Background In spondyloarthritis (SpA) patients in low disease activity (LDA) treated with biologics it is possible to decrease dose or increase the interval of administration (tapering strategy: TS) It is hypothesized whether the use of the TS could increase the development of anti-drug antibodies (ADA) with the consequent secondary inefficacy.
Objectives To analyze the influence of the TS of TNF inhibitors (TNFi) in a cohort of SpA patients at least in LDA on the clinical activity (Bath Ankylosing Spondylitis Disease Activity Index: BASDAI and incidence of flares) and serum drug and ADA levels.
Methods Retrospective observational study of a cohort of SpA patients under TNFi: Infliximab (Ifx), Adalimumab (Ada), Etanercept (Etn) and Golimumab (Gol)] on a TS. Sixty two out of 148 SpA patients under TS treated with the first anti-TNF were included. All included patients had to be at least 6 months in LDA (defined by BASDAI <4 plus one of the following items: normal C-reactive protein (CRP) or Delta-BASDAI ≥2). Flare was defined as BASDAI ≥4 associated with elevated CRP (>5mg/L) and/or Delta-BASDAI ≥2. Clinical activity (BASDAI and Ankylosing Spondylitis Disease Activity Score (ASDAS), serological data of disease activity (CRP) were measured at baseline, prior starting the TS (pre-visit) and last visit available in the first 2 years after TS (final-visit).
Results 62 patients: 44 males (71%) and 82.2% of patients were HLA B27 positive. the subtypes of SpA are shown in the tables. No differences in clinical activity by ASDAS (p=0.219), BASDAI (p=0.271) or CRP levels (0.051) were detected between pre-visit and final-visit (see tables). Nine (14.52%) patients were ADA positive: 5 with Ifx, 3 with Ada and 1 with Gol. Two patients were already ADA positive in the pre-visit and 7 were ADA positive at final-visit. During follow-up only 8 patients (12.9%) experienced a flare and 80% recovered the LDA after shortening the interval of administration. Patients without detectable drug levels at flare visit, developed ADA at the end of follow up (p=0.035), reaching statistical significance. None ADA positive results were found in patients with use of concomitant methotrexate (MTX) at baseline.
Conclusions In SpA patients in LDA, the tapering strategy of TNFi seems to be feasible in most patients without a relevant clinical worsening and with a low incidence of flares. Monitoring drug and ADA levels could help to predict patients with flares. Furthermore, the use of concomitant MTX seem to have a protective effect on ADA development.
Disclosure of Interest I. Monjo Henry Grant/research support from: This study has received unrestricted grants from Pfizer, C. Plasencia: None declared, D. Pascual-Salcedo: None declared, B. Paredes: None declared, A. Pieren: None declared, C. Tornero: None declared, E. Moral: None declared, G. Bonilla: None declared, L. Nuño: None declared, D. Peiteado: None declared, A. Villalba: None declared, T. Jurado: None declared, C. Diego: None declared, J. Díez: None declared, E. Martin Mola: None declared, A. Balsa: None declared