When should RTX be repeated? Can other immunosuppressive medications be used with it?
Among RA patients, the response is variable. Patients who are seropositive (rheumatoid factor and/or anticyclic citrullinated peptide) and have hypergammaglobulinemia are more likely to respond. Most RA patients deplete their B cells after RTX. Those who deplete their plasmablasts (CD27 + CD38 + ) get the best response. B-cell repopulation occurs at a mean of 8 months post-therapy. Patients who respond tend to by 4 to 6 months. The duration of response varies (median 30 weeks) and patients tend to relapse with reappearance of memory B cells (CD19 + CD27 + CD38 – ) and not naïve B cells (CD19 + CD27 – CD38 – ). Retreatment is done when clinical symptoms recur and are not based on B-cell counts; however, retreatment is usually not done sooner than 4 months after previous therapy unless patients fail to deplete their B cells. Recently, some physicians are giving one infusion of 500–1000 mg of RTX every 6 months to maintain remission in responders to prevent relapse. Primary nonresponders usually do not respond to additional RTX courses, although one study disputes that impression ( Arthritis Rheum 62: 1273, 2010). RA patients who fail to respond to RTX can be started on another biologic agent at 6 months after the initial course of two RTX infusions even if B cells are still depleted without a significant increase in infection risk.
Among ANCA-associated vasculitis patients, RTX is noninferior to cyclophosphamide. Patients can be treated with an RA dose schedule or lymphoma (4 weekly doses) schedule. All patients deplete their B cells. Patients relapse with recurrence of B cells at an average of 12 months. Patients can relapse before the reappearance of ANCA. Many physicians advocate giving 500 mg every 6 months to maintain remission and avoid relapse. In patients that relapse, a second course of RTX is as effective as the first course. RTX is reportedly effective in GPA and MPA in patients who are ANCA-negative.
