TNFSF13B and systemic lupus erythematosus: Successful off‐label usage of rituximab in some patients with SLE further suggests that therapies unsuccessful in clinical trials with SLE may yet have efficacy in selected patients.34, 35 Indeed, the expression levels of key drug‐targeted molecules such as BAFF and CD40L suggest that certain clusters of patients might be more suitable for the rationale of certain targeted biologics than other clusters (Figure 4).