Astellas Pharma and Vir Biotechnology signed a global co‑development agreement worth up to $1.3 billion to advance VIR‑5500, Vir’s PRO‑XTEN dual‑masked CD3 T‑cell engager targeting PSMA for prostate cancer. Vir will receive substantial up‑front and near‑term payments and is eligible for development and sales milestones plus royalties. The deal accelerates Vir’s oncology pivot and provides Astellas with an engineered T‑cell engager aimed at solid‑tumor biology. Additional reporting indicates Astellas paid an upfront cash component (reported separately) to secure rights, underscoring buyer urgency in the hot T‑cell engager space as firms race to deliver tumor‑directed immune activators with manageable safety profiles.