The stability of the test compounds (1 µM) was measured following incubation at 37 °C with hepatic microsomes (0.5 mg protein/mL for all species) in the presence of the cofactor, NADPH. Incubates were prepared in duplicate, with aliquots removed at 0, 5, 10, 20 and 40 minutes and reactions terminated and compound extracted by the addition of acetonitrile containing an analytical internal standard. The disappearance of parent compound was monitored by LC-MS/MS and the half-life determined over the time-course of incubation. The half-life values were used to calculate their in vitro intrinsic clearance expressed as µL/min/mg protein.