Opinions
Amgen’s EP 797 under fire: EPO stands firm against earlier UPC revocation.
In a striking turn, the European Patent Office (EPO) has upheld Amgen’s patent EP 3 666 797 (EP 797), covering PCSK9 antibodies used in cholesterol-lowering drugs, despite a prior revocation by the Unified Patent Court (UPC).
This divergence marks a significant moment in the interplay between two of Europe’s most influential patent authorities, raising questions about legal certainty and strategy for innovators and challengers alike.
A tiny bit of background: Amgen vs Sanofi and Regeneron
Amgen’s battle with Sanofi and Regeneron is one of the pharmaceutical industry’s most protracted and contentious disputes.
Sanofi and Regeneron market its cholesterol-lowering drug under the brand name Praluent©, while Amgen markets its product under the brand name Repatha©, shown below:
Both sides have faced a patchwork of conflicting court decisions across Europe with several proceedings still pending, and neither party securing a decisive advantage.
UPC Revokes, EPO Upholds
UPC. In a nutshell, the procedural conflict at stake began when the UPC’s Central Division in Munich revoked Amgen’s patent on July 16, 2024, siding with Sanofi and Regeneron. The court found that the claimed medical use of the PCSK9 antibodies was obvious in light of prior art.
EPO. While the case was pending before the UPC, Sanofi and Regeneron also filed oppositions with the EPO against EP 797. This move opens up the scenario of a conflict between the decisions of the UPC and the EPO.
Indeed, with a decision dated May 21, 2025 – therefore subsequent to that of the UPC revocation, the EPO’s Opposition Division took a markedly different stance. Rejecting the UPC’s reasoning, the EPO emphasized the importance of a “reasonable expectation of success” in second medical use claims—an aspect the UPC had not sufficiently addressed. In simple words, this term refers to the skilled person’s ability to predict that a known substance will effectively achieve the claimed therapeutic effect in the new medical use. On this ground, the EPO, therefore, upheld Amgen’s patent as granted.
The fate of Amgen’s infringement claim now rests with the UPC Court of Appeal, which is expected to rule soon on whether the Central Division’s revocation will stand. Both Sanofi and Regeneron can also appeal the EPO’s decision to the Boards of Appeal, prolonging the uncertainty.
Implications for litigation and strategy
The divergence between the UPC and EPO, even when assessing the same patent and facts, underscores the complexity of patent enforcement and defense strategies in Europe. For companies, this means a patent may remain valid before the EPO while being simultaneously invalidated within the UPC’s jurisdiction, creating significant challenges for consistent protection across the continent.
Strategically, it should always be kept in mind when choosing between UPC and EPO proceedings, it is essential to consider the key differences in territorial scope, costs, and timing. EPO opposition proceedings: (i) cover all EPC member states (broader scope); (ii) involve low official fees with each party bearing its own costs and (iii) are typically lengthy. On the other hand, UPC revocation actions are: (i) limited to UPCA member states, (ii) require higher initial costs, but offer the possibility of recovering legal fees if successful, and (iii) generally provide a faster resolution.
These differences and any discrepancies that may arise between the decisions of the EPO and the UPC are not inherently negative, but they must be carefully weighed when developing a litigation strategy, as the strategical choice of these courts can have a decisive impact on the outcome and efficiency of patent disputes.
This newsletter is for the sole purpose of providing updates and general information and is not intended as legal advice on any particular or specific issue.
For clarifications or information, please contact the authors or your reference professional in the Intellectual Property area at our Firm.
Niccolò Ferretti, Partner
E: n.ferretti@nmlex.it
T.: +39 026575181
Valentina D’Adda, Trainee
E: v.dadda@nmlex.it
T.: +39 026575181
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