On March 14, 2025, the United States Court of Appeals for the Federal Circuit issued a decision in Regeneron Pharmaceuticals, Inc. v. Amgen Inc., affirming the district court’s denial of a preliminary injunction sought by Regeneron. This ruling is significant in the realm of patent law, particularly in the biologic pharmaceutical industry, as it centers on claim construction and the principles governing patent infringement.
Background of the Case
Regeneron sued Amgen, alleging that Amgen’s biosimilar product, ABP 938 (Pavblu), infringed its U.S. Patent 11,084,865 (the ’865 patent). This patent claims a pharmaceutical formulation for an ophthalmic drug, Eylea, which contains a vascular endothelial growth factor (VEGF) antagonist, a buffer, an organic co-solvent, and a stabilizing agent.
Amgen developed ABP 938 as a biosimilar to Eylea but with a key difference: it eliminated the need for a separate buffer component by utilizing a self-buffering VEGF antagonist. Regeneron argued that Amgen’s formulation still fell within the scope of its patent, while Amgen maintained that its approach did not infringe because it lacked a distinct buffer component.
Key Legal Issues
The central legal question in this case revolved around claim construction—specifically, whether the language of the ’865 patent required the VEGF antagonist and the buffer to be separate components. The court’s analysis focused on the following issues:
1. Claim Construction and the Becton Doctrine
The court applied the principle established in Becton, Dickinson & Co. v. Tyco Healthcare Grp., which states that where a patent claim lists components separately, there is a presumption that they are distinct. Since the ’865 patent separately lists the VEGF antagonist and the buffer, the Federal Circuit found that the presumption of distinctness applied.
Regeneron argued that the buffer requirement could be satisfied by the VEGF antagonist itself, given its buffering capacity. However, the court rejected this argument, emphasizing that the claim structure and specification reinforced the requirement that the buffer must be a separate component.
2. The Role of Intrinsic and Extrinsic Evidence
The court reviewed both intrinsic evidence (the patent claims and specification) and extrinsic evidence (expert testimony and scientific literature) to determine the meaning of the disputed claim terms. The specification described formulations where a VEGF antagonist was always accompanied by a separate buffer. Moreover, the examples and embodiments consistently treated the buffer as a distinct component.
While Regeneron presented extrinsic evidence suggesting that proteins like aflibercept could function as buffers, the court found this insufficient to override the intrinsic evidence. The ruling underscored the principle that claim construction must align with the patent’s written description rather than rely on broad interpretations supported by external sources.
3. Implications for Biosimilar Litigation
A key takeaway from this case is how courts interpret claims involving biosimilars. The ruling reinforces that companies developing biosimilars can avoid infringement if they modify formulations in a way that eliminates explicitly claimed components. Amgen’s strategy of using a self-buffering formulation proved successful in distinguishing ABP 938 from Eylea in a legally meaningful way.
Conclusion
The Federal Circuit’s decision in Regeneron v. Amgen sets an important precedent for biologic patent disputes. It highlights the significance of precise claim drafting and underscores the challenges in asserting broad interpretations of patent scope. For companies engaged in biosimilar development, this ruling provides a roadmap for designing around existing patents by focusing on structural distinctions in formulation components.
This case serves as a reminder that in patent litigation, the wording of claims and the clarity of specifications are critical. While Regeneron’s patent remains valid, its enforceability against biosimilars like Amgen’s ABP 938 has been significantly weakened. As the biosimilar market continues to grow, expect more litigation focused on claim construction and the interpretation of formulation patents.
By Charles Gideon Korrell
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