Biologics are a class of therapeutics first identified in the 1980s and have become the focus for development of novel drugs for a wide variety of diseases. The specificity and high affinity of biologics for their target has resulted in an increase in the number of therapeutic monoclonal antibodies (mAbs) approved for use by the FDA each year . This has resulted in a growing need for robust bioanalytical and pharmacokinetic (PK) assays. The most common bioanalytical assay to quantify biologics are ligand-binding assays (LBAs) . LBAs are often preferred due to their low cost, high sensitivity, and high throughput compared to other bioanalytical platforms, such as liquid chromatography mass spectrometry . An additional advantage of LBAs is the ability to quantify "free" (unbound), "bound" and/or total amount of the therapeutic mAbs enabling the development of robust PK/pharmacodynamic (PD) models. Popular LBA assays include widely used plate-based enzyme-linked immunosorbent assays (ELISAs) and more sensitive electrochemiluminescence (ECL) assays . These assays utilize reagents that specifically target the complementarity-determining region (CDR), a part of the variable chain, of the therapeutic mAb, increasing the specificity of the PK assay.