This is a randomized, double-masked, placebo-controlled, parallel-group, multicenter trial. Participants will be screened for the trial within 4 weeks prior to Baseline (Day 1). Approximately 57 participants who meet the trial eligibility criteria will be randomized on Day 1 in a 2:1 ratio to receive 8 infusions of TEPEZZA or placebo once every 3 weeks.~All participants will enter a 24-week double-masked Treatment Period, during which trial drug will be infused on Day 1 (Baseline) and Weeks 3, 6, 9, 12, 15, 18 and 21 (with a final visit at Week 24 of the 24-week Treatment Period). At the end of the double-masked Treatment Period (Week 24), all patients will be assessed for treatment response. Non-responders may choose to receive 8 infusions of TEPEZZA in an open-label fashion q3W at Weeks 24, 27, 30, 33, 36, 39, 42 and 45.
The overall objective is to investigate the efficacy, safety and tolerability of TEPEZZA® in participants with chronic (inactive) TED (thyroid eye disease). Approximately 57 participants will be enrolled. There will be a treatment period (through Week 24) and a follow up period (where TEPEZZA will not be infused).