Background/Purpose:  As published in The Lancet online, March 4, 2016, the first randomized, placebo-controlled trial (RCT) of tocilizumab (TCZ) in giant cell arteritis (GCA) showed clinical efficacy of the anti-IL-6 receptor biologic agent in the induction and maintenance of remission for up to 52 weeks. However, very little is known about inflammatory signals in the vessel walls of TCZ-treated patients. Therefore, the aim of this analysis was to evaluate the inflammation of the vessel wall as seen on magnetic resonance angiograms (MRAs) during the RCT and to compare the signals in the two treatment arms.

Methods: In this single-center RCT participants who satisfied the 1990 American College of Rheumatology criteria were randomly assigned in a 2:1 ratio to receive either TCZ (8 mg/kg of body weight) + glucocorticoids (GC) or placebo + GC. Participants received infusions at 4-weekly intervals for 52 weeks, and GC were started at 1 mg/kg/d and then tapered down to zero. GCA was proven by positive temporal artery biopsy and/or assessed as large vessel vasculitis by MRA using a score 0 to 3; 0= no mural thickening (vessel wall diameter < 0.6 mm), no enhancement; 1= no thickening, slight mural enhancement; 2= mural thickening (> 0.6 mm), significant mural enhancement; 3= strong thickening (> 0.7 mm), strong mural and perivascular enhancement. Scores 2 and 3 were considered to represent active mural inflammation. The MRAs were analyzed by two experienced radiologists who were blinded to treatment allocation. If positive at inclusion, MRA was repeated after 3 month and at end of the study. The primary outcome for this analysis was the number of patients with complete remission on MRA based on the vasculitis score at week 12 (GC dose of 0.1 mg/kg/d). The secondary outcome was the number of patients with complete MRA remission at week 52 and the change in the vasculitis score.

Results:  Twenty-eight of 30 randomized patients underwent baseline MRA, 20 in the TCZ + GC group and 8 in the placebo + GC group. 11 MRAs at baseline (9 in the TCZ + GC group and 2 in the placebo + GC group) had no signs of vasculitis. At week 12, MRAs were performed in 9 patients in the TCZ + GC group, all of whom were in clinical remission, and 4 patients in the placebo + GC group, 2 of whom were in remission. Three (33%) patients in the TCZ + GC group were in complete MRA remission, compared to 1 (25%) in the placebo + GC group. At week 52, there was additional improvement, but no complete remission, on MRA in 3 participants in the TCZ + GC group, resulting in a median change in the vasculitis score of -1.0, and no improvement in the remaining 2 participants in the placebo + GC group, resulting in a median change in the vasculitis score of -0.5.

Conclusion:  TCZ induces and sustains clinical remission of GCA but does not completely suppress MR signals of vessel inflammation. Whether these signals are of prognostic importance remains to be determined and should be further evaluated in long-term studies.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tocilizumab-for-the-treatment-of-giant-cell-arteritis-mr-angiography-results-from-the-first-randomized-placebo-controlled-trial/