PCSK9 Patent Saga – Introduction:

On Nov 25, 2025, the Unified Patent Court’s Court of Appeal made headlines with its detailed decision on the fiercely contested European patent EP3666797B1, held by Amgen Inc. This landmark patent covers monoclonal antibodies targeting PCSK9 core to cholesterol-lowering drugs like Repatha (Amgen) and Praluent (Sanofi/Regeneron). The decision sheds new light on pivotal patent law principles like claim interpretation, medical use claims, sufficiency of disclosure, and inventive step.

PCSK9 Patent Saga – Background:

  • Amgen Inc: The patent owner, a global biotech firm, developed Repatha, a PCSK9 inhibitor for high cholesterol.
  • Sanofi & Regeneron: Competitors, holders of Praluent, another PCSK9 inhibitor.
  • The Patent: Titled “Antigen Binding Proteins to Proprotein Convertase Subtilisin Kexin Type 9 (PCSK9),” filed in 2008, granted in 2023.
  • Dispute Origins: Sanofi sought to revoke Amgen’s patent, while Amgen accused Sanofi/Regeneron of infringement. Initial judgment by the Munich Central Division revoked Amgen’s patent for lack of inventiveness, leading Amgen to appeal.
  • Technical Primer: PCSK9, Cholesterol, and Monoclonal Antibodies

PCSK9 Patent Saga – Understanding the science:

  • PCSK9 is an enzyme affecting liver cell receptors responsible for removing LDL (“bad” cholesterol) from blood.
  • Monoclonal antibodies like those in Repatha/Praluent are engineered proteins designed to block PCSK9, boosting LDL receptor recycling and lowering blood cholesterol levels.

The dispute centered on whether Amgen’s claimed antibodies which bind specifically to the catalytic domain of PCSK9 were inventive, sufficiently disclosed, and not over-broad or additive in their claims.

PCSK9 Patent Saga – Key Legal Issues: Claim Interpretation and Medical Use Claims

The Court of Appeal deeply analyzed:

  • Claim Interpretation: What protections does Amgen’s patent actually offer? The Court confirmed that patents must be read by the skilled person in context, using the full description and drawings, not just the claim wording. Dependent claims only clarify main claims if they materially limit or specify the invention.
  • Medical Use Claims: For pharmaceutical patents, it’s not enough that an antibody lowers cholesterol there must be a “therapeutically meaningful” improvement for the patient. The Court emphasized that medical use claims inherently require proven therapeutic effectiveness, even if the claim doesn’t specify a minimum effect.

The “Sufficiency” Requirement: Can the Skilled Person Reproduce the Invention?

European patent law demands that inventions are sufficiently described, so others (skilled in the art) can reproduce the claimed products without undue effort or inventive skill.

  • The Court found Amgen’s patent provided enough technical information including experimental examples for experts to produce the claimed antibodies, even allowing for reasonable “trial and error.”
  • Arguments against sufficiency like the need for complex X-ray crystallography were rejected. The Court held that multiple standard screening and mapping methods were available; occasional scientific failures do not render the patent insufficient.

Inventive Step: Was Amgen’s Antibody “Obvious” to the Skilled Person?

The crux of the case: Did Amgen’s invention represent a genuine leap, or was it an obvious solution given earlier science?

1. The Problem-Solution Approach:

  • First, establish the technical problem solved by the invention here, an effective treatment for hypercholesterolemia using PCSK9-targeting antibodies.
  • Compare the complete invention, not isolated features, to the prior art.

2. Reasonable Expectation of Success:

  • The skilled person in 2008 could not predict that blocking PCSK9’s extra-cellular activity alone would result in a meaningful therapy, due to scientific uncertainty about PCSK9’s actual functions under physiological conditions.
  • The Court noted: It’s not enough to “hope” a therapy works; patent law requires a rational expectation that it will succeed.

3. Prior Art Analysis:

  • Key references (Lagace, Graham) highlighted PCSK9 as a drug target but did not provide certainty that neutralizing it with antibodies would deliver therapeutic results.
  • The Court ruled that, at the date, researchers were incentivized by promising genetic data but did not have decisive pointers to the claimed solution.

Result: Amgen’s antibodies were NOT “obvious.” The revocation was overturned.

Added Matter: Did Amgen Overreach in Amending Its Claims?

Opponents argued that Amgen created new combinations of features not originally disclosed so-called “added matter.” The Court disagreed, ruling:

  • Literal support across the whole application is not necessary.
  • As long as a skilled person can derive the claimed invention from the entire application especially preferred, linked features the amendments are allowed.

PCSK9 Patent Saga – Key Outcomes of the Appeals:

  • The patent stands: The Court of Appeal set aside the revocation, rejected counter-claims, and instructed Sanofi/Regeneron to pay Amgen’s legal costs over €1.3 million each.
  • Legal value assigned: The proceedings were valued at €100 million per action, underlining the economic and strategic significance in the pharma industry.

PCSK9 Patent Saga – Market and Innovation Impact:

This judgment will echo across the pharmaceutical and biotechnology sectors:

  • PCSK9 inhibitors remain a protected class in key European markets.
  • Legal certainty for innovators: The decision clarifies how thorough inventive-step and sufficiency arguments must be. Simply being first or using routine techniques doesn’t guarantee patent protection what matters is solving technical uncertainties with a rational expectation of success.
  • Encourages robust patent drafting: Clear linkage between technical solution, experimental data, and claim scope is crucial.

PCSK9 Patent Saga – Unified Patent Court: Harmonizing European Patent Law

The UPC, with multi-national panels and transnational effect, aims to resolve fragmentation and inconsistency in European patent litigation.

  • Claim Interpretation: Harmonized principles prioritize fairness for both patent holders and competitors.
  • Inventive Step: Emphasizes a “problem-solution” approach, bridging technical and legal understanding.

PCSK9 Patent Saga – Conclusion: Bigger Than One Patent

This UPC decision upholds not just Amgen’s PCSK9 antibody patent, but also sets guiding principles for the entire pharma-biotech sector regarding patentability. It reinforces the importance of thorough experimentation, robust drafting, and sound legal strategy for protecting cutting-edge therapeutics.

For innovators, legal teams, and pharma professionals, the case is a lesson in the power and limitations of patent rights as drivers of research, investment, and patient benefit across Europe.

PCSK9 Patent Saga – Key Takeaways:

  • Precedent strengthens meaningful innovation over routine “next steps.”
  • Litigation success hinges on combining legal clarity with scientific credibility.
  • Pharma patent strategy must integrate real-world therapeutic effects, not just molecular targets.
  • If you’re navigating the maze of pharmaceutical patenting, watching the UPC, or planning your own IP strategy let this case serve as a practical blueprint for future innovation.
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