LC-MS/MS quantification of nusinersen in rat cerebrospinal fluid and preclinical pharmacokinetics study application

Background: An oligonucleotide drug named nusinersen sodium is used to treat Spinal Muscular Atrophy (SMA), requires accurate detection for therapeutic research. There are no published reports on liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods for detecting nusinersen in rat cerebrospinal fluid (CSF). An LC-MS/MS method has been created and verified to detect nusinersen in Sprague-Dawley (SD) rat CSF. The method employed solid-phase extraction for post-extraction analysis and used dT20 as an internal standard. Negative ion multiple reaction monitoring (MRM) mode scanning and the electrospray ionization (ESI) source were used. The method was validated over a concentration range of 5–2000 ng/mL with a Lower Limit of Quantification (LLOQ) of for nusinersen at 5 ng/mL. The method achieves extremely high accuracy and precision, good linearity, high extraction recovery, and provides a useful approach for evaluating the pharmacokinetics of nusinersen in rats.