Mitigating ADA matrix interferences: semiquantitative double immunoprecipitation for anti-bevacizumab antibody in plasma

Hybrid LC – MS/MS methodology offers orthogonal ADA quantitation but is limited by endogenous immunoglobulin matrix interference challenges. We developed a novel semi-quantitative LC-MS/MS isotyping assay for rabbit IgG/IgM immunogenicity in K2EDTA plasma using double immunoprecipitation with double acid dissociation. As compared to single immunoprecipitation, double immunoprecipitation reduced endogenous IgG by ≥90% and IgM by >95% (W1B1) or >55% (W3B2), improved peak-area ratios, and achieved an LLOQ of 100 ng/mL, with acceptable accuracy and precision. Double immunoprecipitation plus acid dissociation mitigates matrix interference and enables robust semi-quantitative hybrid LC-MS/MS ADA isotyping in rabbit plasma.