ICOS and systemic lupus erythematosus: To provide just one example, whereas the study of Sullivan et al. asserted that evidence of anti‐KLH IgG modulation by AMG 557 (prezalumab) “demonstrates a PD effect of AMG 557 in subjects with SLE consistent with the biology of the ICOS pathway and supports further studies of AMG 557 as a potential therapeutic for autoimmune diseases,” this drug failed to meet primary end points in a subsequent phase II trial in SLE, and development has since been discontinued.