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Updated: Jan 27, 2026

Absolute Quantification of Plasma MicroRNA Levels in Cynomolgus Monkeys, Using Quantitative Real-time Reverse Transcription PCR
Published on: February 12, 2018
An LC-MS/MS approach to assess total and free protein target in the serum of cynomolgus monkey
Hongmei Cao1, Guodong Zhang1, Kristina Ciociola1
1Bioanalytical & Biomarker Development, Takeda Pharmaceuticals International Co., 125 Binney Street, Cambridge, MA 02142, USA.
Aim:
Develop LC-MS/MS-based assays to measure total and free complement C5 in cynomolgus monkey serum as a target engagement biomarker for pharmacokinetic/pharmacodynamic correlation study. Materials & methods/results: The C5-specific signature peptide derived from pellet digestion of serum proteins with and without prior immunodepletion of the drug-bound C5 by protein A beads was quantified to assess free and total C5 levels, respectively. Conditions for immunodepletion by protein A were optimized to ensure complete depletion of IgGs (and drug-bound C5). The effect of sample dilution on drug-target dissociation and thus free C5 measurement was evaluated by applying a mathematical simulation.
Conclusion:
The procedure described here allows for the assessment of protein target engagement, aiding in pharmacokinetic/pharmacodynamic correlation analysis and human dose projection.
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