Highly selective and sensitive measurement of active forms of FGF21 using novel immunocapture enrichment with LC–MS/MS

Aim: Recombinant FGF21 analogs are under wide ranging investigations as a potential therapeutic agent for Type 2 diabetes, as well as other metabolic disorders. The endogenous FGF21 is often used as a surrogate pharmacodynamic(PD) biomarker to assess drug efficacy and safety. Results/methodology: Immunocapture was performed using a monoclonal antibody which had been generated to bind to specific domain of native FGF21 as the capture reagent. After immunocapture, enzymatic digestion was performed and a native FGF21-specific tryptic peptide was monitored using LC–MS/MS by selective reaction monitoring. Conclusion: We have successfully developed and validated a bioanalytical assay which provides the specificity to differentiate the endogenous FGF21 from the recombinant therapeutic agent which has nearly identical sequence to the endogenous molecule.