Outcomes of Biologic and Targeted DMARD Therapy in Rheumatoid Arthritis—Overview of Estonian Biologic Treatment Registry

Objective: To provide the first nationwide description of biologic and targeted synthetic DMARD (b/tsDMARD) use among Estonian patients with rheumatoid arthritis (RA), focusing on treatment effectiveness, persistence, and reasons for discontinuation across sequential lines of therapy. Methods: Data were obtained from the Estonian Biologic Therapy Registry covering years 2006–2022. All adult RA patients (ICD-10 M05.8, M06.0) who had received at least one dose of a b/tsDMARD were included. Effectiveness at 6 months was evaluated using DAS28-CRP as a continuous measure (ΔDAS28) and categorical response definitions: remission (DAS28 ≤2.6), low disease activity (LDA ≤3.2), and EULAR response criteria. Treatment persistence was analyzed using Kaplan–Meier estimates, and reasons for discontinuation were categorized systematically. Results: A total of 1,074 patients were analysed (78% female, mean age 53.7 years, 86% sero-positive). Mean baseline DAS28-CRP was 5.3. The mean 6-month reduction in DAS28-CRP during first-line therapy was ~2.3 points. Remission was achieved in ~20% of patients in lines 1–3 and ~15% in later lines, while LDA occurred in 7–10% across lines 1–4. Drug survival was comparable between treatment lines: 60% of patients remained on therapy at 2 years, and the median time to discontinuation for first-line therapy was 1.66 years. Most patients initiated therapy with a TNF inhibitor and many continued within the same class before switching to IL-6 inhibitors, rituximab, or JAK inhibitors. The main reasons for discontinuation were loss or lack of efficacy (~50%) and adverse events (27.5%), predominantly allergic reactions and infections. Conclusions: In real-world Estonian RA practice, biologic and targeted therapies were effective across multiple treatment lines, with the greatest improvement observed during first-line therapy and sustained clinical benefit in later lines. Treatment persistence remained stable despite multiple switches, and the distribution of discontinuation causes mirrored other European registries. These findings support the continued value of sequential b/tsDMARD therapy in achieving disease control among patients with difficult-to-treat RA.