The purpose of this study is to evaluate the safety, tolerability, PK, PD, immunogenicity, and preliminary clinical activity of cizutamig in patients with thyroid eye disease (TED).

This is a Phase 1b, open-label, multicenter study evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, immunogenicity, and preliminary clinical activity of cizutamig in patients with thyroid eye disease (TED).

Inclusion Criteria:

• 18-75 years old at the time of signing the Informed Consent Form
• Diagnosis of Graves' Disease with active, moderate to severe TED in accordance with the Chinese Guidelines for the Diagnosis and Treatment of Thyroid-Associated Ophthalmology (2022) at Screening and Day 1

Exclusion Criteria:

• Inadequate clinical laboratory parameters at Screening
• Active infection present
• Receipt of, or inability to discontinue, any of the excluded therapies
• History of progressive multifocal leukoencephalopathy
• History of primary immunodeficiency
• Central nervous system disorders that the investigator considers would increase risk to the subject
• Investigator-determined significant comorbidity(ies)
• Have a diagnosis or history of malignant disease within 5 years prior to Screening
• Active tuberculosis or lack of documentation of completed treatment for active pulmonary tuberculosis
• History of severe allergic or anaphylactic reactions to mAb therapy (or recombinant antibody-related fusion proteins) or any constituents of cizutamig
• Pregnant or breastfeeding women
• Patients who do not agree to use highly effective contraception as specified in the protocol