A Study to Assess Efficacy and Safety of Efgartigimod PH20 SC PFS in Adult Participants With Graves' Disease

Inclusion Criteria: * Is at least 18 years of age and the local legal age of consent for clinical studies when signing the ICF. * Has a documented diagnosis of GD with TRAb (anti-thyrotropin receptor antibody) levels \>=ULN (upper limit of normal) at screening. * Has active hyperthyroidism due to GD with TSH (thyroid-stimulating hormone) \<0.1 mIU/L at screening. * Has been treated with MMI (methimazole) or CBZ (carbimazole) for at least 3 months before screening. Exclusion Criteria: * History of hyperthyroidism not caused by GD (eg, toxic adenoma or toxic multinodular goiter). * History of RAI (radioactive iodine) therapy or received a total thyroidectomy. * T3- or T4-containing medication or supplement (eg, levothyroxine, liothyronine, desiccated thyroid preparations, or thyroid-support supplements) received \<6 weeks before screening. * Any complication of hyperthyroidism or underlying medical condition that would put the participant at undue risk. This includes arrhythmia or tachyarrhythmia related to GD, such as atrial fibrillation or atrial flutter not sufficiently controlled with medications. * Graves' orbitopathy/Thyroid Eye Disease (GO/TED) requiring systemic therapy (eg, corticosteroids), orbital injections, orbital surgery, or orbital radiation, or expected immediate surgical intervention and/or planned corrective surgery/irradiation or medical therapy during the study.