The doctrine of equivalents in the UK – background

The starting point when determining the scope of protection of patent claims is Article 69 EPC. This Article states that the extent of protection conferred by European patent claims is determined by the language of the claims, using the description and drawings to interpret them. That is the basic rule. But, Article 69 is itself to be understood using the Protocol on Interpretation of Article 69 of the EPC (the “Protocol”). Article 1 of the Protocol states as follows (slightly paraphrased for brevity):

Article 69 should not be understood as saying that the protection given by a European Patent is defined by the strict, literal meaning of the wording used in the claims, the description and drawings being employed only for the purpose of resolving any ambiguity found in those claims. But Article 69 should also not be understood as saying that the claims serve only as a guideline and that the actual protection conferred may extend to what, from considering the description and drawings, the patentee may have more widely contemplated as their invention. Instead, claims must be interpreted as defining a position between these two extremes which combines a fair protection for the patentee with a reasonable degree of certainty for third parties.

The Protocol says that, on the one hand, there is an approach in which the words used in the patent are restricted to their literal meaning, and the patent draftsman is taken to mark out the claims of the patent precisely. This approach provides the reasonable degree of certainty to third parties that the Protocol refers to. But it also risks an injustice to the patentee if a minor variant they thought they had claimed is excluded as a result. On the other hand, the wording of the claims could be taken only as a guideline that aims to identify a more indistinct ‘inventive concept’ protected by the patent. This approach will provide a fair protection for the patentee, but it has the problem of leaving third parties in doubt as to the activities that may infringe.

The Protocol says that both these extremes are wrong and that instead a middle-way must be found. The difficulty for the national courts, who must apply Article 69 and the Protocol when assessing infringement, is to work out exactly how to do this in a way that can be applied consistently for the different facts of each case they come across. As an English judge once put it:

Like the hippopotamus, the middle way is difficult to define but the hope is that one will recognise it when one sees it.

A particular concern with the literal approach is that it is likely to exclude immaterial variants (or ‘equivalents’). An immaterial variant is a small variation of a product or process that effectively uses the patented inventive concept, but is designed so that it is not covered by the language of the patent claim. It may also be a later technological advance on the product or process that uses the claimed invention but that could not have been envisaged by the inventor at the priority date of the patent.

In an attempt to deal with this, the Protocol was revised by the EPC 2000 to add Article 2, which says:

…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.

The specific mention of equivalents in Article 2 of the Protocol was a source of interest in the UK because a ‘doctrine of equivalents’, as such, has not been considered a part of English law. In fact, the approach to claims in the UK has long been referred to as ‘purposive construction’. This asks, what was it the inventor’s purpose to claim? This is ascertained by asking an objective but notional legal character or team (referred to as the skilled reader, skilled person or team), what they would understand the claims to mean. To do this, the skilled reader (whose view is in reality established from expert evidence) must look at the claims in the context of the description and drawings of the patent, together with the benefit of their common general knowledge at the publication date of the patent. At least, this is how it was stated by the House of Lords (now the UK Supreme Court) in the Kirin-Amgen case – the last time the issue was examined at this level of appeal. In that case, even when it was known that Article 2 of the Protocol was soon to come into force in the UK, it was held that Article 69 EPC shut the door on any doctrine which extends protection outside the claims.

Eli Lilly at first instance and appeal

The first sign since Kirin-Amgen that the approach to the scope of protection of claims may be more flexible came with the Court of Appeal decision in the Eli Lilly v Actavis case, which is now the focus of the Supreme Court decision. The case concerns Lilly’s European patent, EP 1 313 508, claiming a combination of pemetrexed disodium with vitamin B12 for the prevention of the growth of tumours. Actavis sought declarations that its proposed pemetrexed diacid, pemetrexed dipotassium and pemetrexed ditromethamine products would not infringe this patent. The focus of the case was on the limitation of the language ‟pemetrexed disodiumˮ – does the scope of the claim nonetheless extend to pemetrexed dipotassium, pemetrexed diacid or pemetrexed ditromethamine?

In Eli Lilly, the Court of Appeal said that just because there is no general doctrine of equivalence it does not mean that the existence of equivalents which have no material effect on the way the invention works have no bearing on purposive construction of a patent claim. Instead, the court states, it has long been the law that such equivalents form part of the background of facts known to the skilled reader which would affect what he understands the claim to mean. The Court of Appeal went on to say that English law recognises the impact of equivalents in the so-called ‘Improver Questions’ (sometimes referred to as the Protocol Questions). The Improver Questions were formulated in earlier cases to test whether a feature of an allegedly infringing product or process that falls outside the literal meaning of a word or phrase in the claim should nevertheless be interpreted as within the claim.

There was no dispute in Eli Lilly that pemetrexed diacid is not pemetrexed disodium according to its “primary, literal or acontextual meaning”. Instead, the Patents Court (at first instance), and Court of Appeal, used the Improver Questions to determine whether the alternative pemetrexed compounds were variants of the potassium compound. The Improver Questions as applied in these courts ask:

  1. Does the variant have a material effect upon the way the invention works? If yes, the variant is outside the claim. If no, ask:
  2. Would the fact the variant has no material effect have been obvious at the date of publication of the patent to a reader skilled in the art? If no, the variant is outside the claim. If yes, ask:
  3. Would the reader skilled in the art nevertheless have understood from the language of the claim that the patentee intended that strict compliance with the primary meaning was an essential requirement of the invention? If yes, the variant is outside the claim. On the other hand, a negative answer to the third question would lead to the conclusion that the patentee was intending the word or phrase to have a figurative meaning as a class of things which may include the variant.

As regards the first Improver Question, on the facts, the parties accepted that the difference between pemetrexed diacid, dipotassium and ditromethamine on one hand, and disodium, on the other, had no material effect. This is because from the point of view of the skilled oncologist (one member of the skilled team addressing the patent), the active anti-cancer principle in an aqueous solution of pemetrexed disodium for intravenous administration is the pemetrexed anion, the source of which is immaterial. From the perspective of a chemist, pemetrexed diacid, dipotassium and ditromethamine are all pharmaceutically acceptable and sufficiently soluble.

Resolving the second Improver Question depended on the meaning of “the way in which the invention works”, and the level of generality at which that is assessed. The problem is much the same, the judge at first instance commented, if one asks whether the variant solves the problem underlying the invention by means that have the same technical effect. From the skilled oncologist’s perspective, it would be obvious that, provided the diacid yielded a sufficient concentration of pemetrexed anions in solution and did not introduce side effects, then using the diacid would have no material effect on the invention. However, the evidence of the skilled chemist (the other member of the skilled team, in this case) was that it did not know if there was no material effect until the alternative compound was tested. The chemist would not be confident of success before testing (in particular because of the potential toxicity of potassium given the quantities of pemetrexed required). This, in the judgment of the lower courts, was far from the level of confidence required for an affirmative answer to the second Improver Question.

As regards the third Improver Question, it was necessary to consider overall which construction of the expression “pemetrexed disodium” combines fair protection for the patentee and reasonable certainty for third parties under the Protocol. On this, there was nothing in the specification or the common general knowledge of the skilled team to suggest the expression “pemetrexed disodium” meant anything other than its conventional sense. In particular, at first instance, the Judge was influenced by the prosecution history showing that the claims had been deliberately limited to pemetrexed disodium . The court held that the claim was limited to the use of pemetrexed. This would provide fair protection, without the risk of the “Patent” being invalidated on the grounds of added matter and/or insufficiency. Construing the claim as extending to (at least) any form of pemetrexed which is pharmaceutically acceptable and sufficiently soluble would not provide a reasonable degree of certainty for third parties. Any other conclusion, it was held, would fail to give effect to the Protocol and would be tantamount to treating the claims as a mere guideline.

As a result of the considerations above, the Patents Court and the Court of Appeal held that pemetrexed salts other than pemetrexed disodium were not covered by the claim. There was no direct infringement1.

Eli Lilly in the Supreme Court

The UK Supreme Court has now overturned the decisions of the lower courts, holding that there is direct infringement of the pemetrexed disodium claims. Without referring to it in these terms, the decision clearly implies the application of a form of ‘doctrine of equivalents’ in the UK. But, the Supreme Court does not do so by taking a radically new approach. Instead, reasoning that previous decisions have placed too much emphasis on construing claim language and not enough emphasis on Article 2 of the Protocol, the court makes two broad clarifications of the law:

Variants dealt with separately to claim language

Firstly, the court acknowledges that direct infringement cannot be determined solely by whether a product or process falls within the language of the claim. Instead, equivalents must be taken into account as a second step. The court must therefore ask:

  • does the variant infringe any of the claims as a matter of normal interpretation; and, if not,
  • does the variant nonetheless infringe because it varies from the invention in a way or ways which is or are immaterial?

If the answer to either issue is “yes”, there is an infringement; otherwise, there is not. This approach, it is stated Lord Neuberger (who gave the leading judgment), complies with article 2 of the Protocol, because the second issue squarely raises the possibility of infringing equivalents, but limits their inclusion within the claim to those variants which are immaterial to the invention. It is also apparent, in Lord Neuberger’s judgment, that the two issues comply with article 1 of the Protocol. This is because they involve balancing the competing interests of the patentee with the need for clarity for third parties.

Adapting the Improver Questions

Secondly, in order to provide guidance as to precisely what constitutes an equivalent or how they are to be taken into account, the Supreme Court adopts the Improver Questions, but it also amends them. This is because Lord Neuberger considered the second Improver Question, as used by the lower instance courts, imposes too high a burden on the patentee. The reason is that this Question requires the skilled addressee or team to figure out whether the variant would work. At first instance and appeal it was held that they would not do so (see above). This, in the Supreme Court’s judgment, fails to accord “a fair protection for the patent proprietor” as required by article 1 of the Protocol.

In the judgment of Lord Neuberger, the second Improver Question is better expressed as asking whether, on being told what the variant does, the notional addressee would consider it obvious that it achieved substantially the same result in substantially the same way as the invention. In other words, the second Improver Question should be asked on the assumption that the notional addressee knows that the variant works to the extent that it actually does work (an approach that the court believes to be consistent with Germany, Italy and the Netherlands). The three Improver Questions, as reformulated by the Supreme Court, are therefore:

  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, ie 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?

In order to establish infringement in a case where there is no literal infringement, a patentee would have to establish that the answer to the first two questions was “yes” and that the answer to the third question was “no”.

As regards the third Improver Question, the Supreme Court also came to a different conclusion to the lower instance courts. Here, Lord Neuberger states that the Court of Appeal had placed too much emphasis on the wording of the claim at this step and not enough on Article 2 of the Protocol – answering step 3 is not another opportunity to construe the claims. The judge instead appears persuaded by the specification’s teaching that: other anti-folates with similar properties to pemetrexed disodium can be used; the fact that it was generally known at the priority date that cations other than sodium could be successfully used with anti-folates; and, the fact the specification did not teach that there was any relevance or importance of the sodium cation. Although he does not suggest it is determinative, the judge sums-up his approach to the third Question by quoting Lord Diplock in a much earlier case, Catnic: ‟No plausible reason has been advanced why any rational patentee should want to place so narrow a limitation on his inventionˮ as to limit it to sodium pemetrexed.

The prosecution file

The issue of why a patent might have wanted to limit the claim leads on to the role of the prosecution file in determining claim scope; the use of the prosecution history of a patent to assist in determining claim scope has also been at issue in the pemetrexed litigation in the course of its progress from the Patents Court to the Supreme Court. Before the Supreme Court decision, the Court of Appeal had held that it is not useful for a party to argue from the prosecution history that the patentee deliberately accepted a restriction to the scope of their claim. This is because, the Court of Appeal held, it is always open to the patentee to say simply that any such concession made in prosecution was not actually necessary and/or was wrongly made. The Supreme Court is similarly skeptical about reliance on the prosecution file, but it sets out two situations in which it may be appropriate to use its contents:

  • 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
  • it would be contrary to the public interest for the contents of the file to be ignored. This situation is 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.

These two sets of circumstances are relatively narrow: the granted patent does not itself resolve the issue, and the file does; or there has been an express statement that the patent would not be asserted against the type of variant at issue. This narrow application is viewed by the Supreme Court as consistent with other European approaches, particularly those of the Netherlands and Germany.

What is the impact of the Supreme Court’s decision?

The Eli Lilly decision appears far-reaching: a claim to one salt of a compound has been held to protect a salt of that compound that is not claimed. How will the decision impact on other cases?

Undoubtedly, the Supreme Court decision in Eli Lilly will be tested by patentees and third parties in the months and years to come. It will be argued by patentees that the decision now applies to extend claim protection to products or processes that would have earlier been thought far-fetched. Indeed, the decision appears intended to tip the balance when examining infringement towards protection for patentees and away from certainty for third parties. It does so in a number of ways:

  1. The possibility of infringement by immaterial variants / equivalents of what is claimed has been accepted in principle;
  2. The hurdle for patentees to overcome in the second step of the Improver Questions has been lowered, by deeming that the skilled person knows that the variant / equivalent works. This may also extend claims to protect later technological advances that use the invention but that were not envisaged by the inventor;
  3. Although unchanged, the approach taken by the Supreme Court to the third Improver Question suggests the third party should show why the patentee would not have meant to include equivalents.

As regards third parties, they will naturally have to scrutinize this decision when considering those patents that potentially block launch strategies and other activity, and how they might work-around them. Furthermore, the Supreme Court has clarified two, narrow circumstances in which the contents of the prosecution file may apply. As a result, even more attention will need to be paid to what was said and done in this file when considering claim scope.

There are, however, reasons for reading Eli Lilly circumspectly. Firstly, despite the result of the decision, the Supreme Court appears to regard it as a clarification of the law, rather than a change of course – “our domestic law has long recognised that an immaterial variant does not get the infringer off the hook” and Lord Neuberger finds English cases dating back to as early as 1843 in which protection was held to extend to variants that are outside the claim language. This may allow the first instance courts to take a cautious approach to the application of the decision, wary of “opening the floodgates”.

Secondly, contrary to the norm in English patent cases, there was no validity counterclaim to infringement in Eli Lilly for the Supreme Court to consider. Such validity counterclaims can place an important ‘squeeze’ on the scope that a patentee contends for its patent claims. The most obvious such squeeze is the risk that a claim too broadly construed will be found insufficient. The Supreme Court, perhaps inadvertently, alludes to this when it states that the disclosure of the patent should not be confused with its scope of protection. What the court does not say is that disclosure does matter when it comes to considering sufficiency.

Thirdly, the Supreme Court draws attention to the significance of the variant to the invention. The court suggests that a variant is more likely to be immaterial if it is not part of the inventive concept claimed. In the present case, the sodium cation is not part of the inventive concept, which is instead the administration of the pemetrexed anion together with vitamin B12. Not all claim features will be part of the inventive concept as construed in every case. Therefore, this way of looking at a claim, although it is raised in the context of Improver Question 2 specifically by the Supreme Court, may serve as a broader guide as to whether a variant is likely to fall within the scope of protection or not.

There is a final point to consider. The Supreme Court refers to the fact that it believes the approach to the scope of protection of claims set out in Eli Lilly is consistent with other European courts, particularly Germany and the Netherlands; these jurisdictions have made allowance for many years for certain features to be included within the scope of protection of claims even though they fall outside the language used. However, in practice, it is fair to say that this is used as something of a last resort in these countries, to avoid an unfair result. If this experience is any guide, decisions in the English courts that a variant that lies outside the language of a claim is none-the-less protected by it, may remain exceptional.