Why carry out this study?

Giant cell arteritis (GCA) is the most common form of primary systemic vasculitis, predominantly affecting people aged ≥ 50 years.

Oral glucocorticoids (the mainstay treatment for GCA) require dose adjustment upon disease flare, which can lead to prolonged glucocorticoid tapers, high cumulative glucocorticoid exposure, and substantial toxicity; therefore, there is a need for remission maintenance with glucocorticoid-sparing medications in GCA.

Sirukumab, a selective, high-affinity human interleukin (IL)-6 monoclonal antibody, may have therapeutic benefit in GCA by interrupting the IL-6 pathway, which plays a major role in GCA pathophysiology; this two-part, phase 3 randomised, placebo-controlled study aimed to evaluate the efficacy and safety of sirukumab (administered subcutaneously every 2 weeks or every 4 weeks, in addition to a prednisone taper) in patients with GCA, over 52 weeks.

What was learned from the study?

In a subset of patients who completed the study (or discontinued before the study was terminated), sustained GCA remission at week 52 was achieved by a small number of patients, all receiving sirukumab; in the larger, intent-to-treat population of all randomised patients, the proportion of patients with disease flares up to week 52 was lower with sirukumab than placebo.

Although data interpretation was limited due to early termination of the study, and thus a shortened treatment duration, the proportion of patients with disease flare by week 52 tended to be lower with sirukumab versus placebo, and overall, safety findings were consistent with the known safety profile of sirukumab.