Biogen to Acquire Apellis for $5.6 Billion

Biogen Inc. announced on Tuesday that it will acquire Apellis Pharmaceuticals Inc. in an all-cash transaction valued at approximately $5.6 billion, providing Apellis shareholders with $41 per share plus potential additional payments tied to future sales milestones. The deal, revealed early on March 31, 2026, sent Apellis shares soaring more than 135 percent to around $40.30 in morning trading on the Nasdaq, while Biogen's stock dipped about 5 percent to $178.94.

The acquisition offers Apellis investors an immediate premium of roughly 140 percent over the company's closing price of $17.10 on Monday and 86 percent above its 90-day volume-weighted average price. In addition to the upfront cash, shareholders will receive a contingent value right worth up to $4 per share, structured as two $2 payments if Apellis's lead drug Syfovre meets specific global sales targets in the coming years. The transaction is expected to close in the second quarter of 2026, subject to regulatory approvals and customary closing conditions.

For Biogen, the purchase represents a strategic expansion into immunology, rare diseases and nephrology, areas that align with the company's efforts to diversify...