Inclusion Criteria:

-Clinical diagnosis of Graves' disease associated with moderate to severe active TED
-Onset of active TED symptoms within approximately 12 months
-Proptosis (exophthalmos) ≥3 mm above the normal range (based upon race and gender) for the study eye
-CAS ≥4 (on the 7-item scale) for the study eye
-Presence of thyroid stimulating immunoglobulin (TSI) above the upper limit of normal 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 steroid (oral or IV) 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 <1 g methylprednisolone (or equivalent dosage for other systemic corticosteroid) for the treatment of TED is allowed if the corticosteroid is discontinued at least 6 weeks before screening.
-Systemic (oral or IV) corticosteroid use for conditions other than TED within 3 months before screening.
-Any major illness/condition or evidence of an unstable clinical condition that, in the investigator's judgment, will substantially increase the risk to the participant, or confound the interpretation of safety assessments, if they were to participate in the study
-Any other condition that, in the opinion of the investigator, would impair the ability of the participant to comply with the study procedures or impair the ability to interpret data from the participant's participation in the study
-Pregnant or lactating Additional exclusion criteria are defined in the study protocol.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 5/23/2024. Questions regarding updates should be directed to the study team contact.