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StocksMediumUpdated•Originally published 23 February 2026•Updated 23 February 2026•
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Astellas and Vir Report Positive Phase 1 Data for VIR-5500 Prostate Cancer Therapy

Key Facts

1Vir Biotechnology will receive $335M in upfront and near-term milestone payments.
2Additional development, regulatory, and sales milestones could reach up to $1.37B.
3U.S. profit and loss will be split equally (50/50) between Astellas and Vir.
4Astellas obtained exclusive rights to commercialize VIR-5500 outside of the United States.

Astellas Pharma and Vir Biotechnology have announced positive Phase 1 clinical trial results for VIR-5500, an investigational immunotherapy for prostate cancer. The therapy utilizes the proprietary PRO-XTEN® dual-masked T-cell engager technology, specifically targeting patients with metastatic castration-resistant prostate cancer (mCRPC). These clinical findings provide critical technical validation for the drug candidate following the companies' $1.7 billion strategic collaboration agreement. Under the partnership, Vir and Astellas share U.S. profits and losses equally, while Astellas manages exclusive commercialization in international markets. The successful trial data reinforces the potential of Vir’s technology platform to address complex oncological challenges. This milestone marks a significant transition from the initial financial partnership to tangible clinical progress in advanced cancer treatment. Both companies aim to leverage these results to accelerate the next phases of clinical development and regulatory engagement.