Key Highlights
- Biogen has entered into an agreement to purchase Apellis Pharmaceuticals for roughly $5.6 billion in an all-cash transaction.
- The offer price of $41 per share represents approximately a 140% premium over Apellis’ previous closing price.
- Additional contingent value rights of up to $4 per share may be earned based on Syfovre sales performance targets.
- The acquisition provides Biogen with two commercial products, Empaveli and Syfovre, which delivered $689 million in total sales last year.
- Transaction completion is anticipated during Q2 2026.
Shares of Apellis Pharmaceuticals (APLS) exploded more than 136% during pre-market hours on Tuesday, March 31, following news that Biogen (BIIB) reached a definitive agreement to purchase the biotech company for approximately $5.6 billion. Meanwhile, Biogen’s shares declined around 7% on the announcement.
Apellis Pharmaceuticals, Inc., APLS
The all-cash transaction values Apellis at $41 per share, delivering shareholders a premium of roughly 140% compared to the prior day’s closing price.
This strategic acquisition aligns with Biogen’s efforts to diversify beyond its aging multiple sclerosis franchise by strengthening its presence in the immunology and rare disease therapeutic areas.
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
The deal secures Biogen ownership of two commercially available therapies. Empaveli has received approval for treating two uncommon kidney conditions along with a rare blood disorder. Syfovre addresses geographic atrophy in its advanced stages, a significant contributor to vision loss globally.
The combined therapies generated roughly $689 million in revenue during 2025. Both companies anticipate sustained revenue growth in the mid-to-high teens percentage range through 2028 at minimum.
Additional Value Through Milestone Payments
In addition to the upfront $41-per-share consideration, Apellis shareholders stand to gain up to two separate $2 payments — for a maximum of $4 additional per share — tied to achieving predetermined worldwide sales benchmarks for Syfovre.
This structure means shareholders could ultimately receive as much as $45 per share if the commercial targets are successfully met.
Christopher Viehbacher, CEO of Biogen, characterized the transaction as aligned with the company’s strategic evolution. “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 stated.
The transaction requires customary regulatory clearances and shareholder approval, with closing expected in the second quarter of 2026.
Biogen Shares Decline on Announcement
While Apellis shareholders celebrated substantial gains, Biogen investors responded less enthusiastically, sending shares down nearly 7% in early trading.
This response is typical when acquiring companies pay significant premiums. Multibillion-dollar cash acquisitions often pressure the buyer’s stock price initially, especially at this valuation level.
According to TipRanks, BIIB holds a Moderate Buy consensus rating derived from 11 Buy, 15 Hold, and 1 Sell recommendations from analysts. The average price target stands at $206.70, suggesting approximately 10% upside potential from current levels, with a high forecast of $250.
This acquisition represents another step in Biogen’s strategic pivot away from its traditional MS-focused business model toward faster-growing rare disease therapeutic areas.
Based on the premium calculation, Apellis shares were trading near $17 before the acquisition announcement became public.
