Effectiveness and drug retention of biologic disease-modifying antirheumatic drugs in Korean patients with late-onset ankylosing spondylitis: Retrospective Cohort Study

Abstract Background: 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).Methods: 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. Results: 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. Conclusion: Inferior clinical efficacy and drug retention rates were found in patients with LOAS receiving bDMARDs using real-world nationwide data. There were no differences among each bDMARD type.