Fluorinated quinazolinones as potential radiotracers for imaging kinesin spindle protein expression

Abstract

Anti-mitotic anti-cancer drugs offer a potential platform for developing new radiotracers for imaging proliferation markers associated with the mitosis-phase of the cell-cycle. One interesting target is kinesin spindle protein (KSP)—an ATP-dependent motor protein that plays a vital role in bipolar spindle formation. In this work we synthesised a range of new fluorinated-quinazolinone compounds based on the structure of the clinical candidate KSP inhibitor, ispinesib, and investigated their properties in vitro as potential anti-mitotic agents targeting KSP expression. Anti-proliferation (MTT and BrdU) assays combined with additional studies including fluorescence-assisted cell sorting (FACS) analysis of cell-cycle arrest confirmed the mechanism and potency of these biphenyl compounds in a range of human cancer cell lines. Additional studies using confocal fluorescence microscopy showed that these compounds induce M-phase arrest via monoaster spindle formation. Structural studies revealed that compound 20-(R) is the most potent fluorinated-quinazolinone inhibitor of KSP and represents a suitable lead candidate for further studies on designing 18F-radiolabelled agents for positron-emission tomography (PET).