the other antineoplastic agents tested. The sensitivity and specificity of the radioimmunoassay for bleomycin should provide a new means for pharmacokinetic and toxicity studies of bleomycin.