HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ASSAY FOR CI-980, A NOVEL 1-DEAZA-7,8-DIHYDROPTERIDINE ANTICANCER AGENT, IN HUMAN PLASMA AND URINE

CI-980, a 1-deaza-7,8-dihydropteridine, is a novel anticancer agent th at is a potent mitotic inhibitor acting as a tubulin binder similar to the vinca alkaloids. CI-980 has shown equivalent or superior anticanc er activity in vitro compared to vincristine and retains full activity against vincristine resistant tumors in vitro. A high-performance liq uid chromatographic (HPLC) assay was developed and validated for human plasma and urine to support Phase 1 clinical trials. CI-980 and PD 08 0658, internal standard, were isolated from 2-ml samples of human plas ma and urine by solid-phase extraction with Bond-Elut C-18 cartridges. Urine samples must be pretreated with bovine serum albumin (BSA) to m inimize the binding of CI-980 to glass and some plastics. The eluate f rom the cartridges for both matrices was evaporated to dryness and tak en up in mobile phase. Zorbax RX C-18 columns, mobile phase buffer of 10 mM ammonium dihydrogen phosphate at pH 7.5 and a flow-rate of 0.75 ml/min were used for both matrices. Column dimensions, column temperat ure and mobile phase acetonitrile-buffer ratio were 300 mm x 4.6 mm I. D., 30 degrees C and 38:62 (v/v), respectively, for the plasma assay a nd 250 mm x 4.6 mm I.D., 35 degrees C and 40:60 (v/v), respectively, f or the urine assay. Column effluent was monitored fluorometrically for the plasma method using excitation and emission wavelengths of 388 nm and 473 nm, respectively. Ultraviolet detection at 380 nm was used fo r the urine method. Peak-area ratios were proportional to CI-980 conce ntrations from 0.2 to 25 ng/ml and 1 to 100 ng/ml for plasma and urine , respectively. CI-980 in water will bind to glass and plastics but no t PTFE or stainless steel. Urine calibration standards were frozen pri or to use in order to compensate for loss of CI-980 due to freezing in this matrix. The accuracy of the assay was within 4.7%, with a precis ion of 5.6% for both matrices. Recoveries ranged from 93.8 to 102% and 90.7 to 92.3% for plasma and urine, respectively. CI-980 was stable i n plasma and urine for at least 275 and 217 days, respectively, when s tored at -70 degrees C. The assay is suitable for studying the clinica l pharmacokinetics of CI-980.