A Study to Investigate Efficacy and Safety of TOUR006 in Participants 18 to 80 Years of Age With Thyroid Eye Disease

Inclusion Criteria: * Clinical diagnosis of Graves' disease associated with moderate to severe active TED * Onset of active TED symptoms within approximately 15 months * Proptosis (exophthalmos) ≥3 mm above the normal range per investigator judgment (based upon race and gender) for the study eye * CAS ≥4 (on the 7-item scale) for the study eye * Presence of TSI \>130% of the normal reference standard or \>0.55 IU/L (depending on assay method) and laboratory reference ranges Additional inclusion criteria are defined in the study protocol. Exclusion Criteria: * Anticipated need for intervention due to sight-threatening complications or other significant and acute deterioration in vision * Any previous treatment with teprotumumab or other agent that inhibits the IGF-1 receptor * History of systemic (eg, oral or IV) steroid use with a cumulative dose equivalent to \>1 g of methylprednisolone for the treatment of TED. Previous oral steroid use with a cumulative dose of ≤1g methylprednisolone (or equivalent dosage for other systemic corticosteroid) for the treatment of TED, however, is allowed if the corticosteroid was discontinued at least 6 weeks before baseline (Day 1) and completely tapered by Baseline (if applicable). * Systemic (oral or IV) corticosteroid use for conditions other than TED within 6 weeks of baseline (Day 1) or not completely tapered by baseline (if applicable). * Any major illness/condition or evidence of an unstable clinical condition that, in the investi…