To evaluate the efficacy of batoclimab 680 milligrams (mg) subcutaneous (SC) once a week (QW) for 12 weeks followed by 340 mg SC QW for 12 weeks versus placebo on proptosis responder rate at Week 24.

Inclusion criteria:

1. Are ≥18 years of age at screening.

2. Have a clinical diagnosis of TED associated with active, moderate to severe TED with the following at screening and Visit 0:

   • A CAS ≥ 4 in either eye, and

   • Clinical evidence of worsened proptosis with:

     • Proptosis ≥ 18 mm and/or
     • Proptosis ≥ 3 mm increase from participant's baseline (prior to diagnosis of TED), as estimated by the Investigator/assessor

3. Have moderate to severe active TED, as defined by European Group on Graves' Orbitopathy (EUGOGO) guidelines.

4. Have onset of active TED within 12 months prior to screening.

5. Have documented evidence of detectable anti-TSHR-Ab at screening.

6. Are not expected to require immediate surgical intervention and are not planning corrective surgery/irradiation or medical therapy for TED during the course of the study.

7. Are euthyroid with the Baseline disease under control or have mild hypo- or hyperthyroidism.

Additional inclusion criteria are defined in the protocol.

Exclusion criteria:

1. Have decreased best corrected visual acuity due to optic neuropathy.
2. Have at least a 2-point decrease in CAS or ≥2 mm decrease in proptosis between screening and Baseline assessments in either eye.
3. Have used any steroid (intravenous or oral) for the treatment of TED or other conditions within 4 weeks prior to screening.
4. Have used any steroid (Intravenous or oral) with a cumulative dose equivalent to ≥ 1 g of methylprednisolone for the treatment of TED.
5. Have known autoimmune disease other than TED, that, in the opinion of the Investigator, would interfere with the course and conduct of the study.
6. Had previous orbital irradiation or surgery for TED.

Additional exclusion criteria are defined in the protocol.

Sponsor Staff is also masked, so the study is Quadruple-blind.