Astellas Pharma Inc. and Vir Biotechnology, Inc. have entered into a global strategic collaboration to develop and commercialize VIR-5500, an investigational PRO-XTEN dual-masked CD3 T-cell engager (TCE) targeting prostate-specific membrane antigen (PSMA) for the treatment of prostate cancer.

The collaboration is intended to accelerate the development of VIR-5500 while strengthening Astellas’ oncology pipeline and leadership in prostate cancer. The asset is currently in Phase 1 clinical development for patients with advanced metastatic prostate cancer.

VIR-5500 is designed as a potential best-in-class PSMA-targeting T-cell engager. It combines a bispecific PSMA and CD3-binding construct with Vir’s proprietary PRO-XTEN masking technology. The dual-masked design keeps the T-cell engager inactive until it reaches the tumour microenvironment, aiming to reduce off-target effects and improve the therapeutic index.

Despite recent treatment advances, metastatic castration-resistant prostate cancer (mCRPC) remains aggressive, with an estimated five-year survival rate of approximately 30 Percent. Patients who progress to mCRPC often develop resistance to current therapies and face limited treatment options.

Under the agreement, Vir Biotechnology will receive USD 335 million in upfront and near-term payments, including USD 240 million in cash, a USD 75 million equity investment at a 50 Percent premium, and a USD 20 million milestone payment. Vir is also eligible to receive up to USD 1.37 billion in additional development, regulatory and sales milestones, along with tiered, double-digit royalties on ex-US net sales.

Global development costs will be shared, with Astellas responsible for 60 Percent and Vir Biotechnology responsible for 40 Percent. Vir will continue the ongoing Phase 1 trial until responsibility transitions to Astellas, after which Astellas will oversee all development activities. In the US, Vir will have the option to co-promote VIR-5500 with profit and loss shared equally. Outside the US, Astellas will hold exclusive commercialization rights.

Under the terms of Vir Biotechnology’s licensing agreement with Sanofi, a portion of certain collaboration proceeds will be shared. Lazard acted as Vir Biotechnology’s exclusive financial advisor. The transaction is subject to customary closing conditions, including clearance under the Hart-Scott-Rodino Act.

Astellas continues to expand its biologics and immuno-oncology portfolio across multiple therapeutic areas, while Vir Biotechnology advances immune-based therapies targeting serious infectious diseases and cancer.