THU0394 Worsening of Systemic Activity and Increases of B-Cell Biomarkers in sjögren's Syndrome after Suspension of Belimumab Treatment: Long-Term Follow-Up After the End of the Beliss Study

Background Belimumab is preliminary found to be effective in Sjogren9s syndrome (SS) (1). It was administered in 30 SS patients coming from two Centres (Udine, Italy and Paris, France) (1). The ESSDAI score and the serum levels of rheumatoid factor (RF) and IgM immunoglobulins were significantly affected by this treatment in the long term. Objectives The aim of this study is to report the one year follow-up data after the end of the BELISS study in the Italian cohort, in order to further support the benefits of belimumab in SS during treatment. Methods Clinical and laboratory data of 13 SS patients were collected at one year after the end of the belimumab treatment in the BELISS study. Importantly, no immunosuppressors were employed in all these patients after the end of the trial. Statistical comparisons by t-test or Wilcoxon test, were performed between data at month +12 after the end of the study, and data at the beginning and at the end of the trial itself (i.e., week 0 and 52). Results are reported as mean ± standard deviation. Results The ESSDAI score was 8,8±6,9 at baseline, 3,5±3,7 at week 52 (end of the trial) and 7,0±5,7 at month 12 after the end of the trial (baseline vs. month +12, p=0,2; week 52 vs. month +12, p=0,003). Thus, a significant increase in the ESSDAI score was observed between week 52 and month +12 after the end of the trial, with the mean score coming back in the range of moderate disease activity from the low level. RF was 93,7±101,2 IU/ml at baseline, 74,7±74,5 IU/ml at week 52, 174,1±220,3 IU/ml at month 12 after the end of the trial (baseline vs. month +12, p=0,5; week 52 vs. month +12, p=0,008). Thus, a significant increase in RF serum level was observed between week 52 and month +12 after the end of the trial, serum RF almost doubling the baseline level. IgM level was 2456±975,6 mg/dl at baseline, 2173±885,3 mg/dl at week 52, 2381,6±1152,4 mg/dl at month 12 after the end of the trial (baseline vs. month +12, p=0,3; week 52 vs. month +12, p=0,04). Thus, a significant increase in the IgM serum level was observed between week 52 and month +12 after the end of the trial, serum IgM coming back to the baseline level. BLyS level was 1211±429 pg/ml at baseline, 1704±1044 pg/ml at week 52 and 1896±950 pg/ml 12 months after belimumab suspension. Interestingly, BLyS levels were significantly higher even four weeks after the last belimumab infusion (week 52) if compared to baseline levels (p=0,04), and increased 12 months later (baseline vs. month +12 after the end of the trial, p=0,01; week 52 vs. month +12 after the end of the trial, p=0,2). Interestingly, the development of malignant B-cell lymphoma from non neoplastic parotid sialadenitis was observed in two patients two years after the end of the trial in both patients. Conclusions Worsening in systemic activity and in B-cell biomarkers occurs in SS after the suspension of belimumab, supporting the role of targeting BLyS in SS. A possible control of non malignant B cell lymphoproliferation in SS by belimumab is suggested. A more prolonged therapy with belimumab may be useful in SS. References Mariette X, et al. ARD 2013 Disclosure of Interest None declared