Evaluation of a generic immunoassay with drug tolerance to detect immune complexes in serum samples from cynomolgus monkeys after administration of human antibodies

Current state of the art bridging ELISA technologies for detection of anti-drug antibodies (ADAs) against therapeutic antibodies bear the risk of false-negative results due to interference by circulating drug. Methods to remove the drug in the sample or sample pre-treatment techniques such as acid dissociation of the immune complexes are limited, laborious and may destroy ADAs resulting again in false-negative results. The immune complex ELISA described in this publication provides a simple solution. It is designed to analyze samples from cynomolgus monkeys dosed with human antibodies; it can be used for all human antibodies since it is independent of the specific antibody and its target. The generic applicability of the ADA assay is enabled by the use of (1) a murine anti-human Fc monoclonal antibody (MAb) as capture reagent; (2) a murine anti-cynomolgus monkey IgG MAb as detection reagent; and (3) an ADA positive control conjugate consisting of cynomolgus IgG complexed with human IgG. In its basic version, the generic ADA ELISA specifically detects only immune complexes formed in vivo. Validation of the ADA assay revealed a lower limit of quantitation of 15.6 ng/mL in serum samples. Intra-assay and inter-assay precision was characterized by a coefficient of variation of less than 10% and accuracy was within 8%. Matrix effects were low as evidenced by a mean recovery of 95%. In vitro pre-incubation of the serum samples with drug makes also the free ADA in the sample amenable to measurement by the immune complex ELISA as demonstrated by analysis of ADAs from two cynomolgus monkey studies with two different antibodies. The generic and versatile nature of this ADA assay favors its use in pilot pharmacokinetic and safety studies in cynomolgus monkeys during candidate selection of antibodies. The assay can help to explain unexpected drug clearance profiles, loss of efficacy or safety events caused by immune complexes and guide further development.