To establish a method for the determination of carfilzomib in rat plasma by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and to investigate the pharmacokinetic characteristics of carfilzomib in rat plasma.

The rat plasma samples were processed by a protein precipitation approach using methanol∶acetonitrile (1∶1, v/v). Chromatographic column: Thermo Scientific^TM Hypersil GOLD^TM C₁₈ Column (2.1 mm×50.0 mm, 3 μm); mobile phase: 2 mmol·L^-1 ammonium acetate-0.02% formic acid water (A)-methanol (B) in gradient elution mode; flow rate: 0.45 mL·min^-1; injection volume: 5 μL. Electrospray ionization source in positive ion mode and multiple reaction monitoring were adopted. The specificity, standard curve and lower limit of quantification, residue effect, precision and extraction recovery rate, dilution reliability, matrix effect and stability of this method were examined. After a single intravenous injection of 4 mg·kg^-1 carfilzomib into 6 healthy male SD rats, blood was collected from the inner corner of the eye, and the concentration of carfilzomib in the plasma was detected. The pharmacokinetic parameters were calculated using DAS 3.0.

Carfilzomib exhibited good specificity and linearity within the range of 0.5 to 1 250.0 ng·mL^-1, with a standard curve of y=2.40×10^-2x+6.81×10^-2 (r=0.996 4), the quantitative limit of detection was 0.5 ng·mL^-1, the sample residues were 7.64% and 1.00% of the quantitative limit of detection and the internal standard, respectively, the intra-day and inter-day precision were ≤7.51% and ≤8.16%, respectively, the intra-day and inter-day accuracy were -4.54% to 5.14% and -4.41% to 8.26%, respectively, the extraction recovery were 92.49% to 108.33%, and the methodological evaluation results of sample dilution effect, matrix effect and stability were all in accordance with the requirements for the validation of biological sample analysis methods. The main pharmacokinetic parameters of carfilzomib were: C_max was (1.10×10⁶±5.45×10⁵) ng·L^-1, t_1/2 was (23.10±7.38) min, AUC_0-t was (1.85×10⁷±9.85×10⁶) ng·L^-1·min.

The approach formulated in this study is operationally facile, highly discriminatory, sensitive, precise, dependable, and is appropriate for the determination and analysis of carfilzomib in rat plasma specimens.