Avizakimab SummaryAvizakimab (also known as MEDI-5117) is a humanized monoclonal antibody of the IgG1 isotype. It functions as a non-depleting antagonist targeting the Interleukin-21 receptor (IL-21R). By binding to the IL-21R, Avizakimab blocks the signaling initiated by the cytokine Interleukin-21 (IL-21), thereby suppressing the downstream pro-inflammatory effects. IL-21 is a key cytokine produced TH17 cells that drives various aspects of adaptive immunity, including B cell differentiation and T cell proliferation. Avizakimab was developed as a potential therapeutic agent for autoimmune and chronic inflammatory diseases, such as Systemic Lupus Erythematosus (SLE) and Crohn's Disease, where excessive IL-21 signaling contributes to pathology.