A Study to Assess the Efficacy, Safety, and Tolerability of IMVT-1402 as Treatment for Adult Participants With Graves' Disease

Inclusion Criteria:

• Have documented diagnosis of GD.

• Have a TSH value < 0.1 mIU/L as assessed by the local laboratory at the ScreeningVisit.

• Meet one of the following at the Screening Visit:

• Have been on ATD for ≥ 3 months in the period immediately preceding theScreening Visit and both of the following:

• Are on ATD at the Screening Visit with an ATD dose of ≥ 20 mg/daymethimazole or equivalent for the 4-week period immediately preceding theScreening Visit.

• Are anticipated to be on a stable dose of ATD for the 4-week periodimmediately preceding Randomization.

• Have been on ATD for ≥ 6 months in the period immediately preceding theScreening Visit and all of the following:

• Have been treated with ≥ 15 mg/day methimazole or equivalent at any pointduring the participant's treatment history.

• Are on ATD at the Screening Visit with an ATD dose a specified amount ofmethimazole or equivalent for the 4-week period immediately preceding theScreening Visit.

• Are anticipated to be on a stable dose of ATD for the 4-week periodimmediately preceding Randomization.

Additional inclusion criteria are defined in the protocol.

Exclusion Criteria:

• Have previously been treated with radioactive iodine (RAI) therapy or have undergonetotal thyroidectomy.

• Have a T3 (Total T3 or FT3, as available and per standard of care at locallaboratory) or FT4 value < lower limit of normal (LLN) as assessed by the locallaboratory at the Screening Visit.

• Have received levothyroxine, desiccated thyroid extract, or T3 at any dose within 6weeks of the Screening Visit.

• Have a history of hyperthyroidism not caused by GD (e.g., toxic adenoma or toxicmultinodular goiter) and/or history of thyroid storm within 6 months of theScreening Visit.

• Have an autoimmune disease other than GD requiring treatment that, in theInvestigator's judgment, puts the participant at undue risk.

• Have moderate-to-severe active thyroid eye disease (TED) and are expected to requireimmediate surgical intervention and/or are planning corrective surgery/irradiationor medical therapy for TED during study participation.

Additional exclusion criteria are defined in the protocol.