Biogen to acquire RayThera for up to $1 billion in immunology push

Biogen agreed to acquire RayThera for as much as $1 billion, adding a portfolio of anti-inflammatory assets as the company pushes beyond its neurology roots into immunology.

"With this acquisition, we are further deepening our pipeline in immunology by adding a suite of assets that can allow us to expand into new disease areas," said Priya Singhal, executive vice president and head of development at Biogen.

The deal consists of an upfront payment and, predominantly, payments contingent on the achievement of future clinical and regulatory milestones. RayThera's lead candidate is expected to enter Phase 1 development in early Q3 2026. The transaction is subject to customary regulatory approvals and is anticipated to close in the third quarter of this year.

The acquisition marks Biogen's latest push to diversify beyond its core neurology franchise, which has faced pressure from generic competition to its multiple sclerosis drugs. Adding immunology assets could open new revenue streams in a therapeutic area where the company already has some development capabilities, including its approved lupus drug Benlysta.

RayThera, a San Diego-based private biotechnology company co-founded by Qing Dong and Gene Hung, has built a pipeline of small molecule therapies targeting immune-mediated conditions across a range of indications. The company recently completed a Series A financing co-led by Foresite Capital and OrbiMed Advisors, with participation from TTM Capital. Financial terms of that round were not disclosed.

"With its strong global development capabilities in immunology, we believe that Biogen is the natural fit to move these assets forward into Phase 1 development and beyond," said Qing Dong, co-founder, chairman and chief executive officer of RayThera.

Biogen will lead development, manufacturing and global commercialization of the assets once the deal closes. The Cambridge, Massachusetts-based company reported $9.8 billion in total revenue for the full year 2025, according to its annual filing, giving it resources to fund the acquisition and subsequent development costs without straining its balance sheet.

The immunology market represents one of the largest therapeutic categories globally, with spending on immunology drugs reaching approximately $180 billion in 2025, according to IQVIA. Biogen's move follows a broader trend of neurology-focused drugmakers expanding into immunology, where overlapping biological pathways — such as the role of microglia in both neuroinflammation and peripheral immune responses — offer potential for cross-indication development.

For Biogen, the deal also signals a willingness to use M&A to fill pipeline gaps rather than relying solely on internal research. The company has completed several bolt-on acquisitions in recent years, including the purchase of Human Immunology Biosciences in 2023 for an undisclosed sum, as it seeks to build a meaningful immunology franchise alongside its core neurology business.

This article is for informational purposes only and does not constitute investment advice.