The purpose of this study is to evaluate the efficacy and safety of BHV-1300 in adult participants with Graves' disease who are actively hyperthyroid

Key Inclusion Criteria:

1. Participants must have serologically confirmed Graves' disease as documented by presence of elevated autoantibodies
2. Participants must have active hyperthyroidism due to Graves' disease

Key Exclusion Criteria:

1. History of hyperthyroidism not caused by Graves' Disease (e.g., toxic adenoma or toxic multinodular goiter)
2. History of treatment with radioactive iodine or thyroid surgery.
3. Have received levothyroxine, desiccated thyroid extract, or T3 at any dose within six weeks of the Baseline/Day 1 Visit.
4. Thyroid storm, i.e. severe thyrotoxicosis with evidence of systemic decompensation (e.g., Burch-Wartkofsky Point Scale of ≥ 45 or Japanese Thyroid Association category 1 or 2, with accompanying manifestations including hyperpyrexia, tachycardia, arrhythmias, congestive heart failure, agitation, delirium, psychosis, stupor, and coma, as well as nausea, vomiting, diarrhea, or hepatic failure) within 6 weeks of Screening.
5. Have autoimmune disease other than Graves' disease requiring treatment
6. Have moderate to severe 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.
7. Are expected to require urgent or emergent thyroid surgery or ablation within six weeks of Baseline/Day 1 or throughout the study.