Accelerated and robust monitoring for immunosuppressants using triple quadrupole mass spectrometry

Significance of the Topic

Immunosuppressive drugs are critical for preventing organ rejection and managing autoimmune disorders. Precise therapeutic drug monitoring is essential to maintain efficacy while avoiding adverse immunodeficiency. Ultra-fast and reliable quantitation in blood supports timely clinical decisions and enhances patient care.

Study Objectives and Overview

This study aimed to develop a rapid and robust LC-MS/MS method for simultaneous quantification of four key immunosuppressants—tacrolimus, rapamycin, everolimus, and cyclosporin A—in human whole blood. Two internal standards (ascomycin and cyclosporin D) were incorporated to ensure accuracy. The approach leveraged ultra-fast triple quadrupole mass spectrometry to achieve high throughput without compromising sensitivity.

Methodology and Instrumentation

A liquid-liquid extraction protocol using methyl tert-butyl ether/cyclohexane isolated analytes from whole blood, followed by evaporation and reconstitution in methanol-ammonium acetate. Chromatographic separation was performed on a Nexera UHPLC system with a YMC-Triart C18 column (30 mm × 2 mm, 1.9 μm) at 65 °C. A gradient from 60 to 95% methanol (both phases containing 1 mmol/L ammonium acetate) and a flow rate of 0.45 mL/min yielded baseline separation in 1.8 minutes with a 1.5 µL injection.

Mass spectrometric detection employed a Shimadzu LCMS-8050 triple quadrupole configured for negative ESI, monitoring deprotonated precursor-product ion transitions for each analyte and internal standard. Key source parameters included a probe voltage of –3 to –4.5 kV, nebulizing gas (3.0 L/min), drying gas (5.0 L/min), heating gas (15.0 L/min), and interface temperature of 400 °C.

Key Results and Discussion

All immunosuppressants were detected as deprotonated molecules, avoiding adduct formation and improving quantitative reliability. Calibration was linear over wide ranges (0.5–1000 ng/mL for tacrolimus and cyclosporin A; 0.5–500 ng/mL for rapamycin; 0.5–100 ng/mL for everolimus). The lower limit of quantitation (LLOQ) for each compound was 0.5 ng/mL. Accuracy ranged from 88 to 110%, while reproducibility at LLOQ (CV) remained below 20%. Total analysis time per sample was 1.8 minutes, supporting high-throughput workflows.

Benefits and Practical Applications

• Rapid quantitation enables increased sample throughput in clinical laboratories.
• High sensitivity and low LLOQs facilitate accurate therapeutic drug monitoring.
• Robust negative-mode ionization minimizes interference from adducts.
• Minimal injection volume reduces solvent consumption and sample requirements.

Future Trends and Applications

Further developments may include expansion to additional immunosuppressants or metabolites, integration with automated on-line sample preparation, and adoption of microflow or capillary LC-MS formats to enhance sensitivity. Advances in high-resolution mass spectrometry and data processing algorithms could enable multiplexed biomarker panels for personalized medicine.

Conclusion

The presented UHPLC–MS/MS protocol demonstrates fast, sensitive, and reliable simultaneous determination of four immunosuppressants in whole blood. The method’s robustness and throughput make it well-suited for routine therapeutic drug monitoring in clinical settings.

References

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