Bioanalytical methods for quantification of Bevacizumab in human serum: ELISA versus MSD

Bevacizumab (BVZ) is an anti-vascular Endothelial Growth Factor-A monoclonal antibody (mAb) widely used in oncology and ophthalmology indications globally. Accurate quantification of mAbs in biological fluids is an essential prerequisite for determining pharmacokinetic (PK) parameters to assess the relationship between drug exposure and response. We developed and evaluated PK assays for BVZ in human serum using enzyme-linked immunosorbent assays (ELISA) and Meso Scale Discovery (MSD) immunoassay platforms to assess sensitivity and performance. The ELISA method, employing a Streptavidin-Biotin detection system with anti-idiotypic antibodies, demonstrated five times greater sensitivity than the conventional horseradish peroxidase-based ELISA format. The validated PK bridging ELISA achieved a quantification range of 10-220 ng/mL, extendable to 5000 ng/mL via dilution. In contrast, the MSD assay utilized electrochemiluminescence detection with Sulfo Tag labeling, offering a 20-fold higher sensitivity and detecting BVZ at concentrations as low as 500 pg/mL. This parallel evaluation concluded that ELISA is suitable for routine PK analysis due to its robustness and cost-efficiency. At the same time, MSD is advantageous for detecting BVZ at low concentrations in early-phase clinical trials and ophthalmic applications where serum levels are minimal.