Subsequent Event

12 Months Ended

Dec. 31, 2025

Subsequent Events [Abstract]

Subsequent Event

Subsequent Event

On February 19, 2026, the Company and Astellas US LLC (together with its subsidiaries and affiliates (including its indirect parent, Astellas Pharma Inc.), Astellas) entered into a Collaboration and License Agreement (the Astellas Agreement). Upon closing of the transaction contemplated by the Astellas Agreement, the Company and Astellas will enter into a global strategic collaboration to co-develop and co-commercialize VIR-5500, an investigational PRO-XTEN® dual-masked CD3 TCE targeting PSMA (Prostate-Specific Membrane Antigen) for the treatment of prostate cancer that is currently in Phase 1 development, through a sharing of expenses and revenues. The Company has agreed to grant to Astellas, subject to certain intellectual property rights of Sanofi, an exclusive license to develop, manufacture, commercialize and otherwise exploit VIR-5500 and certain related derivative compounds throughout the world for therapeutic, prophylactic, palliative and diagnostic uses.

Under the terms of the Astellas Agreement, in the U.S., the Company will share profits and losses from future sales of VIR-5500 equally with Astellas, should VIR-5500 receive regulatory approval, and the Company will have the option to co-promote VIR-5500. Outside of the U.S., Astellas will obtain exclusive rights to commercialize VIR-5500 and be responsible for all commercialization costs. The Company and Astellas will jointly develop VIR-5500, with global clinical development costs shared 40% by the Company and 60% by Astellas, while costs of U.S.-specific studies will be shared equally, and Astellas will be solely responsible for costs of ex-U.S.-specific studies. In addition, the Company has the option to opt out of development cost sharing responsibilities and U.S. profit sharing, and in such case, Astellas will pay the Company royalties on net sales made in the U.S., as described below.

The Company will receive $335 million in upfront and near-term milestone payments, including $240 million in cash, a $75 million equity investment pursuant to a separate Stock Purchase Agreement (the Astellas SPA, described further below), and a near-term $20 million milestone payment upon completion of manufacturing technology transfer, anticipated in the second quarter or third quarter of 2027. The Company will also be eligible to receive up to $1.37 billion in future development, regulatory and ex-U.S. sales milestones, along with tiered, double-digit royalties on ex-U.S. net sales, which royalties are subject to reduction under certain specified circumstances. If the Company elects to opt out of development cost sharing responsibilities and U.S. profit sharing, it would be eligible to receive up to $1.37 billion (or $1.60 billion if the Company has met a pre-defined limited funding threshold at the time of the opt-out) in future development, regulatory and global sales milestones, along with tiered, double-digit royalties on global net sales, which royalties are subject to reduction under certain specified circumstances. Further, certain opt-out milestones, if met, will include reimbursement of a portion of the Company’s previously expensed development and commercialization spend. The closing of the transaction is subject to the expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended.

Under the terms of the Sanofi Agreement, the Company will share with Sanofi 20% of certain future collaboration proceeds, including the upfront payment, equity premium and the portion of milestones, profit-share and royalties that exceed amounts already owed to Sanofi.

Concurrently with the execution of the Astellas Agreement, the Company also entered into the Astellas SPA, pursuant to which Astellas has agreed to purchase 7,239,382 shares of the Company’s common stock for an aggregate purchase price of approximately $75 million, subject to customary closing conditions and the closing of the Astellas Agreement. The purchase price per share of the Company’s common stock of $10.36 is equal to a 50% premium of the 30-day volume weighted average price of a share of the Company’s common stock as of February 17, 2026. The Astellas SPA includes standstill, voting and lockup provisions, with customary exceptions, that expire one year after the date of the anticipated closing of the Astellas SPA. One year after the anticipated closing of the Astellas SPA, Astellas will have, under certain circumstances, a customary right to require the Company to register the resale of the shares purchased pursuant to the Astellas SPA.