P17.21.A DETERMINATION OF TOTAL AND UNBOUND LEVELS OF A POTENT WEE1 INHIBITOR, ZN-C3, IN HUMAN PLASMA, CSF, AND BRAIN TUMOR BY A VALIDATED LC-MS/MS METHOD.

Abstract BACKGROUND ZN-c3 is a potent and orally bioavailable inhibitor of Wee1, which has promising brain penetration profile and can potentially benefit patients with brain tumor. Herein, an LC-MS/MS method for determination of total and unbound levels of ZN-c3 in human plasma, cerebrospinal fluid (CSF) and glioblastoma tissue is reported. MATERIAL AND METHODS ZN-c3 was extracted from human plasma, CSF and glioblastoma homogenate samples by protein precipitation with methanol. Unbound fractions of ZN-c3 in plasma and brain tissues were determined by equilibrium dialysis. Validation was performed using Sciex ExionLC UHPLC coupled with QTRAP 6500+ MS/MS detector employing positive electrospray ionization mode. The method was validated according to FDA guidelines and CAP/CLIA regulations. RESULTS The method was validated for 0.5-10,000 nmol/L concentration range using plasma as a matrix for all biospecimens. The chromatographic separation was performed on Phenomenex Kinetex™ F5 column with total run time of 2.9 min. Maximum coefficient of variation for intra- and inter-day precision was 9.8% and the accuracy was within 88-114.5% in all matrixes. The analyte is stable in plasma and brain homogenate for at least 4 hours at room temperature (RT) and at least 19 days at -20°C. Stability of stock and working solutions was demonstrated for at least 23.5 hours (RT) and 51 days (4°C). The fraction unbound of ZN-c3 in human plasma and brain were determined to be 0.261 and 0.227, respectively. CONCLUSION A sensitive and rapid bioanalytical method is developed and validated to quantify total and unbound ZN-c3 levels in human plasma, CSF and glioblastoma tissue. This method has been applied to assess the brain penetration profile of ZN-c3 in preclinical animal models and will be employed in an upcoming clinical trial investigating ZN-c3 in glioblastoma patients.