Biogen and Apellis Pharmaceuticals have entered into a definitive agreement under which Biogen has agreed to acquire all outstanding shares of Apellis for USD 41.00 per share in cash at closing, or approximately USD 5.6 billion. Apellis stockholders will also receive a non-transferable CVR for each Apellis share held, entitling the holder to receive two payments of USD 2 per share each, contingent on certain annual global net sales thresholds being met for SYFOVRE.

The addition of Apellis, a leader in advancing treatments for serious, complement-driven diseases, is expected to enhance Biogen’s short- and long-term revenue growth profile by adding two commercialised differentiated immunology and rare disease medicines to its growth portfolio. EMPAVELI and SYFOVRE add immediate sales revenue to Biogen, having achieved combined net sales of USD 689 million in 2025, which is expected to grow at a rate in the mid-to-high teens at least through 2028.

EMPAVELI is FDA-approved in rare immune-mediated kidney diseases (C3G and primary IC-MPGN) and in PNH and SYFOVRE is FDA-approved in geographic atrophy secondary to age-related macular degeneration, an immune-mediated retinal disease. Apellis brings an established US sales infrastructure and capabilities, including in nephrology, that Biogen believes will accelerate and strengthen Biogen’s commercial readiness for felzartamab, which is currently in phase-III studies for three kidney diseases with the first trial readout expected in the first half of 2027. Upon closing, Biogen expects a significant proportion of Apellis employees to join the company. Biogen will continue to work with Sobi, which retains commercial rights to EMPAVELI (Aspaveli in the EU) outside the US.

“Consistent with our strategy, this acquisition immediately advances Biogen’s ongoing transformation. 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 and bolsters our near-and long-term growth potential. We look forward to welcoming Apellis employees to Biogen. We believe our combined capabilities and experience will allow us to maximise 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 Christopher A Viehbacher, President and Chief Executive Officer, Biogen.

EMPAVELI (pegcetacoplan) is a targeted complement component 3 (C3) therapy designed to regulate excessive activation of the complement cascade, a part of the body’s immune system. EMPAVELI has been approved with a broad label for adults and adolescents with C3 glomerulopathy (C3G) or primary IC-MPGN (primary immune-complex membranoproliferative glomerulonephritis) that also includes data on patients with post-transplant C3G disease recurrence. In the phase-III VALIANT study, EMPAVELI demonstrated a 68 percent reduction in proteinuria, stabilisation of kidney function and substantial clearance of C3 deposits (as measured by C3 staining by biopsy), compared to placebo.

“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. With Biogen’s extensive experience with immunology and rare disease, we believe this transaction will accelerate our impact and enable us to reach more patients. This transaction represents a compelling outcome for our shareholders and a strong validation of our strategy, scientific innovation and execution,” said Cedric Francois, MD, PhD, Co-Founder and Chief Executive Officer, Apellis. Positive results were seen in adolescent and adult patients with C3G and primary IC-MPGN and in C3G patients with post-transplant disease recurrence.

EMPAVELI is the only FDA-approved treatment for paediatric patients (12+ years) with C3G and the only FDA-approved treatment for patients with post-transplant C3G disease recurrence.

EMPAVELI is also the first and only FDA-approved treatment for both adult and paediatric (12+ years) populations in primary IC-MPGN.

EMPAVELI/Aspaveli is also approved for the treatment of adults with Paroxysmal Nocturnal Hemoglobinuria (PNH) in the United States, European Union and other countries, globally.

SYFOVRE (pegcetacoplan injection) is an approved therapy for Geographic Atrophy (GA) secondary to age-related macular degeneration. By targeting C3, SYFOVRE has been shown to provide comprehensive control of the complement cascade, part of the body’s immune system. SYFOVRE was approved based on positive results from the phase-III OAKS and DERBY studies at 24 months, which included a broad and representative patient population.

In these studies, SYFOVRE reduced the rate of GA lesion growth compared to sham treatment.

The treatment demonstrated increasing effects over time, with the greatest benefit — up to 36 percent reduction in lesion growth with monthly treatment in the DERBY study — occurring between months 18 and 24.

In November 2025, Apellis presented a post-hoc analysis of its five-year long-term efficacy data from the GALE open-label extension study, showing SYFOVRE delayed GA lesion progression by approximately 1.5 years in patients with non-subfoveal GA when compared to sham/projected sham.

SYFOVRE is approved in the United States and Australia.

Apellis has completed a clinical trial for a SYFOVRE prefilled syringe (PFS) and plans to submit its application for FDA approval in the first half of 2026.

Upon closing of the transaction, expected in the second quarter of 2026, the addition of Apellis is expected to add commercial products to Biogen that together recorded USD 689 million in revenue in 2025, and which are expected to grow at a rate in the mid-to-high teens at least through 2028. 

This transaction is expected to strengthen Biogen’s revenue and EPS growth potential, and is expected to be increasingly accretive to Biogen’s Non-GAAP diluted EPS starting in 2027. Importantly, the transaction is expected to meaningfully increase Biogen’s non-GAAP EPS Compounded Annual Growth Rate (CAGR) 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.

Biogen plans to update full year 2026 guidance when it reports earnings for the first quarter of 2026.

Under the terms of the agreement, Biogen will commence a tender offer to acquire all of the outstanding shares of Apellis common stock for USD 41 per share in cash at closing (representing an 86 percent premium to the 90-day volume-weighted average stock price and a 35 percent premium to the 52-week high stock price) and a non-transferable CVR per share. Each CVR represents the right to receive a cash payment of USD 2 per share if SYFOVRE achieves USD 1.5 billion in annual global net sales in any calendar year between 2027 and 2030, a right to receive an additional cash payment of USD 2 per share if SYFOVRE achieves USD 2 billion in annual global net sales in any of these calendar years, and, if these thresholds are not met and no CVR payment is due for any of these years, but if SYFOVRE achieves USD 2 billion in annual global net sales in the 2031 calendar year, a cash payment of USD 4 per share.

Upon the successful completion of the tender offer, Biogen will acquire all remaining Apellis shares that are not tendered into the tender offer through a second-step merger at the same consideration.

The transaction, which was approved by the boards of directors of both companies, is subject to successful completion of the tender offer, customary closing conditions and the receipt of necessary regulatory approvals.