POS0616 LONG-TERM EFFECTIVENESS AFTER MULTIPLE CYCLES WITH RITUXIMAB FOLLOWING AN ON-FLARE RETREATMENT STRATEGY IN PATIENTS WITH RHEUMATOID ARTHRITIS
Authors: D. Bertrand, N. Pype, T. Conings, D. De Cock, S. Pazmino, M. Doumen, J. Joly, B. Neerinckx, R. Westhovens, P. Verschueren
Journal: Annals of the Rheumatic Diseases (2021)

Background: Rituximab is known as an efficacious drug for the treatment of Rheumatoid Arthritis (RA). The recommended administration schedule consist of 2 infusions of 1000 mg with a 2-week interval. In Belgium an on-flare retreatment strategy is followed, making evaluation of effectiveness over time challenging. Moreover the patient’s view on this strategy is unclear. Objectives: To explore long-term effectiveness and safety of rituximab in daily clinical practice in patients with RA. Methods: Data of patients diagnosed with RA and treated with rituximab in a tertiary university hospital were retrospectively collected. For every cycle, clinical data were recorded at the time of the first and second infusion, the 16-week visit and the visit on which the treating rheumatologist decided to prescribe a new cycle. Data on demographics, previous RA treatment, disease activity, patient-reported outcomes, adverse events related to rituximab, dose and number of cycles were collected from 01/01/2006 until 01/12/2019 or until discontinuation of rituximab. The visit on which rituximab was prescribed for the first time was considered as the baseline visit. The data were analysed descriptively. Results: Data of 66 patients with RA were collected. The median (IQR) age was 57.0 (47.0-65.0) years at baseline and 56% (37/66) were female. Most patients were seropositive (RF 91% and ACPA 92%), and had erosive (71%) or nodular disease (53%). The median (IQR) disease duration was 12.5 (4.0-18.3) years. In total, 94% of the patients had failed at least one other biological Disease-modifying Antirheumatic Drug (bDMARD) before starting rituximab. Overall, patients received a median (IQR) of 3 (2-7) cycles of rituximab. Seven of the 66 patients (11%) discontinued rituximab and changed to another bDMARD after a median (IQR) of 1 (1-6) cycles and 11% were treated with a lower dose than 2x1000mg. The median (IQR) interval between the first 2 cycles was 7.0 (6.0-10.0) months, after which this increased to up to one year (interval between cycle 2-3: 10.0 (7.0-13.0) months, cycle 3-4: 12.0 (7.3-15.5) months). The overall median (IQR) follow-up time was 45.5 (14.8-82.3) months. The efficacy of rituximab remained after repeated cycles: after every treatment with rituximab, a reduction in disease activity based on the disease activity score in 28 joints (DAS28) could be noticed (figure 1A). The evolution in patients’ (PaGH) and physicians’ global health (PhGH) assessment followed the same pattern as the DAS28-score (Figure 1B). High PaGH-scores could be noticed at every start of a new rituximab cycle. The proportion of patients with a PaGH-score above 20 ranged from 84% - 100%, 74% - 100% and 66% - 86% at the first infusion, second infusion and week 16 visits, respectively. Rituximab was considered to be well-tolerated. In total, 23 adverse events in 12 patients were recorded and none of them were serious. Conclusion: Rituximab can be considered a highly efficacious drug for RA treatment in daily practice. There were no major side effects and there was an increasing treatment interval over time. However, a healthy survivor effect should be kept in mind when interpreting the results. It should be noted that with the on-flare retreatment strategy, every new rituximab cycle was preceded by a rise in PaGH-scores, which reflects a state of impaired wellbeing reported by patients. This should be further studied with qualitative methods and in a randomized trial setting comparing on-flare with fixed-interval retreatment to evaluate optimal effectiveness. Figure 1. Evolution in median - interquartile range disease activity (DAS28CRP) (A) and patients’ (PaGH) and physicians’ global health (PhGH) (B) over the different rituximab cycles. The disease activity, PaGH and PhGH were measured at baseline, the time of the first and second infusion, W16 and the visit on which a new rituximab cycle was prescribed. The dotted lines represent a DAS28CRP-score of 2.6 (remission cut-off) and 3.2 (low disease activity cut-off). C: cycle; W: week; VAS: visual analogue scale. Disclosure of Interests: None declared