Vir’s PRO-XTEN platform is designed to keep each T-cell engager inactive until proteases in the tumour microenvironment cleave its mask. The company says the approach is meant to concentrate activity in tumours. It also aims to limit TCE-associated toxicity in solid tumours. A longer molecular half-life is another intended effect. The collaboration announcement reported no clinical findings for these candidates.
On 14 October 2026, Gilead Sciences agreed to pay Vir Biotechnology USD 90 million upfront for exclusive rights to three dual-masked T-cell engager candidates aimed at selected solid tumour-associated antigens. Vir could receive a further USD 1.785 billion in milestone payments, plus tiered royalties on net sales. The deal’s potential value is approximately USD 1.88 billion, including the upfront consideration and milestone payments, as Vir’s announcement set out.
Upfront cash and conditional payments
The upfront consideration comprises USD 65 million in cash and a USD 25 million equity investment priced at a 30% premium. Vir may also earn up to USD 45 million in near-term preclinical milestones. That would bring the upfront and near-term preclinical payments to as much as USD 135 million.
A further USD 1.74 billion is available through development and regulatory milestones. Commercial milestones are also included. Royalties are tiered from high single digits to low double digits on net sales. The disclosed terms do not specify a territory.
This agreement licenses three engineered candidates. Its structure differs from a company-level transaction such as the proposed Nasdaq merger covered in an earlier deal report.
Vir handles discovery before Gilead takes over
Vir will use its PRO-XTEN masking technology and dAIsY platform, short for data AI structure and antibodY, to discover and optimise the candidates. Its protein-engineering capabilities will also support that work. Gilead holds exclusive rights to advance selected candidates through clinical development. It will take charge of manufacturing and commercialisation. The agreement is a multi-program collaboration and licence, not an acquisition of Vir.
This is Vir’s second partnership based on PRO-XTEN masking technology. In February 2026, Vir partnered with Astellas Pharma to co-develop VIR-5500, a PSMA-targeted T-cell engager for prostate cancer. That agreement was reported as having potential value of about USD 1.7 billion. Fierce Biotech described the Gilead agreement as a second partnership using the platform. Vir is also advancing its own clinical-stage PRO-XTEN T-cell engagers for solid tumours.
