Biogen agreed to acquire Apellis Pharmaceuticals in a $5.6 billion deal, extending Biogen’s push into nephrology and complement-driven disease biology. The acquisition follows Biogen’s earlier move into immunology through its purchase of Human Immunology Biosciences, and it positions Biogen around its complement-focused HI-Bio pipeline asset in pivotal testing across three kidney conditions. The company framed the transaction as an acceleration of its expansion strategy and as a means to reinforce its late-stage opportunity in kidney disease. Because the biotech sector is heavily influenced by deal-making liquidity and platform repositioning, a transaction of this size can impact valuation multiples for complement and immunology assets in the near term.