SAT455 A Randomized, Quadruple-masked, Placebo-controlled, Multicenter Trial To Evaluate The Efficacy And Safety Of Teprotumumab In Patients With Chronic (Inactive/Low CAS) Thyroid Eye Disease

Disclosure: R.S. Douglas: Consulting Fee; Self; Horizon Therapeutics plc, Immunovant, Viridian. S. Couch: None. S.T. Wester: Advisory Board Member; Self; Horizon Therapeutics plc. Consulting Fee; Self; Immunovant, Sling. B. Fowler: Consulting Fee; Self; Horizon Therapeutics plc. C. Liu: Other; Self; Walter Kluwer Health. P. Subramanian: Consulting Fee; Self; Gensight, Horizon Therapeutics plc, Viridian. R. Tang: Consulting Fee; Self; Viridian, Alexion, Valenza. Research Investigator; Self; Viridian, Horizon Therapeutics plc, Novartis, Immunovant, Vasaragen. Speaker; Self; Serono Speaker Journal Club. Q.T. Nguyen: None. K. Hsu: Employee; Self; Horizon Therapeutics plc. Stock Owner; Self; Horizon Therapeutics plc. M. Karon: Employee; Self; Horizon Therapeutics plc. Stock Owner; Self; Horizon Therapeutics plc. M.N. Stan: Consulting Fee; Self; Immunovant, Horizon Therapeutics plc, Sling, Genentech, ArgenX. Background: Thyroid eye disease (TED) is characterized by expansion of peri- and retro-orbital fat and muscle, often resulting in disfiguring proptosis (eye-bulging) and diplopia (double vision) which may persist chronically. Teprotumumab, an inhibitor of the insulin-like growth factor-1 receptor, demonstrated improvements in proptosis, diplopia, inflammation and quality of life in clinical trials in patients with TED history of short duration (6-13 months), and active disease (clinical activity score [CAS] ≥4). In a published study of 31 patients with CAS≤3 and TED duration >2 years, teprotumumab reduced proptosis, diplopia and inflammation.(1) We have undertaken the first randomized, placebo (PBO)-controlled trial to evaluate teprotumumab in patients with chronic/inactive/low CAS TED. The trial has completed randomization with results available in May 2023. Here we report characteristics of the randomized patients. Methods: The trial (NCT04583735) is being conducted in 11 centers in the United States. Key inclusion criteria were age≥18 years, TED duration ≥2 years but <10 years and CAS≤1 in both eyes, ≥3mm proptosis from baseline and/normal for sex and race, or no progression in proptosis or diplopia or new inflammatory symptoms in the preceding year. Patients must have been euthyroid or mildly hypo/hyperthyroid, and not require surgical intervention through the trial. Patients could not have received teprotumumab previously, or steroids within 3 weeks before screening. Patients were randomized 2:1 to receive 8 infusions of teprotumumab (10 mg/kg for the first infusion and 20 mg/kg for the remaining 7 infusions) or PBO once every 3 weeks. The primary endpoint is improvement in proptosis (mm) as compared with PBO from baseline at Week 24. Other endpoints include percentage of proptosis responders (improvement of ≥2mm), diplopia responders (improvement of ≥1 grade in diplopia on the Bahn-Gorman scale, 0-3), and improvement in Graves’ Ophthalmopathy- Quality of Life (GO-QoL), all at Week 24. Adverse events (AE) and AE of special interest will be reported. Results: 62 patients were randomized. 80.6% are female, mean (SD) age was 48.7 (14.94) years. 54.8% are White, 24.2 %, Black or African American, and 12.9%, Asian. Mean (SD) TED duration was 5.2 (1.77) years. 87.1% are never/former smokers. At baseline, mean (SD) proptosis in the study eye was 24.4 (2.94) mm, and mean (SD) CAS was 0.4 (0.49). 27.4% had binocular diplopia with a mean diplopia score of 2. The mean overall GO-QoL score was 63.9 indicating similar disutility as observed in the acute trial population (previously published). Results from this 24-week trial will be presented. Conclusions: Despite a long duration of TED and low “activity”, patients enrolled in this trial have high levels of proptosis and impaired quality of life at baseline. Presentation: Saturday, June 17, 2023