The Court of Appeal has also provided valuable insights into the principles applicable to claim construction, added matter, sufficiency and inventive step in the headnotes of the decision.

This decision is particularly relevant for pharmaceutical and biotech inventions concerning second medical use claims, where key considerations often include claim construction, sufficiency of functional features and a lack of reasonable expectation of success for inventive step.

The key takeaways are as follows:

1. Second medical use claims are interpreted as inherently requiring therapeutic efficacy by virtue of the formulation as a medical use claim.
2. For sufficiency of claims containing one or more functional features, it is “not required that the disclosure includes specific instructions as to how each and every conceivable embodiment within the functional definition(s) should be obtained”.
3. The burden of proof for sufficiency and reasonable expectation of success in the assessment of inventive step is high and rests with the party invoking invalidity of the patent.
4. The UPC Court of Appeal adopts a holistic approach to inventive step.
5. Inventive step is generally lacking if “the results of the next step were clearly predictable, or where there was a reasonable expectation of success”. For medical use claims, the skilled person would only have a reasonable expectation of success in developing the claimed treatment if it “had a sufficient indication that this would result in a therapeutically effective treatment”.

The patent

Amgen’s patent EP3666797B granted with claim 1 directed to a monoclonal antibody or an antigen-binding fragment thereof for use in treating or preventing hypercholesterolemia or related conditions.

The antibody or antigen-binding fragment was defined solely by its function of binding to a PCSK9 protein and preventing or reducing the binding of PCSK9 to low density lipoprotein receptor (LDLR).

The patent explained that PCSK9 is involved in regulating the levels of the LDLR, which is in turn important in the removal of cholesterol from the bloodstream into liver cells. Thus, the claimed antibodies have a cholesterol-lowering effect.

First Instance decisions

We have previously reported on the diverging approaches to reasonable expectation of success leading to differing decisions of the Munich Central Division and EPO Opposition Division (see “related articles”).

The Munich Central Division commented that the requirement for a reasonable expectation of success could be left undecided and revoked the patent in July 2024 for lack of inventive step (UPC_CFI_1/2023). By contrast, the Opposition Division considered that a reasonable expectation of success was crucial for a second medical use claim and was lacking. Hence, the Opposition Division rejected the oppositions in April 2025.

Court of Appeal: sufficiency of disclosure

The Court of Appeal provides useful guidance on the assessment of sufficiency of disclosure for claims containing one or more functional features. The Court of Appeal explicitly states that the disclosure of how to obtain every conceivable embodiment within the claim scope is not required. Notably, the Court of Appeal holds that non-availability of some embodiments of a functionally defined claim is “immaterial to sufficiency, as long as the skilled person…is able to obtain suitable embodiments” within the claim scope. The Court of Appeal also states that the burden of proof that the patent cannot be reproduced without inventive skill and without undue burden rests with the party alleging insufficiency. This is perhaps particularly onerous in the case of broad functional claims.

Applying these principles to the facts of the case, the Court of Appeal considers that Amgen’s patent is sufficiently disclosed, since it is possible to obtain suitable embodiments within the claim scope based upon the application and Sanofi has not discharged its burden of proof.

The UPC’s approach to sufficiency of disclosure for functional features aligns with that of the EPO, which may be a welcome development to UPC representatives and users of the UPC system. However, this approach is in direct contrast to the USA Supreme Court decision Amgen Inc v Sanofi No. 21-757 for a corresponding USA patent: a broadly defined genus of antibodies lacked enablement across the whole claim scope due to the unreasonable effort required to produce all the claimed antibodies.

Court of Appeal: claim interpretation

Importantly for the pharmaceutical and biotech sectors, the Court of Appeal provides guidance on the principles for the interpretation of medical use claims. The Court of Appeal confirms that it is an inherent claim feature of medical use claims that the claimed product is therapeutically effective, irrespective of whether the skilled person derives “any minimum required effect from the claim or the description”. The Court of Appeal clarifies that “therapeutically effective” means a “noticeable improvement of the medical condition” or, in other words, that “the treatment must be meaningful”. On the other hand, the Munich Central Division considered that the claimed treatment is not limited to a particular lowering of cholesterol levels as long as there is some reduction of cholesterol levels in vivo. This difference in claim interpretation affects the outcome of the decisions as discussed in more detail below.

Court of Appeal: inventive step

We have reported on the significance of the Court of Appeal’s approach to the assessment of inventive step (see Inventive step at the UPC: Court of Appeal sets definitive test).

In brief, the Court of Appeal sets out the principle that a claimed solution is obvious if the skilled person would (not simply could) have taken the next step in expectation of finding an envisaged solution of the objective problem. The Court of Appeal notes that this “is generally the case when results of the next step were clearly predictable, or where there was a reasonable expectation of success”. Hence, the Court of Appeal confirms that, contrary to the position of the Munich Central Division, it is necessary to consider reasonable expectation of success.

In line with the first instance decisions, the Court of Appeal considers Lagace as the starting point for the assessment of inventive step. This research article described the role of secreted PCSK9 in regulating LDLR protein levels in heptaocytes. Lagace also contained a speculative suggestion to explore antibodies blocking the interaction between PCSK9 and the LDLR for the treatment of hypercholesterolemia. Importantly, Lagace caveated that this is dependent upon whether PCSK9 functions as a secreted factor (as opposed to via an intracellular mechanism).

The Court of Appeal agrees with the Munich Central Division that the skilled person, starting from Lagace, had a strong incentive to block PCSK9 activity to reduce LDL levels to be able to treat hypercholesterolemia and similar diseases. Crucially, the Court of Appeal considers that the skilled person would not consider developing antibodies targeting PCSK9 with a reasonable expectation of success based on their knowledge at the effective date. In particular, the mechanism(s) by which PCSK9 functions was(were) unknown at the effective date. Thus, the skilled person could not know whether therapeutic efficacy could be achieved with anti-PCSK9 antibodies.

Here, the divergence in claim interpretation is key, since the Court of Appeal considers that the implicit requirement is that the claimed antibodies must be therapeutically effective. The Court of Appeal explicitly states that the skilled person would only have a reasonable expectation of success in developing the claimed treatment if it had “a sufficient indication that this would result in a therapeutically effective treatment”. In a further indication of the high burden faced by the party invoking invalidity of the patent, the Court of Appeal also states that the burden of proof for reasonable expectation of success rests with this party (see Inventive step at the UPC: Court of Appeal sets definitive test).

Accordingly, the Court of Appeal has overturned the decision of the Munich Central Division revoking Amgen’s patent for lack of inventive step.

Final comments

Patent practitioners and users of the UPC system will welcome the clarity that the Court of Appeal provides on the principles applicable to claim construction, added matter, sufficiency and inventive step in the headnotes of the decision.

In its approach to claim construction and reasonable expectation of success of second medical use claims, the Court of Appeal diverges from the approach of the Munich Central Division and aligns with established EPO jurisprudence. The Munich Central Division set a lower bar for reasonable expectation of success for second medical use claims and placed the onus on the patentee to prove that a skilled person would not have such an expectation. By contrast, the Court of Appeal confirms that attaining a therapeutically effective treatment is a requirement of a medical use claim such that a reasonable expectation of success plays a crucial role in the assessment of inventive step. The burden is then on the party alleging invalidity to show that the skilled person would possess a reasonable expectation of success.

It will be interesting to see whether the Board of Appeal of the EPO aligns with the decision of the UPC Court of Appeal, with oral proceedings in the pending appeal T 0716/25 scheduled for April 2026.

Related articles

Inventive step at the UPC - Court of Appeal sets definitive test
Differing decisions from the UPC and EPO - Sanofi v Amgen, 12 June 2025.
Lack of inventive step from a “realistic” starting point - Sanofi v Amgen, 04 August 2024.

Case details at a glance

Jurisdiction: UPC
Decision level: Court of Appeal (Luxembourg)
Parties: Amgen Inc v Sanofi-Aventis Deutschland GmbH, Sanofi-Aventis Groupe and Sanofi Winthrop Industrie SA
Citation: UPC_CoA_528/2024
Date: 25 November 2025
Decision: dycip.com/upc-coa-528-2024

Jurisdiction: UPC
Decision level: Munich Central Division
Parties: Sanofi-Aventis Deutschland GmbH, Sanofi Winthrop Industrie SA, Sanofi-Aventis Groupe v Amgen Inc
Citation: ORD_598362/2023
Date: 16 July 2024
Decision: dycip.com/upc-ord-598362-2023