Cambridge, Massachusetts-based Ethyreal Bio has emerged from stealth with USD 101 million in financing to advance ETHY-001, a monoclonal antibody targeting the thyroid stimulating hormone receptor (TSHR), for Graves' disease and thyroid eye disease. The financing reflects growing investor interest in therapies targeting the underlying autoimmune drivers of Graves' disease, an area that has attracted increasing competition in recent years.
The capital was raised across two tranches: a Series A co-led by Atlas Venture and Medicxi Ventures, with participation from Nandi Life Sciences and Checkpoint Capital, followed by a Series B led by Avoro Capital with all Series A investors participating. The company said proceeds will fund advancement of ETHY-001 into first-in-human clinical trials, which it plans to initiate in H2 2026. No prior funding rounds were disclosed.
ETHY-001 is designed to block autoantibody-mediated activation of TSHR, which is widely regarded as the central pathogenic driver of Graves' disease and contributes to thyroid eye disease (TED) through the same autoimmune mechanism, making it an attractive target for therapies that could address both conditions simultaneously. Ethyreal's antibody incorporates half-life extension technology to enable infrequent dosing and is formulated for low-volume subcutaneous administration, with plans for an autoinjector. Current treatments for Graves' disease do not address or prevent TED, and vice versa; Ethyreal is positioning ETHY-001 as a single mechanism-driven therapy capable of addressing both conditions. Preclinical data on ETHY-001 are scheduled for oral presentation at the Endocrine Society's 2026 Annual Meeting on June 15, covering inhibition of TSHR activation by patient sera and effects on TED patient-derived orbital fibroblasts.
Ethyreal is aiming to enter an increasingly competitive field focused on neutralizing TSHR signaling, with Biohaven, Merida Biosciences, and Regeneron all pursuing approaches designed to address the underlying autoimmune biology of Graves' disease rather than simply controlling thyroid hormone levels. Biohaven reported positive Phase Ib data for its IgG MoDE degrader BHV-1300 in Graves' disease, demonstrating greater than 80% reductions in TSHR autoantibodies and rapid thyroid hormone normalization, with Phase III initiation planned for H2 2026. Merida Biosciences has also initiated a Phase I trial of MER511, another TSHR-targeting biologic. Regeneron has disclosed early preclinical data for REGN24493, a novel TSHR blocking antibody. While several competitors are pursuing TSHR-directed therapies, others, including Immunovant, are targeting broader immune pathways such as FcRn inhibition to treat Graves' disease and TED. Immunovant's FcRn inhibitor IMVT-1402 is advancing toward registrational Graves' disease trials expected in 2027, following the Phase III failure of batoclimab in TED.