Simultaneous online SPE-HPLC-MS/MS quantification of gefitinib, osimertinib and icotinib in dried plasma spots: Application to therapeutic drug monitoring in patients with non-small cell lung cancer.

Gefitinib, osimertinib and icotinib are the most commonly used tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC) with EGFR mutation. Therapeutic drug monitoring (TDM) for these TKIs has become a standard and essential procedure. Dried plasma spots (DPS) was choosen for microsampling strategies for TDM, allowing easy and cost-effective logistics in many settings. This study developd and validated an assay for the simultaneous quantitative determination of gefitinib, osimertinib and icotinib in DPS by online solid-phase extraction-liquid chromatography-tandem mass spectrometry (online SPE-LC-MS) system. The TKIs were extracted from DPS with methanol and enriched on a Welch Polar-RP SPE column (30 × 4.6 mm, 5 µm), followed by separation on Waters X Bridge C18 analytical column(4.6 × 100 mm, 3.5 µm). The method achieved LLOQ of 2 ng mL-1 for gefitinib and osimertinib (4 ng mL-1 for icotinib), respectively (r2 > 0.99). Precision (within-run 1.54-7.41 % RSD; between-run 3.03-12.84 % RSD), accuracy (range from 81.47 % to 105.08 %; between-run bias 87.87-104.13 %). Osimertinib and icotinib were stable in DPS stored at - 40 °C for 30 days, 4 °C, 42 °C and 60 °C for 5 days and well-sealed 37 °C,75 % humidity (except gefitinib). Lastly, the assay was applied to TDM of TKIs in 46 patients and the results were compared to SALLE assisted LC-MS analysis, it could be confirmed that the developed method achieves similarly good results as the already established one and no bias could be detected. It implies that this method capable of supporting clinical follow-up TDM of TKIs in DPS from poor medical environment.