Serum rituximab levels and efficiency of b cell depletion: Differences between patients with rheumatoid arthritis and systemic lupus erythematosus

摘要

Sir, Variability in clinical response to rituximab-induced B cell depletion therapy (BCDT) is well described in both RA and SLE [1, 2]. Recent evidence suggests that an inadequate depletion is associated with poor clinical response in both RA and SLE [3, 4]. Importantly, it was shown that clinical response depended on the degree of depletion and not the dose of rituximab in RA [4].In a study of patients with RA, the majority of inadequate responders (IRs) to the first cycle of rituximab treatment had a greater number of circulating plasmablasts at baseline, with 90% not achieving adequate depletion, defined as CD19+ B cells <0.0001 x 109/l [using highly sensitive flow-cytometry (HSFC)], when compared with 60% of responders. Importantly, 72% of the first-cycle IRs subsequently showed a clinical improvement following a second cycle of rituximab given 6 months after the first cycle [5].