Vir Biotechnology finalizes Astellas partnership to advance VIR-5500, a PSMA-targeted dual-masked T-cell engager for metastatic prostate cancer, with up to $1.37B in milestones.
Written By: Karthik Teja Macharla, PharmD
Reviewed By: Pharmacally Editorial Team
Vir Biotechnology has completed its global collaboration and licensing agreement with Astellas, originally announced in February 2026, after clearance under U.S. antitrust regulations. The partnership centers on the development of VIR-5500, an investigational T-cell engager designed for metastatic prostate cancer.
Under the terms of the agreement, Vir receives $240 million upfront along with a $75 million equity investment priced at $10.36 per share. In addition, the company is eligible for a near-term $20 million milestone payment. The structure also includes a 50/50 split of U.S. profits and losses, while offering up to $1.37 billion in potential development, regulatory, and commercial milestones, as well as tiered double-digit royalties on ex-U.S. sales. Vir also noted that a portion of these proceeds will be shared with Sanofi under an existing agreement.
The collaboration is focused on advancing VIR-5500, a prostate-specific membrane antigen (PSMA)-targeted T-cell engager currently in a Phase 1 clinical trial for metastatic castration-resistant prostate cancer. T-cell engagers are designed to direct immune cells to recognize and destroy cancer cells, offering a targeted therapeutic approach in oncology.
What differentiates VIR-5500 is its use of PRO-XTEN® dual-masking technology, which keeps the therapy inactive while in circulation. Once the drug reaches the tumor microenvironment, tumor-associated enzymes remove the masking components, activating the therapy locally. This approach is intended to reduce systemic toxicity while improving drug exposure at the tumor site.
By combining bispecific targeting of PSMA on tumor cells and CD3 on T-cells with this masking strategy, VIR-5500 aims to enhance both efficacy and tolerability. The collaboration with Astellas is expected to support further clinical development as the companies work to address limitations historically associated with T-cell engager therapies.
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About the Writer
Karthik Teja Macharla, PharmD is a Pharm.D. graduate with a strong interest in clinical research, pharmacovigilance, and medical writing. In his words, he is passionate about converting complex medical information into clear, evidence-based scientific communication, committed to contributing to patient safety and advancing healthcare through accurate and impactful medical content.