ABSTRACT
FGF21-164 is a fusion protein obtained by structural modification and coupling of endogenous FGF21. It is a candidate drug used in the treatment of glucose and lipid metabolic disorders caused by obesity. In this study, the candidate peptide mass spectrometry information of the protein hydrolyzed by trypsin was predicted by Skyline software and verified by high resolution mass spectrometry. The specific surrogate peptide (YLYTDDAQQTEAHLEIR) with the best mass response was selected after optimizing ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Under ESI positive ion mode, the parent ion m/z 689.3 with 3 charge and the product ion m/z 738.4 with single charge can be monitored. After dilution by PBS, the serum samples were denatured under 60 ℃ and alkylated to reduce the matrix effect, then incubated with trypsin at 37 ℃ for 2 h, to obtain the surrogate peptide. The chromatographic separation was carried out on an EclipsePlus C18 column (2.1 mm×50 mm, 1.8 μm) using aqueous solution containing 0.1% formic acid (phase A) and acetonitrile solution containing 0.1% formic acid (phase B). Finally, the concentration of FGF21-164 fusion protein in mouse serum was quantitatively analyzed by external standard method by monitoring the above ion pairs using triple quadrupole mass spectrometer. This method showed a good linearity in the range of 2.50-500 μg·mL-1 (r = 0.998 8), and was successfully applied to the pharmacokinetic study of FGF21-164 fusion protein in mice. This experiment was approved by the Experimental Animal Ethics Committee of Shanghai Institute of Materia Medica, Chinese Academy of Sciences (batch number: 20180004040450). Compared with the endogenous FGF21, the t1/2 of FGF21-164 fusion protein was prolonged from 0.5 h to 2.6 h, which is expected to prolong the therapeutic efficacy of this protein.