A Simple and Rapid LC-MS/MS Method for TherapeuticDrug Monitoring of Lenalidomide

Immunomodulatory drugs lenalidomide (LENA) andpomalidomide (POMA) are syntheticcompounds derived by modifying the chemical structure of thalidomide to improve its potencyand reduce its side effects.LENA is used as a treatment for myeloma and blood disorders calledmyelodysplastic syndromes.The maximum clinical dose ofLENAfor some haematologicalcancers is generally≤25mg.Therapeutic drug monitoring (TDM) is important for theindividualization of drug dosage.A highly sensitive and high performance liquid chromatographytandem mass spectrometry(HPLC–MS/MS) assay was developed and validated for thequantification of LENA in human plasma. LENA was extracted from human plasma by liquid-liquid extraction by ethyl acetate and analysed using a reversed phase isocratic elution on aPoroshell 120 EC-C18, (4.6-50 mm, 2.7μm) column.A.0.1% formic acid: methanol (10:90%v/v), was used as mobile phase and detection was performed by triple quadrupole massspectrometry LC-MS/MS using jet stream electrospray ionization in negative mode. POMA wasused as the internal standard (IS). Analyte and IS were detected by tandem mass spectrometryusingmultiple reaction monitoring (MRM)of precursor–product ion transitions with 0.100 s dwelltime, at m/z 258.0 > 213.0 for LENA and m/z 272.0 > 161.0 for POMA. The calibration curveswere consistently accurate and precise over the concentration range of 20 to 1000 ng/mL inplasma for LENA. This novel LC–MS/MS method competes with all the regulatory requirementsand shows satisfactory accuracy and precision. It is sufficiently sensitive for the performance ofpharmacokinetic, bioequivalence and TDM studies in humans.