Apellis Pharmaceuticals Inc. ( APLS ) shares are up during Tuesday’s premarket session following news that Biogen Inc. ( BIIB ) has agreed to acquire Apellis for $41 per share in cash or approximately $5.6 billion.

The acquisition is expected to enhance Biogen’s growth portfolio in immunology and rare diseases and add significant value to both companies as they navigate the evolving healthcare landscape.

The deal consideration includes a contingent value right (CVR) for each share, allowing shareholders to receive two payments of $2 per share based on certain sales thresholds for Apellis.

Empaveli And Syfovre Anchor Long-Term Expansion

The deal will bolster Biogen’s revenue growth, particularly as the combined net sales of Empaveli and Syfovre reached $689 million in 2025 and is expected to grow at a mid-to-high teens rate through 2028.

The addition of Apellis brings two FDA-approved therapies to Biogen’s portfolio, enhancing its capabilities in treating complement-driven diseases.

The transaction is expected to strengthen Biogen’s revenue and earnings growth potential and to increasingly accrete to its adjusted earnings per share starting in 2027.

Financing And Balance Sheet Strategy

The transaction is expected to meaningfully increase Biogen’s adjusted earnings per share compounded annual growth rate through the end of the decade.

Biogen expects to finance the acquisition with a combination of cash and borrowings and believes it can fully de-lever by the end of 2027, allowing it to maintain financial flexibility for future investments.

Price Action: Apellis Pharmaceuticals ( APLS ) shares were up 136.16% at $40.36 at the time of publication on Tuesday. The stock is trading at a new 52-week high, according to Benzinga Pro data. Biogen shares were down 4.60% at $178.94.