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A1.27 Serum rituximab level and other predictors for good eular response before re-treatment in rheumatoid arthritis
  1. Diana Mazilu1,2,
  2. Cecilia Gainaru2,
  3. Natalia Apetrei4,
  4. Georgiana Luca3,
  5. Tania Gudu1,
  6. Alexandra Peltea1,
  7. Laura Groseanu1,2,
  8. Cosmin Constantinescu1,2,
  9. Ioana Saulescu1,2,
  10. Violeta Bojinca1,2,
  11. Andra Balanescu1,2,
  12. Denisa Predeteanu1,2,
  13. Ruxandra Ionescu1,2,
  14. Daniela Opris1,2
  1. 1Department of Rheumatology and Internal Medicine, “Sfanta Maria” Hospital, Bucharest, Romania
  2. 2“Carol Davila” University of Medicine, Bucharest, Romania
  3. 3Biology Faculty, "Alexandru Ioan Cuza" University, Iasi, Romania
  4. 4Biology Faculty, Bucharest University, Bucharest, Romania

Abstract

Background and Objectives Predictive factors for rituximab (RTX) response in rheumatoid arthritis (RA) patients are currently still under debate. Repeated re-treatment is now the rule, but it is worth knowing if there are predictive factors for good or moderate EULAR response after a new course of RTX.

Materials and Methods Twenty five long term RTX-treated patients with RA were included in this prospective study. Their average time with RTX treatment was 41.79 months. RTX serum level was measured by sandwich ELISA (Promonitor-RTX Ref. PG-PRTX-12700), after 6 months from last re-treatment. Patients were divided into detectable versus non-detectable drug levels based on assay cut-off. Clinical and pharmacological data were collected at the time of dosing serum RTX level and 6 months later.

Results At 6-month follow-up, 8 (32%) of the RA patients have achieved a good EULAR response and 7 patients (28%) - a moderate EULAR response. Regarding the serum RTX level, 9 patients (36%) had no detectable drug level. From this group at 6 month after last infusion, 6 (66.6%) patients had no EULAR response. All patients tested negative for anti-RTX antibodies. A significant correlation was found between detectable drug level and EULAR response after re-treatment (p = 0.034, r = 0.424). Patient status of anti-citrullinated protein antibodies (ACPA) was strongly correlated to RTX drug level (p = 0.021, r = 0.460) but not to the EULAR response (p = 0.216, r = 0.256). Another interesting finding was the significant correlation between RTX serum level and number of previous anti tumor necrosis agents used before RTX was initiated (p = 0.009, r = 0.514).

Conclusions This observational study suggests that detectable RTX serum level before re-treatment can be predictive for a good EULAR response at 6 month. ACPA positivity and higher number of previous anti TNF agents used are correlated with RTX level. As non-detectable RTX level increases chances for no response, drug level monitoring may be used to optimise treatment in patients with RA.

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