Evaluation of YB-101 for Safety, Tolerability, Pharmacokinetics, and Efficacy in Graves' Disease

This study is being conducted to look at the effect YB-101 has on thyroid function. This study will also evaluate how safe and well tolerated YB-101 is and how it is distributed through the body. The study consists of a part 1, blinded treatment period, and a part 2 double-blinded treatment period. Participants will receive YB-101 or Placebo subcutaneously. Participants who participate in Part 1 can not participate in Part 2. Participants will complete 34-39 in-clinic visits in Part 1 or Part 2 over an approximate 40 week period.

Inclusion Criteria: * Have a documented diagnosis of Graves' Disease confirmed by the presence of thyroid-stimulating hormone receptor antibodies (TRAbs) by medical history or screening laboratory assessment * Have a pre-existing diagnosis of TED or, conversely, no evidence of TED at the ophthalmological examination performed during screening * Additional inclusion criteria are defined in the protocol Exclusion Criteria: * Previously treated with radioactive iodine (RAI) therapy or underwent total thyroidectomy * Received any dose of levothyroxine, desiccated thyroid extract, or T3 within 6 weeks before screening * Current treatment with teprotumumab or exposure to teprotumumab within 15 weeks prior to screening * History of hyperthyroidism not caused by Graves' disease (eg. toxic adenoma, or toxic multinodular goiter) within 6 months before the screening visit * Pregnant or lactating women * Additional exclusion criteria are defined in the protocol