Apellis Pharmaceuticals (APLS) Stock Rockets 136% on $5.6B Biogen Acquisition

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.

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.

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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