To investigate the safety and efficacy of ofatumumab, a novel human anti-CD20 monoclonal antibody (mAb), in patients with active rheumatoid arthritis (RA) whose disease did not respond to ≥1 disease-modifying antirheumatic drug.


This combined phase I/II study investigated the safety and efficacy of 3 doses of ofatumumab. In part A (phase I), 39 patients received 2 intravenous (IV) infusions of ofatumumab (300 mg, 700 mg, or 1,000 mg) or placebo in a 4:1 ratio 2 weeks apart, using a specified premedication and infusion regimen. In part B (phase II), 225 patients received study treatment as per phase I in a 1:1:1:1 ratio. Safety was assessed by adverse events (AEs) and laboratory parameters. Efficacy was assessed by the American College of Rheumatology 20% criteria for improvement (ACR20), the Disease Activity Score in 28 joints, and the European League Against Rheumatism (EULAR) response criteria. B cell pharmacodynamics were also investigated.


AEs were predominantly reported at the first infusion and were mostly mild to moderate in intensity. Rapid and sustained peripheral B cell depletion was observed in all dose groups. In phase II, patients in all ofatumumab dose groups had significantly higher ACR20 response rates (40%, 49%, and 44% for the 300 mg, 700 mg, and 1,000 mg doses, respectively) than did patients receiving placebo (11%) at week 24 (P < 0.001). Overall, 70% of patients receiving ofatumumab had a moderate or good response according to the EULAR criteria at week 24.


Our findings indicate that ofatumumab, administered as 2 IV infusions of doses up to 1,000 mg, is clinically effective in patients with active RA.