Biogen pens $1bn deal to buy immunology biotech RayThera

Biogen has dipped its toe into the M&A waters once again, agreeing to buy San Diego-based RayThera for up to $1 billion in its second takeover this year.

Buying RayThera will give Biogen rights to various small-molecule anti-inflammatory drugs, including an undisclosed lead asset that is due to start human testing in the third quarter. Specific financial details of the deal have not been disclosed, but include an upfront payment and milestones tied to clinical and regulatory achievements.

RayThera was founded in 2023 by biotech veterans Qing Dong and Gene Hung, who previously set up two other San Diego biotech companies, FronThera and XinThera, which were also acquired a few years after their formation by Alumis and Gilead Sciences, respectively.

There's very little information available on the company's R&D focus, but the company has applied for US patents on small-molecule TNF alpha modulators and is also working on CCR4 antagonists. The company raised $110 million in a Series A last year, backed by Foresite Capital, OrbiMed Advisors, and TTM Capital.

"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, Biogen's head of development. "We believe these assets can meaningfully contribute to our long-term pipeline potential, and we’re excited about the opportunity to rapidly advance the first candidate into the clinic."

The new agreement comes less than a month after Biogen closed its $5.6 billion acquisition of Apellis, giving it two approved therapies for kidney and eye disorders.

The company has been working to shore up its product portfolio and pipeline as it faces biosimilar competition to its big-selling multiple sclerosis therapy Tysabri (natalizumab) in the US. That has added to pressure stemming from competition to its other top products, including oral MS therapy Tecfidera (dimethyl fumarate) and spinal muscular atrophy (SMA) therapy Spinraza (nusinersen), as well as a complex and slow rollout of Eisai-partnered Alzheimer's disease therapy Leqembi (lecanemab).

According to a just-published report from management consultancy and accountancy giant PwC, the first quarter of 2026 delivered one of the strongest quarters of biopharma M&A in recent years, surpassing $65 billion, which is the strongest quarter since 2020. There has been a surge in $1 billion-plus acquisitions, totalling 16 in the first three months of the year.

The activity has been driven by large pharma companies seeking to offset an estimated $300 billion in loss of exclusivity for branded products this decade.