Rituximab levels are associated with the B cell homeostasis but not with the clinical response in patients with rheumatoid arthritis

Abstract

Objective: To study the levels of rituximab (RTX) and anti-RTX antibodies (ARAs) in patients with rheumatoid arthritis (RA) at 30, 90, and 180 days after the first infusion, in relation to clinical and serologicalparameters and B cell homeostasis.Methods: Thirty-four patients with RA who failed to respond to anti-tumor necrosis factor therapyreceived RTX. At baseline, 4, 12, and 24 weeks after the first infusion of RTX, we performed a clinicalassessment and determined the levels of RTX, ARAs, B cells, rheumatoid factors, anti-cyclic citrullinated peptide antibodies, immunoglobulins, and complements.Results: RTX levels varied widely among patients. No ARAs were detected during the follow-up. Patients with lower levels of RTX presented with higher decreases in erythrocyte sedimentation rate,immunoglobulins, and complement 6 months after the first infusion. Patients with higher levels ofRTX showed a higher B cell depletion at 90 days but an earlier B cell recovery than those with lowerlevels of RTX. No differences in clinical response were observed between the two groups at 6 monthsafter starting the treatment.Conclusion: Our findings suggest that RTX levels in the serum of patients with RA are related to Bcell homeostasis and the severity of immunological parameters but not to the clinical response at 6months.