Overcoming Stability Challenge During the Quantification of SHR6508 in Human Plasma by LC-MS/MS

SHR6508, a novel calcimimetic agent, is currently being developed for treating secondary hyperparathyroidism in chronic kidney disease (CKD) patients requiring maintenance hemodialysis. For the purpose of quantifying SHR6508 in human plasma, a sensitive and reliable LC-MS/MS method was first developed and successfully validated. Since SHR6508 is a disulfide bond-containing peptide, ascorbic acid was supplemented into blood samples during collection to prevent thiol-disulfide exchange reactions. Plasma matrix samples were processed by protein precipitation with a water-acetonitrile solution (1:4, v/v) containing 0.05% formic acid. Chromatographic separation was conducted on an XBridge Peptide BEH C18 column (4.6 × 100 mm, 5.0 μm) under gradient elution with water and methanol, each containing 0.1% trifluoroacetic acid. SHR6508 was quantified by tandem mass spectrometry in positive electrospray ionization using multiple reaction monitoring with transitions of m/z 532.0 → 455.5 for SHR6508 and m/z 537.0 → 456.5 for SHR180296 (isotope-labelled internal standard). The quantification linear range was 1.00-1000 ng/mL. All validation parameters including selectivity, carryover, precision, accuracy, recovery, and matrix effect fell within the predefined acceptance criteria. The stabilization strategy developed in this work may also offer valuable insights for the collection and analysis of other disulfide bond-containing peptide drugs.