{"id":10242,"date":"2024-07-30T10:37:53","date_gmt":"2024-07-30T10:37:53","guid":{"rendered":"https:\/\/www.dhenne-avocats.fr\/?p=10242"},"modified":"2026-08-31T08:55:02","modified_gmt":"2026-08-31T08:55:02","slug":"sanofi-versus-amgen-success-of-the-first-legal-challenge-to-withdraw-a-patent-and-strict-evaluation-of-the-patentability-of-therapeutic-antibodies","status":"publish","type":"post","link":"https:\/\/www.dhenne-avocats.fr\/en\/sanofi-versus-amgen-success-of-the-first-legal-challenge-to-withdraw-a-patent-and-strict-evaluation-of-the-patentability-of-therapeutic-antibodies\/","title":{"rendered":"Sanofi v. Amgen: the UPC's first revocation action and therapeutic antibody patentability, from revocation to reversal"},"content":{"rendered":"

Updated on 30 August 2026.<\/em><\/p>\n

On 16 July 2024, the Munich Central Division of the Unified Patent Court (UPC) revoked a European patent for the first time: Amgen's patent EP 3 666 797, relating to anti-PCSK9 antibodies, fell at the end of the first successful revocation action before the new court (UPC_CFI_1\/2023).<\/p>\n

The sequence has since been reversed: on 25 November 2025, the UPC Court of Appeal set aside that decision and upheld the patent. Same title, same prior art, two opposite answers: the entire question of assessing theinventive step<\/a> of therapeutic antibodies played out between the two instances.<\/p>\n

For holders of biologics portfolios and challengers alike, this saga sets the European benchmark for antibody patentability, within a body of UPC case law<\/a> that is being built at speed.<\/p>\n

The PCSK9 dispute, a worldwide litigation<\/h2>\n

The case belongs to a confrontation under way since 2014 around Amgen's patents covering evolocumab (Repatha\u00ae), asserted against alirocumab (Praluent\u00ae) marketed by Sanofi and Regeneron. The litigation unfolded across several continents, up to the United States Supreme Court which, in May 2023, invalidated Amgen's US claims for lack of enablement. Few patent families have been tested before so many courts, under so many doctrines, and with such divergent outcomes.<\/p>\n

As soon as the UPC opened, on 1 June 2023, Sanofi and Regeneron brought a revocation action against patent EP 3 666 797 before the Munich Central Division, while Amgen brought an infringement action before the Munich Local Division. The first patent revocation<\/a> in the Court's history would follow.<\/p>\n

16 July 2024: the first revocation ordered by the UPC<\/h2>\n

The Central Division first rejected the strictly functional reading of the claim language: absent a clear indication of an exclusive binding site, the skilled person would not have understood the claim as covering all antibodies binding to the catalytic domain of PCSK9. In doing so, the division gave the description significant weight in claim interpretation, departing from the then dominant practice at the EPO.<\/p>\n

On inventive step, the division set aside the classic problem-solution approach in favour of a \"realistic starting point\" in the prior art. Noting the prior art's explicit orientation towards antibodies blocking the PCSK9-LDLR interaction, it concluded that the skilled person had a reasonable chance of success, without inventive effort despite the scale of the work required: developing antibodies against a known target was routine. The message to the market was severe: functional antibody claims directed at a known target entered the UPC era under a presumption of fragility. The patent was revoked in its entirety, underArticle 56 EPC<\/a>.<\/p>\n

Claim interpretation: the weight of the description<\/h2>\n

The first lasting contribution of the 2024 decision: before the UPC, the description is not a subsidiary resort reserved for ambiguous claims, it always plays a part in interpretation. The Alexion<\/em> appeals (UPC_CoA_402\/2024 and UPC_CoA_405\/2024) confirmed that line for antibodies: strict textual construction, with no judicial rescue of defective wording.<\/p>\n

The gap with the EPO has since closed: in decision G 1\/24 of 18 June 2025<\/a>, the Enlarged Board of Appeal held that the description and drawings must always be consulted when interpreting the claims. On this ground, it is the UPC's practice that set the standard.<\/p>\n

25 November 2025: the reversal on appeal<\/h2>\n

Ruling on the appeals (UPC_CoA_529\/2024 and UPC_CoA_528\/2024), the Court of Appeal set aside the revocation and upheld patent EP 3 666 797. The judgment, available in the UPC register of decisions<\/a>, adopts a holistic approach to obviousness: the skilled person's motivation and the reasonable expectation of success are assessed together, starting from an objective technical problem, providing an effective treatment of hypercholesterolemia, and from a realistic starting point in the prior art.<\/p>\n

The tipping point is evidentiary: for the Court of Appeal, the skilled person could not reasonably predict that an anti-PCSK9 antibody would be therapeutically effective, given the scientific uncertainties then surrounding PCSK9's pathways of action. The Court also gave full effect to the claim language: the claimed antibodies must be genuinely effective for the intended treatment, any reduction in cholesterol not being enough.<\/p>\n

The outcome converges with that of the opposition proceedings before the EPO, which had likewise left the patent standing. The divergence between the two UPC instances thus concerned neither the method of interpretation nor the rejection of the problem-solution approach: it concerned the threshold of the reasonable expectation of success, that is, the plausibility<\/a> of therapeutic success at the priority date. That threshold, and the evidence available to meet it, will now be the true battleground of European antibody litigation.<\/p>\n

Therapeutic antibodies: the European benchmark after the saga<\/h2>\n

The transatlantic contrast remains instructive. In the United States, Amgen's functional claims perished through enablement: too broad, the monopoly exceeded what the disclosure allowed to be reproduced. In Europe, the debate has shifted to inventive step and its reasonable expectation of success: the path to an antibody patent remains narrow, but it exists, provided the uncertainties overcome and the therapeutic efficacy achieved are documented from filing.<\/p>\n

On the infringement side, the D\u00fcsseldorf Local Division completed the picture on 13 May 2025 (UPC_CFI_505\/2024) by subjecting second medical use claims to a two-limb test, causality and the defendant's knowledge. For patentees, the overall lesson is clear: the value of an antibody family turns on the quality of the scientific and evidentiary record, from drafting through to the preservation of evidence before the UPC<\/a>, and can flip at every level of the proceedings.<\/p>\n

Key takeaways<\/h2>\n