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June 17 (Reuters) - Biogen BIIB.O has struck a deal to acquire private biotechnology company RayThera for up to $1 billion, the companies said on Wednesday, as the U.S.-listed drugmaker seeks to expand its pipeline in immunology.

• The transaction will include an upfront payment to RayThera shareholders, along with additional payments tied to clinical and regulatory milestones, the companies said in a statement.

• San Diego-based RayThera's portfolio includes several anti-inflammatory drug candidates, with its lead program expected to enter Phase 1 clinical trials in early third quarter, 2026.

• The deal comes at a time of biotech dealmaking frenzy, with large drugmakers on a spending spree to expand their product pipelines this year.

• In March, Biogen acquired Apellis Pharmaceuticals for about $5.6 billion, expanding its presence in kidney disease treatments.