Teprotumumab N01 for thyroid eye disease in China: clinical outcomes and quantitative MRI correlations

Teprotumumab is an IGF-1R-targeted therapy for thyroid eye disease (TED). In routine practice, response assessment remains challenging and standardized imaging biomarkers are lacking.

To evaluate the real-world effectiveness of domestically produced teprotumumab N01 injection (SYCUME®) in Chinese patients with TED and to identify inferior rectus (IR)-focused quantitative MRI measures associated with changes in proptosis and disease activity.

We conducted a retrospective real-world study of patients with active moderate-to-severe TED who completed a full course of teprotumumab N01 between March and December 2025. Orbital MRI was acquired before and after treatment. IR, lacrimal gland (LG), and orbital fat (OF) were obtained using ROI-based analysis on MAGiC (T1, T2, proton density) and IDEAL-IQ (fat fraction). MRI proptosis and coronal morphologic measures were quantified in 3D Slicer. Eye-level changes and associations between clinical outcomes and MRI parameter changes (Δ, post minus pre) were analyzed using linear mixed-effects models with a subject-specific random intercept, with Benjamini-Hochberg adjustment for MRI parameters. Laboratory indices and GO-QOL were analyzed at the patient level.

Twenty-two patients (44 orbits) were analyzed. Hertel proptosis and CAS decreased after treatment (both p < 0.001). MRI proptosis decreased (p < 0.001) with reductions in IR maximum coronal length and width (both p < 0.001). IR ADC decreased (p = 0.010). Mapping metrics showed decreases in IR T1 and proton density (both p < 0.001), while IR T2 did not reach statistical significance. Fat fraction increased in IR and OF. In Δ analyses, ΔMRI proptosis was associated with ΔIR maximum coronal length and width, and ΔCAS was associated with ΔIR morphologic changes and ΔIR ADC, with additional associations involving selected LG and OF quantitative parameters after multiple-comparison adjustment. Thyroid hormone levels remained stable overall. Selected antibodies and IGF-1 changed significantly. GO-QOL improved (all p < 0.001). At the patient level, only Δ TRAb and ΔIGF-1 were associated with ΔCAS, and no laboratory change was associated with ΔGO-QOL.

In this real-world Chinese cohort, teprotumumab N01 was associated with concordant clinical improvement and quantitative MRI changes. IR-focused morphologic measures and diffusion-derived ADC showed the most consistent associations with changes in proptosis and disease activity, supporting their further evaluation for treatment monitoring in TED.