Inclusion Criteria

• Diagnosis of giant cell arteritis classified according to
  • Age ≥ 50 years
  • History of ESR ≥ 50 mm/hour
  • And at least one of the following
    • Unequivocal cranial symptoms of giant cell arteritis
    • Symptoms of polymyalgia rheumatica
  • And at least one of the following
    • Temporal artery biopsy revealing features of giant cell arteritis
    • Evidence of large-vessel vasculitis
• New onset active disease with diagnosis within 6 weeks of baseline, or refractory active disease with diagnosis > 6 weeks before baseline and previous treatment with ≥ 40 mg/day prednisone (or equivalent) for at least 2 consecutive weeks at any time
  • Active disease defined as presence of clinical signs and symptoms and ESR ≥ 30 mm/hour or CRP ≥ 1 mg/dl within 6 weeks of baseline

Exclusion Criteria

• Recent or oncoming major surgery
• Organ transplantation recipient (except corneas) within 3 months prior to baseline visit
• Major ischemic event, unrelated to giant cell arteritis, within 12 weeks of screening
• Prior treatment with any of the following
  • Investigational agent within 12 weeks (or 5 half-lives of the investigational drug, whichever is longer) of screening visit
  • Cell-depleting agents (e.g. anti CD 20)
  • Tocilizumab
  • Tofacitinib
  • Alkylating agents including CYC within 6 months of baseline
  • HCQ, CsA, AZA, or MMF within 4 weeks of baseline
  • Tumor necrosis factor inhibitors within 2-8 weeks of baseline
  • Anakinra within 1 week of baseline
  • Corticosteroids for conditions other than GCA
  • IV corticosteroids within 6 weeks of baseline
• History of severe allergic reactions to monoclonal antibodies
• Evidence of serious uncontrolled concomitant disease (e.g. cardiovascular, respiratory, renal, endocrine)
• Current liver disease that could interfere with the trial as determined by the investigator
• History of diverticulitis, inflammatory bowel disease, or other symptomatic GI tract condition that might predispose to bowel perforation
• Active current or history of recurrent bacterial, viral fungal, mycobacterial, or other infection
• Prior episode of major infection
• Active TB requiring treatment within the previous 3 years
• Untreated latent TB infection (LTBI)
• Primary or secondary immunodeficiency
• Malignancy, except for basal or squamous cell carcinoma of the skin or carcinoma in situ of the cervix uteri that has been excised and cured
• Inadequate hematologic, renal or liver function
• Positive for hepatitis B or hepatitis C infection