<img src="https://ml.globenewswire.com/Resource/Download/908f2a02-40c5-4b31-8e73-8741262ee614?size=2" nborder="0" align="left" hspace="5" vspace="5" title="Ethyreal Logo.png" alt="Ethyreal Bio, Inc."/>– ETHY-001 produced complete blockade of autoantibody-mediated TSHR activation across all patient serum samples tested, demonstrating breadth and consistency of effect – – In TED patient-derived orbital fibroblasts, ETHY-001 fully suppressed both hyaluronan (HA) and interleukin-6 (IL-6) secretion, offering a differentiated profile compared to IGF-1R antagonism – – ETHY-001 demonstrated sub-nanomolar binding affinity to TSHR with no off-target binding across more than 5,000 human membrane proteins – – Data support ETHY-001 as a potential treatment for TED and GD, with first-in-human clinical trial planned for the second half of 2026 – CAMBRIDGE, Mass., June 15, 2026 (GLOBE NEWSWIRE) -- Ethyreal Bio (“Ethyreal” or “the Company”), a biotechnology company developing precision therapies for thyroid diseases with high unmet need, today reported preclinical data for its lead program, ETHY-001, in an oral presentation at the Endocrine Society’s 2026 Annual Meeting (ENDO 2026). ETHY-001 is an internally discovered, half-life-extended monoclonal antibody designed to block autoantibody-mediated activation of the thyroid stimulating hormone receptor (TSHR), the shared pathogenic driver of Graves’ disease (GD) and thyroid eye disease (TED). “The data presented today underscore the promise of ETHY-001 for the treatment of TED and GD,” said Niranjan Kameswaran, Ph.D., Chief Executive Officer of Ethyreal Bio. “The depth and consistency of signaling blockade across all tested patient sera samples, combined with its differentiated activity compared to IGF-1R antagonism in TED models, reinforce our conviction in ETHY-001’s product profile. We believe that ETHY-001’s unique combination of potent receptor blockade, subcutaneous administration, and extended half-life supports a best-in-class, convenient, single-agent approach for both conditions. We are excited to advance ETHY-001 into the clinic this year.” Key preclinical results for ETHY-001 shared in the oral presentation include: <ul type="disc"><li style="margin-top:16pt; margin-bottom:9pt;">Potent binding with high specificity for TSHR. ETHY-001 binds TSHR with sub-nanomolar monovalent affinity and no off-target binding in a membrane protein array of over 5,000 membrane proteins.</li><li style="margin-top:16pt; margin-bottom:9pt;">Complete, consistent, and broad blockade of TSHR activation. ETHY-001 completely blocked autoantibody-driven TSHR activation elicited from all patient samples tested to date.</li><li style="margin-top:16pt; margin-bottom:9pt;">Differentiated activity versus anti-IGF-1R in TED patient-derived orbital fibroblasts. In primary TED patient-derived orbital fibroblast cultures stimulated by M22, a potent stimulating antibody of TSHR, ETHY-001 produced complete inhibition of both HA and IL-6 secretion. An IGF-1R antagonist comparator inhibited HA secretion but not IL-6 secretion. These observations demonstrate ETHY-001’s potential for more robust inhibition of pathogenic signaling in comparison to anti-IGF-1R in TED. </li></ul> Together, these data support the advancement of ETHY-001 into clinical development for TED and GD, with potential to be a single, best-in-class, mechanism-driven therapy. Ethyreal plans to initiate a first-in-human trial in the second half of 2026. Presentation Details <ul><li>Title: “ETHY-001, a Half-Life Extended, TSHR Monoclonal Antibody Antagonist, Potently Inhibits TSHR Activation Induced by Patient Sera and M22-Induced Hyaluronan and IL-6 Secretion from TED Patient-Derived Orbital Fibroblasts”</li><li>Authors: Lauren Pepper, Phillip Truong, Elisa Roztocil, Gina-Eva Görtz, Mareike Horstmann, Jasvinder Paul Banga, Collyn Woeller, Anja Eckstein, Stephen Huang, Kelly Foster</li><li>Presenter: Kelly Foster, Ph.D., SVP, Translational Medicine, Ethyreal Bio</li><li>Date: Monday, June 15, 2026</li><li>Time / Session: 1:45 PM – 3:15 PM CT / “See through TED” </li></ul> About Graves’ Disease and Thyroid Eye Disease Graves’ disease (GD) is the most common cause of hyperthyroidism, affecting approximately 1–2% of the adult population. GD is driven by pathogenic autoantibodies that activate the thyroid stimulating hormone receptor (TSHR), leading to excess thyroid hormone production and significant systemic consequences, including cardiovascular, neurological, and metabolic complications. Approximately half of patients with GD develop thyroid eye disease (TED). Today, treatment options for GD are limited, do not address the underlying cause, are associated with high rates of relapse, and carry risks of serious side effects. Many patients eventually undergo permanent thyroid removal. Existing therapies do not treat or prevent TED. Thyroid eye disease is a serious, disfiguring, and potentially vision-threatening manifestation of GD that arises when pathogenic autoantibody-mediated TSHR activation occurs within the orbit of the eye. Most patients with TED have coexisting hyperthyroidism due to GD. TED can cause inflammation, proptosis, pain, diplopia, and in severe cases, permanent vision loss. Treatment options are limited and may be associated with burdensome systemic side effects including hyperglycemia and risk of hearing loss, as well as risk of relapse. There remains a significant unmet need for safe, effective, durable, and targeted therapies for GD and TED that can address the full spectrum of disease. About Ethyreal Bio Ethyreal Bio is a biotechnology company headquartered in Cambridge, Massachusetts, developing precision therapies for thyroid diseases with high unmet need. The company’s lead program, ETHY-001, is a monoclonal antibody antagonist of the thyroid stimulating hormone receptor (TSHR). ETHY-001 is designed to rapidly and comprehensively block autoantibody-mediated activation of TSHR, the shared pathogenic driver of Graves’ disease and thyroid eye disease. ETHY-001 is formulated for patient-friendly subcutaneous administration and incorporates half-life extension technology to enable infrequent dosing. Ethyreal plans to initiate first-in-human clinical trials in the second half of 2026. For more information, please visit <a href="https://www.globenewswire.com/Tracker?data=qrDzWuMjDSr6BYY-cBJXGzw5tfDEoLH1eFN8lso4-j6cnFxfPSYqiVMy75tUkQpXfdYXi_Oa6oSGRFhNyLLUhBdHeZx3broP8wiu47QpRb4=" rel="nofollow" target="_blank" title="www.ethyrealbio.com">www.ethyrealbio.com</a> and follow the Company on LinkedIn. Media &amp; Investor Contact Investor Contact Christina Tartaglia Precision AQ <a href="https://www.globenewswire.com/Tracker?data=uhkytuX6504w5Mh9aRka0lo0BGSmainbaSn_v8R83yTmSBcyRghmv6wgn6p0GOv5C5KwR93rJiA0_RrHTH3dVkGRLN1-IaEJDNY4LcC5JPDKVsLu7KSuPY_DZMdZD9kfhq9oBZbjnsv0UGY3BOp9bQ==" rel="nofollow" target="_blank" title="christina.tartaglia@precisionaq.com">christina.tartaglia@precisionaq.com</a> Media Contact Kelsey Goff Precision AQ <a href="https://www.globenewswire.com/Tracker?data=pGYfuxt1bXZL3HitvOtOgm4dO353BwRp41ZfQ1bpDEv-OxSitPDebXKWRIG0sgaK9GKKQFxPUOtREVwpbnKX1dj2HlHomNOiAg90uVjFvRsIHbsE0u0yaTg_ZKrS_Sm0" rel="nofollow" target="_blank" title="kelsey.goff@precisionaq.com">kelsey.goff@precisionaq.com</a> <img alt="" src='https://ml.globenewswire.com/media/ZDMyNGUwZTctMjFiOC00YzI0LWJlZWMtODQ0ZGE2OWI4Nzg0LTUwMDE2MzUwNy0yMDI2LTA2LTE1LWVu/tiny/Ethyreal-Bio-Inc-.png' referrerpolicy='no-referrer-when-downgrade' />

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Ethyreal Bio Presents First Preclinical Data on ETHY-001 at ENDO 2026, Demonstrating Complete Blockade of Autoantibody Activation of TSHR and Differentiated Activity in TED

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