A Label-Free blocking immunoassay to evaluate Anti-Adalimumab antibody activity in clinical samples

Adalimumab (ADL), a monoclonal antibody targeting TNF-⍺, is widely used to treat autoimmune diseases, but its efficacy can diminish over time due to the development of antidrug antibodies (ADAs), particularly neutralizing or blocking ADAs. Immunoassays used for mAb drug TDM typically measure ADA concentrations rather than their functional impact. This article describes an attempt to establish a label-free blocking immunoassay (LF-BIA) to measure the ADA blocking activity in serum samples.

The LF-BIA was designed to measure the ADA blocking activity against the interaction between ADL and its therapeutic target, TNF-⍺. The complete time course of ADL-ADAs and ADL-TNF-⍺ immune complex formation on each sensing probe was recorded as a sensorgram, and an ADA blocking rate was calculated from the sensorgram.

The LF-BIA detected ADA blocking activity in serum samples. A 1:25 dilution was selected to determine ADA blocking activity, and 42 patient samples were analyzed. The LF-BIA results showed partial concordance with ELISA results, likely reflecting methodological differences: LF-BIA measures blocking ADAs, whereas ELISA quantifies total ADAs.

The LF-BIA may provide an efficient approach to specifically measure blocking ADAs rather than total ADAs. Alongside with previously reported applications of label-free immunoassays in clinical testing, the LF-BIA highlights a promising area in which label-free technologies such as BLI can play an important role.