With respect to patient safety and long-term efficacy, immunogenicity of therapeutic antibodies remains an important issue. Pre-treatment of samples using either higher temperature or acidification in order to separate drug/anti-drug antibody complexes has been implemented in the traditional bridging assay and an in-house-developed affinity capture elution assay but only a limited drug tolerance was obtained. In this study, we aim to apply a drug-resistant anti-drug antibody assay to adalimumab through a combination of adalimumab/anti-adalimumab antibody complex precipitation and acid dissociation. A linear dose-response curve ranging from 3.1 to 200 ng/mL was obtained in 1/125 diluted serum, allowing detection of anti-adalimumab antibody concentrations up to 25 μg/mL equivalents MA-ADM6A10, a calibrator anti-adalimumab antibody. The cut-off point for detection was determined using 16 samples of adalimumab naïve patients and set at 0.39 μg/mL equivalents. Validation of the assay revealed that no detectable anti-adalimumab antibody concentrations were found in samples with either a positive anti-infliximab antibody concentration, a physiologic concentration of TNFα, or a high concentration of rheumatoid factor. Full recoveries were obtained when various concentrations of adalimumab (0, 1, 10, and 50 μg/mL) were spiked to 1, 2, and 4 μg/mL of MA-ADM6A10. Spiking of 50 μg/mL adalimumab to eight individual sera revealed similar anti-adalimumab antibody concentrations as in the absence of adalimumab, with a Pearson r correlation of 0.99 and an interclass correlation of 0.99. The assay allows accurate evaluation of adalimumab immunogenicity during induction or upon dose intensification and in serum samples not taken at trough.
Keywords: adalimumab; anti-drug antibody; drug interference; drug-resistant assay; immunogenicity.