A Trial to Investigate Teprotumumab Subcutaneous Administration Compared With Placebo in Male and Female Adult Participants With Moderate-to-severe Active Thyroid Eye Disease

Eligibility Criteria

• 1. Participant must provide written informed consent.
• 2. Participant can be male or female and must be between the ages of 18 and 80 years, inclusive, at Screening.
• 3. Participant must have a clinical diagnosis of Graves' disease associated with active TED with a CAS ≥ 3 (on the 7-item scale) for the most severely affected eye at Screening and Baseline.
• 4. Participant must have moderate-to-severe active TED (not sight-threatening but has an appreciable impact on daily life), usually associated with 1 or more of the following: lid retraction ≥ 2 mm, moderate or severe soft tissue involvement and/or inconstant or constant diplopia. (Note: Participants with no diplopia at Baseline will be limited to approximately 25% of the total number enrolled.)
• 5. Participant has proptosis ≥ 3 mm from Baseline (prior to diagnosis of TED), as estimated by treating physician, and/or proptosis ≥ 3 mm above normal for race and gender.
• 6. Participant had onset of active TED symptoms (as determined by participant records) within 15 months prior to Baseline.
• 7. Participants must be euthyroid with the baseline disease under control or have mild hypoor hyperthyroidism (defined as free thyroxine \[FT4\] and free triiodothyronine \[FT3\] levels \< 50% above or below the normal limits) at Screening. Every effort should be made to correct the mild hypo- or hyperthyroidism promptly and to maintain the euthyroid state for the full duration of the trial.
• 8. Participant does not require immediate surgical ophthalmological intervention and is not planning corrective surgery/irradiation during the trial.
• 9. Women of childbearing potential must have a negative serum pregnancy test at Screening and negative urine pregnancy tests at all protocol-specified time points (ie, prior to each dose and throughout participation in the trial).
• 10. Participant is willing and able to comply with the protocol requirements for the duration of the trial.
• 1. Participant has decreased best-corrected visual acuity due to optic neuropathy, defined by a decrease in vision of 2 lines on the Snellen chart (or equivalent), new visual field defect or color defect secondary to optic nerve involvement within the last 6 months.
• 2. Participant has corneal decompensation unresponsive to medical management.
• 3. Participant has a decrease in CAS of ≥ 2 points between Screening and Baseline.
• 4. Participant has a decrease in proptosis of ≥ 2 mm between Screening and Baseline.
• 5. Participant had prior orbital irradiation, orbital decompression or strabismus surgery (excluding childhood strabismus surgeries unrelated to TED/Graves' disease).
• 6. Participant is planning to have eyelid surgery during the trial.
• 7. Participant received periocular botulinum toxin injection within 12 months prior to Screening.
• 8. Participant has any systemic use of a steroid (IV or oral) or steroid eye drops for the treatment of TED or other conditions within 3 weeks prior to Screening. Exceptions include local administration (excluding periocular), eg, topical, intra-articular, and inhaled steroids, as well as steroids used to treat infusion reactions.