Has biotech litigation entered a new era?

This article is part of our Biotech Review of the Year - Issue 13 publication.

2025 was an important year for biotech patent litigation, in Europe and further afield. We saw not only a change in the volume of litigation but a change in its nature too, with a mixture of national disputes, cross-border disputes and disputes in the Unified Patent Court (UPC).

It seems that biotech litigation is entering a new era, potentially fuelled by changing landscapes for biosimilars. Traditionally there have been fewer competitors for blockbuster biologics as compared to small molecule products, largely because it has been more expensive and complex to produce and market biosimilars than it is for small molecule generics. However, with an increased number of companies entering the biosimilar sphere from countries with lower manufacturing and development costs and an increased use of marketing partners, allowing entities to develop large molecules to co-market with companies with established marketing presence in other jurisdictions, we have seen the biosimilar field becoming more competitive.

European litigation

Much of the litigation in 2025 centred around aflibercept, a recombinant fusion protein marketed as Eylea® by Bayer and Regeneron. This medicine is approved for the treatment of wet age-related macular degeneration. In Europe, the supplementary protection certificate (SPC) protecting aflibercept expired in November 2025 and the focus of the litigation was on the patents that remained in force after that date, namely the formulation patents EP 2 364 691 (EP 691) and EP 2 944 306 (EP 306).

As is often the case for formulation patents, a key question in the court proceedings was whether the formulation used by the biosimilars infringed the patents. The biosimilars had developed formulations which were not the same as Eylea’s but differed in certain aspects and were therefore variants of Eylea’s formulation. The formulations are shown in the table below:

In English court proceedings¹ Regeneron and Bayer asserted infringement of EP 691 and EP 306 under the doctrine of equivalents. This doctrine allows patentees to allege that there is infringement of a patent even in the absence of a literal infringement. The test the English courts must consider when assessing infringement under the doctrine was laid down by the Supreme Court in Actavis v Lilly² in 2017. It requires an assessment of (i) whether the variant achieves substantially the same result in substantially the same way as the invention; (ii) if so, whether it would have been obvious to the skilled person at the priority date, knowing that the variant achieves substantially the same result as the invention, that it does so in substantially the same way; and (iii) whether, even if the variant achieves the result referred to above, the patentee nonetheless intended strict compliance with the wording of the claim. 

EP 306 was found invalid for added matter by Meade J. EP 691 was upheld as valid but, when considering the facts of the case, the Judge found that it was not infringed by either biosimilar product. Applying the Actavis v Lilly test for equivalence, Meade J had little doubt that the variant did not achieve substantially the same result in substantially the same way as the invention (the first limb of the test). Relevant to this decision was the fact that the patentee had chosen to assert a narrower, dependent claim directed to a preferred embodiment in the specification (claim 5). Accordingly, the inventive concept of the claim was found to be narrow and the biosimilar products were found to fall outside it. The Judge also determined that strict compliance with the literal meaning of the claim was intended by the patentee (the third limb of the test) on the basis that the specification had disclosed a number of possibilities but had only claimed some of them.

The English court’s findings can be contrasted with the decision of the Munich Regional Court, which not only found EP 691 to be infringed, but also granted a cross-border permanent injunction against Formycon in 20 EU Member States. Although the same patent (EP 691) was asserted in the German action, Regeneron and Bayer asserted claim 1, which was wider in scope than the claim asserted in the UK, providing for a range in the values and alternative excipients. Following an assessment under the doctrine of equivalents in each jurisdiction where injunctive relief was sought, the Munich Court found that each jurisdiction would likely find claim 1 infringed where the ‘variant’ used a histidine buffer rather than the claimed sodium phosphate buffer, as is the case for Formycon’s product. As we entered 2026, the Munich Regional Court also granted a cross-border preliminary injunction against Advanz Pharma under EP 691 covering 21 jurisdictions. Both decisions relied on the CJEU’s decision in BSH v Electrolux³ to grant cross-border relief. Moreover, preliminary injunctions were granted in Germany against three further biosimilar manufacturers: Stada, Hexal and Celltrion. The decisions demonstrate that the option to seek relief using long-arm jurisdiction will be a powerful tool in this new era of biosimilar litigation. Choice of venue may also be critical, although the fact that different claims were asserted in the UK and German proceedings means that the decisions are not directly comparable.

Although aflibercept patents have not been litigated in the UPC, a centralised court system that handles patent litigation across 18 EU Member States in Europe, this forum will be an important consideration for future biotech litigation. There have been comparatively few biotech cases to date, but as the court develops its body of case law, this is likely to change. One notable biotech dispute in the UPC is the originator dispute between Amgen, Sanofi and Regeneron in relation to PCSK9 inhibitors. There are various patents at issue in UPC proceedings, with decisions shaping future considerations for biotech companies, including the UPC Court of Appeal setting out a ‘holistic’ inventive step test⁴ and the Düsseldorf local division addressing the infringement of a second medical use patent on the basis of a product’s Summary of Product Characteristics.⁵ Despite the willingness of the German courts to issue cross-border injunctions - once a powerful selling point of the UPC - we expect more companies to utilise the UPC in the next few years to attempt to centrally revoke European patents that are not opted out of the system and to seek quick decisions on the merits, which the court aims to provide within 12 months. It will be interesting to see if the UPC and the EPO align on validity issues, which may determine the focus of future litigation. 

Global litigation

Europe was not the only jurisdiction to see a wave of Eylea® litigation in 2025. In the United States, Regeneron secured injunctions against nearly all biosimilars - except Amgen - based on its formulation patents. In South Korea, the courts upheld the validity of the patents and granted an injunction against Samsung Bioepis, preventing manufacture of its biosimilar, though relief was denied against Celltrion. In Japan, the dispute took a different form: Samsung Bioepis pursued an unfair competition claim, alleging that Regeneron had acted improperly by notifying regulators that Samsung Bioepis’s biosimilar might infringe its patents. The claim was dismissed, affirming Regeneron’s right to inform authorities of its intellectual property rights.

The future of biosimilar litigation strategies

The landscape of biosimilar litigation is entering a period of accelerated evolution. Both innovators and biosimilar manufacturers will need to reassess longstanding approaches to loss of exclusivity planning. The assertion of different claims against different biosimilars in different jurisdictions needs careful alignment. The challenge for biosimilars to assess which changes to make to a formulation which may lead to a non-infringing product is a delicate line to tread.

A series of regulatory and legislative developments across major jurisdictions will also reshape the opportunity and timing in biosimilar market entry strategies. The new EU Pharma Package and proposed Biotech Act (covered on page 27 in an article by Xisca Borrás) is one such example. Regulatory developments in the United States are moving in a similar direction too. The FDA has recently issued draft guidance indicating that comparative clinical studies will not always be required to demonstrate biosimilarity, with such studies becoming necessary only in limited circumstances. Should this guidance be adopted, it would significantly reduce the cost and duration of biosimilar development in the US, potentially accelerating market entry. 

Alongside these changes, several other major authorities, including the EMA, MHRA and WHO, have expressed support for waiving Phase III clinical studies for biosimilars. The publication of guidance across these organisations reflects a growing consensus that Phase III data are often unnecessary for biosimilar approval, further reducing development burdens and shifting the litigation landscape by altering the timing and nature of regulatory submissions.

The SPC manufacturing waiver in Europe will also continue to influence strategic behaviour. The most recent decisions and the outlook in Europe is discussed by Luke Norton in the next article in this publication.

Taken together, these developments signal a future in which biosimilar litigation becomes more front-loaded, more international in scope and more closely intertwined with evolving regulatory frameworks. Innovators and biosimilar manufacturers alike will need to adapt quickly, reassessing the timing of patent challenges, the role of patents, and the interplay between regulatory and litigation strategies in an increasingly competitive biologics market.

Footnotes

[1]Formycon & Samsung Bioepis v Regeneron & Bayer [2025] EWHC 2527 (Pat)

[2] Actavis UK Limited and others v Eli Lilly and Company [2017] UKSC 48

[3] (C-339/22)

[4] UPC_CoA_528/2024, Decision of 25 November 2025

[5] UPC_CFI_505/2024.,Decision of 13 May 2025