On October 19, 2025 Taiho Pharmaceutical Co., Ltd. ("Taiho") and Arcus Biosciences, Inc. (NYSE:RCUS, "Arcus") reported that Taiho exercised its option to develop and, if approved, commercialize casdatifan (International Nonproprietary Name; development code: AB521), an investigational small molecule HIF (Hypoxia Inducible Factor)-2α inhibitor, in Japan and certain other territories in Asia (excluding mainland China). This option exercise is based on a 2017 option and license agreement between Taiho and Arcus. This is the fifth option exercise by Taiho to an Arcus program.
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In exchange for the exclusive license to casdatifan, Taiho will make an option exercise payment, as well as additional payments upon achievement of clinical, regulatory and commercialization milestones, and, if any products from the program are approved, will pay royalties on net sales of such products.
Casdatifan is an investigational small molecule compound developed by Arcus. Arcus is currently conducting an ongoing global, registrational Phase 3 study, PEAK-1,* comparing the combination therapy of casdatifan and a VEGFR-targeted tyrosine kinase inhibitor (TKI) to monotherapy using a VEGFR-targeted TKI alone in patients with clear cell renal cell carcinoma (ccRCC). Japan is also expected to participate in the study starting in the first half of 2026.
*PEAK-1: A Randomized, Placebo-Controlled, Double-Blind, Multicenter Phase 3 Trial of Casdatifan and Cabozantinib Versus Placebo and Cabozantinib in Patients with Advanced Clear Cell Renal Cell Carcinoma
Through this collaboration, Taiho and Arcus are committed to delivering casdatifan as a potentially innovative new medicine to patients and healthcare professionals as swiftly as possible.
About Casdatifan (AB521)
Casdatifan is a small-molecule inhibitor of HIF-2α, a master switch that turns on hundreds of genes in response to low oxygen levels; when oxygen levels return to normal, HIF-2α is turned off. In a majority of people with the most common form of kidney cancer (clear cell renal cell carcinoma), this shut-off mechanism is deficient and HIF-2α remains activated even in the presence of oxygen, causing normal kidney cells to become cancerous. Casdatifan is designed to provide deeper and more durable inhibition of the HIF-2α pathway.
About clear cell renal cell carcinoma (ccRCC)
Kidney cancer is a disease with a rising worldwide incidence estimated at 400,000 new cases annually, and a worldwide mortality rate approaching 175,000 deaths per year. Current projections suggest incidence continuing to increase over the next decade, emphasizing the urgency of addressing this significant global health trend. ccRCC is the most common type of kidney cancer in adults, making up 75-80% of all cases.
(Press release, Taiho, OCT 19, 2025, View Source [SID1234656800])