A Study to Evaluate Guselkumab for the Treatment of Participants With New-onset or Relapsing Giant Cell Arteritis

Giant cell arteritis (GCA) is a non-necrotizing granulomatous systemic vasculitis of unknown etiology affecting medium-sized and large arteries usually accompanied or preceded by systemic inflammation. Guselkumab is a monoclonal antibody (mAb) that binds to the p19 sub-unit of human interleukin (IL)-23 with high affinity and blocks binding of extracellular IL-23 to cell surface IL-23 receptor, inhibiting IL 23 specific intracellular signaling and subsequent activation and cytokine production. It is used in treatment of psoriatic arthritis, generalized pustular psoriasis, erythrodermic psoriasis. The study consists of a screening period (less than or equal to \[\<=\] 6 weeks), double-blind treatment period (48 weeks), and safety follow-up period (12 weeks). Participants who complete the Week 52 visit and are assessed to be in glucocorticoid (GC)-free remission, may have the option to participate in the long-term extension (LTE) period of the study for up to 12 months. This study will evaluate the efficacy, safety, Pharmacokinetics (PK), and immunogenicity of guselkumab in combination with a 26-week GC taper regimen for the treatment of active new-onset or relapsing GCA in adult participants. The total duration of the study is up to 66 weeks for the main study and for participants that continue in the LTE period, the total study duration will be up to 112 weeks.