Ethyreal Bio has exited stealth with $101 million, joining the queue of companies preparing to challenge Amgen’s Tepezza.
Backed by series A and B round investors including Atlas Venture and Medicxi Ventures, the Massachusetts-based biotech has quietly advanced an anti-TSHR antibody to the cusp of clinical development. A first-in-human trial of the asset, dubbed ETHY-001, is scheduled to start this year. Ethyreal is developing the drug candidate in thyroid eye disease (TED) and Graves’ disease (GD).
“These two conditions frequently coexist in the same individual, yet current treatments for GD do not treat or prevent TED, and conversely, TED treatments do not address the hyperthyroidism characteristic of GD,” Ethyreal CEO Niranjan Kameswaran, Ph.D., said in a statement.
Amgen markets Tepezza in TED. With an FDA approval decision due this month, Viridian Therapeutics is at the front of a pack of companies aiming to compete with Amgen’s blockbuster. Tepezza and Viridian’s veligrotug both target IGF-1R. The GD pipeline includes argenx’s efgartigimod, Biohaven Therapeutics’ BHV-1300, Immunovant Sciences’ IMVT-1402 and Sanofi’s rilzabrutinib.
Ethyreal has identified TSHR blockade as a way to treat TED and GD. By stopping autoantibodies from activating the receptor, the biotech aims to treat TED symptoms in the eye while tackling GD by reducing excess thyroid hormone production in thyroid cells.
Other companies are pursuing similar approaches. Changchun GeneScience Pharmaceutical advanced an anti-TSHR antibody into the clinic and sold ex-China rights to the candidate to Yarrow Bioscience for $70 million upfront. Ollin Biosciences also entered the space by partnering with a Chinese biotech, agreeing to a financial package worth up to $440 million for rights to VelaVigo Bio’s TSHRxIGF-1R bispecific.
The TSHR race includes oral antagonists. Crinetics Pharmaceuticals and Septerna have shared preclinical data on “nonpeptide” and small molecule TSHR antagonists, respectively, in recent years, although both biotechs are focused on other programs.
Ethyreal will share more information on its contender next week at the Endocrine Society’s 2026 Annual Meeting. The presentation will cover preclinical data on an anti-TSHR antibody with half-life extension technology that is designed for subcutaneous administration using an autoinjector. Ethyreal has taken the asset toward the clinic using the proceeds of previously undisclosed series A and B rounds.