Treatment of Graves' Orbitopathy (Thyroid Eye Disease) to Reduce Proptosis With Teprotumumab Infusions in a Randomized, Placebo-Controlled, Clinical Study

This is a randomized, double-masked, placebo-controlled, parallel-group, multicenter study. Approximately 76 participants (38/group) who meet the study eligibility criteria will be randomized on Day 1 in a 1:1 ratio (stratified by tobacco use status) to receive 8 infusions of teprotumumab or placebo q3W. All participants will enter a 24-week double-masked Treatment Period, during which study 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). All study drug dosing will be performed at the clinic under the supervision of clinic staff. On each dosing day, scheduled assessments (except for adverse event \[AE\] and concomitant medication use monitoring, which will be monitored throughout the clinic visit) will be completed prior to study drug dosing. At the end of the double-masked Treatment Period (Week 24), participants who are proptosis non-responders (study eye has \< 2 mm decrease in proptosis) will be eligible to enter an open-label extension study in which participants receive 8 infusions of teprotumumab in an open-label fashion. At Week 24, proptosis responders, as well as non-responders who choose not to enroll in the open-label extension study, will enter a 48-week Follow-Up Period, during which study drug will not be administered and clinic visits are scheduled for Weeks 28, 36, 48, 60, and 72. Participants who are considered responders at Week 24 but who meet criteria for re-treatment due to relapse during the Follow-Up Period may enroll in the open-label extension study. Participants who complete the Week 72 Visit will be contacted 6 and 12 months later via phone or email by research staff to enquire if any treatment for TED has been received since last study contact. Study acquired from Horizon in 2024.