Sensitive Bioanalysis of Antisense Oligonucleotides of Various Lengths and Modifications

Importance of Topic

Antisense oligonucleotides (ASOs) are critical tools in therapeutic research and demand precise quantitation in biological samples to guide pharmacokinetic and safety assessments. High-sensitivity LC-MS/MS methods enable detection of trace ASO concentrations across diverse chemical modifications.

Study Objectives and Overview

This application brief extends previously established ultra-sensitive workflows to an array of ASOs varying in length (18–33 nucleotides), backbone linkers, and base modifications. Key objectives were to evaluate method linearity, sensitivity limits, and inter-day reproducibility for ASO quantitation in human plasma.

Methods and Instrumentation

• Sample Preparation: Human plasma spiked with ASOs at 0.1–1000 ng/mL; liquid–liquid extraction of 100 µL aliquots with GEM91 internal standard (100 ng/mL).
• Chromatography: ACQUITY Premier UPLC with Premier Oligonucleotide C18 column; mobile phases were 100 mM HFIP + 15 mM DIPEA in water (A) and in 90% acetonitrile (B).
• Mass Spectrometry: Waters Xevo TQ Absolute triple quadrupole MS operated in enhanced negative ion mode to optimize signal-to-noise and detection fidelity.

Main Results and Discussion

• Calibration and Reproducibility: Linear response (r² > 0.99) over 0.1–1000 ng/mL with 1/x² weighting; QC samples met ±15% criteria (±20% at LLOQ) across three days.
• Sensitivity: Achieved LLOQ of 0.1 ng/mL (0.2 ng/mL for GalNAc-conjugated ASO) with clear MRM chromatographic peaks at the lowest concentrations.
• Enhanced Detection: MaxPeak HPS technology minimized nonspecific adsorption and metal interaction; optimized precursor and fragment transitions improved detection of multiple charge states.

Benefits and Practical Applications

• Sub-ng/mL sensitivity supports detailed pharmacokinetic profiling of modified ASOs in preclinical and clinical studies.
• Wide dynamic range and robust reproducibility enable routine LC-MS/MS bioanalysis across varied oligonucleotide chemistries.
• Adaptable workflow suited for emerging nucleic acid therapeutics beyond ASOs.

Future Trends and Possibilities

• High-throughput integration to accommodate large sample cohorts and accelerated drug screening.
• Method expansion to siRNA, miRNA, aptamers, and other oligonucleotide modalities.
• Continued innovation in ionization techniques and column chemistries to lower detection thresholds further.

Conclusion

The presented LC-MS/MS method on the Xevo TQ Absolute platform combines sensitive extraction, advanced chromatography, and enhanced MS detection to deliver reliable quantitation of antisense oligonucleotides in human plasma over a broad dynamic range. This workflow meets the rigorous demands of modern bioanalytical and pharmacokinetic studies.

References

• Veeramachineni S., Wrona M.D. Sensitive LC-MS/MS Bioanalytical Quantitation of Antisense Oligonucleotides. Waters Application Note 720007574, March 2022.