Belimumab

B-lymphocyte stimulator, a survival factor for B cells, is the protein neutralised by belimumab. Autoreactive B cells depend on that signal to persist, and removing it reduces their survival and with it the autoantibody-driven damage characteristic of systemic lupus erythematosus. The monoclonal antibody was the first new agent approved for lupus in more than fifty years, a gap that reflects the difficulty of demonstrating benefit in a disease of heterogeneous presentation. Targeting a soluble cytokine rather than the B cell itself separates this approach from B-cell-depleting antibodies. The product is classified as an antibody therapeutic and has completed the final phase of clinical development.