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

Regeneron Pharmaceuticals has reached a settlement agreement with South Korean drugmaker Celltrion, resolving their patent dispute over the blockbuster eye drug Eylea (aflibercept). This development marks a significant shift in the competitive landscape for age-related macular degeneration treatments, as it allows for the introduction of another biosimilar to the U.S. market.

Settlement Details and Market Implications

Under the terms of the agreement, Celltrion will be permitted to launch its recently approved Eylea biosimilar, Eydenzelt, in the United States on December 31, 2026. The settlement encompasses all patent litigation between the two companies, although specific financial terms remain confidential.

This resolution follows a pattern of similar agreements Regeneron has made with other biosimilar developers. Notably, Sandoz and the partnership of Biocon Biologics and Mylan Pharmaceuticals have also secured launch dates for their respective Eylea biosimilars in the latter half of 2026.

The FDA granted approval to Celltrion's Eydenzelt on October 9, 2025, authorizing its use for the same indications as Eylea. These include neovascular (wet) age-related macular degeneration, macular edema following retinal vein occlusion, diabetic macular edema, and diabetic retinopathy.

Competitive Landscape and Market Dynamics

Regeneron's decision to settle with multiple biosimilar manufacturers signals a strategic shift in its approach to maintaining market share. The company has been embroiled in legal battles with several firms, including Amgen, Formycon, and Samsung Bioepis, in an effort to protect its Eylea franchise.

Amgen currently holds the distinction of being the only company to have successfully challenged Regeneron in court, allowing it to market the first Eylea biosimilar in the U.S. However, the landscape is set to become more competitive with the impending launches from Celltrion, Sandoz, and others.

The impact of this increased competition is already evident in Regeneron's financial reports. U.S. sales of Eylea declined by 25% in the most recent quarter, totaling $1.1 billion. This drop underscores the challenges facing branded biologics as biosimilars enter the market.

Biosimilar Development and Regulatory Landscape

The approval of Eydenzelt and other Eylea biosimilars represents a significant milestone in the broader context of biosimilar development. Celltrion reported that Eydenzelt met predefined equivalence criteria in trials, demonstrating similar efficacy, safety, and immunogenicity profiles to the reference product.

Of particular note is the FDA's approval of interchangeable biosimilars, such as Sandoz's Enzeevu and Biocon/Mylan's Yesafili. These products can be substituted at the pharmacy level without requiring a new prescription, potentially accelerating market penetration and cost savings for patients.

As the pharmaceutical industry continues to navigate the complex landscape of biosimilar development and patent litigation, the resolution of disputes like the one between Regeneron and Celltrion will play a crucial role in shaping market dynamics and patient access to innovative therapies.