Unveiling difficult-to-treat rheumatoid arthritis: long-term impact of biologic or targeted synthetic DMARDs from the KOBIO registry

BACKGROUND: While the availability of biological or targeted synthetic disease-modifying anti-rheumatic drugs (b/tsDMARDs) has improved outcomes for rheumatoid arthritis (RA) patients, there remains a subset of individuals who fail to achieve low disease activity or remission despite multiple cycles of b/tsDMARDs. This state is referred to as 'difficult-to-treat (D2T)' RA. METHODS: Data from the Korean College of Rheumatology Biologics registry were utilized to analyze patients with RA who were treated with b/tsDMARDs. RESULTS: Among 2,321 RA patients with RA treated with b/tsDMARDs, 271 (11.7%) were diagnosed with D2T RA. Lower age (OR = 0.98, p < 0.001), longer disease duration (OR = 1.06, p < 0.001), lower patient global assessment (OR = 0.89, p = 0.045), higher SDAI (OR = 1.06, p = 0.014) and RAPID3 (OR = 1.06, p = 0.002), lower RF positivity (OR = 0.65, p = 0.04), and lower prior use of methotrexate (OR = 0.44, p = 0.008), sulfasalazine (OR = 0.59, p = 0.003), and leflunomide (OR = 0.67, p = 0.013) were associated with D2T RA. The drug survival rate of b/tsDMARDs did not differ between patients with D2T RA and non-D2T RA (p = 0.35). However, the drug survival of individual b/tsDMARD differed between patients with D2T RA and non-D2T RA after eight years. Patients with D2T RA withdrew from b/tsDMARDs due to inefficacy more frequently than those without D2T RA (p < 0.001). CONCLUSIONS: D2T RA patients experienced higher disease activity despite maintaining b/tsDMARD therapy. Withdrawal rates due to inefficacy were higher in D2T RA. Effective therapeutic strategies are needed to improve disease control and treatment outcomes in this unique patient population.