Poster presented at EBF, Barcelona 2022
Comparison of bioanalytical methods to measure free analyte
Ligand binding assays are commonly used for the quantification of biotherapeutics in complex matrices. For therapeutic compounds binding to a soluble target, the drug can either be unbound (free) or circulating in complex with its target or other serum proteins. As the free concentration of the drug is theoretically responsible for the pharmacological effect, accurate measurements of the free drug are of importance. Along the same line, knowing what fraction of the target is free or in complex, supports getting a complete picture of the pharmacokinetic and pharmacodynamic properties of the therapeutic.
Plate-based immunoassays present technical challenges for the determination of free analyte. Long incubation steps can lead to equilibrium shifts and overestimation of the free analyte (Figure 1). In the Gyrolab® platform, the samples flow through a capture column embedded in a microfluidic CD. This results in short contact times and limited matrix effects, making Gyrolab a very suitable platform for accurate free analyte measurements. This is illustrated with an example where free bevacizumab (Avastin®) was quantified in presence of its target VEGF, both with Gyrolab and plate-based ELISA.