Ethyreal Bio raises $101M to develop antibody targeting Graves disease and thyroid eye disease

Ethyreal Bio, a Cambridge-based biotech that has just emerged from stealth mode, announced it has closed a $101 million financing round to advance its lead candidate.

The company’s candidate, a monoclonal antibody called ETHY-001, is designed to block the thyroid-stimulating hormone receptor (TSHR) on thyroid cells, a pathway that drives both Graves disease and thyroid eye disease. By inhibiting this receptor, the drug aims to halt hyperthyroidism and the inflammatory eye symptoms that accompany the conditions.

ETHY-001 is being formulated for a long-acting subcutaneous injection, which could simplify dosing compared with existing therapies. Ethyreal plans to begin first-in-human trials in the second half of 2026 and will present preclinical data at an upcoming medical conference.