Quality assurance program for cyclosporin G (OG37-325).

Abstract

Cyclosporine-G (CsG) (OG37-325) an analogue of cyclosporine-A (CsA) is presently undergoing clinical trials. As therapeutic monitoring of CsG was an integral part of these evaluations, the performance of laboratories measuring the drug was assessed through an external quality assurance program, which included all North American centers participating in the trials. The assays used by participating centers were high-performance liquid chromatography (HPLC) (n = 3), radioimmunoassay (RIA) (n = 5), and fluorescence polarization immunoassay (FPIA) (n = 24). The latter two assays, developed for measurement of CsA, were adapted for measurement of CsG. The FPIA was the most precise, with the largest proportion of laboratories reporting coefficients of variation (CNs) of < 10%. RIA was the least accurate method, with approximately 74% of results differing by > 20% from target values. FPIA and RIA methods exhibited mean recoveries of CsG of 112 and 129%, respectively. The ranking of the specificity of the assays from measurement of parent drug was HPLC > RIA > FPIA. FPIA and RIA produced values that were, on average, approximately 60% higher than those reported by HPLC in pooled whole blood specimens obtained from renal transplant patients. It is recommended that if CsG is approved for routine clinical use, then assays developed specifically for measurement of the drug be used.