Astellas and Vir Biotechnology to co-develop and co-commercialize VIR-5500 through a sharing of expenses and revenues
Astellas Pharma Inc., led by President and CEO Naoki Okamura, has entered into a worldwide strategic partnership with Vir Biotechnology Inc. Further developing VIR-5500, an investigational PSMA-targeting PRO-XTEN dual-masked CD3 T cell engager designed for the treatment of prostate cancer. The agreement is intended to speed up clinical development of the candidate while reinforcing Astellas’ long-standing focus on oncology and its leadership position in prostate cancer therapies.
Adam Pearson, Chief Strategy Officer at Astellas, stated that the company has supported approximately 1.5 million people living with prostate cancer and remains committed to expanding its contribution through focused research and development efforts. He noted that Astellas brings extensive expertise in prostate cancer along with a growing immuno-oncology portfolio that includes biologics and T cell engager programs. According to Pearson, combining these capabilities with Vir Biotechnology’s innovation around VIR-5500 positions the program strongly as it advances through development. He emphasized that the collaboration reflects Astellas’ continued dedication to delivering meaningful advances for patients facing prostate cancer.
Marianne De Backer M.Sc., Ph.D., MBA, Chief Executive Officer of Vir Biotechnology, described Astellas as a strong strategic fit for the VIR-5500 program. She highlighted Astellas’ history of guiding therapies across multiple stages of care, building successful oncology franchises, and working productively with biotechnology partners. De Backer explained that the collaboration is expected to accelerate clinical progress for VIR-5500 and potentially expand its reach to more patients. She added that the partnership also underscores confidence in Vir’s PRO-XTEN platform, which is designed to enhance the precision and safety profile of T cell engagers and may have broader applications across solid tumors.
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Although therapeutic options for prostate cancer have expanded in recent years, advanced disease continues to present significant challenges. Metastatic castration-resistant prostate cancer remains particularly difficult to manage, with a five-year survival rate of about 30 percent. Patients whose disease progresses to this stage often develop resistance to available treatments, leaving them with limited alternatives and underscoring the need for new therapeutic strategies.
VIR-5500 is currently being evaluated in a Phase 1 clinical study for patients with advanced metastatic prostate cancer. The therapy is engineered as a bispecific T cell engager that binds both Prostate-Specific Membrane Antigen and CD3. It incorporates Vir’s PRO-XTEN masking technology, which is designed to keep the molecule inactive while circulating in the body and activate it primarily within the tumor microenvironment. This approach aims to reduce unintended effects on healthy tissue and improve the overall therapeutic index.
Under the financial terms of the collaboration, Vir Biotechnology will receive 335 million dollars in upfront and near-term consideration. This includes 240 million dollars in cash, a 75 million dollar equity investment at a premium to market value, and a 20 million dollar milestone payment in the near term. The companies will share global development expenses, with Astellas covering 60 percent of costs and Vir responsible for 40 percent. Vir will continue managing the ongoing Phase 1 study until development oversight transitions to Astellas, after which Astellas will lead further clinical activities.
In the United States, Vir retains the option to co-promote VIR-5500 alongside Astellas, with profits and losses shared equally. Outside the United States, Astellas will hold exclusive commercialization rights. Vir may also receive up to 1.37 billion dollars tied to development, regulatory, and sales milestones, in addition to tiered double-digit royalties on net sales outside the United States. Certain proceeds from the collaboration will be shared with Sanofi under Vir’s existing licensing arrangements.
Lazard served as exclusive financial advisor to Vir Biotechnology for the transaction. Completion of the agreement remains subject to customary closing requirements, including regulatory clearance under the Hart-Scott-Rodino Act.
Vir Biotechnology will discuss the collaboration and provide updated Phase 1 data for VIR-5500 during its fourth quarter and full year 2025 financial results call scheduled for 2:30 p.m. PT and 5:30 p.m. ET. Members of the executive leadership team, together with Dr. de Bono, are expected to review the clinical findings that are also being presented at the 2026 ASCO Genitourinary Cancers Symposium on February 26.
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