Towards the Lowest Efficacious Dose: Results From a Multicenter Noninferiority Randomized Open-Label Controlled Trial Assessing Tocilizumab or Abatacept Injection Spacing in Rheumatoid Arthritis in Remission.

Objective: We assess the clinical and structural impact at two years of progressively spacing tocilizumab (TCZ) or abatacept (ABA) injections versus maintenance at full dose in patients with rheumatoid arthritis in sustained remission.

Methods: This multicenter open-label noninferiority (NI) randomized clinical trial included patients with established rheumatoid arthritis in sustained remission receiving ABA or TCZ at a stable dose. Patients were randomized to treatment maintenance (M) at full dose (M-arm) or progressive injection spacing (S) driven by the Disease Activity Score in 28 joints every 3 months up to biologics discontinuation (S-arm). The primary end point was the evolution of disease activity according to the Disease Activity Score in 44 joints during the 2-year follow-up analyzed per protocol with a linear mixed-effects model, evaluated by an NI test based on the one-sided 95% confidence interval (95% CI) of the slope difference (NI margin 0.25). Other end points were flare incidence and structural damage progression.

Results: Overall, 202 of the 233 patients included were considered for per protocol analysis (90 in S-arm and 112 in M-arm). At the end of follow-up, 16.2% of the patients in the S-arm could discontinue their biologic disease-modifying antirheumatic drug, 46.9% tapered the dose and 36.9% returned to a full dose. NI was not demonstrated for the primary outcome, with a slope difference of 0.10 (95% CI 0.10-0.31) between the two arms. NI was not demonstrated for flare incidence (difference 42.6%, 95% CI 30.0-55.1) or rate of structural damage progression at two years (difference 13.9%, 95% CI -6.7 to 34.4).

Conclusion: The Towards the Lowest Efficacious Dose trial failed to demonstrate NI for the proposed ABA or TCZ tapering strategy.