Implementation of the OMERACT Psoriatic Arthritis Magnetic Resonance Imaging Scoring System in a randomized phase IIb study of abatacept in psoriatic arthritis

Objectives

Investigate if the OMERACT Psoriatic Arthritis MRI Scoring System (PsAMRIS), including a novel total inflammation score, shows sensitivity to change with an agent (abatacept) known to impact clinical outcomes in PsA.

Methods

Post hoc analysis of randomized phase IIb study of abatacept in patients with PsA and inadequate DMARD response. Participants received one of three abatacept dosing regimens (ABA3, ABA10 or ABA30/10 mg/kg [30 mg/kg switched to 10 mg/kg after two doses]) or placebo until day (D)169, then ABA10 through D365. MRIs at baseline, D85, D169 and D365 were centrally evaluated by two readers blinded to chronological order and treatment arm. Synovitis, osteitis, tenosynovitis, periarticular inflammation, bone erosions, joint space narrowing and bone proliferation were assessed using PsAMRIS. A novel total inflammation score was tested.

Results

MRIs for 123 patients were included. D169: ABA10 and ABA30/10 significantly reduced MRI synovitis and tenosynovitis, respectively, vs placebo (differences −0.966 [p = 0.039] and −1.652 [p = 0.014], respectively). Synovitis in the placebo group increased non-significantly from baseline to D169; total inflammation and tenosynovitis decreased non-significantly; all measures improved significantly after switch to ABA10 (−1.019, −0.940, −2.275 [p < 0.05], respectively, D365 vs D169). Structural outcomes changed minimally across groups.

Conclusion

Adults with PsA receiving ABA10 and ABA30/10 demonstrated significant resolution of inflammatory components of disease, confirmed by MRI, with synovitis and tenosynovitis improvements consistent with previously reported clinical responses for these doses. Results indicate that reduction in OMERACT PsAMRIS inflammation scores may provide proof of tissue-level efficacy in PsA clinical trials.

ClinicalTrials.gov registration

ClinicalTrials.gov, https://clinicaltrials.gov, NCT00534313