Regeneron Settles Eylea Patent Dispute with Celltrion, Paving Way for Biosimilar Launch

Regeneron Pharmaceuticals has reached a settlement agreement with South Korean drugmaker Celltrion in their ongoing patent dispute over the blockbuster eye drug Eylea (aflibercept). This development marks a significant shift in the competitive landscape for aflibercept biosimilars in the United States.

Settlement Details and Market Impact

The settlement, announced on October 20, 2025, allows Celltrion to launch its recently approved Eylea biosimilar, Eydenzelt, on December 31, 2026. This agreement resolves all patent litigation between the two companies, though specific financial terms remain confidential.

Celltrion's Eydenzelt received FDA approval on October 9, 2025, for use in the same indications as Eylea, including:

• Neovascular (wet) age-related macular degeneration
• Macular edema following retinal vein occlusion
• Diabetic macular edema
• Diabetic retinopathy

The approval came after clinical trials demonstrated that Eydenzelt "met the predefined equivalence criteria" to Eylea and showed similar results in secondary endpoints of efficacy, safety, and immunogenicity.

Competitive Landscape and Legal Battles

Regeneron has been embroiled in legal disputes with several biosimilar developers seeking to enter the lucrative aflibercept market. The company has sued Celltrion, Sandoz, Amgen, Formycon, Samsung Bioepis, and Mylan Pharmaceuticals (in partnership with Biocon Biologics) in attempts to protect its market position.

Amgen currently stands as the only company to have won a legal victory against Regeneron, allowing it to market the first Eylea biosimilar in the U.S. However, recent settlements suggest increased competition is on the horizon:

• Sandoz's Enzeevu, an interchangeable biosimilar, is set to launch in Q4 2026 or potentially earlier under certain circumstances.
• Biocon and Mylan's interchangeable biosimilar, Yesafili, is slated for launch in the second half of 2026.

Regeneron continues to challenge Samsung Bioepis' Opuviz and Formycon's Ahzantive in court, while also pursuing further legal action against Amgen as recently as June 2025.

Market Performance and Future Outlook

The impending influx of biosimilar competition comes as Eylea faces declining sales. In the most recent quarter, Eylea reported U.S. sales of $1.1 billion, representing a 25% decrease compared to the same period in the previous year.

As the aflibercept market braces for increased competition, stakeholders will be closely watching how these new entrants impact pricing, market share, and patient access in the coming years.