Effectiveness and drug retention of biologic disease modifying antirheumatic drugs in Korean patients with late onset ankylosing spondylitis

The clinical data on the biologic disease-modifying antirheumatic drug (bDMARD) use in late-onset ankylosing spondylitis (LOAS) is limited. Thus, this study aimed to evaluate the drug efficacy and retention rate of bDMARDs in LOAS and compare it to young-onset ankylosing spondylitis (YOAS). Data of patients with AS receiving bDMARDs were extracted from the Korean College of Rheumatology Biologics and Targeted Therapy registry. Patients whose age of onset was > 50 years and ≤ 50 years were classified as having LOAS and YOAS, respectively. Their baseline characteristics and disease-associated parameters were evaluated. Drug efficacy [Ankylosing Spondylitis Disease Activity Score (ASDAS)-clinically important improvement (CII), ASDAS-major improvement (MI), Assessment of SpondyloArthritis International Society (ASAS) 20, and ASAS 40] at 1-year follow-up and drug retention rates were assessed. A total of 1708 patients (comprising 1472 patients with YOAS and 236 patients with LOAS) were included in this analysis. The LOAS group had a lower prevalence among males, lower HLA-B27 positivity and a higher prevalence of peripheral arthritis. Patients with LOAS were more likely to have higher disease-associated parameters (inflammatory reactants, patient global assessment, ASDAS-erythrocyte sedimentation rate, and ASDAS-C-reactive protein). LOAS was negatively associated with achieving ASDAS-CII, ASAS 20, and ASAS 40. The drug retention rate was lower in LOAS; however, the propensity score-matched and covariate-adjusted hazard ratios for bDMARD discontinuation were comparable to YOAS. There were no differences in the drug retention rates based on the type of bDMARD used in LOAS. Inferior clinical efficacy and shorter drug retention time were found in patients with LOAS receiving bDMARDs using real-world nationwide data. There were no differences among each bDMARD type.