IBI311 Efficacious and Safe in Reducing Proptosis in Thyroid Eye Disease

IBI311, an insulin-like growth factor 1 receptor (IGF-1R) inhibitor, has successfully improved proptosis and disease activity in patients with moderate-to-severe thyroid eye disease (TED) who responded poorly to glucocorticoid therapy.1

These data, presented at the American Association of Clinical Endocrinology (AACE) Annual Meeting 2026 in Las Vegas, Nevada, by Xiuying Zhang, PhD, department of endocrinology and metabolism, Peking University People’s Hospital, followed up the phase 3 RESTORE-1 study in China, which saw IBI311 (teprotumumab N01) demonstrate promising results in TED.1

The present study was a randomized, double-masked, placebo-controlled clinical trial, enrolling patients between 18 and 80 years and with a weight between 45 and 100 kg (99 and 220.5 lb). Additionally, patients were required to have a clinical diagnosis of Graves’ disease associated with active TED, with a Clinical Activity Score (CAS) ≥3 for ≥1 eye at screening and baseline, as well as moderate-severe active TED. Patients with optimal corrected vision loss due to optic neuropathy, corneal ulcers, or baseline CAS decreased by >2 points versus screening, among other criteria, were excluded.2

Following enrollment, patients were stratified by baseline activity and randomly assigned in a 2:1 ratio to receive either IBI311 or placebo. Both treatments were given every 3 weeks for 4 infusions of 10mg/kg at day 1 and 20 mg/kg at weeks 3, 6, and 9. Patients were then evaluated at week 12, after which both arms were given another 4 infusions of IBI311 from week 12 to 21.1

The study’s primary outcome was proptosis responder rate of the study eye, which was defined as the percentage of patients with a ≥2 mm reduction from baseline in proptosis without deterioration proptosis in the non-study eye. Secondary outcomes included the overall responder rate in the study eye, the percentage of subjects with a CAS value of 0 or 1 in the study eye, and the mean change from baseline in proptosis measurement, among others.2

A total of 53 patients were included in the study, of whom 36 received IBI311 and 17 received placebo. Baseline characteristics were relatively balanced across both arms. By week 12, proptosis response was substantially higher with IBI311 than with placebo (58.3% vs 29.4%; P = .034). The IBI311 group also demonstrated greater mean reductions in proptosis (-2.28 vs -0.77 mm; P = .001) and CAS (-1.8 vs -0.7; P = .003).1

Patients with active TED in the IBI311 arm achieved a superior overall response rate (46.2% vs 16.7%; P = .043), and a higher proportion of patients reached a CAS of 0 or 1 in the IBI311 arm. Diplopia response was numerically higher in the IBI311 arm. After transitioning from placebo to IBI311, patients in both arms saw sustained and further improved therapeutic benefits through week 24.1

“In participants with moderate-to-severe TED with poor response to glucocorticoid therapy, IBI311 demonstrated significant efficacy in improving proptosis and disease activity and was well tolerated,” Zhang and colleagues wrote. “These findings support IGF-1R inhibitors as a promising treatment option for this population with unmet clinical need.”1

References

1. Zhang XY, Zhao W, Li TY, et al. Efficacy and Safety of IBI311 in Thyroid Eye Disease (TED) Poorly Responsive to Glucocorticoids: A Randomized, Double-Masked, Placebo-Controlled Trial. Abstract presented at the American Association of Clinical Endocrinology Annual Meeting 2026, Las Vegas, NV. April 22-24, 2026.

2. Innovent Biologics (Suzhou) Co. Ltd. A Study of IBI311 in Subjects With Active Thyroid Eye Disease. ClinicalTrials.gov Identifier: NCT05795621. Updated February 8, 2024. Accessed April 22, 2026. https://clinicaltrials.gov/study/NCT05795621