A Trial Investigating Lu AG22515 in Adult Participants With Moderate-to-Severe Thyroid Eye Disease

Inclusion Criteria: * The participant has Graves' disease associated Thyroid Eye Disease (TED) symptoms characterized by: * ophthalmologic symptom onset \<12 months prior to the Baseline Visit * proptosis ≥3 millimeter (mm) above normal for race and sex measured using the Hertel exophthalmometer (at the Screening Visit and the Baseline Visit) in the most severe eye * Clinical Activity Score (CAS) ≥3 in the most severe eye at the Screening Visit. * The participants must be euthyroid or have mild hypo- or hyperthyroidism (defined as free thyroxin \[FT4\] and/or free triiodothyronine \[FT3\] levels not exceeding the normal limits +/-50%) at the Screening Visit. Exclusion Criteria: * The participant has a decreased best-corrected visual acuity due to optic neuropathy, defined as a decrease in vision of 2 lines on the Snellen chart, new visual field defect, or colour defect secondary to optic nerve involvement, within 6 months prior to the Screening Visit. * The participant has corneal decompensation unresponsive to medical management. * The participant has a decrease in proptosis of ≥2 mm between the Screening Visit and the Baseline Visit. * The participant has a decrease in CAS of ≥2 points between the Screening Visit and the Baseline Visit. * The participant has had previous orbital irradiation or surgery for TED. * The participant requires immediate surgical ophthalmological intervention or has other eye conditions impacting the assessments. * The participant has contraindications for an magnetic resonance imaging (MRI) scan. * The participant has an active infection at Baseline or recent serious infection (for example, requiring hospitalization) within 8 weeks prior to the Baseline Visit. * The participant takes any of the following disallowed or restricted concomitant medications (the list is not comprehensive): * Disallowed: any investigational products within 30 days or 5 half-lives, whichever is longer, prior to the Screening Visit, systemic corticosteroids within 6 weeks prior to the Screening Visit (topical steroids for dermatological conditions, inhaled or intranasal steroids are allowed), systemic immunosuppressive/immunomodulating drugs (for example, rituximab, tocilizumab, methotrexate, cyclosporine, azathioprine, mycophenolate-sodium/mofetil, Janus kinase inhibitors) within 5 half-lives prior to the Screening Visit, live attenuated vaccines within 30 days prior to the Baseline Visit, biotin within 1 day prior to the Screening Visit. * Allowed with restriction: stable dose for \>3 weeks prior to the Screening Visit of selenium. Inactivated/killed/RNA-based vaccinations are allowed provided they are not administered within 5 days before/after any investigational medicinal product (IMP) trial visits.