Background/Purpose: The STRASS trial was an 18-month randomized controlled trial, conducted in established RA patients in DAS28 remission with etanercept (ETA) or adalimumab (ADA), comparing the impact of a DAS28-driven step-down strategy based on TNF-blocker injection spacing (S arm) to a maintenance strategy (M arm). It demonstrated that, although relapses were more frequent with the spacing strategy arm, no substantial increase in disease activity or structural damage progression occurred throughout the 18-month follow-up. We aimed to assess in a subgroup analysis if the feasibility of TNF-blocker injection spacing differs by molecule –ADA or ETA – and/or its use as monotherapy (MONO) or in combination with synthetic DMARD (COMBO).

Methods: Inclusion criteria were: ETA or ADA > 1 year, DAS28 remission > 6 months, no progression of structural damage on X-rays. Patients were randomized and followed every 3 months for 18 months. In the S arm, the inter-injection interval was increased every 3 months up to complete interruption at 4th step. In these stratified analyses, disease activity was assessed by DAS28 repeated measures and analyzed in a mixed linear model (GLM). Relapse, defined by DAS28 >2.6 and ΔDAS28 >0.6, was in a Cox model and statistical comparison by Wald chi-square test.

Results: 137 patients were included, 64 and 73 in the S and M arm (mean/%: age 55 yrs, female 78%, RA duration 9.5 yrs, ACPA+ 78%, erosive 88%, DAS28 1.8, HAQ 0.5). Sixty-three patients were treated with ADA and 74 with etanercept; 33 received the TNF-blocker as MONO (ADA 11, ETA 22) and 104 in combination with either methotrexate or leflunomide (ADA 52, ETA 52). There were no significant differences in either trial arm in disease activity between the ADA- and the ETA-treated populations, with mean DAS28 of 2.7 ±1.2 and 2.3 ±1.2 respectively (p=0.55). The relapse incidence was higher in the ADA than in ETA group: 77.4% vs. 60.3% (p=0.03). The median time to relapse was 12 months in the S arm and 18 months in the M-arm for ETA, and 9 months in the S arm, 18 months in the M-arm for ADA. Comparisons between the use of TNF-blockers as MONO or COMBO showed no significant differences in disease activity: mean DAS28 of 2.7 ±1.3 and 2.4 ±1.1 respectively (p=0.88), nor in relapse rates: 69.7% vs. 67.6% (p=0.8). The median time to relapse was 12 months in the S arm and 18 months in the M-arm for MONO, and 9 months in the S arm, 18 months in the M-arm for COMBO.

Conclusion: The molecule and the way TNF-blockers are prescribed do not influence RA disease activity control. However, the risk of relapse appears higher with ADA compared to ETA in this subgroup analysis.

(ClinicalTrials.gov n°: NCT00780793).

Disclosure of Interest: None Declared