Development of a robust reporter-based ADCC assay with frozen, thaw-and-use cells to measure Fc effector function of therapeutic antibodies

Antibody-dependent cell-mediated cytotoxicity (ADCC) is one of the main mechanisms of action for many therapeutic antibodies. Classic ADCC assays measure antibody-dependent target cell cytotoxicity induced by primary effector cells that are isolated from human blood. They suffer from high assay variability due to the genetic and immune-status-mediated variation from blood donors. Here we report the development of a robust reporter-based ADCC assay that uses an engineered Jurkat stable cell line as the source of effector cells. These engineered effector cells were further developed as frozen, thaw-and-use format that can be plated for assay immediately after thaw. We demonstrate that frozen, thaw-and-use Jurkat effector cells showed appropriate Fc effector function similar to fresh cells from continuous culture, with added benefits of convenience and consistency. This robust assay is able to measure antibody potency for several therapeutic antibodies targeted to hematopoietic or solid tumors. The assay can distinguish effector functions for different antibody IgG isotypes in two antibody model systems: anti-CD20 and anti-EGFR. It is able to detect changes in ADCC biological activity for heat-stressed rituximab and trastuzumab, demonstrating that it possesses proper stability-indicting property. When compared with a classic PBMC-based ADCC assay, the ADCC reporter assay showed better assay precision and similar correlation of antibody glycosylation with ADCC biological activity for a panel of glyco-modified trastuzumab mixtures. Together these data demonstrate that this robust ADCC reporter assay meets the requirement of a potency bioassay that can quantify antibody Fc effector function in ADCC mechanism of action during drug discovery and development.