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

This is a study to assess the efficacy, safety, and tolerability of IMVT-1402 in adult participants with Graves' disease (GD) who are hyperthyroid despite antithyroid drug (ATD) treatment. The primary objective of this study is to evaluate the efficacy of IMVT-1402 versus placebo as assessed by T3 (total triiodothyronine \[T3\] or free triiodothyronine \[FT3\]), free thyroxine (FT4), thyroid-stimulating hormone (TSH), and ATD dose at Week 26.

Inclusion Criteria: * Participants with the ability to understand the requirements of the trial, provide written informed consent, and comply with the trial protocol procedures. * Male or female participants aged ≥ 18 years. * Participants with diagnosis of GD who are hyperthyroid despite ATD treatment. * Other, more specific inclusion criteria are defined in the protocol. Exclusion Criteria: * Have previously been successfully treated with radioactive iodine (RAI) therapy or have undergone total thyroidectomy. * Have an autoimmune disease other than GD requiring treatment that, in the Investigator's judgment, puts the participant at undue risk. * Have moderate-to-severe active thyroid eye disease (TED) and are expected to require immediate surgical intervention and/or are planning corrective surgery/irradiation or medical therapy for TED during study participation. * Additional exclusion criteria are defined in the protocol.