Biogen Inc. has successfully completed its acquisition of Apellis Pharmaceuticals for $5.3 billion, enabling Apellis to function as a subsidiary. This strategic move comes as Apellis reported a 10.6% year-over-year revenue decline despite posting a Q4 2025 revenue of $200 million, exceeding expectations. Apellis's stock is currently fluctuating, with a recent monthly gain of 6.6%, as the merger aims to leverage combined strengths to enhance biopharmaceutical innovations.