Treatment of Graves' Ophthalmopathy

Eligibility Details: Inclusion Criteria: 1. Male or female ≥ 18 years of age. 2. Clinical diagnosis of Graves' disease with hyperthyroidism associated with active, moderate to severe GO with a Clinical Activity Score (CAS) ≥ 4 for the most severely affected eye at Screening and Baseline (on the 7-item scale). 3. Onset of active GO within 9 months of screening. 4. Moderate-to-severe active GO (not sight-threatening but has an appreciable impact on daily life), usually associated with one or more of the following: lid retraction ≥ 2 mm, moderate or severe soft tissue involvement, proptosis ≥ 3 mm above normal for race and gender, and/or inconstant or constant diplopia. 5. Other, more specific inclusion criteria are defined in the protocol Exclusion Criteria: 1. Use of any steroid (IV, oral, steroid eye drops) for the treatment of GO or other conditions within 3 weeks prior to Screening. Steroids cannot be initiated during the trial. Exceptions include topical and inhaled steroids which are allowed. 2. Use of rituximab, tocilizumab, or any monoclonal antibody for immunomodulation within the past 9 months prior to Baseline. 3. Total IgG level < 6g/L at Screening. 4. Absolute neutrophil count <1500 cells/mm3 at Screening. 5. Participants with decreased best corrected visual acuity due to optic neuropathy as defined by a decrease in vision of 2 lines on the Snellen chart, new visual field defect, or color defect secondary to optic nerve involvement within the last 6 months at Screening. 6. Previous orbital irradiation or surgery for GO. 7. Other, more specific exclusion criteria are defined in the protocol