To establish the safety and efficacy of repeat infusions of tocilizumab (previously known as MRA), a humanized anti-interleukin-6 (IL-6) receptor antibody, alone and in combination with methotrexate (MTX), for the treatment of rheumatoid arthritis (RA).
The study group comprised 359 patients with active RA in whom the response to MTX was inadequate. During a stabilization period, these patients received their current dose of MTX for at least 4 weeks. Following stabilization, they were randomized to 1 of 7 treatment arms, as follows: tocilizumab at doses of 2 mg/kg, 4 mg/kg, or 8 mg/kg either as monotherapy or in combination with MTX, or MTX plus placebo.
A 20% response (improvement) according to the American College of Rheumatology criteria (ACR20 response) was achieved by 61% and 63% of patients receiving 4 mg/kg and 8 mg/kg of tocilizumab as monotherapy, respectively, and by 63% and 74% of patients receiving those doses of tocilizumab plus MTX, respectively, compared with 41% of patients receiving placebo plus MTX. Statistically significant ACR50 and ACR70 responses were observed in patients receiving combination therapy with either 4 mg/kg or 8 mg/kg of tocilizumab plus MTX (P < 0.05). A dose-related reduction in the Disease Activity Score in 28 joints was observed from week 4 onward, in all patients except those receiving monotherapy with 2 mg/kg of tocilizumab. In the majority of patients who received 8 mg/kg of tocilizumab, the C-reactive protein level/erythrocyte sedimentation rate normalized, while placebo plus MTX had little effect on these laboratory parameters. Tocilizumab was mostly well tolerated, with a safety profile similar to that of other biologic and immunosuppressive therapies. Alanine transaminase and aspartate transaminase levels followed a sawtooth pattern (rising and falling between infusions). There were moderate but reversible increases in the nonfasting total cholesterol and triglyceride levels and reversible reductions in the high-density lipoprotein cholesterol and neutrophil levels. There were 2 cases of sepsis, both of which occurred in patients who were receiving combination therapy with 8 mg/kg of tocilizumab plus MTX.
These results indicate that targeted blockade of IL-6 signaling is a highly efficacious and promising means of decreasing disease activity in RA.