Novel strategy using tryptic peptide immunoaffinity-based LC-MS/MS to quantify denosumab in monkey serum

Aim: Denosumab is a recombinant fully human IgG2 that has a high affinity and specificity for human RANKL. Commercially available RANKL labeled with an Fc fragment cannot be used to establish an indirect ELISA. To characterize denosumab pharmacokinetic a robust and accuracy method should be developed urgently. Results: In this study, an immunoaffinity enrichment method coupled with LC-MS/MS was established. The LC-MS/MS method acquired a linear range from 0.1 to 30 mu g/ml. The intra-and inter-run precision (CV%) was within 11.5 and 10.5%, respectively. More importantly, the LC-MS/MS pharmacokinetic data were consistent with ELISA. Conclusion: This approach accelerated the quantification, reduced the costs and provided an alternative in case of lacking the special antigen to denosumab or a RANKL-biotinylated reagent.