Background/Purpose: GiACTA, a randomized, double-blind, placebo-controlled trial of the interleukin-6 receptor alpha inhibitor tocilizumab (TCZ) in patients (pts) with giant cell arteritis (GCA), is the largest trial conducted in GCA to date (NCT01791153) and the first trial in any disease to use a variable-dose, blinded corticosteroid (CS) taper. The hypothesis is that TCZ is effective at achieving sustained, CS-free remission in pts with GCA. For this analysis, 241 of 251 pts had been enrolled. We report baseline characteristics and compare features of pts with newly diagnosed vs relapsing disease. 

Methods: The 4 major inclusion criteria are age ≥50 y, historical ESR ≥50 mm/h or CRP ≥2.45 mg/dL, unequivocal cranial GCA or polymyalgia rheumatica (PMR) symptoms, and positive temporal artery biopsy (TAB) or imaging study (positron emission tomography, computed tomography angiography, or magnetic resonance angiography) showing large-vessel vasculitis. There are 4 arms: TCZ 162 mg subcutaneous (SC) QW + 6-mo prednisone taper; TCZ 162 mg SC Q2W + 6-mo prednisone taper; 6-mo prednisone taper only; 12-mo prednisone taper only. Initial prednisone dose (20-60 mg/d) is at investigator discretion. The taper is blinded at doses <20 mg/d. Data are from a live study database.

Results: Of the enrolled pts, 119 (49%) have newly diagnosed GCA and 122 (51%) have relapsing GCA; mean ages are 68 y (range, 52-84) and 70 y (range, 52-85), respectively; 76% are women, and 75% of all pts have met the ACR 1990 criteria for GCA in addition to the GiACTA inclusion criteria. At diagnosis, 61% of newly diagnosed and 57% of relapsing pts had PMR symptoms, 75% and 78% had cranial symptoms, and 20% and 17% had PMR symptoms only. At diagnosis, 57% of newly diagnosed and 59% of relapsing pts had positive TAB; 47% and 41% had positive imaging results. More than one-third of pts had negative TAB results or no TAB performed but positive imaging results. Baseline comorbidities in newly diagnosed and relapsing pts include hypertension (50% and 59%), osteoporosis (12% and 19%), and diabetes (13% and 15%). Mean [SD] baseline BMI is higher in relapsing vs newly diagnosed pts (men, 28.8 [6.1] vs 25.8 [4.2]; women, 26.2 [4.8] vs 24.7 [3.9]). Mean [SD] baseline prednisone dose for newly diagnosed GCA pts was 39.8 mg [13.2] vs 29.8 mg [11.8] for relapsing pts; 18% of newly diagnosed and 5% of relapsing pts entered the study on 60 mg/d prednisone, whereas 8% of newly diagnosed and 39% of relapsing pts entered the study at 20 mg/d.

Conclusion: Demographics of the GiACTA population reflect the epidemiologic profile of GCA (Arthritis Care Res. 2015;67:390). Many pts were enrolled based on large-vessel imaging rather than TAB, reflecting the increased use of imaging to diagnose large-vessel vasculitis since development of the 1990 ACR criteria for GCA. The higher baseline prednisone dose in newly diagnosed pts reflects concern about preventing acute damage (eg, vision loss) in that subpopulation; the lower starting dose received by relapsing pts may indicate early detection of relapse and the need to limit toxicity in this CS-exposed subpopulation. Relapsing pts have more comorbidities, likely due to long-term CS treatment for GCA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/baseline-data-on-patients-enrolled-in-a-randomized-double-blind-trial-of-tocilizumab-in-giant-cell-arteritis/