Yarrow Bioscience begins Phase 2 testing of YB-101, a potential first-in-class anti-TSHR antibody for Graves’ disease and thyroid eye disease after FDA Fast Track designation.
Written By: Kalyani Boharapi,
M.Pharm (Reg. Affairs)
Reviewed By: Pharmacally Editorial Team
Yarrow Bioscience has initiated patient dosing in its Phase 2a/2b clinical trial evaluating YB-101, a potential first-in-class anti-thyroid stimulating hormone receptor (TSHR) monoclonal antibody for the treatment of Graves’ disease (GD), with or without concurrent thyroid eye disease (TED). The milestone follows the completion of the company’s merger with VYNE Therapeutics, creating a clinical-stage biotechnology company focused on advancing targeted therapies for autoimmune thyroid diseases.
Scientific and Clinical Context
YB-101 directly blocks TSHR signaling, the central autoimmune pathway driving both Graves’ disease and thyroid eye disease. By targeting the shared disease mechanism rather than managing downstream symptoms, the antibody has the potential to treat both conditions with a single therapeutic approach.
The investigational therapy is administered subcutaneously and is being developed with the potential for infrequent dosing and future autoinjector presentation.
Graves’ disease is the most common cause of autoimmune hyperthyroidism, while thyroid eye disease is a potentially sight-threatening complication characterized by orbital inflammation, tissue expansion, proptosis, diplopia, and impaired quality of life. Current treatment options remain limited, particularly for therapies that directly interrupt the autoimmune process responsible for disease progression.
Trial and Development Details
The ongoing Phase 2a/2b study (NCT07682896) is a randomized, blinded, placebo-controlled, two-part clinical trial evaluating YB-101 in patients with Graves’ disease, with or without concurrent thyroid eye disease.
The Phase 2a proof-of-concept portion is expected to enroll 32 patients across four cohorts and will evaluate safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy through 24 weeks. Key efficacy endpoints include the proportion of patients who achieve euthyroidism without anti-thyroid medication, together with assessments of orbitopathy in participants with concurrent TED.
A Phase 2b dose-finding study enrolling approximately 200 patients is planned for the first half of 2028. Dose selection will be guided by the safety, pharmacokinetic, pharmacodynamic, and efficacy findings generated during Phase 2a.
Yarrow’s licensing partner, Changchun GeneScience Pharmaceutical Co., Ltd. (GenSci), is also advancing YB-101 in China through ongoing Phase 1 studies in Graves’ disease and thyroid eye disease. Earlier single ascending dose data in patients with TED demonstrated dose-dependent proof of mechanism, evidence of clinical responses, and a favorable safety profile, with no clinically meaningful safety differences compared with placebo. Data from the ongoing multiple ascending dose study in TED are expected in the second half of 2027 and will help guide the global development strategy for YB-101.
Clinical Implications
Rebecca V. Frey, PharmD, President and Chief Executive Officer of Yarrow Bioscience, said YB-101 has the potential to become the first therapy to directly block TSHR signaling, addressing the underlying autoimmune mechanism shared by Graves’ disease and thyroid eye disease. She noted that existing therapies often fail to interrupt the disease-driving pathway or are associated with significant treatment-related limitations, highlighting the need for more targeted treatment options.
Regulatory Path Forward
Following the completion of its merger with VYNE Therapeutics, Yarrow Bioscience has secured approximately $200 million in previously announced private financing, which is expected to fund operations into 2028. Near-term priorities include completing Phase 2a enrollment, generating the anticipated Phase 2a data in the second half of 2027, advancing the planned Phase 2b study in the first half of 2028, and integrating findings from GenSci’s ongoing Phase 1 program in China to support the continued global development of YB-101 for autoimmune thyroid diseases.
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About the Writer
Kalyani Boharapi (LinkedIn) is a pharmacy professional and healthcare writer currently pursuing an M.Pharm in Regulatory Affairs at Dr. D. Y. Patil College of Pharmacy, with interests in pharmaceutical regulations, drug development, and healthcare innovation. She has academic exposure to dossier preparation, scientific writing, and regulatory documentation. Kalyani has also completed certification courses in Generative AI, AI in Pharma, and Bioinformatics, and actively participates in pharmaceutical conferences to stay updated with emerging trends and advancements in the healthcare and pharmaceutical industry.