Biogen acquires Apellis Pharmaceuticals in a deal that brings two marketed complement therapies into its portfolio, strengthening its position in immunology.
Biogen agreed to acquire Apellis Pharmaceuticals for approximately $5.6 billion in cash in a definitive agreement.
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The deal adds two commercialized complement therapies to Biogen’s immunology and rare disease portfolio while also laying the groundwork for an expanded push into nephrology.
Biogen is set to pay $41.00 per share in cash at closing, an 86% premium to Apellis' 90-day volume-weighted average stock price and a 35% premium to its 52-week high.1 Shareholders will also receive a non-transferable contingent value right worth up to $4.00 per share, tied to Syfovre reaching annual global net sales thresholds of $1.5 billion and $2 billion between 2027 and 2031.
The transaction, approved by both boards, is expected to close in the second quarter of 2026 and will be financed through a combination of cash and borrowings, with Biogen expecting to fully de-lever by the end of 2027.1
The deal brings two approved complement therapies into Biogen's portfolio. Syfovre (pegcetacoplan injection) is the first and only approved treatment for geographic atrophy secondary to age-related macular degeneration, an immune-mediated retinal disease that causes progressive and irreversible vision loss.3
In the Phase III Oaks and Derby studies, Syfovre reduced the rate of GA lesion growth compared to sham treatment, with effects increasing over time, reaching up to a 36% reduction in lesion growth with monthly treatment between months 18 and 24. Long-term data from an open-label extension study showed the drug delayed GA lesion progression by approximately 1.5 years in patients with nonsubfoveal GA.3 Apellis plans to submit an FDA application for a prefilled syringe formulation in the first half of 2026.
Empaveli (pegcetacoplan) is a targeted C3 therapy approved for rare immune-mediated kidney diseases, C3 glomerulopathy and primary IC-MPGN, in patients aged 12 and older, as well as for paroxysmal nocturnal hemoglobinuria in adults.2
It is the only FDA-approved treatment for pediatric patients with C3G, the only approved option for post-transplant C3G disease recurrence, and the first and only approved therapy for both adult and pediatric populations in primary IC-MPGN.2 In the Phase III Valiant study, Empaveli demonstrated a 68% reduction in proteinuria and stabilization of kidney function compared to placebo.
Together, the two products generated combined net sales of $689 million in 2025, with growth expected in the mid-to-high teens at least through 2028.
“I am incredibly proud of the Apellis team and what we have achieved, including bringing two transformational medicines, Syfovre and Empaveli, to patients and building an innovative pipeline leveraging our deep expertise in complement science,” said Cedric Francois, M.D., Ph.D., co-founder and chief executive officer of Apellis.
Beyond the immediate revenue contribution, the acquisition gives Biogen established commercial infrastructure in nephrology, a capability it needs as it advances felzartamab, its own complement-targeting antibody currently in Phase III studies for three kidney diseases, with a first trial readout expected in the first half of 2027.Apellis' field force and nephrology expertise are expected to accelerate Biogen's commercial readiness for that program.1
Christopher Viehbacher, Biogen's president and CEO, said the acquisition immediately advances the company's ongoing transformation by expanding its growth portfolio in immunology and rare disease.
“We look forward to welcoming Apellis employees to Biogen. We believe our combined capabilities and experience will allow us to maximize the potential of Syfovre and Empaveli, while Apellis’ talent, expertise and field capabilities will further strengthen Biogen, deepening the foundation for our growing nephrology franchise with felzartamab and serving many more patients with immune-mediated retinal disease," said Viehbacher.
