CD38 and systemic lupus erythematosus: <h4>Objective</h4>To evaluate safety and mechanism of action of mezagitamab (TAK-079), an anti-CD38 monoclonal antibody, in patients with moderate to severe systemic lupus erythematosus (SLE).<h4>Methods</h4>A phase 1b double-blind, placebo-controlled, multicentre study was conducted in patients with SLE receiving standard background therapy.