Rapid and simultaneous quantification of a mixture of biopharmaceuticals by a liquid chromatography/quadrupole time‐of‐flight mass spectrometric method in rat plasma following cassette‐dosing

Rationale The cassette‐dosing technique is a technique that administers various drugs to a single animal at once and quantitated simultaneously. The purpose of this study was to evaluate the feasibility of cassette‐dosing as a means of increasing throughput and decreasing animal usage for pharmacokinetic studies of biopharmaceuticals using liquid chromatography/time‐of‐flight mass spectrometric (LC/TOF‐MS) analysis. Methods Brentuximab, trastuzumab, cetuximab and adalimumab were used as model biopharmaceuticals. The method consisted of immunoprecipitation followed by tryptic digestion for sample preparation and LC/TOF‐MS analysis of specific signature peptides in the positive ion mode using electrospray ionization. The specific signature peptides used for quantification were from the complementarity‐determining regions of each mAb. All rats received a single intravenous bolus injection containing either a single mAb or a mixture of four mAbs. Results The proposed method has been qualified in linearity range of 1–100 μg/mL with correlation coefficients higher than 0.990. The qualification run met the acceptance criteria of ±25% accuracy and precision values for quality control (QC) samples. This qualified LC/TOF‐MS method was successfully applied to a pharmacokinetic study in the rat. The PK properties of mAbs administered as a cassette‐dosage were similar to the pharmacokinetics of each antibody drug when administered as a single entity. Conclusions These findings suggest that the cassette‐dosing approach could be used to evaluate the PK properties of biopharmaceuticals in the early drug discovery stage. Also, this method would be useful for other preclinical sample analysis without developing new reagents for sample preparation.