Biogen to Acquire Apellis Pharmaceuticals for $5.6 Billion

NEW YORK, March 31 —

Biogen agreed to acquire Apellis Pharmaceuticals (APLS) for $5.6 billion in cash, plus contingent milestone payments. APLS shares climbed more than 100% in a single session. The transaction prices the complement therapy specialist at a substantial premium to its pre-announcement trading range.

The acquisition gives Biogen full ownership of Apellis's C3 complement inhibitor franchise, led by Syfovre (pegcetacoplan) — the first treatment approved for geographic atrophy, a progressive form of age-related macular degeneration affecting an estimated 1 million U.S. patients who previously had no approved options. Syfovre launched in 2023 and competes with AstraZeneca's Izervay in the indication, though Apellis established early commercial leadership. Apellis posted $1.0 billion in trailing-twelve-month revenue but has not turned a profit, carrying a forward P/E of -157.3x as it funds the Syfovre launch and expands its pipeline across complement-mediated diseases. The deal solves a specific problem for Biogen. Its MS franchise has posted declining revenues, and the near-term pipeline offers limited offset. Apellis brings a cash-generating rare disease product and a complement biology platform with potential applications in immunology, nephrology, and hematology.

With APLS last quoted at $40.26, investors are playing pure merger arb. The remaining return is the spread between the current share price and the per-share consideration implied by $5.6 billion, plus any value from contingent payments — whose triggers and amounts Biogen has not yet disclosed. Cantor Fitzgerald cut its price target to $31 from $35 before the announcement; that figure now marks the approximate deal-fail downside, not a forward fundamental view. Antitrust review is the primary execution risk. The FTC has scrutinized pharma consolidation closely, with particular attention to markets where approved competitors are scarce. Geographic atrophy currently has two: Syfovre and Izervay. The HSR filing date and any second-request notice are the clearest signals on close timing and deal completion probability.

For a full fundamental breakdown of Apellis Pharmaceuticals, generate a Basis Report on APLS.

Basis Report does not hold positions in securities discussed. This is not investment advice.