To characterize the safety of rituximab (RTX) in combination with biologic disease-modifying antirheumatic drugs (DMARD) in patients with rheumatoid arthritis (RA).

We did an open-label study of the safety and efficacy of RTX in adult patients with active RA and an inadequate response to ≥ 1 biologic for ≥ 12 weeks (stable dose ≥ 4 weeks). RTX (2 × 500 mg) was added to patients' current biologic and nonbiologic DMARD treatment. After 24 weeks, patients with 28-joint Disease Activity Score ≥ 2.6 were eligible for RTX retreatment. The primary endpoint was the proportion of patients developing a serious adverse event (SAE) within 24 weeks of initiating RTX.

Patients (n = 176) received RTX with 18 different biologic/DMARD combinations. Adalimumab alone (n = 46; 26.1%) or etanercept alone (n = 37; 21.0%) plus RTX were the most common combinations. Overall, 90.9% and 76.1% of patients completed 24 and 48 weeks, respectively; 147 patients (83.5%) received a second course of RTX. Over 24 weeks, 9.1% of patients reported SAE (24.3 events/100 patient-yrs, 95% CI 15.5-38.1). The SAE rate was similar over 48 weeks (22.4 events/100 patient-yrs, 95% CI 15.9-31.5). Four serious infections were reported over 48 weeks (2.7 events/100 patient-yrs, 95% CI 1.0-7.2). No SAE occurred within 24 h of any RTX infusion. Efficacy responses improved numerically at Week 48 compared with Week 24.

The overall safety profile of RTX in combination with 1 other biologic was consistent with that previously reported for RTX plus methotrexate or other nonbiologic DMARD. (Clinicaltrials.gov NCT00443651).