Efficacy and safety of various repeat treatment dosing regimens of rituximab in patients with active rheumatoid arthritis: results of a Phase III randomized study (MIRROR)

OBJECTIVE To evaluate the efficacy and safety of three dosing and repeat treatment regimens of rituximab (RTX) plus MTX in patients with active RA. METHODS Patients with active RA despite stable MTX (10-25 mg/week) were randomly assigned to one of the three treatment regimens comprising two courses of RTX given 24 weeks apart: 2 x 500 and 2 x 500 mg; 2 x 500 and 2 x 1000 mg (dose escalation); and 2 x 1000 and 2 x 1000 mg. The primary endpoint was proportion of patients achieving ACR20 at Week 48. RESULTS At Week 48, ACR20 responses were not statistically significantly different between the dose regimens. Compared with RTX 2 x 500 mg (n = 134) or dose escalation (n = 119), ACR and European League Against Rheumatism (EULAR) outcomes in the RTX 2 x 1000 mg group (n = 93) were consistently higher, with significantly more patients achieving EULAR responses (P = 0.0495). At Week 48, rituximab 2 x 1000 mg was associated with a higher proportion of patients who, following retreatment, maintained or improved their Week 24 responses. Dose escalation from 2 x 500 to 2 x 1000 mg did not appear to be associated with improved outcomes compared with continual 2 x 500 mg. All RTX regimens demonstrated comparable safety. CONCLUSIONS RTX 2 x 500 and 2 x 1000 mg could not be clearly differentiated, although some efficacy outcomes suggest improved outcomes in the rituximab 2 x 1000 mg group. Retreatment from Week 24 resulted in a sustained suppression of disease activity through to Week 48.