Mitigating target interference challenges in bridging immunogenicity assay to detect anti-tocilizumab antibodies.

An assay to detect anti-tocilizumab antibodies in the presence of high levels of circulating target and drug is needed for immunogenicity assessment in comparative clinical studies. An assay was developed and validated using a combination of blocking agents and dilutions to overcome target interference challenges. No false-positive signal was detected in serum samples spiked with 350-500 ng/ml of IL-6 receptor. As low as 50 ng/ml of positive control antibodies could be detected in the presence of either 500 ng/ml of IL-6 or 250 μg/ml of the drug product. Assay also demonstrated high sensitivity, selectivity and precision. A robust, easy to perform immunogenicity assay was developed and validated for detecting anti-tocilizumab antibodies.