A phase 3 clinical trial has confirmed that regular treatment with tocilizumab, an inhibitor of interleukin–6, successfully reduced both symptoms of and the need for high–dose steroid treatment for giant cell arteritis.

Results of the trial were published in the New England Journal of Medicine.

“This trial is the first to demonstrate beyond any doubt that an alternative to chronic, unending steroid treatment exists. One of the most surprising findings was just how poorly the traditional, steroid–only regimens worked. These results are likely to have an immediate, sustained impact on the lives of hundreds of thousands of patients across the world,” said John Stone, MD, MPH, of the Massachusetts General Hospital (MGH) Rheumatology Unit, lead and corresponding author of the NEJM report.

Tocilizumab is a monoclonal antibody that targets the receptor for the inflammatory cytokine IL–6. Subcutaneous administration of tocilizumab has been FDA approved for treatment of rheumatoid arthritis, and intravenous administration is approved for several other forms of arthritis. For giant cell arteritis, previous studies, including a phase 2 clinical trial, indicated that intravenous tocilizumab allowed a reduction in the steroid doses required to reduce symptoms and maintain remission. The year–long GiACTA trial, the largest ever conducted for giant cell arteritis, enrolled 251 patients at 76 sites in the U.S. and Europe. Participants were randomized into four groups – 100 receiving weekly tocilizumab injections along with prednisone injections that were tapered over 26 weeks; 50 receiving tocilizumab every other week, with a 26–week tapered prednisone dose; 50 receiving weekly placebo injections, with 26–week tapered prednisone doses; and 51 receiving weekly placebo injections with prednisone tapered over 52 weeks. All participants received a weekly or biweekly injection of either tocilizumab or a placebo through the year–long study period.

In both groups receiving tocilizumab, at 52 weeks more than half of the participants had maintained symptom reduction with no steroid dose, compared with 14 percent of those receiving placebo plus prednisone over 26 weeks and 18 percent of those receiving placebo with prednisone over 52 weeks. Around one quarter of those in the two tocilizumab groups experienced symptom exacerbations called flares during the study period, compared with 68 percent of the placebo/26–week prednisone group and 49 percent of the placebo/52–week prednisone group.

Over the entire study period, members of the tocilizumab groups received total prednisone doses averaging 1862 mg, while the placebo/26–week prednisone group averaged 3296 mg and the placebo/52–week prednisone group averaged 3838 mg. Serious adverse events were more likely in the placebo/prednisone groups, probably attributable to the higher cumulative prednisone doses; and participants receiving tocilizumab experienced consistent and significant improvements in their quality of life, details of which will be reported in the future. A two–year extension study, in which patients are eligible to receive tocilizumab on an open–label basis in the event of disease flare, will evaluate the need for and safety of continuing tocilizumab treatment.

“Our data strongly indicate that patients with giant cell arteritis should receive this drug as early in their treatment course as possible, since delay would simply extend the time they must remain on steroids,” said Stone, a professor of Medicine at Harvard Medical School and the Edward A. Fox Chair in Medicine at MGH. “We were also very gratified that none of these patients – even those not receiving tocilizumab – suffered permanent vision loss during the trial, which is a tribute to the rigor with which the trial was conducted and the excellent clinical care delivered at trial sites.”