SAT0191 Reducing Rituximab Dose in Retreatment Results in Similar Initial DAS28 Reduction, But Significantly Shorter Time to Retreatment

BackgroundThe optimal long-term treatment regime for rituximab rheumatoid arthritis is unclear. In the first cycle, 2x1000mg is superior to 2x500mg. In repeat cycles, B cell numbers are often lower than baseline and 2x500mg has been reported to be similarly effective to 2x1000mg. [1] However, duration of response with dose reduction has not previously been investigated.ObjectivesIn responders to full dose of rituximab: to evaluate the level and duration of response to retreatment using reduced dose rituximab on relapse.MethodsPatients who had received at least one cycle of 2x1000mg rituximab with EULAR moderate or good response were treated with 2x500mg on clinical relapse (increase in DAS28>0.6) and comparison was made between 4-month DAS28 and duration of response (time to retreatment) between the last cycle of 2x1000mg and the first cycle of 2x500mg.Results137 patients were studied. Mean (SD) age at baseline was 63.6y (10.1), 78% were female, 67% received concomitant methotrexate, 29% received alternative concomitant DMARDs and 4% received no concomitant DMARD. Median (range) number of prior non-biologic and biologic DMARDs were 2 (0-7) and 1 (0-4) respectively. Patients had received median 5 (2-10) prior cycles of rituximab. Mean (SD) DAS28 4 months after the last 2x1000mg cycle and first 2x500mg cycle were 2.83 (1.09) and 3.08 (2.47) respectively (p=0.324). Median (IQR) time to retreatment after the 2x1000mg and 2x500mg cycles were 49.86 (40.14-65.71) and 39.14 (31.21-55.29) weeks respectively. (p