Doctrine of Equivalents and Infringement in the UK Courts

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Volume 52, Issue 3

Doctrine of Equivalents and Infringement in the UK Courts

Sarah Kostiuk-Smith, PhD Partner, European and UK Patent Attorney, Mewburn Ellis LLP Julie Carlisle, PhD Partner, European and UK Patent Attorney, Patent Litigator, Mewburn Ellis LLP

Historically, a doctrine of equivalents approach was not used when determining patent infringement under UK law. However, a landmark judgement by the UK Supreme Court in 2017 introduced this concept to UK patent cases, fundamentally altering the understanding of patent infringement in the UK. Now, 4 years later, we look at how this issue has been considered in subsequent cases and what it might mean for patent enforcement in the UK. Prior to the Actavis UK Limited v Eli Lilly and Company ([2017] UKSC 48) UK Supreme Court decision in 2017, any extension of patent scope beyond the literal wording of the claims was determined under a so-called ‘purposive construction’ analysis. Under that analysis, the question was “always what the person skilled in the art would have understood the patentee to be using the language of the claim to mean. And for this purpose, the language he has chosen is usually of critical importance” [Kirin-Amgen Inc v Hoechst Marion Roussel Ltd ([2005] RPC 9)]. Importantly, UK Courts generally frowned upon interpretations that, in their understanding, allowed the monopoly to creep beyond the words of the claims.

This approach, albeit with variations and tweaks, was settled UK law for about 35 years, until Actavis v Lilly. In that case, the patent claims specifically recited “pemetrexed disodium”, while the products under consideration were either the free acid or different salt forms. Despite falling outside any literal reading of the claims (it was accepted that under “normal interpretation” the products would not infringe), the Court found that the products were covered by the claim, finding infringement by immaterial variation.

Infringement was determined by application of the following questions:

i) Does the variant infringe any of the claims as a matter of normal (purposive) interpretation?

ii) If not, does the variant nevertheless infringe because it varies from the invention in a way or ways which is or are immaterial?

Whether a variant infringes in an immaterial way is then determined by asking three further questions (the so-called ‘Actavis questions’ or ‘Protocol questions’):

1) Notwithstanding that it is not within the literal 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?

Answers of yes, yes, and no mean the variant should be considered as an infringing equivalent.

The UK Supreme Court’s ruling fundamentally altered the assessment of patent infringement in the UK, but as is so often the case with decisions of this type, the analysis was heavily dependent on the facts of the case. Patentees have therefore watched with interest as the lower UK courts have applied the precedent.

So, four years later, is the scope of protection for UK patents any clearer?

What is clear is that the courts are following the test set out in Actavis v Lilly. Of note, the application of the test set out earlier in this article is based upon how the Courts determine the “inventive concept” of the patent. This inventive concept is not necessarily the concept the inventors originally envisaged - it can be influenced by a number of factors, such as the prior art and the common general knowledge of the skilled person, which the inventors may not have been fully aware of.

Whether a variant can be considered an equivalent may, in principle, also be affected by what the applicant has said previously during prosecution, effectively introducing a form of “file wrapper estoppel” previously unseen in UK patent cases.

As the scope of protection reaches beyond what the skilled person would understand the claims to mean based on the words alone, the interplay of infringement with novelty and inventive step becomes more interesting. This is especially relevant because most UK patents are examined and granted by the European Patent Office, a body which does not consider infringement. This idea of a broader claim interpretation being used for infringement than was used for validity is well-recognised in the UK courts and sometimes referred to as the “Angora cat paradox” after the following rather memorable portion of the decision in European Central Bank v DSS ([2008] EWCA Civ 192):

When validity is challenged, the patentee says his patent is very small: the cat with its fur smoothed down, cuddly and sleepy. But when the patentee goes on the attack, the fur bristles, the cat is twice the size with teeth bared and eyes ablaze.

As a result, the possibility of a so-called ‘Formstein defence’ – that is, that the allegedly infringing variant would have lacked novelty or inventive step at the time of the priority date of the patent – is becoming more commonly discussed in UK infringement cases.

Finally, the intention of the alleged infringer may also be taken into account when determining infringement by equivalents.

These factors add up to a lot of potential uncertainty, both for patentees and their competitors. It has perhaps always been true to say that no one knows the exact scope of a patent claim until it is tested in the Courts, but it is more so now than ever before.

Inventive Concept

The inventive concept of a patent is defined by the UK Courts as being the new technical insight or the “clever bit” of the invention, as perceived by the skilled person. However, the inventive concept is difficult to determine without the context of the invention in relation to the prior art and what is considered common general knowledge by the skilled person. Simply reading the patent without this context may inadvertently lead to a different inventive concept. Without the correct inventive concept, it will be difficult to determine the answers to any of the Actavis questions. Certainly, the correct answers will not be forthcoming! The advantages or aims described in the patent are often a reasonable starting point for determining the inventive concept. However, expert evidence provided in Court can provide important insight into the context of the invention and the common general knowledge of the skilled person, influencing the determination of the inventive concept. For example, in Icescape Ltd v Ice-World International BV ([2018] EWCA Civ 2219), the aim of the patent was to provide a cooling member for an ice rink, which could be installed rapidly to allow for the rink to be made with different surface areas. However, based upon expert evidence at trial, the judge found that the “inventive concept” was the provision of the joint member to allow connected pipe sections to fold relative to one another for the purposes of transportation. Other features within claim 1, particularly features describing a “series” connection between cooling elements, were considered to be part of the common general knowledge of the skilled person and not part of the inventive concept. Therefore, whilst the variant used a “parallel” connection between cooling elements and therefore would not infringe the claims under a normal (purposive) interpretation, the variant was held to be an equivalent due to the use of the inventive joint member. Tactically, some care is needed when deploying expert evidence. In particular, expert evidence must be treated very carefully to avoid undermining one’s own arguments. In Regen Lab SA v Estar Medical Ltd ([2019] EWHC 63 (Pat)), the patent was directed towards a method for the preparation of blood plasma enriched in platelets and other factors. The defendants argued that their variant process had two differences from the claims: the thixotropic gel was not polyester-based and the buffered sodium citrate was of a different molarity.

However, the defendants’ own expert evidence undermined their arguments: a report prepared by their expert apparently “did not suggest that either of these [differences] matters much”. Based on this evidence, the Judge believed that the inventive concept was employing a thixotropic gel wherein: (a) there was only one centrifugation in the process; and (b) after centrifugation about half the supernatant was removed and the platelets were then re-suspended in the enriched plasma. The differences of the non-polyester based gel and the molarity of the buffered sodium citrate, upon which the defendant’s argument was based, were held to be inconsequential.

Accurately characterising the inventive concept is clearly vital to identifying the scope of a claim, especially where equivalents are being considered. A patentee may strive for a simple inventive concept as this is more likely to be found to have been exploited by an alleged infringer in substantially the same way to achieve substantially the same result. Of course, an alleged infringer may argue for a more detailed inventive concept for just the same reason! The Courts must find a balance between both points of view, based on the facts and evidence presented, to determine infringement under the doctrine of equivalents.

Prosecution History Estoppel

The well-established practice in the US of prosecution history estoppel is only recently starting to appear in UK Courts, allowing them to look back at arguments and amendments made during prosecution to judge some limitation of the scope of the granted claims.

Actavis v Lilly briefly reviewed the circumstances in which prosecution history may be considered in a UK Court (paras 87-89). The Court decided that these circumstances must be limited, and that reference to the file would only be appropriate when: (i) the point at issue was truly unclear when looking at the specification and the claims, and (ii) where it would be contrary to public interest for the content of the file to be ignored, for example when the patentee had made it clear that they were not seeking to extend the claim scope to a variant they now suggest is infringing.

These strict limitations stem from the idea a patent should be self-contained; it is well-established jurisprudence in the UK that the scope of protection is determined by claims, interpreted in view of the description and drawings (see s.125 UKPA and Art. 69 EPC). It is therefore reasonable to conclude that the claim’s meaning should not change according to whether the skilled person has access to the file or not.

Furthermore, the Courts have held that the contents of the file rarely includes the private thoughts of the patentee and their advisors, that might provide an explanation of or reason for a particular limitation of the claim scope (see Kirin-Amgen v Hoeschst Marion Roussel Limited [2004] UKHL 46; para 35). Similar principles are used to discourage the use of prosecution history in other European courts, such as the Netherlands and Germany.

However, as we have learned, the doctrine of equivalents has catalysed a paradigm shift in the UK Courts approach to infringement. The scope of protection afforded by a claim is now undoubtably beyond what may once have been considered the “normal” purposive interpretation under s.125 PA and Art. 69 EPC. If the true inventive concept may differ from that described in the patent, based on the reading of the prior art and expert evidence, perhaps the consideration of other external factors, such as the prosecution history, is also back on the table?

In theory: yes. In practice: not so much. UK courts remain very reluctant to give any weight to the prosecution history. In the majority of the UK cases where the defendant has sought to use the prosecution history in their arguments, the arguments have been rejected and did not change the outcome of the finding of infringement (Actavis v Lilly, para 87-89; Illumina Inc. v Premaitha Health PLC [2017] EWHC 2930 (Pat), para 226-229; L’Oréal Société Anonyme v R N Ventures Limited [2018] EWHC 173 (Pat), para 71-77; Icescape v Ice-World, para 254-256; Regen v Estar, para 254-256; Excel-Eucan Limited v Source Vagabond Systems Limited [2019] EWHC 3175 (Pat), para 96; Edwards Lifesciences Corporation v Meril GmbH [2020] EWHC 2562 (Pat); para 194-201).

However, there are a few cases where prosecution history has come into play, and so this factor must join those others discussed above as now potentially relevant to UK infringement proceedings.

For example, in Akebia Therapeutics Inc v FibroGen, Inc ([2020] EWHC 866 (Pat)), the defendant’s arguments for considering the prosecution history of one of the patents at issue were taken into account in the determination of the non-infringement of the claims under the doctrine of equivalents, although it was not decisive. The patents were directed to inhibitors of a hypoxia inducible factor-prolyl hydroxylase (HIF-PH) for anaemia and related conditions. The only valid patent in question (EP2289531) contained a claim to a “Compound C” comprising an isoquinolinyl moiety. Akebia had allegedly infringed the patent with their product vadadustat, which comprised a chlorophenyl-substituted pyridinyl ring instead of the isoquinolinyl moiety.

Vadadustat was held not to infringe under the normal interpretation of the claim. In determining the first of the Actavis questions, the Court held that the inventive concept of this claim was the use of the specific molecule Compound C for treating anaemia associated with kidney disease, not the use of any compound for the same use. The skilled person would not understand that the isoquinolinyl ring was not essential to the invention nor that it could be replaced by a chlorophenyl-substituted pyridinyl ring with no material effect on binding or specificity. Therefore, the Court determined the answer to the first question to be “no”: thus, vadadustat also did not infringe under the doctrine of equivalents.

Nevertheless, the Court reviewed the answers to the remaining Actavis questions, particularly question 3 on the requirement (or otherwise) for strict compliance with the literal meaning of the claim. It was found that FibroGen had limited claim 1, originally directed to a broader “heterocyclic carboxamide compound”, to a compound of Formula (I), a narrower carboxamide compound, during prosecution in order to overcome a novelty objection. Therefore, the Court believed that the exclusion of this broader definition meant the applicant was not seeking to extend their scope of protection beyond the original confines of Formula (I). Similarly, FibroGen had then further limited the claims to Compound C. The Court held that FibroGen cannot have it both ways – if they wanted a broader claim they should have maintained their position instead of accepting a narrower claim.

Interestingly, the protection of this subject matter was not ‘saved’ by the use of commonly used precautionary disclaimers such as “any deleted subject matter is not abandoned” made in the prosecution file. The Court believed that attempting to state that the claim extends beyond what is claimed was inconsistent with the acceptance of a narrower claim scope.

Whilst non-binding, the conclusion in relation to the prosecution history in Akebia v Fibrogen will likely unsettle a lot of patentees. Patentees in the UK (and, by extension, at the EPO) may have to treat their prosecution history with increased caution and avoid statements explicitly excluding certain embodiments from the claim scope, if the hope of doctrine of equivalents broadening is to stay alive. It will not be safe to assume that deleted embodiments and subject matter excluded by amended claims will not be used as a defence against infringement, if they come to enforce their UK patent.

Such caution will of course be familiar to US applicants. However for the first time such considerations are starting to apply in the UK, making careful linguistic management of letters to the UK and European patent offices of greater importance.

Formstein Defence

An alternative defence to an allegation of infringement, somewhat related to the above discussed prosecution file wrapper estoppel considerations, is the so-called “Formstein defence”. The Formstein defence originates from German patent law. It is a defence wherein the alleged infringer argues that the embodiment alleged to be an equivalent is unpatentable (for example, lacks novelty or inventive step) over the prior art at the priority date. Accordingly, the embodiment must fall outside the scope of the claim if that claim is to be found valid (see Case X ZR 28/25 Formstein GRUR 1986, 803).

A Formstein defence appears somewhat consistent with earlier UK caselaw such as the Merrell Dow principle, whereby a patentee should not be able to prevent a person from doing what they had lawfully been entitled to do before the patent was granted (Merrel Dow Pharmaceuticals Inc. v H.N. Norton & Co. Limited [1995] UKHL 14; para 25); and the earlier Gillette defence, whereby the defendant demonstrates that the alleged infringement would have lacked novelty or inventive step at the priority date, without the need to resolve whether the patent is valid or infringed (Gillette Safety Razor Co v Anglo-American Trading Co [1913] 30 RPC 465; para 480). However, the Formstein defence, as such, has yet to be successfully applied in a UK court.

The first attempt at raising a Formstein defence was in Technetix B.V. v Teleste Limited ([2019] EWHC 126 (IPEC)) regarding the infringement of a patent directed to a cable tap unit for receiving a cable tv or internet signal. Although the patent was held invalid for lack of novelty, the Judge reviewed the possibility of infringement under the doctrine of equivalents and the potential use of the Formstein defence (had the defendant been found to be infringing).

The Court formulated a broad, simple inventive concept that might have applied if the patent was valid: a directional coupler that was separable and insertable into the base unit independent of the group of signal outputs (para 116). With this inventive concept, the defendant would have been found to be infringing the claims under the doctrine of equivalents, had the patent been found valid. However, the Court found that the directional coupler was part of the common general knowledge and therefore lacked inventive step, going so far as to say “if a Formstein defence exists in English law, Teleste is entitled to the defence” (para 126-133). It appears that a simpler inventive concept will increase the likelihood that a Formstein defence will apply.

So far, there has only been one other case that raised the Formstein defence. In E. Mishan & Sons, Inc v Hozelock Limited ([2019] EWHC 991 (Pat)), regarding an expandable hose assembly, the defendants argued that if claim 1 of the EP patent were to be held invalid for lack of priority, there would be no valid claim for a hose other than one which was unattached along its entire length.

The allegedly infringing Superhoze was not unattached along its entire length, which meant it would not infringe the claims under the normal interpretation. The defendants argued that the Superhoze should not infringe under the doctrine of equivalents either, otherwise the patentee would obtain protection for something he could not have obtained directly due to the lack of priority. However, the Judge declined to comment on the argument: he had already found the patent invalid and had not accepted the priority attack required for the Formstein defence to apply (para 199-201). This line of argument did not resurface on appeal ([2020] EWCA Civ 871). Accordingly we are no closer to knowing whether it might have held any sway with the Judge in this case.

It seems reasonably likely that a line of Formstein defence case law will develop in the UK Courts in the future. However, to get that started will require an infringement case where the patent is not invalidated during the proceedings!

Intention of Alleged Infringer

Finally, another aspect that may be taken into consideration when determining infringement under the doctrine of equivalents is the intention of the alleged infringer.

In ViiV Healthcare Company v Gilead Sciences, Inc. ([2020] EWHC 615 (Pat)), Gilead had attempted to strike out the part of the pleaded case on the doctrine of equivalents. In particular, the patentee ViiV had argued that the compound bictegravir (BIC) developed by Gilead was based upon their commercial product dolutegravir (DTG). Both compounds were HIV integrase transfer inhibitors for use in combination therapies against AIDS caused by HIV. In support of their arguments, ViiV provided a research paper (“Lazerwith”) written by employees of Gilead. The paper detailed the development of BIC and confirmed that it had been based on DTG, with the aim of maintaining the same characteristics.

Although Gilead’s BIC was not alleged to infringe the claims under a normal interpretation, the patentee argued that the intention of the defendant can be probative, as found in the established case law on passing off (related to branded products), and that Gilead’s intention was relevant for the assessment of whether BIC works in substantially the same way as DTG. Gilead countered, stating that intentions or mental acts are not part of the test for the doctrine of equivalents.

In agreement with Gilead, the Court decided that whether a defendant has copied an invention does not in and of itself establish infringement, which is a question which must be answered objectively. However, the Court ultimately sided with ViiV, stating that evidence of Gilead’s intention was relevant for the assessment of whether BIC worked in substantially the same way as DTG under the doctrine of equivalents, and that the patentee should be able to put Lazerwith to an expert witness. In particular, the question “was Gilead’s intention to find something which did in fact work in substantially the same way as DTG?” is a relevant one for infringement.

It was also noted that, whilst the intention of the infringer may be relevant to the first Actavis question, a claimant cannot simply go to court and assert that the defendant intended to copy the invention without any basis or evidence to infer such intention. In this case, of course, ViiV had the Lazerwith paper to help them: without it, the conclusion would likely have been very different.

Conclusion

Whilst there are now a number of infringement cases since Actavis v Lilly that have passed through the UK Courts and looked at the possibility of infringement by a doctrine of equivalents, there have only been a few where the doctrine was pivotal in the Court’s decision. Since Actavis v Lilly, cases such as Marflow v Cassellie ([2019] EWHC 410 (IPEC)), Excel-Eucan v Source Vagabond ([2019] EWHC 3175 (Pat)), Evalve v Edwards ([2020] EWHC 514 (Pat)), and IPCom v Vodafone ([2021] EWCA Civ 205) have relied on the doctrine of equivalents in the finding of infringement. Several other cases have found infringement under the doctrine of equivalents, but the patent itself was found invalid. Nevertheless, the Court’s conclusions on equivalents in these cases are persuasive and will help develop the doctrine in future cases.

As for the scope of protection afforded by UK patents, it is clear that the doctrine of equivalents does expand the scope of the claims in favour of the patentee. This means that the wording in the claims may not be as limited as it might appear at first blush. This may in turn encourage patentees to avoid risking a broader amendment which might be considered added matter and instead to limit their claims more narrowly without as much concern for excluding potential infringers – because many such infringers will be ‘caught’ by the doctrine of equivalents. However, this should not encourage poor drafting. It will always be recommended that claims are drafted to ensure competitors are caught infringing under the normal interpretation of the claims and not just under the doctrine of equivalents!

For third parties, thorough freedom-to-operate and prior art searches are important to form a clear view of the true landscape of the prior art as context for what the skilled person would understand is the inventive concept of a patent’s claim scope. Whilst these searches are far trickier now under the doctrine of equivalents and will always come with caveats, they are as important as ever to ensure that any commercial activities do not fall foul of infringement.

Overall, the UK still has a way to go in developing its doctrine of equivalents: this is a new and ever-changing area here. The interplay of the inventive concept and other factors, such as the prosecution history, the intention of the alleged infringer, and the possibility of a Formstein defence, will require more court decisions addressing these issues for a clearer view on how the doctrine will be interpreted in the future.

This article is provided for overview only. Parties should seek legal advice related to their particular circumstances and should not rely on it.

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