Biogen agreed to buy RayThera in a deal that could total up to $1 billion, securing an immunology-focused early pipeline with limited public disclosure from the target. The portfolio includes anti-inflammatory candidates, including at least one prospect expected to move into the clinic in the third quarter. The transaction is backloaded, with an undisclosed upfront payment and additional milestone payments tied to clinical and regulatory progress. RayThera, founded in 2023, raised $110 million in a Series A led by Foresite Capital and OrbiMed Advisors in 2025. For Biogen, the acquisition continues a shift beyond neurology—following its earlier Apellis Pharmaceuticals purchase—and adds more upstream immunology exposure after it acquired marketed products and research programs tied to complement.