Regeneron Pharms., Inc. v. Mylan Pharms. Inc

Authored by: Jeremy J. Gustrowsky

In a recent decision, the Federal Circuit affirmed that when a patent claim lists components separately—like a “VEGF antagonist” and a “buffer”—those elements must be distinct in the accused product. This case centered on Regeneron Pharmaceuticals’ U.S. Patent No. 11,084,865, which covers formulations of its eye drug EYLEA®. Regeneron sought a preliminary injunction to stop Amgen from selling its biosimilar, ABP 938 (now branded as Pavblu), arguing that Amgen’s product infringed its patent. However, Amgen’s formulation did not include a separate buffer; instead, it relied on the active ingredient itself to provide buffering capacity.

The key legal issue was whether the patent’s requirement for a “VEGF antagonist” and a “buffer” could be satisfied by a single ingredient, or whether the patent required them to be physically separate. The court applied its precedent, known as the Becton presumption, which holds that separately listed claim elements are presumed to be distinct components. The judges found that nothing in the patent’s claims or specification suggested that a single ingredient could serve both roles. In fact, the patent consistently described the VEGF antagonist and buffer as separate items, and even measured them in different units.

Regeneron argued that experts in the field would have understood that proteins like aflibercept could act as buffers, and pointed to extrinsic evidence and prior court decisions. However, the Federal Circuit emphasized that clear claim language and the patent’s own description outweighed any outside evidence. Since Amgen’s product did not contain a separate buffer, the court concluded there was at least a substantial question of noninfringement, making a preliminary injunction inappropriate.

This decision reinforces the importance of clear and precise claim drafting in patents, especially for pharmaceutical formulations. If a patent lists ingredients separately, future challengers can avoid infringement by omitting one of those components—even if the active ingredient can perform multiple functions.