Background/Purpose: The efficacy of tocilizumab (TCZ), an anti-IL-6 targeted monoclonal antibody, in patients with refractory GCA has been demonstrated. The purpose of this study was to investigate the persistence of clinical remission after TCZ interruption. We also evaluated the role of acute-phase reactants and ¹⁸F-Fluorodeoxyglucose Positron Emission Tomography (¹⁸F-FDG –PET) in predicting the relapse and remission, and the occurrence of adverse event (AEs).

Methods:

All refractory GCA patients with involvement of aorta and its thoracic branches received prednisone (PDN) 50 mg/day and intravenous TCZ (TCZiv) 8 mg/Kg/monthly or subcutaneous TCZ (TCZsc) 162 mg/weekly. PDN was tapered and withdrawn at month 2.

At month 6, in patients achieving a stable remission, TCZ was bimonthly tapered as follows: TCZiv 2 mg/Kg, and TCZsc 1 injection every 2, 3 and 4 weeks until month 12. In responders both treatments were interrupted at month 12.

Remission was assessed at months 6, 12, and 18 by the evaluation of GCA symptoms and signs, patient global health assessment by visual analogue scale 1 to 10 (VAS), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP). ¹⁸F-FDG –PET was performed at baseline, month 6, and 2 months after TCZ withdrawn. A Standardized Uptake Value normalized for liver uptake (nSUVmax) ≤ 1 was assumed as normal.

Anova test and Person test were used to measure the difference between groups and for correlations respectively.

Results:

15 patients were enrolled, 12 females and 3 males, mean age at diagnosis was 69.8 years (±7.70 SD). Seven patients were treated with TCZiv and 8 patients with TCZsc. After 2 months of TCZ therapy all patients stopped CS, and after 6 months of TCZ treatment all patients were in clinical (VAS mean value 2.01 ±0.76SD), laboratory (ESR 9 mm/1h ±6.66 SD; CRP 0.29 mg/dl ±0.27SD) remission. 11 patients completed the 12-month scheduled follow-up. Of these, 7 maintained the drug-free remission that persisted over a median follow up of 12 months afterward. After 2 months from TCZ discontinuation, in the 7 remitting patients SUVmax and nSUVmax were significantly reduced as compared with baseline, while no differences resulted with ¹⁸F-FDG –PET values at month 6. (table 1).

A correlation between nSUVmax and VAS and CRP was found (Pearson 0.9: p 0.0005 and 0.59 p 0.006, respectively).

Four patients reactivated after two months of TCZ discontinuation with median VAS 7,9, median ESR 50, median CRP 1.66. Two patients had stable disease with every other week TCZsc and 2 patients with monthly TCZsc. None of the patients required CS. No AEs were recorded. The remaining 4 patients with incomplete follow up, were in remission with no flares after 8,10, and 12 months of treatment.

Conclusion: Drug-free remission maintenance after TCZ discontinuation seems to be a proposable strategy in GCA.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/tocilizumab-interruption-in-patients-with-giant-cell-arteritis-achieving-the-clinical-remission-interim-analysis-of-an-open-label-18-month-pilot-study/