Reply.

Thank you for allowing us to respond to the letter by Samson and Bonnotte regarding our recent manuscript "Ustekinumab for the treatment of giant cell arteritis" [1]. Our results demonstrated that ustekinumab (UST) was well tolerated, but did not prevent disease relapse in a significant proportion of giant cell arteritis (GCA) patients once prednisone was discontinued or tapered to a low daily dose. The letter suggests that it may be too early to draw conclusions regarding the efficacy of UST as a glucocorticoid-sparing drug in GCA for two reasons. First, the study was not controlled, and second, the prednisone taper used was short, perhaps not allowing UST to exert its putative corrective actions in GCA [2], which would be expected 8-12 weeks after treatment initiation.