Novel isoelectric target depletion (ITaD) protocol reduces the need for specific reagents for immunogenicity testing.

The development of immunogenicity assays for clinical drug candidates targeting soluble proteins is challenging when the soluble target might produce either false-positive or false-negative signals in bridging anti-drug antibody screening assays. A generic soluble target removal protocol that uses a pH-dependent depletion was evaluated. An anti-drug antibody bridging assay with a pH-dependent soluble target depletion step was successfully developed. Endogenous target levels of ∼600 nM could be depleted below 8 pM. The assay was highly drug tolerant and met regulatory requirements. A reagent-independent target depletion protocol can be used for immunogenicity testing in the presence of a soluble target. The generic protocol circumvents common depletion or masking protocols.