Viridian partners with Kissei Pharmaceutical to develop thyroid eye disease therapies in Japan

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Viridian Therapeutics has entered an exclusive licensing agreement with Japan-based Kissei Pharmaceutical to develop and commercialize both TED drug candidates in Japan. Viridian will receive a $70 million up-front payment, with the potential for an additional $315 million in milestone payments, as well as tiered royalties on net sales ranging from the 20s to mid-30s percent.¹

Announced on July 30, 2025, the deal pairs Viridian’s TED treatments with Kissei’s experience selling rare disease drugs in Japan. TED is an autoimmune disorder that causes inflammation and tissue remodeling around the eyes, often leading to proptosis, discomfort, and vision impairment. Even though treatments are available, they often fall short, leaving many patients still untreated.

“After running a very competitive partnering process, we are thrilled to partner with Kissei to bring these potential best-in-class medicines to TED patients in Japan,” said Steve Mahoney, president and CEO of Viridian Therapeutics, in the release. “Kissei shares our enthusiasm and commitment to these programs, and we believe Kissei is an ideal partner for us in Japan.”¹

Veligrotug, also known as VRDN-001, is currently being evaluated in 2 phase 3 global trials, THRIVE and THRIVE-2, both of which have met all primary and secondary end points. Veligrotug is an intravenously administered anti–IGF-1R antibody and has demonstrated strong efficacy and tolerability in patients with active TED. In phase 3 data, veligrotug showed significant improvements in proptosis and diplopia with a rapid onset of action and a favorable safety profile, including low discontinuation rates and no treatment-related serious adverse events.²

VRDN-003, a longer-lasting, subcutaneous anti-IGF-1R antibody, shares the same binding mechanism as veligrotug and is under study in the REVEAL-1 and REVEAL-2 trials. These 2 assets represent Viridian’s TED portfolio and are aimed at addressing both active and chronic forms of the disease.

Kissei will take on full responsibility for clinical development, regulatory submissions, and commercialization of both veligrotug and VRDN-003 within Japan. Viridian will keep all rights outside of Japan. Kissei’s Chairman and CEO, Mutsuo Kanzawa, emphasized the partnership’s strategic alignment with the company’s rare disease focus, noting, “This collaboration reinforces our mission to contribute to the health of people around the world through innovative pharmaceutical products.”¹

A recent claims-based study, published in the Journal of the Endocrine Society, provided the first nationwide data on TED, estimating an incidence of 7.3 to 11.0 per 100,000 person-years and a prevalence of 24.65 to 37.58 per 100,000 adults in fiscal year 2020. The majority of cases were mild and inactive, with the highest burden observed in women aged 35 to 59.³

These figures align with global TED demographics; however, Japan has fewer severe cases, with most patients receiving conservative treatment and little use of steroids, surgery, or radiation. Still, the study’s results emphasize the need for standardized diagnostic practices and more therapies, particularly for moderate to severe cases. The introduction of new, targeted treatments such as veligrotug and VRDN-003 may address the unmet needs and improve care for patients with TED in Japan and eventually across Asia.³

Viridian is also developing therapies for other autoimmune diseases, but this partnership focuses solely on TED. The company expects this agreement to accelerate access for Japanese patients and support long-term strategy in Asia.

References:

1. Viridian Therapeutics Announces Collaboration and License Agreement with Kissei Pharmaceutical to Develop and Commercialize Veligrotug and VRDN-003 in Japan with an Upfront Payment of $70 Million and up to $315 Million in Milestone Payments. News release. Viridian. July 30, 2025. Accessed July 31, 2025. https://investors.viridiantherapeutics.com/news/news-details/2025/Viridian-Therapeutics-Announces-Collaboration-and-License-Agreement-with-Kissei-Pharmaceutical-to-Develop-and-Commercialize-Veligrotug-and-VRDN-003-in-Japan-with-an-Upfront-Payment-of-70-Million-and-up-to-315-Million-in-Milestone-Payments/default.aspx.

2. Harp MD. Viridian announces positive topline data from Phase 3 THRIVE trial assessing veligrotug in patients with active TED. Optometry Times. September 17, 2024. Accessed July 31, 2025. https://www.optometrytimes.com/view/viridian-announces-positive-topline-data-from-phase-3-thrive-trial-assessing-veligrotug-in-patients-with-active-ted

3. Watanabe N, Kozaki A, Inoue K, Narimatsu H, Shinohara M, LoPresti MG. Prevalence, Incidence, and Clinical Characteristics of Thyroid Eye Disease in Japan. Journ Endocr Soc. 2023;8(1). doi:https://doi.org/10.1210/jendso/bvad148