Predictors of therapeutic response in ankylosing spondylitis patients initiating therapy with adalimumab in a german non-interventional study

Background/Purpose: Ankylosing spondylitis (AS) is associated with a significant burden of illness and has limited treatment options. The identification of predictors of response to anti-tumor necrosis factor (TNF) therapy may help clinicians select therapy and address patient expectations. Methods: We analyzed data from a large German multicenter, prospective, observational study of patients with active AS who initiated adalimumab (ADA) therapy during routine clinical care. Multiple regression models were used to evaluate significant predictors of improvement at month 12 in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Bath Ankylosing Spondylitis Functional Index (BASFI). For both indices, higher scores indicate greater disease activity/impairment. Results: Patients in the full analysis set (N = 3756) had a mean age of 43.0 ± 12.2 years and a mean disease duration of 14.2 ± 10.9 years. During ADA therapy, mean BASDAI scores improved from 5.5 ± 1.9 at baseline to 3.1 ± 2.1 at month 12 and BASFI scores improved from 4.9 ± 2.4 at baseline to 3.2 ± 2.4 at month 12 in evaluable patients remaining on therapy. Although both HLAB27 status and baseline erythrocyte sedimentation rate (ESR) were positive predictors of therapeutic response for BASDAI and BASFI (Table), the strongest positive predictors were not shared between these two indices (dactylitis and baseline BASDAI for BASDAI, baseline BASFI and employment for BASFI). In contrast, most of the negative predictors of response were shared between the BASDAI and BASFI, including the two strongest predictors, mental disorder/depression and a greater number of previous biologics. Conclusion: AS patients showed marked improvement in BASDAI and BASFI during 12 months of treatment with ADA in routine clinical practice. Positive predictors of response to ADA therapy differ between BASDAI and BASFI in AS patients, but negative predictors are generally shared.