Determination of an echinocandin, MK-0991, in mammalian plasma by radioimmunoassay

A quantitative method based on radioimmunoassay for the determination of th e antifungal agent, CANCIDAS (TM) (MK-0991) has been developed and validate d. The immunogen was prepared by coupling MK-0991 to bovine serum albumin t hrough a two-step reaction with difluorodinitrobenzene. An antiserum specif ic to MK-0991 was selected for RIA. The assay was based on the competitive immunoassay principle in which the drug competes with iodinated drug for a limited quantity of specific antibody. The bound tracer was separated via g oat anti-rabbit globulin. The assay demonstrates good accuracy and reproduc ibility at plasma concentration down to 10 ng/ml. The specificity of the RI A method was confirmed by cross-validating against an established HPLC meth od. (C) 2001 Elsevier Science B.V. All rights reserved.