A COLUMN-SWITCHING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ASSAY FOR A NOVEL CYTOTOXIC THIOXANTHONE DERIVATIVE (WIN-33377) IN MOUSE PLASMA WITH TOXICOKINETIC RESULTS FROM A MOUSE LD(10) STUDY

WIN 33377 (I) is a member of a novel class of cytotoxic antitumor agen ts, 4-aminomethyl thioxanthone derivatives. A simple, rapid and reprod ucible method has been developed for the assay of I in mouse plasma us ing a high-performance liquid chromatographic method utilizing a colum n-switching technique. The method involves direct injection of buffere d plasma to the extraction column for sample clean-up followed by swit ching onto an analytical column for analysis with UV detection at 256 nm. The method has demonstrated accuracy and precision over the range 10-2500 ng/ml using a 100-mu l plasma sample with a minimum quantifiab le level at 10 ng/ml. Stability of mouse plasma samples was demonstrat ed after storage for 4 weeks at -15 to -20 degrees C, as was the abili ty of samples to be accurately quantified after a maximum of three fre eze-thaw cycles. Recovery was greater than 87% for the compound and th e internal standard. The assay was accurate and reproducible with meas ured values lying within the limits of defined acceptance criteria. Th e utility of the method was demonstrated by analyzing plasma samples o btained from mice dosed with I as part of a pre-clinical safety study intended to assist in the design of a pharmacokinetically guided dose escalation strategy.