Analysis of Busulfan in Plasma for Clinical Research

Significance of the Topic

Busulfan is a bifunctional alkylating agent widely used in preparative regimens for hematopoietic stem cell transplantation. Its pharmacokinetics vary greatly among patients due to factors such as age, disease state and co-medications. A sensitive and selective analytical method for plasma busulfan measurement is essential for clinical research into dose optimization and therapeutic monitoring.

Objectives and Study Overview

This study presents the development and validation of a rapid UPLC-MS/MS assay to quantify busulfan in human plasma. Key aims included achieving high analytical selectivity, a broad dynamic range, minimal sample volume and simplified preparation to support clinical research workflows.

Methodology

• Sample Preparation: 50 μL plasma, protein precipitation with methanol containing busulfan-2H8 internal standard, vortex mixing, centrifugation, and dilution of supernatant prior to analysis.
• Chromatography: ACQUITY UPLC HSS T3 column (1.8 μm, 2.1×50 mm) at 35 °C, flow rate 0.6 mL/min, gradient from 90% aqueous to 98% organic within 1.5 min; total run time 2.5 min.
• Mass Spectrometry: Xevo TQD in ESI+ mode with MRM transitions 264.0→151.1 (quantifier), 264.0→55.0 (qualifier) for busulfan; 272.0→159.1 for internal standard; optimized cone voltage and collision energy.
• Calibration and QC: Linear range 0.025–5 μg/mL; QC levels at 0.05, 0.75, 1.5 and 3.5 μg/mL in pooled plasma matrix.

Instrumentation

• Waters ACQUITY UPLC I-Class System with Flow Through Needle sampler
• ACQUITY UPLC HSS T3 Column
• Xevo TQD triple quadrupole mass spectrometer
• MassLynx v4.1 and TargetLynx Application Manager

Main Results and Discussion

• High chromatographic selectivity separated busulfan from phospholipid interferences within 2.5 min.
• Limit of quantification 0.020 μg/mL with bias <15% and precision RSD <20%.
• Interday precision (n=25) RSD ≤7.3%; repeatability RSD ≤5.1% across QC levels.
• Excellent linearity from 0.0175 to 6.51 μg/mL.
• Minimal matrix effects (matrix factor 0.92–1.12), fully compensated by internal standard (0.95–1.02).
• Recovery in presence of endogenous and exogenous interferents ranged 85–106%; co-medications showed 93–103% recovery.
• Strong correlation with an independent LC-MS/MS method (Deming fit slope 1.01, intercept 0.04).

Benefits and Practical Applications

• Only 50 μL plasma required, reducing patient burden.
• Fast, cost-effective sample preparation supports high throughput.
• Wide dynamic range accommodates clinical concentration variability.
• High sensitivity and selectivity enable robust pharmacokinetic studies.

Future Trends and Potential Applications

Advances may include integration with automated sample handling, microflow UPLC setups, high-resolution mass spectrometry and real-time therapeutic drug monitoring. Multi-analyte panels and platform miniaturization could further enhance clinical research capabilities.

Conclusion

A rapid, sensitive and selective UPLC-MS/MS method for busulfan in plasma was established. With excellent precision, accuracy, linearity and agreement to an independent method, it is well suited for clinical pharmacokinetic and pharmacodynamic research.

References

1. Savic RM, Cowan MJ, Dvorak CC, Sung-Yun Pai MD, Pereira L, Bartelink IH, Boelens JJ, Bredius RGM, Wynn RF, Cuvelier GDE, Shaw PJ, Slatter MA, Long-Boyle JR. Effect of Weight and Maturation on Busulfan Clearance in Infants and Small Children Undergoing Hematopoietic Cell Transplantation. Biol Blood Marrow Transplant. 2013;19(11).