TLDR
- Biogen agreed to acquire Apellis Pharmaceuticals for approximately $5.6 billion in cash.
- Apellis stockholders will receive $41 per share, a roughly 140% premium to the stock’s last close.
- Shareholders may also receive up to $4 per share in contingent payments tied to sales milestones for Syfovre.
- Biogen gains access to Empaveli and Syfovre, which generated combined revenue of $689 million last year.
- The deal is expected to close in the second quarter of 2026.
Apellis Pharmaceuticals (APLS) stock surged over 136% in pre-market trading on Tuesday, March 31, after Biogen (BIIB) announced it would acquire the rare disease drugmaker for around $5.6 billion. Biogen stock fell roughly 7% on the news.
Apellis Pharmaceuticals, Inc., APLS
Biogen’s offer of $41 per share in cash represents a premium of about 140% to where APLS closed the previous session.
The deal reflects Biogen’s strategy to offset slowing revenue from its multiple sclerosis drug lineup by building out a broader portfolio in immunology and rare diseases.
Biogen agreed to buy Apellis Pharmaceuticals for $5.6 billion, expanding its treatments in immunology and rare diseases in one of the company’s largest acquisitions https://t.co/enfkABltuX
— Bloomberg (@business) March 31, 2026
Apellis brings two key approved drugs to the table. Empaveli is cleared for two rare kidney diseases and a rare blood disorder. Syfovre targets an advanced form of geographic atrophy, a leading cause of blindness worldwide.
Together, the two drugs brought in approximately $689 million in combined revenue in 2025. Biogen and Apellis project that figure to grow in the mid-to-high teens percentage range annually through at least 2028.
Contingent Payments on the Table
Beyond the base $41 per share, Apellis stockholders could receive two additional payments of $2 each — totaling up to $4 extra per share — contingent on hitting specific global sales milestones for Syfovre.
That puts the maximum potential payout at $45 per share if those milestones are reached.
Biogen CEO Christopher Viehbacher described the acquisition as consistent with the company’s ongoing transformation. “The addition of Apellis expands our growth portfolio in immunology and rare disease with two approved, best-in-class medicines that complement our existing portfolio,” he said.
The deal is expected to close in the second quarter of 2026, pending standard regulatory and shareholder approvals.
Biogen Takes a Hit
While APLS investors came out well ahead, Biogen stock was under pressure following the announcement, falling close to 7% in pre-market trading.
That reaction is not unusual for an acquirer paying a substantial premium. Large cash deals can weigh on the buyer’s stock in the short term, particularly when the price tag runs into the billions.
On TipRanks, BIIB carries a Moderate Buy consensus rating based on 11 Buy, 15 Hold, and 1 Sell analyst ratings. The consensus price target sits at $206.70, implying around 10% upside from recent levels, with the highest target at $250.
The acquisition is Biogen’s latest move to reposition itself away from its legacy MS business toward higher-growth rare disease treatments.
Apellis stock had a closing price of approximately $17 prior to the announcement, based on the implied discount to the $41 per share offer price.
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