TocilizuMab discontinuAtion in GIant Cell Arteritis

Giant cell arteritis (GCA) is a large-vessel vasculitis that typically occurs in people over the age of 50. Corticosteroids (GC) are the cornerstone of treatment for GCA. French guidelines recommend starting at 0.7 or 1 mg/kg/day at diagnosis, depending on the occurence of ischemic complication(s). Then, it is recommended to gradually decrease their dose to achieve withdrawal in 12 to 24 months. Despite this treatment, 47% of patients relapse. Relapses are favored by rapid reduction of corticosteroid doses and large vessel involvement at diagnosis. Fortunately, relapses are severe in only 3.3% of cases and ischemic complications are very rare. However, this contributes to prolonging the duration of corticosteroid treatment and thus the risk of cortico-induced adverse events, which have not been significantly reduced in the last 20 years. The main risk factors for the development of steroid-related complications are advanced age and cumulative steroid dose. For this reason, the development of cortisone-sparing strategies is necessary to improve the management of patients with GCA. Thanks to major advances in the understanding of the pathophysiological mechanisms of GCA, new therapeutic targets have been discovered. For example, the efficacy of tocilizumab (TCZ), an anti-IL-6 receptor monoclonal antibody, has been demonstrated in two phase 2 trials and one phase 3 trial, leading to its approval for the management of patients requiring rapid reduction in corticosteroid doses and/or those relapsing repeatedly on prednisone \>7.5 mg/day. In recently published US guidelines, TCZ can even be used at diagnosis to reduce the need for corticosteroid therapy.5 Indeed, TCZ appears to be remarkably effective in controlling GCA activity and saves approximately 2000 mg of prednisone in cumulative dose. At present, the place of TCZ compared to methotrexate in the therapeutic strategy is still being evaluated, notably through the METOGiA study (PHRC-N 2017), which is being condu