Biogen agreed to acquire Apellis Pharmaceuticals for $5.6 billion, adding two commercialized immune-complement assets alongside Apellis’ late-stage kidney pipeline. The purchase is expected to strengthen Biogen’s push in immunology and rare disease, and to accelerate launch readiness for felzartamab, Biogen’s CD38-directed investigational antibody. Apellis’ marketed portfolio includes Empaveli (pegcetacoplan) for rare kidney conditions and Syfovre (pegcetacoplan) for late-stage age-related macular degeneration, providing immediate revenue rather than relying solely on late-stage trial outcomes. The deal structure includes contingent value rights tied to Syfovre global net sales milestones, and Biogen said it will fund the transaction through a mix of cash and borrowings with a stated goal of de-leveraging by the end of 2027. In the wider sector context, the transaction reinforces how large-cap biopharma is using M&A to rapidly fill immunology franchises—especially where near-term commercial assets can offset pipeline execution risk.