8 Trillion Won Rare Disease Acquisition Battle: Biogen Pursues Stake in New Drug Developer

On March 31, 2026, Apellis Pharmaceuticals, Inc. (Nasdaq: APLS) entered into a Tender and Support Agreement with Biogen and its subsidiary, Aspen Purchaser Sub, under which key shareholders—including Morningside Venture Investments and company insiders—agreed to tender their entire holdings in Biogen’s proposed public tender offer, vote in favor of the merger, oppose any competing proposals, and restrict future share sales.

On the same day, Biogen announced a definitive agreement to acquire Apellis through a public tender offer and merger, offering $41.00 per share in cash plus up to $4.00 per share in contingent consideration, valuing the transaction at approximately $5.6 billion (about KRW 8.5 trillion).

Apellis is a U.S. biotech company developing novel complement C3 inhibitors, including SYFOVRE for geographic atrophy and EMPAVELI for rare blood and kidney disorders. The acquisition will strengthen Biogen’s rare disease and immunology portfolio and diversify its growth drivers.