The Evolution Of Patent Infringement By Equivalents

In the eight years post Actavis, UK courts have developed the test set out by the UK Supreme Court to be applied in assessing patent infringement by equivalents, though some important issues are still not settled. The Unified Patent Court has been in operation for two years and it has had the opportunity to consider infringement by equivalents. At first instance in Plant-e, the UPC applied the test used by the Dutch courts but there has yet to be a Court of Appeal decision. This article considers UK developments and any parallels with the UPC in relation to equivalents.

In the UK, the Actavis questions for determining infringement by equivalents are as explained by Lord Kitchin in Icescape Ltd v Ice-World International BV [2018] EWCA Civ 2219 at [66]:

(1) Notwithstanding that it is not within the literal (that is to say, I interpolate, normal) meaning of the relevant claim(s) of the patent, does the variant achieve substantially the same result in substantially the same way as the invention, i.e. the inventive concept revealed by the patent?

(2) Would it be obvious to the person skilled in the art, reading the patent at the priority date, but knowing that the variant achieves substantially the same result as the invention, that it does so in substantially the same way as the invention?

(3) Would such a reader of the patent have concluded that the patentee nonetheless intended that strict compliance with the literal meaning of the relevant claim(s) of the patent was an essential requirement of the invention?

By normal meaning is meant the purposive interpretation [70].

The UPC Local Division in The Hague in Plant-e Knowledge v Arkyne Technologies UPC_CFI-239/2023 (22 November 2024) set out the following test for infringement by equivalents at [88]:

a variation is equivalent to an element specified in a claim if the answer to the following four questions is "yes".

1. Technical equivalence: does the variation solve (essentially) the same problem that the patented invention solves and performs (essentially) the same function in this context?
2. Is extending the protection of the claim to the equivalent proportionate to a fair protection for the patentee: in view of his contribution to the art and is it obvious to the skilled person from the patent publication how to apply the equivalent element (at the time of infringement)?

iii. Reasonable legal certainty for third parties: does the skilled person understand from the patent that the scope of the invention is broader than what is claimed literally?

1. Is the allegedly infringing product novel and inventive over the prior art? (i.e. no successful Gillette/Formstein defence)

The Plant-e test is the same as the Dutch national test (Eli Lilly v Fresnius C/09/541424/ HA ZA 17-1097 (27 October 2020)).

While there have been many other substantive decisions of the UK courts following Actavis, other decisions of the UPC (both before and after Plant-e) have not provided substantial guidance other than emphasising that technical-functional equivalence is a requirement to a finding of infringement by equivalents. See, for example, Ballinno v UEFA UPC_CFI_151/2024 (3 June 2024, Hamburg LD), OrthoApnea v Vivisol UPC_CFI_376/2023 (17 January 2025, Brussels LD) and DISH v AYLO UPC_CFI_471/2023 (6 June 2025, Mannheim LD).

Even then, there is arguably inconsistency in relation to whether the modified means needs to fulfil essentially the same function in order to achieve essentially the same effect.

In Ballinno, the court held at page 28: 'For the assessment of an infringement by equivalent means it is not sufficient to reduce the question of equivalence just to the effect... Decisively is how this effect is achieved.'

On the other hand, in Dish at [167], having observed that the equivalence tests of individual UPC states require technical-functional equivalence, the court appears to suggest that the same effect might suffice.

Inessential Integers? (Actavis Q1 and Plant-e Qi)

An 'inessential integer' of a claim is one that can be effectively ignored during the assessment of infringement. Patents for Inventions, Blanco White, 5th Edition (1983 – ie, well before Actavis) records the scarcity of findings of inessential integers in UK patent infringement claims (paragraph 2-111). Has the position now changed?

It should not have (either in the UK or elsewhere in EPC member states). Underpinning a doctrine of equivalents in the EPC member states (and the UPC – see article 24(1)(c) of the UPC Agreement) is article 2 of the Protocol on the Interpretation of article 69 of the EPC (Protocol, article 2):

For the purpose of determining the extent of protection conferred by a European patent, due account shall be taken of any element which is equivalent to an element specified in the claims.

It is not a question of ignoring an element of a claim; rather, it is finding an equivalent.

However, UK cases following Actavis could be interpreted as going further than the Protocol, article 2.

• In Icescape, claim 1 of the patent, literally construed, described cooling pipes in an ice rink cooling system that were arranged in series, whereas the alleged infringement had them arranged in parallel. The series configuration of pipes did not form part of the inventive concept found by the court (because it was common general knowledge). Further, Lord Kitchin expressly referred in his judgment at [76]-[79] (albeit in the context of the relevance of the prosecution history – see below) to an 'inessential' feature (ie, the series configuration).
• In Regen Lab v Estar Medical [2019] EWHC 63 (Pat), claim 1 (which concerned a blood plasma preparation method) called for a buffered sodium citrate solution at 0.10M. The inventive concept found by the court did not include the molarity and so it did not matter that the Defendant's method used a solution of 0.136M. One wonders, therefore, if any or no molarity would have still led to a finding of infringement.

A more recent example involving what might be described as inessential integers is provided by Cloud Cycle v Verifi [2024] EWHC 2001 (Ch). The case concerned a method for calculating the consistency of concrete before it sets (slump) that involved measuring pressure and speed in a mixing drum. Claim 1 (in the characterising portion of the claim) called for erasing stored measurements if the speed and pressure were not stable and to continuing measurements for a full drum cycle. The latter features were found not to be part of the inventive concept.

In effect, the court found that not storing measurements could be equated with not using them. It also found that full drum rotation did not matter – stability did. So, it could be said that the two relevant claim integers were effectively ignored. On the other hand, an equivalent feature does seem to have been found to the first integer. As to the second integer, it does seem harder to say that partial rotation is an equivalent feature to full rotation.

What of the UPC? The Plant-e case concerned a plant-based microbial fuel cell for converting light energy into electrical energy and/or hydrogen. Claim 1 called for two compartments (anode and cathode), the anode compartment including the plant and its root and an oxidising microorganism. At [85], the court explained that the alleged infringement had the roots of the plant in an upper compartment, whereas the anode (with the micro-organism), and thus the anode compartment, is located at the bottom of the lower compartment. So, the claim integer that 'wherein the root (8) zone of the plant is essentially placed in the anodic material' was not met.

However, at [97], the court found equivalence: the 'set up of the [alleged infringement] is thus considered technically equivalent to the teaching of the patent ...'. On one level, as in every equivalence case, it could be said that an integer had been rendered inessential. Here, however, it is easier to see an equivalent element (as per the Protocol, article 2) than (for example) in Regen. The plant roots may not have been in the same compartment as the anode but there were holes between the two compartments allowing nutrients and microorganisms to pass between them and thus allowing the fuel cell to generate electricity. The equivalent integer was provided by the additional compartment.

On a more general level, there is a parallel between the identification of the inventive concept in the first Actavis question and the identification of the patent's teaching in answering the first Plant-e question. In answering the first Plant-e question, the court looked to the teaching of the patent description. Assessing the breadth or generality of that teaching was clearly important to answering the question. Once it was accepted that the teaching of the patent did not require the plant and its roots to be physically located in the anode compartment, answering the first Plant-e question in the affirmative followed. Similarly, in Cloud Cycle, it was not using measurements (rather than not storing them) that formed part of the inventive concept used for answering the first Actavis question in the affirmative.

Disclosed but not claimed (Actavis Q3 and Plant-e Qiii)

This principle of German law (Okklusionsvorrichtung (Occlusion Device) X ZR 16/09 (10.05.11, BGH) was explained by Lord Justice Arnold (sitting as the trial judge) in Akebia Therapeutics Inc v Fibrogen Inc [2020] EWHC 866 (Pat) at [454]:

If the description discloses a plurality of possibilities for achieving a specific technical effect, but only one of those possibilities is catered for in the patent claim, the utilisation of any of the other possibilities properly does not constitute infringement of the patent with equivalent means.

This principle has been referred to and applied in subsequent UK decisions: Facebook Ireland Ltd v Voxer IP LLC [2021] EWHC 1377 (Pat) at [201]; Shenzhen Carku Technology Co Ltd v The Noco Company [2022] EWHC 2034 (Pat) at [106] to [112]; Philip Morris Products SA v Nicoventures Trading Ltd [2023] EWHC 2616 (Pat) at [89]; and Lufthansa Technik v Astronics [2025] EWHC 375 (Pat) at [275]-[276]. Two of the cases illustrate the principle's ambit.

The Philip Morris case concerned a heat not burn product for tobacco (and other substances), allowing inhalation of nicotine without smoke. Claim 1 was in respect of a system having (1) an apparatus comprising a heater heatable by penetration with a varying magnetic field and (2) an article containing tobacco to be inserted into a heating zone of the apparatus. The alleged infringement had a similar arrangement, but the heater was in the article. The description of the patent illustrated and described an arrangement having the heater in the article, and the patent application as originally filed (but not as granted) included a claim to this arrangement. Considering the facts, the judge found Actavis questions 1 and 2 should be answered yes but that there was no infringement on the basis of the 'disclosed but not claimed principle' under question 3.

The Lufthansa case concerned a voltage supply apparatus in an aeroplane cabin whose socket had detectors that only allowed the supply of power when simultaneously detecting two contact pins. As the patent explained at [12]: 'If both contact pins are detected simultaneously, it can be assumed with a high degree of probability that the socket has not been tampered with, rather that a plug has actually been plugged in. In this way a high level of security against tampering and unwanted application of the supply voltage to the socket is achieved.' The characterising feature of Claim 1 included reference numerals (45) and (46) to the pin detectors of Figure 3, which were there shown at the bottom of the plug holes, though the claim did not expressly recite their location. The defendant's detectors were at the sides of the holes. The patent description at [32] disclosed as follows: 'Moreover, the plug hole pairs can also be arranged so that they are not at right angles to each other rather overlay each other, in which case the microswitches are arranged to the sides of the plug holes'.

Following a previous finding that there was no infringement on a normal construction because of the different positioning of the pin detectors, the court considered equivalents. In dealing with the third Actavis question and the issue of 'disclosed but not claimed', at [289], the judge held that: (1) the numbers referenced in the claim were for illustrative purposes of the preferred embodiment; and (2) the skilled reader would appreciate from [32] that 'it was not essential to Claim 1 itself that the plug detectors should be located at the bottom of the holes but that the microswitches could be arranged to the sides to accommodate a wider range of plug types'. The disclosed but not claimed principle did not apply.

Prosecution history

There are two ways in which the patent's history might be relevant in UK infringement proceedings. First, if a patent claim has been amended, the skilled person is deemed to know that and the reason for it. That is a point of construction that may also have a bearing on Actavis question 3. This point was raised in Akebia v FibroGen [2020] EWHC 866 (Pat) (see [452-4]) and Facebook (see [69] and [206]) in the context of post-grant amendments.

Second, and this is the focus of what follows, if the patentee has made a representation about claim scope during prosecution, that may be relied on in limited circumstances by the alleged infringer. Lord Neuberger set out the circumstances when the prosecution history might be referred to in Actavis at [81]-[88]. At [88], he held:

reference to the file would only be appropriate where (i) the point at issue is truly unclear if one confines oneself to the specification and claims of the patent, and the contents of the file unambiguously resolve the point, or (ii) it would be contrary to the public interest for the contents of the file to be ignored. The first type of circumstance is, I hope, self-explanatory; the second would be exemplified by a case where the patentee had made it clear to the EPO that he was not seeking to contend that his patent, if granted, would extend its scope to the sort of variant which he now claims infringes.

Meade J explained the circumstances (first set out in Actavis) in Siemens Gamesa v GE Energy [2022] EWHC 3034 (Pat) and Samsung Bioepis v Alexion [2025] EWHC 1240 (Pat). In Siemens at [78]–[82], he held:

• the circumstances 'will only rarely arise' and 'the conditions for them to do so will be stringent';
• as to (i), 'the point of interpretation has to be truly unclear and ... the file unambiguously resolves the point'; and
• as to (ii) 'the requirements are that the patentee made it clear that he was not seeking to extend the claims to the sort of variant said to infringe'.

In Samsung at [231], the judge referred to the same principles applying whether the doctrine of equivalents is being relied on or purposive construction. Nonetheless, this area of law has only arisen as a result of Actavis.

In Samsung, it was also found ([228]) that, just because the construction of a claim is debatable (and the parties debated it before the court), does not render it ambiguous (or 'truly unclear'). Further, just because the patentee sought (but was refused on added matter grounds) a claim during prosecution that would have been literally infringed does not mean that the patentee said or intimated that it would not assert infringement on a purposive construction of the allowed claim.

By way of contrast, when dealing with Actavis question (iii), Arnold LJ held in Akebia at [459]:

Eighthly, there is the prosecution history. FibroGen chose to limit the scope of claim 1 of EP 531 to compounds of Formula (I) in order to overcome an objection from the examiner that the previous claims, which were directed to "a heterocyclic carboxamide compound", lacked novelty over prior art referred to as D11. FibroGen thereby represented that it was not seeking to contend that the patent, if granted, would have a scope that extended to heterocyclic carboxamides beyond the confines of Formula (I). Yet extending the scope of claim 17A in this way is precisely what the Claimants are now seeking to do. In those circumstances, this is one of those cases referred to by Lord Neuberger in Actavis v Lilly at [88] where it would be contrary to the public interest for the contents of the prosecution file to be ignored

Further, it was no answer that the patentee had said on the file that 'Any deleted subject matter is not abandoned' (see [460]). The judge found that the patentee 'cannot have it both ways'. This case tends to suggest that the requirements of Actavis may not be so stringent after all.

In VusionGroup v Hanshow UPC_CoA_1/2024 (13 May 2024), the UPC Court of Appeal held at [37] that the parts of the prosecution history cited by the parties did not shed any new light on the interpretation of the claims that it found. So, the Court decided that it did not need to consider whether the history can be taken into account when determining the scope of protection. Equivalence had not been raised in that case.

However, in Alexion v Samsung Bioepis UPC_CoA_402/2024 and 405/2024 (20 December 2024) at [43], the UPC Court of Appeal found that representations made to, and findings made by, the EPO Technical Board of Appeal during examination were relevant. It held that the patent claim must be interpreted from the perspective of the person skilled in the art and Alexion's representations and the TBA's endorsement of them 'can be seen as an indication of the view of the person skilled in the art at the filing date'. Again, equivalence had not been raised but presumably the same or similar principles will, in future, be found to apply.

Formstein

In Safestand v Weston [2024] EWHC 2807 (Pat) at [22], the court summarised the Formstein defence thus:

a product or process which would nominally fall within the scope of a claim as an equivalent pursuant to the law on equivalents as explained in Actavis will be deemed to fall outside the claim's scope if the equivalent would have lacked novelty or embodied no inventive step over the prior art at the priority date of the patent in suit.

In the author's view, if it is accepted that the inventive concept for the Pozzoli inventive step analysis (Pozzoli SPA v BDMO SA [2007] EWCA Civ 588) is the same (or at least substantially the same) as the inventive concept for equivalents, it logically follows that a Formstein-type defence ought to be available.

In Edwards Lifesciences v Meril GmbH [2020] EWHC 2562 (Pat) (29 September 2020), Birss J (as he then was) explained at [223] '[s]ince it will be necessary to deal with the inventive concept when addressing equivalents, I will address equivalents after addressing obviousness'. Further, recent cases illustrate the same inventive concept being used for both tests. See Philip Morris (25 October 2023) at [80] and [124] and more recently Salts Healthcare v Pelican Healthcare [2025] EWHC 497 (Pat) (5 March 2025) at [121] and [167]. However, some judges have declined to comment and the point may well not yet be settled.

Although there have not been any UK cases where the defence has been successfully deployed, in Celltrion v Genentech [2025] EWHC 174 (Pat) (30 January 2025) at [84], the court observed that 'the Formstein defence has become part of English law subject to a ruling to the contrary by the Court of Appeal or the Supreme Court'.

As to the UPC, a Formstein defence was recognised in Plant-e (but the defendant did not rely on it). While there has not yet been a Court of Appeal judgment on the equivalents test, it is to be expected that, whatever test is adopted, a Formstein defence will be available.

Concluding remarks

In conclusion, UK courts have taken the Actavis equivalents test forward by adopting German law principles (disclosed not claimed; Formstein). Lord Hoffmann's statement in Kirin Amgen v Amgen [2005] RPC 9 that 'life is too short' to engage in a review of the prosecution history in UK proceedings has been shown to have been superseded. First instance courts of the UPC have been reluctant to opine on the test to be applied and uncertainty will remain until there is case law from the Court of Appeal.

Referenced in this article

• Actavis UK Ltd v Eli Lilly & Co [2017] UKSC 48
• Icescape Ltd v Ice-World International BV [2018] EWCA Civ 2219
• Plant-e Knowledge v Arkyne Technologies UPC_CFI-239/2023 (22 November 2024, The Hague LD)
• Ballinno v UEFA UPC_CFI_151/2024 (3 June 2024, Hamburg LD)
• OrthoApnea v Vivisol UPC_CFI_376/2023 (17 January 2025, Brussels LD)
• DISH v AYLO UPC_CFI_471/2023 (6 June 2025, Mannheim LD)
• Regen Lab v Estar Medical [2019] EWHC 63 (Pat)
• Cloud Cycle v Verifi [2024] EWHC 2001 (Ch)
• Okklusionsvorrichtung (Occlusion Device) X ZR 16/09 (10 May 2011, BGH)
• Akebia Therapeutics Inc v Fibrogen Inc[2020] EWHC 866 (Pat)
• Facebook Ireland Ltd v Voxer IP LLC[2021] EWHC 1377 (Pat)
• Shenzhen Carku Technology Co Ltd v The Noco Company[2022] EWHC 2034 (Pat)
• Philip Morris Products SA v Nicoventures Trading Ltd[2023] EWHC 2616 (Pat)
• Lufthansa Technik v Astronics [2025] EWHC 375 (Pat)
• Siemens Gamesa v GE Energy[2022] EWHC 3034 (Pat)
• Samsung Bioepis v Alexion [2025] EWHC 1240 (Pat)
• VusionGroup v Hanshow UPC_CoA_1/2024 (13 May 2024, CoA)
• Alexion v Samsung Bioepis UPC_CoA_402/2024 and 405/2024 (20 December 2024, CoA)
• Safestand v Weston [2024] EWHC 2807 (Pat)
• Pozzoli SPA v BDMO SA [2007] EWCA Civ 588
• Edwards Lifesciences v Meril GmbH [2020] EWHC 2562 (Pat)
• Salts Healthcare v Pelican Healthcare [2025] EWHC 497 (Pat)
• Celltrion v Genentech [2025] EWHC 174 (Pat)
• Kirin Amgen v Amgen [2005] RPC 9

Originally published by IAM, September 2025

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