WASHINGTON — Baseline seropositivity for rheumatoid factor and anticyclic citrullinated peptide among patients with rheumatoid arthritis is associated with a more favorable response to treatment with rituximab, Dr. Paul P. Tak reported at the annual meeting of the American College of Rheumatology.
A post hoc analysis was undertaken to explore the relationship between baseline autoantibody status and rituximab therapy in patients who participated in the 24-week Randomized Evaluation of Long Term Efficacy of Rituximab (REFLEX) study, according to Dr. Tak of the University of Amsterdam.
In REFLEX, patients with long-standing RA who had inadequate responses to one or more anti-tumor necrosis factor (TNF)-α drugs were randomized to receive a course of intravenous rituximab, which consisted of two infusions of 1,000 mg each, separated by 2 weeks, or placebo. All patients also were on background methotrexate in doses of 10–25 mg/week.
Among 309 patients analyzed at week 24, there was a high degree of efficacy for those who were seropositive for either or both of the autoantibodies (see box). Baseline RF greater than 20 IU/mL and anti-CCP greater than 5 IU/mL were considered seropositive.
With regard to the lower level ACR 20 responses, seronegative patients on rituximab also achieved this level to a greater degree than did seronegative patients on placebo.
Seronegative patients receiving rituximab did not achieve greater ACR 50 or 70 responses, however. “This suggests that other mechanisms such as antigen presentation, T-cell co-stimulation, and cytokine release may account for low levels of response, with higher responses to rituximab therapy being mediated primarily by suppression of pathogenic autoantibodies,” Dr. Tak wrote in a poster session.
Dr. Tak disclosed that he received research grants and consulting fees from Roche Laborotories Inc.