Biogen Expands Complement Disease Portfolio Through Acquisition of Apellis Pharmaceuticals

Biogen announced its acquisition of Apellis Pharmaceuticals, bringing the complement-focused biotech and its commercial products fully under Biogen ownership.¹ The transaction expands Biogen’s footprint in rare disease, ophthalmology, and nephrology while reinforcing broader industry interest in complement-mediated disease therapies.

Complement therapeutics drive strategic growth

The acquisition adds two marketed complement-targeting therapies to Biogen’s commercial portfolio: pegcetacoplan injection (brand name Syfovre) for geographic atrophy (GA) secondary to age-related macular degeneration (AMD), and pegcetacoplan (brand name Empaveli/Aspaveli) for paroxysmal nocturnal hemoglobinuria (PNH), C3 glomerulopathy (C3G), and primary immune-complex membranoproliferative glomerulonephritis (IC-MPGN).¹

Together, the products generated $689 million in net product revenue during 2025, according to Biogen.¹

The move also strengthens Biogen’s nephrology capabilities through Apellis’ commercial and medical infrastructure, potentially supporting future launches including felzartamab, an investigational monoclonal antibody currently in Phase 3 development for antibody-mediated rejection in kidney transplant patients.¹ A related clinical trial evaluating felzartamab in late antibody-mediated rejection is listed on ClinicalTrials.gov.²

Geographic atrophy remains major unmet need

Syfovre became the first FDA-approved treatment for GA secondary to AMD, a progressive retinal disease affecting more than one million individuals in the US and an estimated five million globally.^1,3 Researchers project AMD prevalence will continue rising substantially as populations age.⁴

The therapy targets complement component C3, aiming to modulate excessive complement activation implicated in retinal degeneration. However, the treatment carries important safety considerations. According to prescribing information cited by Biogen, Syfovre administration has been associated with retinal vasculitis, retinal vascular occlusion, intraocular inflammation, and increased rates of neovascular AMD.¹

In clinical development, pegcetacoplan demonstrated efficacy across multiple complement-mediated indications through a series of late-stage trials evaluating both ophthalmologic and hematologic outcomes. In the Phase 3 DERBY and OAKS studies, intravitreal pegcetacoplan significantly slowed geographic atrophy lesion growth compared with sham treatment, supporting Syfovre’s eventual FDA approval as the first therapy for GA secondary to AMD.¹ Investigators reported increasing treatment effects over time, reinforcing the role of complement inhibition in slowing retinal degeneration progression. Meanwhile, Empaveli’s approval in PNH was supported by the Phase 3 PEGASUS trial, which evaluated patients switching from eculizumab therapy to pegcetacoplan.² The study demonstrated superior hemoglobin improvement and transfusion avoidance in patients treated with pegcetacoplan versus continued eculizumab therapy. Beyond approved indications, Apellis has continued evaluating complement inhibition in additional renal and rare disease settings, reflecting broader industry interest in targeting upstream complement cascade pathways to address chronic inflammatory and immune-mediated diseases.³ The acquisition therefore provides Biogen not only with commercial products, but also with a clinically validated platform in complement biology that may support future pipeline expansion across multiple therapeutic categories.

Meanwhile, Empaveli continues to expand in rare complement-mediated renal diseases. C3G and primary IC-MPGN remain serious kidney disorders associated with progressive renal damage and high rates of kidney failure within 5 to 10 years of diagnosis.¹

Consolidation reflects broader biopharma trends

The acquisition underscores increasing biopharmaceutical investment in complement biology, an area that has attracted growing scientific and commercial attention across ophthalmology, nephrology, hematology, and immunology. Industry analysts have pointed to complement inhibition as a potentially durable therapeutic platform for multiple chronic inflammatory and rare diseases.³

References

1. Biogen Inc. (2026, May 14). Biogen completes acquisition of Apellis Pharmaceuticals. GlobeNewswire. https://www.globenewswire.com/news-release/2026/05/14/3071234/0/en/Biogen-Completes-Acquisition-of-Apellis-Pharmaceuticals.html
2. A study of felzartamab in late antibody-mediated rejection in kidney transplant recipients (TRANSCEND). (2026). Clinicaltrials.gov. https://clinicaltrials.gov/study/NCT05021484
3. Wong, W. L., Su, X., Li, X., et al. (2014 Feb). Global prevalence of age-related macular degeneration and disease burden projection for 2020 and 2040: A systematic review and meta-analysis. The Lancet Global Health. https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(13)70145-1/fulltext
4. Smith, R. J. H., Appel, G. B., Blom, A. M., et al. (2019 Mar 15). C3 glomerulopathy — understanding a rare complement-driven renal disease. Nature Reviews Nephrology. https://pubmed.ncbi.nlm.nih.gov/30692664/