Environmentally Friendly LC-MS/MS Method for the Determination of Etrasimod in Human Plasma via Advanced Phospholipid Matrix Removal

Background/Objectives: Etrasimod is a novel, oral, selective sphingosine-1-phosphate (S1P) receptor modulator approved for the treatment of ulcerative colitis. Due to its high lipophilicity and strong plasma protein binding, quantification of etrasimod in human plasma is significantly challenged by co-extracted proteins and phospholipids that induce column degradation and severe mass spectrometry matrix effects. This study presents the first eco-friendly LC–MS/MS assay for etrasimod in human plasma utilizing advanced phospholipid removal technology, combining protein precipitation and targeted phospholipid depletion into a single step. It achieved matrix purification while reducing sample processing time and solvent volumes. Methods: Chromatographic separation was achieved on a C18 column using a gradient elution of 0.1% formic acid in water and acetonitrile. Detection was performed on a triple quadrupole mass spectrometer in positive electrospray ionization (ESI) mode using multiple reaction monitoring (MRM) transitions at m/z 458 → 159 for etrasimod and m/z 405 → 146 for ozanimod (internal standard). Results: The method was fully validated according to ICH M10 guidelines, demonstrating excellent linearity, accuracy, precision, and robustness. Comprehensive sustainability assessment using AGREE (0.55), AGREEprep (0.58), ComplexMoGAPI (78), and BAGI (52.5) confirmed an eco-friendly profile and high operational practicality. Conclusions: The proposed method provides a reliable and green tool suitable for analysis of etrasimod in human plasma.