Astellas entered a co‑development and co‑commercialization agreement with Vir Biotechnology for VIR‑5500, a PSMA‑targeted, PRO‑XTEN masked T‑cell engager for prostate cancer, in a deal potentially worth more than $1.7 billion. Vir will leverage its PRO‑XTEN masking technology intended to keep TCEs inactive in circulation and activate them in the tumor microenvironment to reduce off‑tumor toxicity. The pact expands Vir’s oncology footprint and gives Astellas access to an advanced TCE candidate with a masking platform designed to improve therapeutic index. Both companies highlighted potential to accelerate clinical development while exploring combination strategies with checkpoint inhibitors.