Intravenously administered chemotherapy drug Bendamustine is readily hydrolyzed in vivo to mainly inactive metabolites, and partly to cytotoxic M3. Because Bendamustine is also unstable in aqueous solution, different dosing formulations have been tested to reduce this instability.
Some of these excipients remain in the extracts following protein precipitation of the plasma samples and caused severe ionization suppression when using HILIC chromatography coupled with positive mode electrospray ionization. Labeled internal standards (ISTDs), Bendamustine-D11 and M3-D8, didn’t sufficiently track the target analytes during this suppression.
To enable accurate quantitation and reduce ionization suppression, a supported liquid extraction was developed to remove the excipients. The LC-MS/MS method was successfully validated, and used to support the pharmacokinetic portion of numerous clinical trials with various dosing formulations.