What Yarrow does

Yarrow Bioscience is a clinical-stage biotechnology company developing YB-101 (also known as GS-098), a first-in-class humanized monoclonal antibody that selectively targets the thyroid-stimulating hormone receptor (TSHR) to block the pathogenic activity of thyroid-stimulating autoantibodies. The company's stated therapeutic focus is on two autoimmune thyroid conditions — Graves' disease (GD) and thyroid eye disease (TED) — where it positions TSHR antagonism as a more tissue-restricted alternative to existing IGF-1R-directed therapies and as an approach that may avoid systemic immunosuppression. Yarrow was founded in 2021 and is headquartered in New York, NY, with the company itself built as the seventh biotechnology creation of RTW Investments, a New York-based life sciences investment firm.

YB-101 was originated by GenSci (Changchun GeneScience Pharmaceutical Co., Ltd.) at its Shanghai R&D center. In December 2025, Yarrow secured exclusive global ex-China development and commercialization rights under a license agreement valued at up to $1.365 billion, comprising a $70 million non-refundable upfront payment, a $50 million near-term development milestone, additional development/regulatory/commercial milestones, and tiered double-digit royalties on ex-China net sales; GenSci retains China rights and is running a Phase 1 trial in TED in China. Yarrow's U.S. development plan is a Phase 1b/2b trial in Graves' disease patients, expected to initiate in the first half of 2026 with Phase 1b data anticipated in the second half of 2027.

The business model is pre-commercial biotechnology: Yarrow is currently pre-revenue and plans to generate revenue through pharmaceutical sales and potential licensing arrangements following regulatory approval. The company has no approved products, no pricing model, and no distribution channels. It is supported by approximately $200 million in pre-closing private financings from a syndicate of healthcare investors co-led by RTW Investments and OrbiMed Advisors, with participation from Janus Henderson Investors, venBio Partners, Logos Capital, LifeSci Venture Partners, and Perceptive Advisors. The company is concurrently executing an all-stock reverse merger with VYNE Therapeutics to list on Nasdaq under ticker YARW (expected close Q2 2026), and is led by Rebecca Frey, Pharm.D. as President and CEO, with Lori Payton, Ph.D. joining as Chief Development Officer and Mona Ashiya, Ph.D. (OrbiMed) joining the board at closing.

Name

Yarrow

Legal name

Yarrow Bioscience, Inc.

Website

https://yarrowbioscience.com

Company type

Private

Founded year

2021

Operating status

Operating

Headcount range

11–50 employees

Short description

Yarrow Bioscience is a clinical-stage biotechnology company developing YB-101, a first-in-class humanized monoclonal antibody targeting TSHR for the treatment of Graves' disease and thyroid eye disease, with ex-China rights licensed from GenSci.

Ownership category

akta.pro rank

Product category

Autoimmune Disease Therapeutics

NAICS

Research and Development in Biotechnology (except Nanobiotechnology) (541714)

SIC

Pharmaceutical Preparations (2834)

akta.pro primary industry

Therapeutic Peptides & Protein/Peptide Biologics (HLAAAAAH)

akta.pro secondary industry

Antibody Discovery & Engineering Platforms (display tech, bispecifics, Fc engineering) (HLAAAIAB)

Keywords

• Autoimmune disease therapeutics
• Monoclonal antibody development
• Graves disease treatment
• Thyroid eye disease therapy
• Clinical-stage biotechnology

Headquarters

HQ city

New York

HQ country

United States

HQ region

North America

Offices1 record

Markets served

GTM type

B2B

Offering type

Hardware or Manufacturing

Cost components

Technology or R&D, Personnel, Operations, Supply Chain

Revenue model

1. Pharmaceutical Development and Commercialization: Pre-revenue clinical-stage biotech focused on developing YB-101 for Graves' disease and thyroid eye disease. The company plans to commercialize the therapy upon successful clinical trials and regulatory approval. Revenue potential includes drug sales and potential licensing arrangements.

Go-to-market motion1 record

Marketing channels3 records

Core offering

Yarrow Bioscience is a clinical-stage biotechnology company developing YB-101 (GS-098), a first-in-class humanized monoclonal antibody targeting the thyroid-stimulating hormone receptor (TSHR). The antibody is designed to block pathogenic thyroid-stimulating autoantibodies that drive disease progression in Graves' disease and thyroid eye disease. The company holds exclusive global ex-China development and commercialization rights licensed from GenSci.

Product overview

Yarrow Bioscience is a clinical-stage biotechnology company developing a single lead product, YB-101 (also known as GS-098), a humanized monoclonal antibody targeting TSHR. The company acquired ex-China rights to this drug candidate from GenSci in a potential $1.37 billion deal and is advancing it through clinical trials for Graves' disease and thyroid eye disease. The company's product portfolio consists of this one lead program, which is being developed through a U.S.-based Phase 1b/2b trial for GD and a Phase 1 trial in China for TED.

Differentiator

Problem solved

Functional benefit

Products and services

• YB-101 (GS-098) YB-101 is a clinical-stage, first-in-class humanized monoclonal antibody targeting the thyroid-stimulating hormone receptor (TSHR) for the treatment of Graves' disease (GD) and thyroid eye disease (TED). The antibody is designed to rapidly and efficiently block the pathogenic activity of thyroid-stimulating autoantibodies that drive disease progression by selectively binding the TSHR and preventing autoantibody-induced receptor activation.

Quantifiable outcome

• Phase 1b data expected in second half of 2027
• +1 more outcomes

Segments1 record

Ideal customer profiles1 record

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature1 record

Partnerships

Two partnerships are on record, tiered core.

• VYNE TherapeuticscoreStrategic or Co-development Partner · 17 December 2025Merger agreement whereby companies will combine in an all-stock transaction. Upon completion, combined company will operate as Yarrow Bioscience, Inc. and trade on Nasdaq under ticker symbol YARW. Pre-Merger VYNE stockholders expected to own approximately 3% of combined company. Merger expected to close in Q2 2026, subject to stockholder approval and customary closing conditions.
• GenSci (Changchun GeneScience Pharmaceutical Co., Ltd.)coreStrategic or Co-development Partner · 15 December 2025Exclusive global ex-China license agreement for GS-098/YB-101. GenSci receives $70 million upfront payment, $50M near-term development milestone, and total potential deal value up to $1.365 billion with tiered double-digit royalties on future net sales. GenSci retains rights for development and commercialization in China. The partnership focuses on building a leading US-based biotech dedicated to underserved patients with autoimmune thyroid diseases.

Scale indicators6 records

Recent moves7 records

Expansion highlights6 records

Direct peers

• Immunovant: Clinical-stage biotech developing engineered monoclonal antibodies (FcRn-targeted batoclimab, IMVT-1402) for autoimmune diseases. Comparable in modality (antibody therapeutics) and target market (autoimmune endocrinology).
• Viridian Therapeutics: Clinical-stage biotech developing monoclonal antibodies for thyroid eye disease (VRDN-001, VRDN-003) targeting IGF-1R, directly competing with Yarrow's YB-101 in the same TED patient population. Most directly comparable competitor in thyroid autoimmunity.

Emerging players

• Madrigal Pharmaceuticals: Recently commercialized clinical-stage biotech that pioneered a novel mechanism (resmetirom/Rezdiffra) for thyroid-related liver disease (MASH). Comparable in development-stage biotech positioning with thyroid-adjacent therapeutic focus.
• Kyverna Therapeutics: Clinical-stage biotech developing cell and antibody therapies for autoimmune diseases. Comparable development-stage positioning and parallel autoimmune therapeutic focus.
• Crinetics Pharmaceuticals: Clinical-stage biotech developing therapeutics for endocrine diseases and endocrine-related tumors (paltusotine for acromegaly). Overlapping target indication space (endocrine) and comparable development-stage positioning.
• Inhibrx Biosciences: Clinical-stage biotech developing engineered antibody therapeutics (INBRX-101 for alpha-1 antitrypsin deficiency). Similar modality (protein/antibody therapeutics) and comparable clinical-stage profile with focused pipeline approach.
• Apogee Therapeutics: Clinical-stage biotech developing monoclonal antibodies for inflammatory and immunology indications (APG777, APG808). Similar modality (engineered mAbs), comparable clinical-stage profile, and parallel autoimmune therapeutic focus.

Broad incumbents

• Argenx: Commercial-stage leader in autoimmune antibody therapeutics (efgartigimod/Vyvgart for myasthenia gravis, ITP). Establishes the commercial validation of antibody therapeutics in autoimmune disease that YB-101 aims to enter.
• Horizon Therapeutics (Amgen): Acquired by Amgen in 2023, Horizon developed and commercializes Tepezza (teprotumumab), the only approved IGF-1R antibody for thyroid eye disease. Represents the established market incumbent YB-101 must compete against in TED.

Others

• Roivant Sciences: Tech-enabled biotech company creator that founds and capitalizes multiple subsidiary biotech companies (Vants). Operates a similar institutional biotech creation model as RTW Investments' Yarrow platform.

Market position

Strengths4 records

Weaknesses4 records

Competitive moat4 records

Key risks6 records

Key highlights6 records

Customer concentration

Revenue estimate

Valuation estimate

Number of profiles

Profiles3 records

Funding overview

Funding rounds2 records

Investors7 records

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A1 record

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Yarrow