The monoclonal antibody belimumab that selectively binds to the soluble counterpart of B cell activating factor (BAFF; also known as B lymphocyte stimulator, BLyS) is licensed for SLE treatment since 2011 (3), and for active lupus nephritis since 2021 (4). This evidence concerns the gene TNFSF13B and systemic lupus erythematosus.