Development of a flow cytometry-based potency assay for prediction of cytokine storms induced by biosimilar monoclonal antibodies

Cytokine release syndrome (CRS) is an undesired immune reaction that may cause dangerous side effects after the administration of novel biological therapies. In vitro cytokine release assays (CRA) are used for preclinical safety assessment prior to first-in-man dose administration of therapeutic monoclonal antibodies (mAbs). A variety of CRA platforms has been developed where the analysis of secreted cytokines is performed. Analysis of T cell activation markers is not performed routinely in CRA platforms and few studies have described intracellular cytokine levels after stimulation with therapeutic mAbs. In the present study, we performed a CRA using intracellular cytokine staining and assessment of extracellular T cell activation markers by flow cytometry. We used commercially available reference mAbs for the stimulation of peripheral blood mononuclear cells (PBMCs). We found that stimulation using solid phase (SP) dry coating with two different CD28 antibodies and muromonab-CD3 increased the percentage of IFN-ɣ + CD4+ and CD8+ T cells as well as of CD3-CD56+ NK cells compared to stimulation with antibodies in aqueous phase (AP). Expression of the T cell activation markers CD25 and CD69 on CD4+ and CD8+ T cells was also increased upon SP muromonab-CD3 stimulation.