Determination of MLN0128, an investigational antineoplastic agent, in human plasma by LC-MS/MS

MLN0128, an mTOR kinase inhibitor, is currently undergoing clinical investigation for treatment of a variety of cancers. To support this work, an LC-MS/MS method has been developed for the determination of MLN0128 in human plasma. A structural analog STK040263 was used as the internal standard. Both MLN0128 and the IS were first extracted from plasma using methyl tert-butyl ether; then separated on a Waters XTerra® MS C₁₈ column using a mobile phase consisting of methanol-acetonitrile-10.0 mm ammonium formate (34:6:60, v/v/v) at a flow rate of 0.300 mL min^-1 . Quantitation of MLN0128 was done by positive electrospray ionization tandem mass spectrometry in multiple-reaction-monitoring mode. This method has a total run time of <4 min with the retention times of 1.95 and 2.94 min for the IS and MLN0128, respectively. The method has been validated per the US Food and Drug Administration guidance for bioanalytical method validation. It has a calibration range of 0.100-50.0 ng mL^-1 in human plasma with a correlation coefficient > 0.999. The overall assay accuracy and precision were ≤ ± 4 and ≤8%, respectively. The IS normalized recovery of MLN0128 was 98-100%. The stability studies showed that MLN0128 was stable under all tested conditions. The method developed may be useful for clinical studies of MLN0128.