Development of an immunoassay for BMS-191352, a single-chain immunotoxin, and its application to toxicokinetic studies.

BMS-191352 is a single-chain fusion protein composed of the variable regions of chimeric BR96 monoclonal antibody and the binding defective form of Pseudomonas Exotoxin A (PE40). The immunotoxin exhibits potent cytotoxicity against tumor cells expressing the Lewis antigen. A sensitive and specific double antibody sandwich ELISA has been developed and validated for the determination of BMS-191352 in rat and dog EDTA plasma. A monoclonal anti-PE40 antibody (EXA2-1H8) was used to capture BMS-191352 in plasma samples. The captured BMS-191352 was then detected using a biotinylated monoclonal BR96 antiidiotypic antibody (757-4-1) followed by the addition of streptavidin-horseradish peroxidase conjugate and chromogen 3,3',5,5'-tetramethylbenzidine. The optical density was measured at 450 nm. The standard curve range in rat and dog plasma was 2-32 ng/mL. The RSD for the inter- and intra-assay precision was within 9.2% and the accuracy was greater than 89.0%. The ELISA method was applied to the analysis of BMS-191352 in plasma samples from toxicokinetic studies conducted in rats and dogs. These studies revealed that the systemic exposure of BMS-191352 was dose proportional and the kinetics of BMS-191352 were linear between the dose range of 1.8-7.2 mg/m2 in the dog.