Direct Quantitation of D-serine in Human Plasma by Enantioselective Liquid Chromatography with Tandem Mass Spectrometry and its Application to a Clinical Study

Estela Skende1, Lei Shi1, Nancy Zheng2, Yu-Luan Chen1,*

1Sunovion Pharmaceuticals Inc., Marlborough, MA 01752, USA. 2PPD Bioanalytical Laboratory, Middleton, WI 53562, USA.

OBJECTIVES: Develop and validate a simple and rapid LC-MS/MS method for plasma D-serine measurement to support clinical development of a potential D-amino-acid oxidase (DAAO) inhibitor.
METHODS: Calibration standards in phosphate buffered saline (PBS), quality control samples (QCs) in both PBS and human plasma were extracted with methanol. Enantioselective separation of D- and L-serine was on a Regis® ChiroSil RCA(+) column with monitoring underivatized D-serine at m/z 106.1→ 60.1 and (D, L)-serine-d3 internal standard at 109.0 → 63.0.
RESULTS: The validation showed all calibration curves with a correlation coefficient of ≥ 0.9997, and plasma QC samples’ inter-run (n = 18) CV of ≤ 8.7% and REs from -7.0% to -6.1%. The plasma samples were stable for 6 freeze-thaw cycles, 36.5 h ambient storage, and 769 days at -20°C or lower.
CONCLUSIONS: The validated method was successfully applied to analyze plasma D-serine level in a Phase I clinical trial and the D-serine level was insignificantly impacted by the studied compound.
KEYWORDS: D-serine, human plasma, endogenous biomarker, enantioselective separation.

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