gms | German Medical Science

Background: Psoriatic arthritis (PsA) is a heterogeneous disease in which treatment selection and patient stratification based on clinical characteristics have been proposed [1][1]. Efficacy and safety of the co-stimulation modulator abatacept in patients with PsA were investigated in the Phase III ASTRAEA study (NCT01860976) [2]. This analysis aimed to identify baseline factors that predict response to abatacept in patients with PsA in ASTRAEA.

Methods: Baseline disease and demographic characteristics of patients who were treated with abatacept (n=213) or placebo (n=211) and achieved ACR50/ACR70 responses and Disease Activity in Psoriatic Arthritis (DAPSA) low disease activity (LDA) (ACR50: abatacept n=41, placebo n=26; ACR70: abatacept n=22, placebo n=14; DAPSA LDA: abatacept n=56, placebo n=32) at Day 169 (Week 24) were compared with those of patients not achieving an ACR20 response (abatacept n=129, placebo n=164) or DAPSA LDA (abatacept n=142, placebo n=152). Due to the inclusion of an early escape (EE) at Day 113 (Week 16), patients who entered the EE were imputed as non-responders at Day 169 and included in the ACR20 and DAPSA non-responders groups in this analysis.

Results: For both abatacept and placebo groups, most baseline demographic and disease characteristics, including age, BMI and disease activity at baseline, were similar among ACR20 non-responders and ACR50 and ACR70 responders, and among DAPSA LDA non-responders and DAPSA LDA responders (Table 1 [Tab. 1] and Table 2 [Tab. 2], placebo not shown). Unlike placebo, abatacept ACR50, ACR70 and DAPSA LDA responders showed a higher degree of baseline structural damage and higher SJC than ACR20 and DAPSA LDA non-responders. Baseline CRP was higher in both abatacept and placebo ACR50 and ACR70 responders than in ACR20 non-responders; the opposite trend was seen in abatacept and placebo DAPSA LDA responders versus non-responders.

Conclusion: These data show that a higher degree of baseline structural joint damage and higher SJC are associated with a greater response to abatacept in PsA. These observations suggest that patients with active PsA and signs of synovitis-driven osteoclast formation may be good candidates for abatacept treatment. These results are in accordance with recent data showing that cytotoxic T lymphocyte-associated antigen-4 controls osteoclast differentiation and bone resorption [3], and the known mechanism of abatacept on T-cell co-stimulation-mediated inflammation [2].